Fix argument retrieval in native functions

Cargo.toml

@@ -1,50 +1,16 @@
-[package]
+[workspace]
-name = "dust-lang"
+members = ["dust-lang", "dust-shell"]
-description = "General purpose programming language"
+default-members = ["dust-lang"]
-version = "0.4.1"
+resolver = "2"
-repository = "https://git.jeffa.io/jeff/dust.git"
+
+[workspace.package]
+authors = ["Jeff Anderson"]
 edition = "2021"
 license = "MIT"
-authors = ["Jeff Anderson"]
+readme = "README.md"
-default-run = "dust"
+repository = "https://git.jeffa.io/jeff/dust.git"
-
-[[bin]]
-name = "dust"
-path = "src/main.rs"
 
 [profile.dev]
 opt-level = 1
 [profile.dev.package."*"]
 opt-level = 3
-
-[dependencies]
-clap = { version = "4.4.4", features = ["derive"] }
-csv = "1.2.2"
-libc = "0.2.148"
-log = "0.4.20"
-rand = "0.8.5"
-rayon = "1.8.0"
-reqwest = { version = "0.11.20", features = ["blocking", "json"] }
-serde = { version = "1.0.188", features = ["derive"] }
-serde_json = "1.0.107"
-toml = "0.8.1"
-tree-sitter = "0.20.10"
-enum-iterator = "1.4.1"
-env_logger = "0.10"
-reedline = { version = "0.28.0", features = ["clipboard", "sqlite"] }
-crossterm = "0.27.0"
-nu-ansi-term = "0.49.0"
-humantime = "2.1.0"
-stanza = "0.5.1"
-colored = "2.1.0"
-lyneate = "0.2.1"
-
-[target.'cfg(not(target_arch = "wasm32"))'.dependencies]
-env_logger = "0.10"
-
-[target.'cfg(target_arch = "wasm32")'.dependencies]
-getrandom = { version = "0.2", features = ["js"] }
-wasm-bindgen-futures = "0.4"
-
-[build-dependencies]
-cc = "1.0"

README.md

@@ -1,188 +1,50 @@
 # Dust
 
-!!! Dust is an experimental project under active development. !!!
+Dust is a high-level interpreted programming language with static types that focuses on ease of use,
-
+performance and correctness.
-Dust is a general purpose programming language that emphasises concurrency and correctness.
-
-A basic dust program:
-
-```dust
-output("Hello world!")
-```
-
-Dust can do two (or more) things at the same time with effortless concurrency:
-
-```dust
-async {
-    output('will this one finish first?')
-    output('or will this one?')
-}
-```
-
-You can use Dust to run complex operations simply and safely. You can even invoke other programs, run them at the same time, capture their output, and pipe them together.
-
-```dust
-# Run each statment in this block in its own thread.
-async { 
-    # Invoke another program and capture its output.
-    ip_info = ^ip address;
-
-    # Pipe the output to another program.
-    ^ls -1 --all --long docs/ | ^rg .md | ^echo;
-
-    # This block is not async and the statements will be run in order.
-    {
-        file = fs:read_file('Cargo.toml')
-
-        # This loop will run each iteration in its own thread. If one of them 
-        # reaches a "break" statement, they will all stop.
-        async for line in str:lines(file) {
-            if str:contains(line, 'author') {
-                output(line)
-                break
-            }
-        }
-    }
-}
-```
-
-Dust is an interpreted, strictly typed language with first class functions, embracing concurrency by allowing any group of statements to be executed in parallel. Dust includes built-in tooling to import and export data in a variety of formats, including JSON, TOML, YAML and CSV. Dust aims to be panic-free. That means that the interpreter will only fail to run a program due to an intended error, such as a type error or syntax error. If your program passes the these checks, it will run correctly.
-
-<!--toc:start-->
-- [Dust](#dust)
-  - [Features](#features)
-  - [Usage](#usage)
-  - [Dust Language](#dust-language)
-  - [Installation](#installation)
-  - [Benchmarks](#benchmarks)
-  - [Implementation](#implementation)
-  - [Acknowledgements](#acknowledgements)
-<!--toc:end-->
-
-## Features
-
-- Simplicity: Dust is designed to be easy to learn.
-- Speed: Dust is built on [Tree Sitter] and [Rust] to prioritize performance and correctness. See [Benchmarks] below.
-- Concurrency: Safe, effortless parallel code using thread pools.
-- Safety: Written in safe, stable Rust.
-- Correctness: Type checking makes it easy to write good code.
-
-## Installation
-
-### Cargo
-
-You must have the default rust toolchain installed and up-to-date. Install [rustup] if it is not already installed. Run `cargo install dust-lang` then run `dust` to start the interactive shell.
-
-### Build From Source
-
-To build from source, clone the repository and build the parser. To do so, enter the `tree-sitter-dust` directory and run `tree-sitter-generate`. In the project root, run `cargo run` to start the shell. If you get errors about a linking with C, read them carefully to determine which prerequisites are needed.
-
-On Fedora, you can install these prerequisites with:
-
-```sh
-sudo dnf group install -y 'C Development Tools and Libraries' && sudo dnf install -y cmake
-```
-
-## Usage
-
-After installation, the command line interpreter can be given source code to run or it can launch the command-line shell. As with intepreters like `sh` and `bash`, you can use the `-c` flag to pass source code directly.
-
-```sh
-dust -c "output('Hello world!')"
-# Output: Hello world!
-```
-
-Or just provide a path to the source file.
-
-```sh
-dust examples/hello_world.ds
-```
-
-Run `dust --help` to see the available commands and options.
-
-```txt
-General purpose programming language
-
-Usage: dust [OPTIONS] [PATH]
-
-Arguments:
-  [PATH]  Location of the file to run
-
-Options:
-  -c, --command <COMMAND>        Dust source code to evaluate
-  -i, --input <INPUT>            Data to assign to the "input" variable
-  -p, --input-path <INPUT_PATH>  A path to file whose contents will be assigned to the "input" variable
-  -t, --tree                     Show the syntax tree
-  -h, --help                     Print help
-  -V, --version                  Print version    
-```
-
-## Dust Language
-
-See the [Language Reference](/docs/language.md) for more information.
-
-## Benchmarks
-
-Dust is at an early development stage and these tests are overly simple. Better benchmarks are needed to get a realistic idea of how Dust performs real work. For now, these tests are just for fun.
-The examples given were tested using [Hyperfine] on a single-core cloud instance with 1024 MB RAM. Each test was run 1000 times. The test script is shown below. Each test asks the program to read a JSON file and count the objects. Dust is a command line shell, programming language and data manipulation tool so three appropriate targets were chosen for comparison: nushell, NodeJS and jq. The programs produced identical output with the exception that NodeJS printed in color.
-
-For the first test, a file with four entries was used.
-
-| Command | Mean [ms] | Min [ms] | Max [ms] 
-|:---|---:|---:|---:|
-| Dust | 3.1 ± 0.5 | 2.4 | 8.4 |
-| jq | 33.7 ± 2.2 | 30.0 | 61.8 |
-| NodeJS | 226.4 ± 13.1 | 197.6 | 346.2 |
-| Nushell | 51.6 ± 3.7 | 45.4 | 104.3 |
-
-The second set of data is from the GitHub API, it consists of 100 commits from the jq GitHub repo.
-
-| Command | Mean [ms] | Min [ms] | Max [ms] |
-|:---|---:|---:|---:|
-| Dust | 6.8 ± 0.6 | 5.7 | 12.0 | 2.20 ± 0.40 |
-| jq | 43.3 ± 3.6 | 37.6 | 81.6 | 13.95 ± 2.49 |
-| NodeJS | 224.9 ± 12.3 | 194.8 | 298.5 |
-| Nushell | 59.2 ± 5.7 | 49.7 | 125.0 | 19.11 ± 3.55 |
-
-This data came from CERN, it is a massive file of 100,000 entries.
-
-| Command | Mean [ms] | Min [ms] | Max [ms] |
-|:---|---:|---:|---:|
-| Dust | 1080.8 ± 38.7 | 975.3 | 1326.6 |
-| jq | 1305.3 ± 64.3 | 1159.7 | 1925.1 |
-| NodeJS | 1850.5 ± 72.5 | 1641.9 | 2395.1 |
-| Nushell | 1850.5 ± 86.2 | 1625.5 | 2400.7 |
-
-The tests were run after 5 warmup runs and the cache was cleared before each run.
-
-```sh
-hyperfine \
-	--shell none \
-	--warmup 5 \
-	--prepare "rm -rf /root/.cache" \
-	--runs 1000 \
-	--parameter-list data_path seaCreatures.json,jq_data.json,dielectron.json \
-	--export-markdown test_output.md \
-	"dust -c '(length (from_json input))' -p {data_path}" \
-	"jq 'length' {data_path}" \
-	"node --eval \"require('node:fs').readFile('{data_path}',(err,data)=>{console.log(JSON.parse(data).length)})\"" \
-	"nu -c 'open {data_path} | length'"
-```
 
 ## Implementation
 
-Dust is formally defined as a Tree Sitter grammar in the tree-sitter-dust directory. Tree sitter generates a parser, written in C, from a set of rules defined in JavaScript. Dust itself is a rust binary that calls the C parser using FFI.
+Dust is implemented in Rust and is divided into several parts, primarily the lexer, compiler, and
+virtual machine. All of Dust's components are designed with performance in mind and the codebase
+uses as few dependencies as possible.
 
-Tests are written in three places: in the Rust library, in Dust as examples and in the Tree Sitter test format. Generally, features are added by implementing and testing the syntax in the tree-sitter-dust repository, then writing library tests to evaluate the new syntax. Implementation tests run the Dust files in the "examples" directory and should be used to demonstrate and verify that features work together.
+### Lexer
 
-Tree Sitter generates a concrete syntax tree, which Dust traverses to create an abstract syntax tree that can run the Dust code. The CST generation is an extra step but it allows easy testing of the parser, defining the language in one file and makes the syntax easy to modify and expand. Because it uses Tree Sitter, developer-friendly features like syntax highlighting and code navigation are already available in any text editor that supports Tree Sitter.
+The lexer emits tokens from the source code. Dust makes extensive use of Rust's zero-copy
+capabilities to avoid unnecessary allocations when creating tokens. A token, depending on its type,
+may contain a reference to some data from the source code. The data is only copied in the case of an
+error, because it improves the usability of the codebase for errors to own their data when possible.
+In a successfully executed program, no part of the source code is copied unless it is a string
+literal or identifier.
 
-## Acknowledgements
+### Compiler
 
-Dust began as a fork of [evalexpr]. Some of the original code is still in place but the project has dramatically changed and no longer uses any of its parsing or interpreting.
+The compiler creates a chunk, which contains all of the data needed by the virtual machine to run a
+Dust program. It does so by emitting bytecode instructions, constants and locals while parsing the
+tokens, which are generated one at a time by the lexer.
 
-[Tree Sitter]: https://tree-sitter.github.io/tree-sitter/
+#### Parsing
-[Rust]: https://rust-lang.org
+
-[evalexpr]: https://github.com/ISibboI/evalexpr
+Dust's compiler uses a custom Pratt parser, a kind of recursive descent parser, to translate a
-[rustup]: https://rustup.rs
+sequence of tokens into a chunk.
-[Hyperfine]: https://github.com/sharkdp/hyperfine
+
+#### Optimizing
+
+When generating instructions for a register-based virtual machine, there are opportunities to
+optimize the generated code, usually by consolidating register use or reusing registers within an
+expression. While it is best to output optimal code in the first place, it is not always possible.
+Dust's compiler has a simple peephole optimizer that can be used to modify isolated sections of the
+instruction list through a mutable reference.
+
+### Instructions
+
+### Virtual Machine
+
+## Previous Implementations
+
+## Inspiration
+
+- [The Implementation of Lua 5.0](https://www.lua.org/doc/jucs05.pdf)
+- [A No-Frills Introduction to Lua 5.1 VM Instructions](https://www.mcours.net/cours/pdf/hasclic3/hasssclic818.pdf)
+- [Crafting Interpreters](https://craftinginterpreters.com/)

build.rs

@@ -1,17 +0,0 @@
-fn main() {
-    let src_dir = std::path::Path::new("tree-sitter-dust/src");
-    let mut c_config = cc::Build::new();
-
-    c_config.include(src_dir);
-    c_config
-        .flag_if_supported("-Wno-unused-parameter")
-        .flag_if_supported("-Wno-unused-but-set-variable")
-        .flag_if_supported("-Wno-trigraphs");
-
-    let parser_path = src_dir.join("parser.c");
-
-    c_config.file(&parser_path);
-    c_config.compile("parser");
-
-    println!("cargo:rerun-if-changed={}", parser_path.to_str().unwrap());
-}

docs/language.md

@@ -1,515 +0,0 @@
-# Dust Language Reference
-
-!!! This is a **work in progress** and has incomplete information. !!!
-
-This is an in-depth description of the syntax and abstractions used by the Dust language. It is not
-necessary to read or understand all of it before you start using Dust. Instead, refer to it when
-you need help with the syntax or understanding how the code is run.
-
-Each section of this document corresponds to a node in the concrete syntax tree. Creating this tree
-is the first step in interpreting Dust code. Second, the syntax tree is traversed and an abstract
-tree is generated. Each node in the syntax tree corresponds to a node in the abstract tree. Third,
-the abstract tree is verified to ensure that it will not generate any values that violate the type
-restrictions. Finally, the abstract tree is run, beginning at the [root](#root).
-
-You may reference the [grammar file](tree-sitter-dust/grammar.js) and the [Tree Sitter docs]
-(https://tree-sitter.github.io/) while reading this guide to understand how the language is parsed.
-
-<!--toc:start-->
-- [Dust Language Reference](#dust-language-reference)
-  - [Root](#root)
-  - [Values](#values)
-    - [Boolean](#boolean)
-    - [Integer](#integer)
-    - [Float](#float)
-    - [Range](#range)
-    - [String](#string)
-    - [List](#list)
-    - [Map](#map)
-    - [Function](#function)
-    - [Option](#option)
-    - [Structure](#structure)
-  - [Types](#types)
-    - [Basic Types](#basic-types)
-    - [Number](#number)
-    - [Any](#any)
-    - [None](#none)
-    - [List Type](#list-type)
-    - [Map Type](#map-type)
-    - [Iter](#iter)
-    - [Function Type](#function-type)
-    - [Option Type](#option-type)
-    - [Custom Types](#custom-types)
-  - [Statements](#statements)
-    - [Assignment](#assignment)
-    - [Blocks](#blocks)
-      - [Synchronous Blocks](#synchronous-blocks)
-      - [Asynchronous Blocks](#asynchronous-blocks)
-    - [Break](#break)
-    - [For Loop](#for-loop)
-    - [While Loop](#while-loop)
-    - [If/Else](#ifelse)
-    - [Match](#match)
-    - [Pipe](#pipe)
-    - [Expression](#expression)
-  - [Expressions](#expressions)
-      - [Identifier](#identifier)
-      - [Index](#index)
-      - [Logic](#logic)
-      - [Math](#math)
-      - [Value](#value)
-      - [New](#new)
-      - [Command](#command)
-  - [Built-In Values](#built-in-values)
-  - [Comments](#comments)
-<!--toc:end-->
-
-## Root
-
-The root node represents all of the source code. It is a sequence of [statements](#statements) that
-are executed synchronously, in order. The output of the program is always the result of the final
-statement or the first error encountered.
-
-## Values
-
-There are ten kinds of value in Dust. Some are very simple and are parsed directly from the source
-code, some are collections and others are used in special ways, like functions and structures. All
-values can be assinged to an [identifier](#identifiers).
-
-Dust does not have a null type. Absent values are represented with the `none` value, which is a
-kind of [option](#option). You may not create a variable without a value and no variable can ever
-be in an 'undefined' state during execution.
-
-### Boolean
-
-Booleans are true or false. They are represented by the literal tokens `true` and `false`.
-
-### Integer
-
-Integers are whole numbers that may be positive, negative or zero. Internally, an integer is a
-signed 64-bit value.
-
-```dust
-42
-```
-
-Integers always **overflow** when their maximum or minimum value is reached. Overflowing means that
-if the value is too high or low for the 64-bit integer, it will wrap around. You can use the built-
-in values `int:max` and `int:min` to get the highest and lowest possible values.
-
-```dust
-assert_equal(int:max + 1, int:min)
-assert_equal(int:min - 1, int:max)
-```
-
-### Float
-
-A float is a numeric value with a decimal. Floats are 64-bit and, like integers, will **overflow**
-at their bounds.
-
-```dust
-42.0
-```
-
-### Range
-
-A range represents a contiguous sequence of integers. Dust ranges are **inclusive** so both the high
-and low bounds will be represented.
-
-```dust
-0..100
-```
-
-### String
-
-A string is a **utf-8** sequence used to represent text. Strings can be wrapped in single or double quotes as well as backticks.
-
-```dust
-'42'
-"42"
-`42`
-'forty-two'
-```
-
-### List
-
-A list is **collection** of values stored as a sequence and accessible by [indexing](#index) their position with an integer. Lists indexes begin at zero for the first item.
-
-```dust
-[ 42 'forty-two' ]
-[ 123, 'one', 'two', 'three' ]
-```
-
-Note that the commas are optional, including trailing commas.
-
-```dust
-[1 2 3 4 5]:2
-# Output: 3
-```
-
-### Map
-
-Maps are flexible collections with arbitrary **key-value pairs**, similar to JSON objects. A map is
-created with a pair of curly braces and its entries are variables declared inside those braces. Map
-contents can be accessed using a colon `:`. Commas may optionally be included after the key-value
-pairs.
-
-```dust
-reminder = {
-    message = "Buy milk"
-    tags = ["groceries", "home"]
-}
-
-reminder:message
-# Output: Buy milk
-```
-
-Internally a map is represented by a B-tree. The implicit advantage of using a B-tree instead of a
-hash map is that a B-tree is sorted and therefore can be easily compared to another. Maps are also
-used by the interpreter as the data structure for holding variables. You can even inspect the active
-**execution context** by calling the built-in `context()` function.
-
-The map stores each [identifier](#identifiers)'s key with a value and the value's type. For internal
-use by the interpreter, a type can be set to a key without a value. This makes it possible to check
-the types of values before they are computed.
-
-### Function
-
-A function encapsulates a section of the abstract tree so that it can be run seperately and with
-different arguments. The function body is a [block](#block), so adding `async` will cause the body
-to run like any other `async` block. Unlike some languages, there are no concepts like futures or
-async functions in Dust.
-
-Functions are **first-class values** in Dust, so they can be assigned to variables like any other
-value.
-
-```dust
-# This simple function has no arguments and no return value.
-say_hi = () <none> {
-    output("hi") # The "output" function is a built-in that prints to stdout.
-}
-
-# This function has one argument and will return a value.
-add_one = (number <num>) <num> {
-    number + 1
-}
-
-say_hi()
-assert_equal(add_one(3), 4)
-```
-
-Functions can also be **anonymous**. This is useful for using **callbacks** (i.e. functions that are
-called by another function).
-
-```dust
-# Use a callback to retain only the numeric characters in a string.
-str:retain(
-	'a1b2c3'
-	(char <str>) <bool> {
-		is_some(int:parse(char))
-	}
-)
-```
-
-### Option
-
-An option represents a value that may not be present. It has two variants: **some** and **none**. 
-
-```dust
-say_something = (message <option(str)>) <str> {
-    either_or(message, "hiya")
-}
-
-say_something(some("goodbye"))
-# goodbye
-
-say_something(none)
-# hiya
-```
-
-Dust includes built-in functions to work with option values: `is_none`, `is_some` and `either_or`.
-
-### Structure
-
-A structure is a **concrete type value**. It is a value, like any other, and can be [assigned]
-(#assignment) to an [identifier](#identifier). It can then be instantiated as a [map](#map) that
-will only allow the variables present in the structure. Default values may be provided for each
-variable in the structure, which will be propagated to the map it creates. Values without defaults
-must be given a value during instantiation.
-
-```dust
-struct User {
-    name <str>
-    email <str>
-    id <int> = generate_id()
-}
-
-bob = new User {
-    name = "Bob"
-    email = "bob@example.com"
-}
-
-# The variable "bob" is a structured map.
-```
-
-A map created by using [new](#new) is called a **structured map**. In other languages it may be
-called a "homomorphic mapped type". Dust will generate errors if you try to set any values on the
-structured map that are not allowed by the structure.
-
-## Types
-
-Dust enforces strict type checking. To make the language easier to write, **type inference** is used
-to allow variables to be declared without specifying the type. Instead, the interpreter will figure
-it out and set the strictest type possible.
-
-To make the type-setting syntax easier to distinguish from the rest of your code, a **type
-specification** is wrapped in pointed brackets. So variable assignment using types looks like this:
-
-```dust
-my_float <float> = 666.0
-```
-
-### Basic Types
-
-The simple types, and their notation are:
-
-- boolean `bool`
-- integer `int`
-- float `float`
-- string `str`
-
-### Number
-
-The `num` type may represent a value of type `int` or `float`.
-
-### Any
-
-The `any` type does not enforce type bounds.
-
-### None
-
-The `none` type indicates that no value should be found after executing the statement or block, with
-one expection: the `none` variant of the `option` type.
-
-### List Type
-
-A list's contents can be specified to create type-safe lists. The `list(str)` type would only allow
-string values. Writing `list` without the parentheses and content type is equivalent to writing
-`list(any)`.
-
-### Map Type
-
-The `map` type is unstructured and can hold any key-value pair.
-
-### Iter
-
-The `iter` type refers to types that can be used with a [for loop](#for-loop). These include `list`,
-`range`, `string` and `map`.
-
-### Function Type
-
-A function's type specification is more complex than other types. A function value must always have
-its arguments and return type specified when the **function value** is created.
-
-```dust
-my_function = (number <int>, text <str>) <none> {
-    output(number)
-    output(text)
-}
-```
-
-But what if we need to specify a **function type** without creating the function value? This is
-necessary when using callbacks or defining structures that have functions set at instantiation.
-
-```dust
-use_adder = (adder <(int) -> int>, number <int>) -> <int> {
-    adder(number)
-}
-
-use_adder(
-    (i <int>) <int> { i + 2 }
-    40
-)
-
-# Output: 42
-```
-
-```dust
-struct Message {
-    send_n_times <(str, int) -> none>
-}
-
-stdout_message = new Message {
-    send_n_times = (content <str>, n <int>) <none> {
-        for _ in 0..n {
-            output(content)
-        }
-    }
-}
-```
-
-### Option Type
-
-The `option(type)` type is expected to be either `some(value)` or `none`. The type of the value
-inside the `some` is always specified.
-
-```dust
-result <option(str)> = none
-
-for file in fs:read_dir("./") {
-    if file:size > 100 {
-        result = some(file:path)
-        break
-    }
-}
-
-output(result)
-```
-
-```dust
-get_line_break_index(text <str>) <some(int)> {
-    str:find(text, '\n')
-}
-```
-
-### Custom Types
-
-Custom types such as **structures** are referenced by their variable identifier.
-
-```dust
-File = struct {
-    path <str>
-    size <int>
-    type <str>
-}
-
-print_file_info(file <File>) <none> {
-  	info = file:path
-    		+ '\n'
-    		+ file:size
-    		+ '\n' 
-    		+ file:type
-		
-  	output(info)
-}
-```
-
-## Statements
-
-TODO
-
-### Assignment
-
-TODO
-
-### Blocks
-
-TODO
-
-#### Synchronous Blocks
-
-TODO
-
-#### Asynchronous Blocks
-
-```dust
-# An async block will run each statement in its own thread.
-async {
-    output(random_integer())
-    output(random_float())
-    output(random_boolean())
-}
-```
-
-```dust
-data = async {
-    output("Reading a file...")
-    read("examples/assets/faithful.csv")
-}
-```
-
-### Break
-
-TODO
-
-### For Loop
-
-TODO
-
-```dust
-list = [ 1, 2, 3 ]
-
-for number in list {
-    output(number + 1)
-}
-```
-
-### While Loop
-
-TODO
-
-A **while** loop continues until a predicate is false.
-
-```dust
-i = 0
-while i < 10 {
-    output(i)
-    i += 1
-}
-```
-
-### If/Else
-
-TODO
-
-### Match
-
-TODO
-
-### Pipe
-
-TODO
-
-### Expression
-
-TODO
-
-## Expressions
-
-TODO
-
-#### Identifier
-
-TODO
-
-#### Index
-
-TODO
-
-#### Logic
-
-TODO
-
-#### Math
-
-TODO
-
-#### Value
-
-TODO
-
-#### New
-
-TODO
-
-#### Command
-
-TODO
-
-## Built-In Values
-
-TODO
-
-## Comments
-
-TODO

dust-lang/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "dust-lang"
+description = "Interpreter library for the Dust programming language"
+version = "0.5.0"
+authors.workspace = true
+edition.workspace = true
+license.workspace = true
+readme.workspace = true
+repository.workspace = true
+
+[dependencies]
+annotate-snippets = "0.11.4"
+colored = "2.1.0"
+log = "0.4.22"
+rand = "0.8.5"
+serde = { version = "1.0.203", features = ["derive"] }
+serde_json = "1.0.117"
+getrandom = { version = "0.2", features = [
+    "js",
+] } # Indirect dependency, for wasm builds
+
+[dev-dependencies]
+env_logger = "0.11.5"

dust-lang/src/chunk.rs

@@ -0,0 +1,402 @@
+//! In-memory representation of a Dust program or function.
+//!
+//! A chunk consists of a sequence of instructions and their positions, a list of constants, and a
+//! list of locals that can be executed by the Dust virtual machine. Chunks have a name when they
+//! belong to a named function.
+
+use std::{
+    cmp::Ordering,
+    fmt::{self, Debug, Display, Formatter},
+};
+
+use serde::{Deserialize, Serialize};
+
+use crate::{Disassembler, Instruction, Operation, Span, Type, Value};
+
+/// In-memory representation of a Dust program or function.
+///
+/// See the [module-level documentation](index.html) for more information.
+#[derive(Clone, PartialOrd, Ord, Serialize, Deserialize)]
+pub struct Chunk {
+    name: Option<String>,
+    pub is_poisoned: bool,
+
+    instructions: Vec<(Instruction, Span)>,
+    constants: Vec<Value>,
+    locals: Vec<Local>,
+
+    current_scope: Scope,
+    block_index: u8,
+}
+
+impl Chunk {
+    pub fn new(name: Option<String>) -> Self {
+        Self {
+            name,
+            is_poisoned: false,
+            instructions: Vec::new(),
+            constants: Vec::new(),
+            locals: Vec::new(),
+            current_scope: Scope::default(),
+            block_index: 0,
+        }
+    }
+
+    pub fn with_data(
+        name: Option<String>,
+        instructions: Vec<(Instruction, Span)>,
+        constants: Vec<Value>,
+        locals: Vec<Local>,
+    ) -> Self {
+        Self {
+            name,
+            is_poisoned: false,
+            instructions,
+            constants,
+            locals,
+            current_scope: Scope::default(),
+            block_index: 0,
+        }
+    }
+
+    pub fn name(&self) -> Option<&String> {
+        self.name.as_ref()
+    }
+
+    pub fn set_name(&mut self, name: String) {
+        self.name = Some(name);
+    }
+
+    pub fn len(&self) -> usize {
+        self.instructions.len()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.instructions.is_empty()
+    }
+
+    pub fn constants(&self) -> &Vec<Value> {
+        &self.constants
+    }
+
+    pub fn constants_mut(&mut self) -> &mut Vec<Value> {
+        &mut self.constants
+    }
+
+    pub fn take_constants(self) -> Vec<Value> {
+        self.constants
+    }
+
+    pub fn instructions(&self) -> &Vec<(Instruction, Span)> {
+        &self.instructions
+    }
+
+    pub fn instructions_mut(&mut self) -> &mut Vec<(Instruction, Span)> {
+        &mut self.instructions
+    }
+
+    pub fn get_instruction(&self, index: usize) -> Result<&(Instruction, Span), ChunkError> {
+        self.instructions
+            .get(index)
+            .ok_or(ChunkError::InstructionIndexOutOfBounds { index })
+    }
+
+    pub fn locals(&self) -> &Vec<Local> {
+        &self.locals
+    }
+
+    pub fn locals_mut(&mut self) -> &mut Vec<Local> {
+        &mut self.locals
+    }
+
+    pub fn get_local(&self, index: u8) -> Result<&Local, ChunkError> {
+        self.locals
+            .get(index as usize)
+            .ok_or(ChunkError::LocalIndexOutOfBounds {
+                index: index as usize,
+            })
+    }
+
+    pub fn get_local_mut(&mut self, index: u8) -> Result<&mut Local, ChunkError> {
+        self.locals
+            .get_mut(index as usize)
+            .ok_or(ChunkError::LocalIndexOutOfBounds {
+                index: index as usize,
+            })
+    }
+
+    pub fn current_scope(&self) -> Scope {
+        self.current_scope
+    }
+
+    pub fn get_constant(&self, index: u8) -> Result<&Value, ChunkError> {
+        self.constants
+            .get(index as usize)
+            .ok_or(ChunkError::ConstantIndexOutOfBounds {
+                index: index as usize,
+            })
+    }
+
+    pub fn push_or_get_constant(&mut self, value: Value) -> u8 {
+        if let Some(index) = self
+            .constants
+            .iter()
+            .position(|constant| constant == &value)
+        {
+            return index as u8;
+        }
+
+        self.constants.push(value);
+
+        (self.constants.len() - 1) as u8
+    }
+
+    pub fn get_identifier(&self, local_index: u8) -> Option<String> {
+        self.locals.get(local_index as usize).and_then(|local| {
+            self.constants
+                .get(local.identifier_index as usize)
+                .map(|value| value.to_string())
+        })
+    }
+
+    pub fn begin_scope(&mut self) {
+        self.block_index += 1;
+        self.current_scope.block_index = self.block_index;
+        self.current_scope.depth += 1;
+    }
+
+    pub fn end_scope(&mut self) {
+        self.current_scope.depth -= 1;
+
+        if self.current_scope.depth == 0 {
+            self.current_scope.block_index = 0;
+        } else {
+            self.current_scope.block_index -= 1;
+        }
+    }
+
+    pub fn expect_not_poisoned(&self) -> Result<(), ChunkError> {
+        if self.is_poisoned {
+            Err(ChunkError::PoisonedChunk)
+        } else {
+            Ok(())
+        }
+    }
+
+    pub fn get_constant_type(&self, constant_index: u8) -> Option<Type> {
+        self.constants
+            .get(constant_index as usize)
+            .map(|value| value.r#type())
+    }
+
+    pub fn get_local_type(&self, local_index: u8) -> Option<Type> {
+        self.locals.get(local_index as usize)?.r#type.clone()
+    }
+
+    pub fn get_register_type(&self, register_index: u8) -> Option<Type> {
+        let local_type_option = self
+            .locals
+            .iter()
+            .find(|local| local.register_index == register_index)
+            .map(|local| local.r#type.clone());
+
+        if let Some(local_type) = local_type_option {
+            return local_type;
+        }
+
+        self.instructions
+            .iter()
+            .enumerate()
+            .find_map(|(index, (instruction, _))| {
+                if let Operation::LoadList = instruction.operation() {
+                    if instruction.a() == register_index {
+                        let mut length = (instruction.c() - instruction.b() + 1) as usize;
+                        let mut item_type = Type::Any;
+                        let distance_to_end = self.len() - index;
+
+                        for (instruction, _) in self
+                            .instructions()
+                            .iter()
+                            .rev()
+                            .skip(distance_to_end)
+                            .take(length)
+                        {
+                            if let Operation::Close = instruction.operation() {
+                                length -= (instruction.c() - instruction.b()) as usize;
+                            } else if let Type::Any = item_type {
+                                item_type = instruction.yielded_type(self).unwrap_or(Type::Any);
+                            }
+                        }
+
+                        return Some(Type::List {
+                            item_type: Box::new(item_type),
+                            length,
+                        });
+                    }
+                }
+
+                if instruction.yields_value() && instruction.a() == register_index {
+                    instruction.yielded_type(self)
+                } else {
+                    None
+                }
+            })
+    }
+
+    pub fn return_type(&self) -> Option<Type> {
+        let returns_value = self
+            .instructions()
+            .last()
+            .map(|(instruction, _)| {
+                debug_assert!(matches!(instruction.operation(), Operation::Return));
+
+                instruction.b_as_boolean()
+            })
+            .unwrap_or(false);
+
+        if returns_value {
+            self.instructions.iter().rev().find_map(|(instruction, _)| {
+                if instruction.yields_value() {
+                    instruction.yielded_type(self)
+                } else {
+                    None
+                }
+            })
+        } else {
+            None
+        }
+    }
+
+    pub fn disassembler(&self) -> Disassembler {
+        Disassembler::new(self)
+    }
+}
+
+impl Display for Chunk {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let disassembler = self.disassembler().styled(false);
+
+        write!(f, "{}", disassembler.disassemble())
+    }
+}
+
+impl Debug for Chunk {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let disassembly = self.disassembler().styled(false).disassemble();
+
+        if cfg!(debug_assertions) {
+            write!(f, "\n{}", disassembly)
+        } else {
+            write!(f, "{}", disassembly)
+        }
+    }
+}
+
+impl Eq for Chunk {}
+
+impl PartialEq for Chunk {
+    fn eq(&self, other: &Self) -> bool {
+        self.instructions == other.instructions
+            && self.constants == other.constants
+            && self.locals == other.locals
+    }
+}
+
+/// A scoped variable.
+#[derive(Debug, Clone, Eq, PartialEq, PartialOrd, Ord, Serialize, Deserialize)]
+pub struct Local {
+    /// The index of the identifier in the constants table.
+    pub identifier_index: u8,
+
+    /// The expected type of the local's value.
+    pub r#type: Option<Type>,
+
+    /// Whether the local is mutable.
+    pub is_mutable: bool,
+
+    /// Scope where the variable was declared.
+    pub scope: Scope,
+
+    /// Expected location of a local's value.
+    pub register_index: u8,
+}
+
+impl Local {
+    /// Creates a new Local instance.
+    pub fn new(
+        identifier_index: u8,
+        r#type: Option<Type>,
+        mutable: bool,
+        scope: Scope,
+        register_index: u8,
+    ) -> Self {
+        Self {
+            identifier_index,
+            r#type,
+            is_mutable: mutable,
+            scope,
+            register_index,
+        }
+    }
+}
+
+/// Variable locality, as defined by its depth and block index.
+///
+/// The `block index` is a unique identifier for a block within a chunk. It is used to differentiate
+/// between blocks that are not nested together but have the same depth, i.e. sibling scopes. If the
+/// `block_index` is 0, then the scope is the root scope of the chunk. The `block_index` is always 0
+/// when the `depth` is 0. See [Chunk::begin_scope][] and [Chunk::end_scope][] to see how scopes are
+/// incremented and decremented.
+#[derive(Debug, Clone, Copy, Default, Eq, PartialEq, PartialOrd, Ord, Serialize, Deserialize)]
+pub struct Scope {
+    /// Level of block nesting.
+    pub depth: u8,
+    /// Index of the block in the chunk.
+    pub block_index: u8,
+}
+
+impl Scope {
+    pub fn new(depth: u8, block_index: u8) -> Self {
+        Self { depth, block_index }
+    }
+
+    pub fn contains(&self, other: &Self) -> bool {
+        match self.depth.cmp(&other.depth) {
+            Ordering::Less => false,
+            Ordering::Greater => self.block_index >= other.block_index,
+            Ordering::Equal => self.block_index == other.block_index,
+        }
+    }
+}
+
+impl Display for Scope {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "({}, {})", self.depth, self.block_index)
+    }
+}
+
+/// Errors that can occur when using a [`Chunk`].
+#[derive(Clone, Debug, PartialEq)]
+pub enum ChunkError {
+    ConstantIndexOutOfBounds { index: usize },
+    InstructionIndexOutOfBounds { index: usize },
+    LocalIndexOutOfBounds { index: usize },
+    PoisonedChunk,
+}
+
+impl Display for ChunkError {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        match self {
+            ChunkError::ConstantIndexOutOfBounds { index } => {
+                write!(f, "Constant index {} out of bounds", index)
+            }
+            ChunkError::InstructionIndexOutOfBounds { index } => {
+                write!(f, "Instruction index {} out of bounds", index)
+            }
+            ChunkError::LocalIndexOutOfBounds { index } => {
+                write!(f, "Local index {} out of bounds", index)
+            }
+            ChunkError::PoisonedChunk => write!(f, "Chunk is poisoned"),
+        }
+    }
+}

dust-lang/src/disassembler.rs

@@ -0,0 +1,366 @@
+//! Tool for disassembling chunks into a human-readable format.
+//!
+//! A disassembler can be created by calling [Chunk::disassembler][] or by instantiating one with
+//! [Disassembler::new][].
+//!
+//! # Options
+//!
+//! The disassembler can be customized with the 'styled' option, which will apply ANSI color codes
+//! to the output.
+//!
+//! # Output
+//!
+//! The output of [Disassembler::disassemble] is a string that can be printed to the console or
+//! written to a file. Below is an example of the disassembly for a simple "Hello, world!" program.
+//!
+//! ```text
+//! ┌──────────────────────────────────────────────────────────────────────────────┐
+//! │                             <file name omitted>                              │
+//! │                                                                              │
+//! │                         write_line("Hello, world!")                          │
+//! │                                                                              │
+//! │             3 instructions, 1 constants, 0 locals, returns none              │
+//! │                                                                              │
+//! │                                 Instructions                                 │
+//! │                                 ------------                                 │
+//! │ i  BYTECODE OPERATION             INFO               TYPE         POSITION   │
+//! │--- -------- ------------- -------------------- ---------------- ------------ │
+//! │ 0        03 LOAD_CONSTANT R0 = C0                    str        (11, 26)     │
+//! │ 1   1390117 CALL_NATIVE   write_line(R0)                        (0, 27)      │
+//! │ 2        18 RETURN                                              (27, 27)     │
+//! │┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈│
+//! │                                    Locals                                    │
+//! │                                    ------                                    │
+//! │            i  IDENTIFIER       TYPE       MUTABLE  SCOPE  REGISTER           │
+//! │           --- ---------- ---------------- ------- ------- --------           │
+//! │┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈│
+//! │                                  Constants                                   │
+//! │                                  ---------                                   │
+//! │                              i       VALUE                                   │
+//! │                             --- ---------------                              │
+//! │                              0   Hello, world!                               │
+//! └──────────────────────────────────────────────────────────────────────────────┘
+//! ```
+use std::env::current_exe;
+
+use colored::Colorize;
+
+use crate::{Chunk, ConcreteValue, Local, Value};
+
+const INSTRUCTION_HEADER: [&str; 4] = [
+    "Instructions",
+    "------------",
+    " i  BYTECODE OPERATION             INFO               TYPE        POSITION ",
+    "--- -------- ------------- -------------------- ---------------- ----------",
+];
+
+const CONSTANT_HEADER: [&str; 4] = [
+    "Constants",
+    "---------",
+    " i       VALUE     ",
+    "--- ---------------",
+];
+
+const LOCAL_HEADER: [&str; 4] = [
+    "Locals",
+    "------",
+    " i  IDENTIFIER       TYPE       MUTABLE  SCOPE  REGISTER",
+    "--- ---------- ---------------- ------- ------- --------",
+];
+
+/// Builder that constructs a human-readable representation of a chunk.
+///
+/// See the [module-level documentation](index.html) for more information.
+pub struct Disassembler<'a> {
+    output: String,
+    chunk: &'a Chunk,
+    source: Option<&'a str>,
+
+    // Options
+    styled: bool,
+    indent: usize,
+}
+
+impl<'a> Disassembler<'a> {
+    pub fn new(chunk: &'a Chunk) -> Self {
+        Self {
+            output: String::new(),
+            chunk,
+            source: None,
+            styled: false,
+            indent: 0,
+        }
+    }
+
+    /// The default width of the disassembly output. To correctly align the output, this should
+    /// return the width of the longest line that the disassembler is guaranteed to produce.
+    pub fn default_width() -> usize {
+        let longest_line = INSTRUCTION_HEADER[3];
+
+        longest_line.chars().count().max(80)
+    }
+
+    pub fn source(mut self, source: &'a str) -> Self {
+        self.source = Some(source);
+
+        self
+    }
+
+    pub fn styled(mut self, styled: bool) -> Self {
+        self.styled = styled;
+
+        self
+    }
+
+    pub fn indent(mut self, indent: usize) -> Self {
+        self.indent = indent;
+
+        self
+    }
+
+    fn push(
+        &mut self,
+        text: &str,
+        center: bool,
+        style_bold: bool,
+        style_dim: bool,
+        add_border: bool,
+    ) {
+        let width = Disassembler::default_width();
+        let characters = text.chars().collect::<Vec<char>>();
+        let content_width = if add_border { width - 2 } else { width };
+        let (line_characters, remainder) = characters
+            .split_at_checked(content_width)
+            .unwrap_or((characters.as_slice(), &[]));
+        let (left_pad_length, right_pad_length) = {
+            let extra_space = content_width.saturating_sub(characters.len());
+
+            if center {
+                (extra_space / 2, extra_space / 2 + extra_space % 2)
+            } else {
+                (0, extra_space)
+            }
+        };
+        let content = if style_bold {
+            line_characters
+                .iter()
+                .collect::<String>()
+                .bold()
+                .to_string()
+        } else if style_dim {
+            line_characters
+                .iter()
+                .collect::<String>()
+                .dimmed()
+                .to_string()
+        } else {
+            line_characters.iter().collect::<String>()
+        };
+        let length_before_content = self.output.chars().count();
+
+        for _ in 0..self.indent {
+            self.output.push_str("│   ");
+        }
+
+        if add_border {
+            self.output.push('│');
+        }
+
+        self.output.push_str(&" ".repeat(left_pad_length));
+        self.output.push_str(&content);
+        self.output.push_str(&" ".repeat(right_pad_length));
+
+        let length_after_content = self.output.chars().count();
+        let line_length = length_after_content - length_before_content;
+
+        if line_length < content_width - 1 {
+            self.output
+                .push_str(&" ".repeat(content_width - line_length));
+        }
+
+        if add_border {
+            self.output.push('│');
+        }
+
+        self.output.push('\n');
+
+        if !remainder.is_empty() {
+            self.push(
+                remainder.iter().collect::<String>().as_str(),
+                center,
+                style_bold,
+                style_dim,
+                add_border,
+            );
+        }
+    }
+
+    fn push_header(&mut self, header: &str) {
+        self.push(header, true, self.styled, false, true);
+    }
+
+    fn push_details(&mut self, details: &str) {
+        self.push(details, true, false, false, true);
+    }
+
+    fn push_border(&mut self, border: &str) {
+        self.push(border, false, false, false, false);
+    }
+
+    fn push_empty(&mut self) {
+        self.push("", false, false, false, true);
+    }
+
+    pub fn disassemble(mut self) -> String {
+        let width = Disassembler::default_width();
+        let top_border = "┌".to_string() + &"─".repeat(width - 2) + "┐";
+        let section_border = "│".to_string() + &"┈".repeat(width - 2) + "│";
+        let bottom_border = "└".to_string() + &"─".repeat(width - 2) + "┘";
+        let name_display = self
+            .chunk
+            .name()
+            .map(|identifier| identifier.to_string())
+            .unwrap_or_else(|| {
+                current_exe()
+                    .map(|path| path.to_string_lossy().to_string())
+                    .unwrap_or("Chunk Disassembly".to_string())
+            });
+
+        self.push_border(&top_border);
+        self.push_header(&name_display);
+
+        if let Some(source) = self.source {
+            self.push_empty();
+            self.push_details(
+                &source
+                    .replace("  ", "")
+                    .replace("\n\n", " ")
+                    .replace('\n', " "),
+            );
+            self.push_empty();
+        }
+
+        let info_line = format!(
+            "{} instructions, {} constants, {} locals, returns {}",
+            self.chunk.len(),
+            self.chunk.constants().len(),
+            self.chunk.locals().len(),
+            self.chunk
+                .return_type()
+                .map(|r#type| r#type.to_string())
+                .unwrap_or("none".to_string())
+        );
+
+        self.push(&info_line, true, false, true, true);
+        self.push_empty();
+
+        for line in INSTRUCTION_HEADER {
+            self.push_header(line);
+        }
+
+        for (index, (instruction, position)) in self.chunk.instructions().iter().enumerate() {
+            let bytecode = format!("{:02X}", u32::from(instruction));
+            let operation = instruction.operation().to_string();
+            let info = instruction.disassembly_info(self.chunk);
+            let type_display = instruction
+                .yielded_type(self.chunk)
+                .map(|r#type| {
+                    let type_string = r#type.to_string();
+
+                    if type_string.len() > 16 {
+                        format!("{type_string:.13}...")
+                    } else {
+                        type_string
+                    }
+                })
+                .unwrap_or(String::with_capacity(0));
+            let position = position.to_string();
+
+            let instruction_display = format!(
+                "{index:^3} {bytecode:>8} {operation:13} {info:^20} {type_display:^16} {position:10}"
+            );
+
+            self.push_details(&instruction_display);
+        }
+
+        self.push_border(&section_border);
+
+        for line in LOCAL_HEADER {
+            self.push_header(line);
+        }
+
+        for (
+            index,
+            Local {
+                identifier_index,
+                r#type,
+                scope,
+                register_index,
+                is_mutable: mutable,
+            },
+        ) in self.chunk.locals().iter().enumerate()
+        {
+            let identifier_display = self
+                .chunk
+                .constants()
+                .get(*identifier_index as usize)
+                .map(|value| value.to_string())
+                .unwrap_or_else(|| "unknown".to_string());
+            let type_display = r#type
+                .as_ref()
+                .map(|r#type| {
+                    let type_string = r#type.to_string();
+
+                    if type_string.len() > 16 {
+                        format!("{type_string:.13}...")
+                    } else {
+                        type_string
+                    }
+                })
+                .unwrap_or("unknown".to_string());
+            let local_display = format!(
+                "{index:^3} {identifier_display:10} {type_display:16} {mutable:7} {scope:7} {register_index:8}"
+            );
+
+            self.push_details(&local_display);
+        }
+
+        self.push_border(&section_border);
+
+        for line in CONSTANT_HEADER {
+            self.push_header(line);
+        }
+
+        for (index, value) in self.chunk.constants().iter().enumerate() {
+            let value_display = {
+                let value_string = value.to_string();
+
+                if value_string.len() > 15 {
+                    format!("{value_string:.12}...")
+                } else {
+                    value_string
+                }
+            };
+            let constant_display = format!("{index:^3} {value_display:^15}");
+
+            self.push_details(&constant_display);
+
+            if let Value::Concrete(ConcreteValue::Function(function)) = value {
+                let function_disassembly = function
+                    .chunk()
+                    .disassembler()
+                    .styled(self.styled)
+                    .indent(self.indent + 1)
+                    .disassemble();
+
+                self.output.push_str(&function_disassembly);
+            }
+        }
+
+        self.push_border(&bottom_border);
+
+        let _ = self.output.trim_end_matches('\n');
+
+        self.output
+    }
+}

dust-lang/src/dust_error.rs

@@ -0,0 +1,66 @@
+//! Top-level Dust errors with source code annotations.
+use annotate_snippets::{Level, Renderer, Snippet};
+
+use crate::{vm::VmError, CompileError, Span};
+
+/// A top-level error that can occur during the execution of Dust code.
+///
+/// This error can display nicely formatted messages with source code annotations.
+#[derive(Debug, PartialEq)]
+pub enum DustError<'src> {
+    Compile {
+        error: CompileError,
+        source: &'src str,
+    },
+    Runtime {
+        error: VmError,
+        source: &'src str,
+    },
+}
+
+impl<'src> DustError<'src> {
+    pub fn report(&self) -> String {
+        let mut report = String::new();
+        let renderer = Renderer::styled();
+
+        match self {
+            DustError::Runtime { error, source } => {
+                let position = error.position();
+                let label = format!("{}: {}", VmError::title(), error.description());
+                let details = error
+                    .details()
+                    .unwrap_or_else(|| "While running this code".to_string());
+                let message = Level::Error.title(&label).snippet(
+                    Snippet::source(source)
+                        .fold(false)
+                        .annotation(Level::Error.span(position.0..position.1).label(&details)),
+                );
+
+                report.push_str(&renderer.render(message).to_string());
+            }
+            DustError::Compile { error, source } => {
+                let position = error.position();
+                let label = format!("{}: {}", CompileError::title(), error.description());
+                let details = error
+                    .details()
+                    .unwrap_or_else(|| "While parsing this code".to_string());
+                let message = Level::Error.title(&label).snippet(
+                    Snippet::source(source)
+                        .fold(false)
+                        .annotation(Level::Error.span(position.0..position.1).label(&details)),
+                );
+
+                report.push_str(&renderer.render(message).to_string());
+            }
+        }
+
+        report
+    }
+}
+
+pub trait AnnotatedError {
+    fn title() -> &'static str;
+    fn description(&self) -> &'static str;
+    fn details(&self) -> Option<String>;
+    fn position(&self) -> Span;
+}

dust-lang/src/formatter.rs

@@ -0,0 +1,224 @@
+//! Formatting tools
+use std::mem::replace;
+
+use colored::{ColoredString, Colorize, CustomColor};
+
+use crate::{CompileError, DustError, LexError, Lexer, Token};
+
+pub fn format(source: &str, line_numbers: bool, colored: bool) -> Result<String, DustError> {
+    let lexer = Lexer::new(source);
+    let formatted = Formatter::new(lexer)
+        .line_numbers(line_numbers)
+        .colored(colored)
+        .format()
+        .map_err(|error| DustError::Compile {
+            error: CompileError::Lex(error),
+            source,
+        })?;
+
+    Ok(formatted)
+}
+
+#[derive(Debug)]
+pub struct Formatter<'src> {
+    lexer: Lexer<'src>,
+    output_lines: Vec<(String, LineKind, usize)>,
+    next_line: String,
+    indent: usize,
+
+    current_token: Token<'src>,
+    previous_token: Token<'src>,
+
+    // Options
+    line_numbers: bool,
+    colored: bool,
+}
+
+impl<'src> Formatter<'src> {
+    pub fn new(mut lexer: Lexer<'src>) -> Self {
+        let (current_token, _) = lexer.next_token().unwrap();
+
+        Self {
+            lexer,
+            output_lines: Vec::new(),
+            next_line: String::new(),
+            indent: 0,
+            current_token,
+            previous_token: Token::Eof,
+            line_numbers: false,
+            colored: false,
+        }
+    }
+
+    pub fn line_numbers(mut self, line_numbers: bool) -> Self {
+        self.line_numbers = line_numbers;
+
+        self
+    }
+
+    pub fn colored(mut self, colored: bool) -> Self {
+        self.colored = colored;
+
+        self
+    }
+
+    pub fn format(&mut self) -> Result<String, LexError> {
+        let mut line_kind = LineKind::Empty;
+
+        self.advance()?;
+
+        while self.current_token != Token::Eof {
+            use Token::*;
+
+            if self.current_token.is_expression() && line_kind != LineKind::Assignment {
+                line_kind = LineKind::Expression;
+            }
+
+            match self.current_token {
+                Boolean(boolean) => {
+                    self.push_colored(boolean.red());
+                }
+                Byte(byte) => {
+                    self.push_colored(byte.green());
+                }
+                Character(character) => {
+                    self.push_colored(
+                        character
+                            .to_string()
+                            .custom_color(CustomColor::new(225, 150, 150)),
+                    );
+                }
+                Float(float) => {
+                    self.push_colored(float.yellow());
+                }
+                Identifier(identifier) => {
+                    self.push_colored(identifier.blue());
+                    self.next_line.push(' ');
+                }
+                Integer(integer) => {
+                    self.push_colored(integer.cyan());
+                }
+                String(string) => {
+                    self.push_colored(string.magenta());
+                }
+                LeftCurlyBrace => {
+                    self.next_line.push_str(self.current_token.as_str());
+                    self.commit_line(LineKind::OpenBlock);
+
+                    self.indent += 1;
+                }
+                RightCurlyBrace => {
+                    self.commit_line(LineKind::CloseBlock);
+                    self.next_line.push_str(self.current_token.as_str());
+
+                    self.indent -= 1;
+                }
+                Semicolon => {
+                    if line_kind != LineKind::Assignment {
+                        line_kind = LineKind::Statement;
+                    }
+
+                    self.next_line.push_str(self.current_token.as_str());
+                    self.commit_line(line_kind);
+                }
+                Let => {
+                    line_kind = LineKind::Assignment;
+
+                    self.push_colored(self.current_token.as_str().bold());
+                    self.next_line.push(' ');
+                }
+                Break | Loop | Return | While => {
+                    line_kind = LineKind::Statement;
+
+                    self.push_colored(self.current_token.as_str().bold());
+                    self.next_line.push(' ');
+                }
+                token => {
+                    self.next_line.push_str(token.as_str());
+                    self.next_line.push(' ');
+                }
+            }
+        }
+
+        let mut previous_index = 0;
+        let mut current_index = 1;
+
+        while current_index < self.output_lines.len() {
+            let (_, previous, _) = &self.output_lines[previous_index];
+            let (_, current, _) = &self.output_lines[current_index];
+
+            match (previous, current) {
+                (LineKind::Empty, _)
+                | (_, LineKind::Empty)
+                | (LineKind::OpenBlock, _)
+                | (_, LineKind::CloseBlock) => {}
+                (left, right) if left == right => {}
+                _ => {
+                    self.output_lines
+                        .insert(current_index, ("".to_string(), LineKind::Empty, 0));
+                }
+            }
+
+            previous_index += 1;
+            current_index += 1;
+        }
+
+        let formatted = String::with_capacity(
+            self.output_lines
+                .iter()
+                .fold(0, |total, (line, _, _)| total + line.len()),
+        );
+
+        Ok(self.output_lines.iter().enumerate().fold(
+            formatted,
+            |acc, (index, (line, _, indent))| {
+                let index = if index == 0 {
+                    format!("{:<3}| ", index + 1).dimmed()
+                } else {
+                    format!("\n{:<3}| ", index + 1).dimmed()
+                };
+                let left_pad = "    ".repeat(*indent);
+
+                format!("{}{}{}{}", acc, index, left_pad, line)
+            },
+        ))
+    }
+
+    fn advance(&mut self) -> Result<(), LexError> {
+        if self.lexer.is_eof() {
+            return Ok(());
+        }
+
+        let (new_token, position) = self.lexer.next_token()?;
+
+        log::info!(
+            "Parsing {} at {}",
+            new_token.to_string().bold(),
+            position.to_string()
+        );
+
+        self.previous_token = replace(&mut self.current_token, new_token);
+
+        Ok(())
+    }
+
+    fn push_colored(&mut self, colored: ColoredString) {
+        self.next_line.push_str(&format!("{}", colored));
+    }
+
+    fn commit_line(&mut self, line_kind: LineKind) {
+        self.output_lines
+            .push((self.next_line.clone(), line_kind, self.indent));
+        self.next_line.clear();
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum LineKind {
+    Empty,
+    Assignment,
+    Expression,
+    Statement,
+    OpenBlock,
+    CloseBlock,
+}

dust-lang/src/instruction.rs

@@ -0,0 +1,902 @@
+//! An operation and its arguments for the Dust virtual machine.
+//!
+//! Each instruction is a 32-bit unsigned integer that is divided into five fields:
+//! - Bits 0-6: The operation code.
+//! - Bit 7: A flag indicating whether the B argument is a constant.
+//! - Bit 8: A flag indicating whether the C argument is a constant.
+//! - Bits 9-16: The A argument,
+//! - Bits 17-24: The B argument.
+//! - Bits 25-32: The C argument.
+//!
+//! Be careful when working with instructions directly. When modifying an instruction, be sure to
+//! account for the fact that setting the A, B, or C arguments to 0 will have no effect. It is
+//! usually best to remove instructions and insert new ones in their place instead of mutating them.
+
+use serde::{Deserialize, Serialize};
+
+use crate::{Chunk, NativeFunction, Operation, Type};
+
+/// An operation and its arguments for the Dust virtual machine.
+///
+/// See the [module-level documentation](index.html) for more information.
+#[derive(Debug, Clone, Copy, Eq, PartialEq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
+pub struct Instruction(u32);
+
+impl Instruction {
+    pub fn with_operation(operation: Operation) -> Instruction {
+        Instruction(operation as u32)
+    }
+
+    pub fn r#move(to_register: u8, from_register: u8) -> Instruction {
+        let mut instruction = Instruction(Operation::Move as u32);
+
+        instruction.set_a(to_register);
+        instruction.set_b(from_register);
+
+        instruction
+    }
+
+    pub fn close(from_register: u8, to_register: u8) -> Instruction {
+        let mut instruction = Instruction(Operation::Close as u32);
+
+        instruction.set_b(from_register);
+        instruction.set_c(to_register);
+
+        instruction
+    }
+
+    pub fn load_boolean(to_register: u8, value: bool, skip: bool) -> Instruction {
+        let mut instruction = Instruction(Operation::LoadBoolean as u32);
+
+        instruction.set_a(to_register);
+        instruction.set_b_to_boolean(value);
+        instruction.set_c_to_boolean(skip);
+
+        instruction
+    }
+
+    pub fn load_constant(to_register: u8, constant_index: u8, skip: bool) -> Instruction {
+        let mut instruction = Instruction(Operation::LoadConstant as u32);
+
+        instruction.set_a(to_register);
+        instruction.set_b(constant_index);
+        instruction.set_c_to_boolean(skip);
+
+        instruction
+    }
+
+    pub fn load_list(to_register: u8, start_register: u8) -> Instruction {
+        let mut instruction = Instruction(Operation::LoadList as u32);
+
+        instruction.set_a(to_register);
+        instruction.set_b(start_register);
+
+        instruction
+    }
+
+    pub fn load_self(to_register: u8) -> Instruction {
+        let mut instruction = Instruction(Operation::LoadSelf as u32);
+
+        instruction.set_a(to_register);
+
+        instruction
+    }
+
+    pub fn define_local(to_register: u8, local_index: u8, is_mutable: bool) -> Instruction {
+        let mut instruction = Instruction(Operation::DefineLocal as u32);
+
+        instruction.set_a(to_register);
+        instruction.set_b(local_index);
+        instruction.set_c(if is_mutable { 1 } else { 0 });
+
+        instruction
+    }
+
+    pub fn get_local(to_register: u8, local_index: u8) -> Instruction {
+        let mut instruction = Instruction(Operation::GetLocal as u32);
+
+        instruction.set_a(to_register);
+        instruction.set_b(local_index);
+
+        instruction
+    }
+
+    pub fn set_local(from_register: u8, local_index: u8) -> Instruction {
+        let mut instruction = Instruction(Operation::SetLocal as u32);
+
+        instruction.set_a(from_register);
+        instruction.set_b(local_index);
+
+        instruction
+    }
+
+    pub fn add(to_register: u8, left_index: u8, right_index: u8) -> Instruction {
+        let mut instruction = Instruction(Operation::Add as u32);
+
+        instruction.set_a(to_register);
+        instruction.set_b(left_index);
+        instruction.set_c(right_index);
+
+        instruction
+    }
+
+    pub fn subtract(to_register: u8, left_index: u8, right_index: u8) -> Instruction {
+        let mut instruction = Instruction(Operation::Subtract as u32);
+
+        instruction.set_a(to_register);
+        instruction.set_b(left_index);
+        instruction.set_c(right_index);
+
+        instruction
+    }
+
+    pub fn multiply(to_register: u8, left_index: u8, right_index: u8) -> Instruction {
+        let mut instruction = Instruction(Operation::Multiply as u32);
+
+        instruction.set_a(to_register);
+        instruction.set_b(left_index);
+        instruction.set_c(right_index);
+
+        instruction
+    }
+
+    pub fn divide(to_register: u8, left_index: u8, right_index: u8) -> Instruction {
+        let mut instruction = Instruction(Operation::Divide as u32);
+
+        instruction.set_a(to_register);
+        instruction.set_b(left_index);
+        instruction.set_c(right_index);
+
+        instruction
+    }
+
+    pub fn modulo(to_register: u8, left_index: u8, right_index: u8) -> Instruction {
+        let mut instruction = Instruction(Operation::Modulo as u32);
+
+        instruction.set_a(to_register);
+        instruction.set_b(left_index);
+        instruction.set_c(right_index);
+
+        instruction
+    }
+
+    pub fn test(to_register: u8, test_value: bool) -> Instruction {
+        let mut instruction = Instruction(Operation::Test as u32);
+
+        instruction.set_a(to_register);
+        instruction.set_c_to_boolean(test_value);
+
+        instruction
+    }
+
+    pub fn test_set(to_register: u8, argument_index: u8, test_value: bool) -> Instruction {
+        let mut instruction = Instruction(Operation::TestSet as u32);
+
+        instruction.set_a(to_register);
+        instruction.set_b(argument_index);
+        instruction.set_c_to_boolean(test_value);
+
+        instruction
+    }
+
+    pub fn equal(comparison_boolean: bool, left_index: u8, right_index: u8) -> Instruction {
+        let mut instruction = Instruction(Operation::Equal as u32);
+
+        instruction.set_a_to_boolean(comparison_boolean);
+        instruction.set_b(left_index);
+        instruction.set_c(right_index);
+
+        instruction
+    }
+
+    pub fn less(comparison_boolean: bool, left_index: u8, right_index: u8) -> Instruction {
+        let mut instruction = Instruction(Operation::Less as u32);
+
+        instruction.set_a_to_boolean(comparison_boolean);
+        instruction.set_b(left_index);
+        instruction.set_c(right_index);
+
+        instruction
+    }
+
+    pub fn less_equal(comparison_boolean: bool, left_index: u8, right_index: u8) -> Instruction {
+        let mut instruction = Instruction(Operation::LessEqual as u32);
+
+        instruction.set_a_to_boolean(comparison_boolean);
+        instruction.set_b(left_index);
+        instruction.set_c(right_index);
+
+        instruction
+    }
+
+    pub fn negate(to_register: u8, from_index: u8) -> Instruction {
+        let mut instruction = Instruction(Operation::Negate as u32);
+
+        instruction.set_a(to_register);
+        instruction.set_b(from_index);
+
+        instruction
+    }
+
+    pub fn not(to_register: u8, from_index: u8) -> Instruction {
+        let mut instruction = Instruction(Operation::Not as u32);
+
+        instruction.set_a(to_register);
+        instruction.set_b(from_index);
+
+        instruction
+    }
+
+    pub fn jump(jump_offset: u8, is_positive: bool) -> Instruction {
+        let mut instruction = Instruction(Operation::Jump as u32);
+
+        instruction.set_b(jump_offset);
+        instruction.set_c_to_boolean(is_positive);
+
+        instruction
+    }
+
+    pub fn call(to_register: u8, function_register: u8, argument_count: u8) -> Instruction {
+        let mut instruction = Instruction(Operation::Call as u32);
+
+        instruction.set_a(to_register);
+        instruction.set_b(function_register);
+        instruction.set_c(argument_count);
+
+        instruction
+    }
+
+    pub fn call_native(
+        to_register: u8,
+        native_fn: NativeFunction,
+        argument_count: u8,
+    ) -> Instruction {
+        let mut instruction = Instruction(Operation::CallNative as u32);
+        let native_fn_byte = native_fn as u8;
+
+        instruction.set_a(to_register);
+        instruction.set_b(native_fn_byte);
+        instruction.set_c(argument_count);
+
+        instruction
+    }
+
+    pub fn r#return(should_return_value: bool) -> Instruction {
+        let mut instruction = Instruction(Operation::Return as u32);
+
+        instruction.set_b_to_boolean(should_return_value);
+
+        instruction
+    }
+
+    pub fn operation(&self) -> Operation {
+        Operation::from((self.0 & 0b0000_0000_0011_1111) as u8)
+    }
+
+    pub fn set_operation(&mut self, operation: Operation) {
+        self.0 |= u8::from(operation) as u32;
+    }
+
+    pub fn data(&self) -> (Operation, u8, u8, u8, bool, bool) {
+        (
+            self.operation(),
+            self.a(),
+            self.b(),
+            self.c(),
+            self.b_is_constant(),
+            self.c_is_constant(),
+        )
+    }
+
+    pub fn a(&self) -> u8 {
+        (self.0 >> 24) as u8
+    }
+
+    pub fn b(&self) -> u8 {
+        (self.0 >> 16) as u8
+    }
+
+    pub fn c(&self) -> u8 {
+        (self.0 >> 8) as u8
+    }
+
+    pub fn a_as_boolean(&self) -> bool {
+        self.a() != 0
+    }
+
+    pub fn b_as_boolean(&self) -> bool {
+        self.b() != 0
+    }
+
+    pub fn c_as_boolean(&self) -> bool {
+        self.c() != 0
+    }
+
+    pub fn set_a_to_boolean(&mut self, boolean: bool) -> &mut Self {
+        self.set_a(if boolean { 1 } else { 0 });
+
+        self
+    }
+
+    pub fn set_b_to_boolean(&mut self, boolean: bool) -> &mut Self {
+        self.set_b(if boolean { 1 } else { 0 });
+
+        self
+    }
+
+    pub fn set_c_to_boolean(&mut self, boolean: bool) -> &mut Self {
+        self.set_c(if boolean { 1 } else { 0 });
+
+        self
+    }
+
+    pub fn set_a(&mut self, to_register: u8) {
+        self.0 |= (to_register as u32) << 24;
+    }
+
+    pub fn set_b(&mut self, argument: u8) {
+        self.0 |= (argument as u32) << 16;
+    }
+
+    pub fn set_c(&mut self, argument: u8) {
+        self.0 |= (argument as u32) << 8;
+    }
+
+    pub fn b_is_constant(&self) -> bool {
+        self.0 & 0b1000_0000 != 0
+    }
+
+    pub fn c_is_constant(&self) -> bool {
+        self.0 & 0b0100_0000 != 0
+    }
+
+    pub fn set_b_is_constant(&mut self) -> &mut Self {
+        self.0 |= 0b1000_0000;
+
+        self
+    }
+
+    pub fn set_c_is_constant(&mut self) -> &mut Self {
+        self.0 |= 0b0100_0000;
+
+        self
+    }
+
+    pub fn yields_value(&self) -> bool {
+        match self.operation() {
+            Operation::Add
+            | Operation::Call
+            | Operation::Divide
+            | Operation::GetLocal
+            | Operation::LoadBoolean
+            | Operation::LoadConstant
+            | Operation::LoadList
+            | Operation::LoadSelf
+            | Operation::Modulo
+            | Operation::Multiply
+            | Operation::Negate
+            | Operation::Not
+            | Operation::Subtract => true,
+            Operation::CallNative => {
+                let native_function = NativeFunction::from(self.b());
+
+                native_function.r#type().return_type.is_some()
+            }
+            _ => false,
+        }
+    }
+
+    pub fn yielded_type(&self, chunk: &Chunk) -> Option<Type> {
+        use Operation::*;
+
+        match self.operation() {
+            Add | Divide | Modulo | Multiply | Subtract => {
+                if self.b_is_constant() {
+                    chunk.get_constant_type(self.b())
+                } else {
+                    chunk.get_register_type(self.b())
+                }
+            }
+            LoadBoolean | Not => Some(Type::Boolean),
+            Negate => {
+                if self.b_is_constant() {
+                    chunk.get_constant_type(self.b())
+                } else {
+                    chunk.get_register_type(self.b())
+                }
+            }
+            LoadConstant => chunk.get_constant_type(self.b()),
+            LoadList => chunk.get_register_type(self.a()),
+            GetLocal => chunk.get_local_type(self.b()),
+            CallNative => {
+                let native_function = NativeFunction::from(self.b());
+
+                native_function.r#type().return_type.map(|boxed| *boxed)
+            }
+            _ => None,
+        }
+    }
+
+    pub fn disassembly_info(&self, chunk: &Chunk) -> String {
+        let format_arguments = || {
+            let first_argument = if self.b_is_constant() {
+                format!("C{}", self.b())
+            } else {
+                format!("R{}", self.b())
+            };
+            let second_argument = if self.c_is_constant() {
+                format!("C{}", self.c())
+            } else {
+                format!("R{}", self.c())
+            };
+
+            (first_argument, second_argument)
+        };
+
+        match self.operation() {
+            Operation::Move => format!("R{} = R{}", self.a(), self.b()),
+            Operation::Close => {
+                let from_register = self.b();
+                let to_register = self.c().saturating_sub(1);
+
+                format!("R{from_register}..=R{to_register}")
+            }
+            Operation::LoadBoolean => {
+                let to_register = self.a();
+                let boolean = self.b_as_boolean();
+                let jump = self.c_as_boolean();
+
+                if jump {
+                    format!("R{to_register} = {boolean} && SKIP")
+                } else {
+                    format!("R{to_register} = {boolean}")
+                }
+            }
+            Operation::LoadConstant => {
+                let register_index = self.a();
+                let constant_index = self.b();
+                let jump = self.c_as_boolean();
+
+                if jump {
+                    format!("R{register_index} = C{constant_index} && SKIP")
+                } else {
+                    format!("R{register_index} = C{constant_index}")
+                }
+            }
+            Operation::LoadList => {
+                let to_register = self.a();
+                let first_index = self.b();
+                let last_index = self.c();
+
+                format!("R{to_register} = [R{first_index}..=R{last_index}]",)
+            }
+            Operation::LoadSelf => {
+                let to_register = self.a();
+                let name = chunk
+                    .name()
+                    .map(|idenifier| idenifier.as_str())
+                    .unwrap_or("self");
+
+                format!("R{to_register} = {name}")
+            }
+            Operation::DefineLocal => {
+                let to_register = self.a();
+                let local_index = self.b();
+                let identifier_display = match chunk.get_identifier(local_index) {
+                    Some(identifier) => identifier.to_string(),
+                    None => "???".to_string(),
+                };
+                let mutable_display = if self.c_as_boolean() { "mut" } else { "" };
+
+                format!("R{to_register} = L{local_index} {mutable_display} {identifier_display}")
+            }
+            Operation::GetLocal => {
+                let local_index = self.b();
+
+                format!("R{} = L{}", self.a(), local_index)
+            }
+            Operation::SetLocal => {
+                let local_index = self.b();
+                let identifier_display = match chunk.get_identifier(local_index) {
+                    Some(identifier) => identifier.to_string(),
+                    None => "???".to_string(),
+                };
+
+                format!("L{} = R{} {}", local_index, self.a(), identifier_display)
+            }
+            Operation::Add => {
+                let to_register = self.a();
+                let (first_argument, second_argument) = format_arguments();
+
+                format!("R{to_register} = {first_argument} + {second_argument}",)
+            }
+            Operation::Subtract => {
+                let to_register = self.a();
+                let (first_argument, second_argument) = format_arguments();
+
+                format!("R{to_register} = {first_argument} - {second_argument}",)
+            }
+            Operation::Multiply => {
+                let to_register = self.a();
+                let (first_argument, second_argument) = format_arguments();
+
+                format!("R{to_register} = {first_argument} * {second_argument}",)
+            }
+            Operation::Divide => {
+                let to_register = self.a();
+                let (first_argument, second_argument) = format_arguments();
+
+                format!("R{to_register} = {first_argument} / {second_argument}",)
+            }
+            Operation::Modulo => {
+                let to_register = self.a();
+                let (first_argument, second_argument) = format_arguments();
+
+                format!("R{to_register} = {first_argument} % {second_argument}",)
+            }
+            Operation::Test => {
+                let to_register = self.a();
+                let test_value = self.c_as_boolean();
+
+                format!("if R{to_register} != {test_value} {{ SKIP }}")
+            }
+            Operation::TestSet => {
+                let to_register = self.a();
+                let argument = format!("R{}", self.b());
+                let test_value = self.c_as_boolean();
+                let bang = if test_value { "" } else { "!" };
+
+                format!("if {bang}R{to_register} {{ R{to_register} = R{argument} }}",)
+            }
+            Operation::Equal => {
+                let comparison_symbol = if self.a_as_boolean() { "==" } else { "!=" };
+
+                let (first_argument, second_argument) = format_arguments();
+
+                format!("if {first_argument} {comparison_symbol} {second_argument} {{ SKIP }}")
+            }
+            Operation::Less => {
+                let comparison_symbol = if self.a_as_boolean() { "<" } else { ">=" };
+                let (first_argument, second_argument) = format_arguments();
+
+                format!("if {first_argument} {comparison_symbol} {second_argument} {{ SKIP }}")
+            }
+            Operation::LessEqual => {
+                let comparison_symbol = if self.a_as_boolean() { "<=" } else { ">" };
+                let (first_argument, second_argument) = format_arguments();
+
+                format!("if {first_argument} {comparison_symbol} {second_argument} {{ SKIP }}")
+            }
+            Operation::Negate => {
+                let to_register = self.a();
+                let argument = if self.b_is_constant() {
+                    format!("C{}", self.b())
+                } else {
+                    format!("R{}", self.b())
+                };
+
+                format!("R{to_register} = -{argument}")
+            }
+            Operation::Not => {
+                let to_register = self.a();
+                let argument = if self.b_is_constant() {
+                    format!("C{}", self.b())
+                } else {
+                    format!("R{}", self.b())
+                };
+
+                format!("R{to_register} = !{argument}")
+            }
+            Operation::Jump => {
+                let jump_distance = self.b();
+                let is_positive = self.c_as_boolean();
+
+                if is_positive {
+                    format!("JUMP +{jump_distance}")
+                } else {
+                    format!("JUMP -{jump_distance}")
+                }
+            }
+            Operation::Call => {
+                let to_register = self.a();
+                let function_register = self.b();
+                let argument_count = self.c();
+
+                let mut output = format!("R{to_register} = R{function_register}(");
+
+                if argument_count != 0 {
+                    let first_argument = function_register + 1;
+
+                    for (index, register) in
+                        (first_argument..first_argument + argument_count).enumerate()
+                    {
+                        if index > 0 {
+                            output.push_str(", ");
+                        }
+
+                        output.push_str(&format!("R{}", register));
+                    }
+                }
+
+                output.push(')');
+
+                output
+            }
+            Operation::CallNative => {
+                let to_register = self.a();
+                let native_function = NativeFunction::from(self.b());
+                let argument_count = self.c();
+                let mut output = String::new();
+                let native_function_name = native_function.as_str();
+
+                if native_function.r#type().return_type.is_some() {
+                    output.push_str(&format!("R{} = {}(", to_register, native_function_name));
+                } else {
+                    output.push_str(&format!("{}(", native_function_name));
+                }
+
+                if argument_count != 0 {
+                    let first_argument = to_register.saturating_sub(argument_count);
+
+                    for (index, register) in (first_argument..to_register).enumerate() {
+                        if index > 0 {
+                            output.push_str(", ");
+                        }
+
+                        output.push_str(&format!("R{}", register));
+                    }
+                }
+
+                output.push(')');
+
+                output
+            }
+            Operation::Return => {
+                let should_return_value = self.b_as_boolean();
+
+                if should_return_value {
+                    "->".to_string()
+                } else {
+                    "".to_string()
+                }
+            }
+        }
+    }
+}
+
+impl From<&Instruction> for u32 {
+    fn from(instruction: &Instruction) -> Self {
+        instruction.0
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn r#move() {
+        let mut instruction = Instruction::r#move(0, 1);
+
+        instruction.set_b_is_constant();
+        instruction.set_c_is_constant();
+
+        assert_eq!(instruction.operation(), Operation::Move);
+        assert_eq!(instruction.a(), 0);
+        assert_eq!(instruction.b(), 1);
+        assert!(instruction.b_is_constant());
+        assert!(instruction.b_is_constant());
+    }
+
+    #[test]
+    fn close() {
+        let instruction = Instruction::close(1, 2);
+
+        assert_eq!(instruction.operation(), Operation::Close);
+        assert_eq!(instruction.b(), 1);
+        assert_eq!(instruction.c(), 2);
+    }
+
+    #[test]
+    fn load_boolean() {
+        let instruction = Instruction::load_boolean(4, true, true);
+
+        assert_eq!(instruction.operation(), Operation::LoadBoolean);
+        assert_eq!(instruction.a(), 4);
+        assert!(instruction.a_as_boolean());
+        assert!(instruction.c_as_boolean());
+    }
+
+    #[test]
+    fn load_constant() {
+        let mut instruction = Instruction::load_constant(0, 1, true);
+
+        instruction.set_b_is_constant();
+        instruction.set_c_is_constant();
+
+        assert_eq!(instruction.operation(), Operation::LoadConstant);
+        assert_eq!(instruction.a(), 0);
+        assert_eq!(instruction.b(), 1);
+        assert!(instruction.b_is_constant());
+        assert!(instruction.b_is_constant());
+        assert!(instruction.c_as_boolean());
+    }
+
+    #[test]
+    fn load_list() {
+        let instruction = Instruction::load_list(0, 1);
+
+        assert_eq!(instruction.operation(), Operation::LoadList);
+        assert_eq!(instruction.a(), 0);
+        assert_eq!(instruction.b(), 1);
+    }
+
+    #[test]
+    fn load_self() {
+        let instruction = Instruction::load_self(10);
+
+        assert_eq!(instruction.operation(), Operation::LoadSelf);
+        assert_eq!(instruction.a(), 10);
+    }
+
+    #[test]
+    fn declare_local() {
+        let mut instruction = Instruction::define_local(0, 1, true);
+
+        instruction.set_b_is_constant();
+
+        assert_eq!(instruction.operation(), Operation::DefineLocal);
+        assert_eq!(instruction.a(), 0);
+        assert_eq!(instruction.b(), 1);
+        assert_eq!(instruction.c(), true as u8);
+        assert!(instruction.b_is_constant());
+    }
+
+    #[test]
+    fn add() {
+        let mut instruction = Instruction::add(1, 1, 0);
+
+        instruction.set_b_is_constant();
+
+        assert_eq!(instruction.operation(), Operation::Add);
+        assert_eq!(instruction.a(), 1);
+        assert_eq!(instruction.b(), 1);
+        assert_eq!(instruction.c(), 0);
+        assert!(instruction.b_is_constant());
+    }
+
+    #[test]
+    fn subtract() {
+        let mut instruction = Instruction::subtract(0, 1, 2);
+
+        instruction.set_b_is_constant();
+        instruction.set_c_is_constant();
+
+        assert_eq!(instruction.operation(), Operation::Subtract);
+        assert_eq!(instruction.a(), 0);
+        assert_eq!(instruction.b(), 1);
+        assert_eq!(instruction.c(), 2);
+        assert!(instruction.b_is_constant());
+        assert!(instruction.b_is_constant());
+    }
+
+    #[test]
+    fn multiply() {
+        let mut instruction = Instruction::multiply(0, 1, 2);
+
+        instruction.set_b_is_constant();
+        instruction.set_c_is_constant();
+
+        assert_eq!(instruction.operation(), Operation::Multiply);
+        assert_eq!(instruction.a(), 0);
+        assert_eq!(instruction.b(), 1);
+        assert_eq!(instruction.c(), 2);
+        assert!(instruction.b_is_constant());
+        assert!(instruction.b_is_constant());
+    }
+
+    #[test]
+    fn divide() {
+        let mut instruction = Instruction::divide(0, 1, 2);
+
+        instruction.set_b_is_constant();
+        instruction.set_c_is_constant();
+
+        assert_eq!(instruction.operation(), Operation::Divide);
+        assert_eq!(instruction.a(), 0);
+        assert_eq!(instruction.b(), 1);
+        assert_eq!(instruction.c(), 2);
+        assert!(instruction.b_is_constant());
+        assert!(instruction.b_is_constant());
+    }
+
+    #[test]
+    fn and() {
+        let instruction = Instruction::test(4, true);
+
+        assert_eq!(instruction.operation(), Operation::Test);
+        assert_eq!(instruction.a(), 4);
+        assert!(instruction.c_as_boolean());
+    }
+
+    #[test]
+    fn or() {
+        let instruction = Instruction::test_set(4, 1, true);
+
+        assert_eq!(instruction.operation(), Operation::TestSet);
+        assert_eq!(instruction.a(), 4);
+        assert_eq!(instruction.b(), 1);
+        assert!(instruction.c_as_boolean());
+    }
+
+    #[test]
+    fn equal() {
+        let mut instruction = Instruction::equal(true, 1, 2);
+
+        instruction.set_b_is_constant();
+        instruction.set_c_is_constant();
+
+        assert_eq!(instruction.operation(), Operation::Equal);
+        assert!(instruction.a_as_boolean());
+        assert_eq!(instruction.b(), 1);
+        assert_eq!(instruction.c(), 2);
+        assert!(instruction.b_is_constant());
+        assert!(instruction.b_is_constant());
+    }
+
+    #[test]
+    fn negate() {
+        let mut instruction = Instruction::negate(0, 1);
+
+        instruction.set_b_is_constant();
+        instruction.set_c_is_constant();
+
+        assert_eq!(instruction.operation(), Operation::Negate);
+        assert_eq!(instruction.a(), 0);
+        assert_eq!(instruction.b(), 1);
+        assert!(instruction.b_is_constant());
+        assert!(instruction.b_is_constant());
+    }
+
+    #[test]
+    fn not() {
+        let mut instruction = Instruction::not(0, 1);
+
+        instruction.set_b_is_constant();
+        instruction.set_c_is_constant();
+
+        assert_eq!(instruction.operation(), Operation::Not);
+        assert_eq!(instruction.a(), 0);
+        assert_eq!(instruction.b(), 1);
+        assert!(instruction.b_is_constant());
+        assert!(instruction.b_is_constant());
+    }
+
+    #[test]
+    fn jump() {
+        let instruction = Instruction::jump(4, true);
+
+        assert_eq!(instruction.operation(), Operation::Jump);
+
+        assert_eq!(instruction.b(), 4);
+        assert!(instruction.c_as_boolean());
+    }
+
+    #[test]
+    fn call() {
+        let instruction = Instruction::call(1, 3, 4);
+
+        assert_eq!(instruction.operation(), Operation::Call);
+        assert_eq!(instruction.a(), 1);
+        assert_eq!(instruction.b(), 3);
+        assert_eq!(instruction.c(), 4);
+    }
+
+    #[test]
+    fn r#return() {
+        let instruction = Instruction::r#return(true);
+
+        assert_eq!(instruction.operation(), Operation::Return);
+        assert!(instruction.b_as_boolean());
+    }
+}

dust-lang/src/lib.rs

@@ -0,0 +1,44 @@
+//! The Dust programming language library.
+
+pub mod chunk;
+pub mod compiler;
+pub mod disassembler;
+pub mod dust_error;
+pub mod formatter;
+pub mod instruction;
+pub mod lexer;
+pub mod native_function;
+pub mod operation;
+pub mod optimizer;
+pub mod token;
+pub mod r#type;
+pub mod value;
+pub mod vm;
+
+pub use crate::chunk::{Chunk, ChunkError, Local, Scope};
+pub use crate::compiler::{compile, CompileError, Compiler};
+pub use crate::disassembler::Disassembler;
+pub use crate::dust_error::{AnnotatedError, DustError};
+pub use crate::formatter::{format, Formatter};
+pub use crate::instruction::Instruction;
+pub use crate::lexer::{lex, LexError, Lexer};
+pub use crate::native_function::{NativeFunction, NativeFunctionError};
+pub use crate::operation::Operation;
+pub use crate::optimizer::{optimize, Optimizer};
+pub use crate::r#type::{EnumType, FunctionType, RangeableType, StructType, Type, TypeConflict};
+pub use crate::token::{Token, TokenKind, TokenOwned};
+pub use crate::value::{ConcreteValue, Function, Value, ValueError};
+pub use crate::vm::{run, Vm, VmError};
+
+use std::fmt::Display;
+
+use serde::{Deserialize, Serialize};
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
+pub struct Span(pub usize, pub usize);
+
+impl Display for Span {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "({}, {})", self.0, self.1)
+    }
+}

dust-lang/src/native_function.rs

@@ -0,0 +1,418 @@
+//! Built-in functions that implement extended functionality.
+//!
+//! Native functions are used either to implement features that are not possible to implement in
+//! Dust itself or that are more efficient to implement in Rust.
+use std::{
+    fmt::{self, Display, Formatter},
+    io::{self, stdin, stdout, Write},
+    string::{self},
+};
+
+use serde::{Deserialize, Serialize};
+
+use crate::{
+    AnnotatedError, ConcreteValue, FunctionType, Instruction, Span, Type, Value, Vm, VmError,
+};
+
+macro_rules! define_native_function {
+    ($(($name:ident, $byte:literal, $str:expr, $type:expr)),*) => {
+        /// A dust-native function.
+        ///
+        /// See the [module-level documentation](index.html) for more information.
+        #[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Serialize, Deserialize)]
+        pub enum NativeFunction {
+            $(
+                $name = $byte as isize,
+            )*
+        }
+
+        impl NativeFunction {
+            pub fn as_str(&self) -> &'static str {
+                match self {
+                    $(
+                        NativeFunction::$name => $str,
+                    )*
+                }
+            }
+
+            #[allow(clippy::should_implement_trait)]
+            pub fn from_str(string: &str) -> Option<Self> {
+                match string {
+                    $(
+                        $str => Some(NativeFunction::$name),
+                    )*
+                    _ => None,
+                }
+            }
+
+            pub fn r#type(&self) -> FunctionType {
+                match self {
+                    $(
+                        NativeFunction::$name => $type,
+                    )*
+                }
+            }
+
+            pub fn returns_value(&self) -> bool {
+                match self {
+                    $(
+                        NativeFunction::$name => $type.return_type.is_some(),
+                    )*
+                }
+            }
+        }
+
+        impl From<u8> for NativeFunction {
+            fn from(byte: u8) -> Self {
+                match byte {
+                    $(
+                        $byte => NativeFunction::$name,
+                    )*
+                    _ => {
+                        if cfg!(test) {
+                            panic!("Invalid native function byte: {}", byte)
+                        } else {
+                            NativeFunction::Panic
+                        }
+                    }
+                }
+            }
+        }
+
+        impl From<NativeFunction> for u8 {
+            fn from(native_function: NativeFunction) -> Self {
+                match native_function {
+                    $(
+                        NativeFunction::$name => $byte,
+                    )*
+                }
+            }
+        }
+    };
+}
+
+define_native_function! {
+    // Assertion
+    (
+        Assert,
+        0_u8,
+        "assert",
+        FunctionType {
+            type_parameters: None,
+            value_parameters: None,
+            return_type: None
+        }
+    ),
+    // (AssertEqual, 1_u8, "assert_equal", false),
+    // (AssertNotEqual, 2_u8, "assert_not_equal", false),
+    (
+        Panic,
+        3_u8,
+        "panic",
+        FunctionType {
+            type_parameters: None,
+            value_parameters: None,
+            return_type: Some(Box::new(Type::Any))
+        }
+    ),
+
+    // // Type conversion
+    // (Parse, 4_u8, "parse", true),
+    // (ToByte, 5_u8, "to_byte", true),
+    // (ToFloat, 6_u8, "to_float", true),
+    // (ToInteger, 7_u8, "to_integer", true),
+    (
+        ToString,
+        8_u8,
+        "to_string",
+        FunctionType {
+            type_parameters: None,
+            value_parameters: Some(vec![(0, Type::Any)]),
+            return_type: Some(Box::new(Type::String { length: None }))
+        }
+    ),
+
+    // // List and string
+    // (All, 9_u8, "all", true),
+    // (Any, 10_u8, "any", true),
+    // (Append, 11_u8, "append", false),
+    // (Contains, 12_u8, "contains", true),
+    // (Dedup, 13_u8, "dedup", false),
+    // (EndsWith, 14_u8, "ends_with", true),
+    // (Find, 15_u8, "find", true),
+    // (Get, 16_u8, "get", true),
+    // (IndexOf, 17_u8, "index_of", true),
+    // (Length, 18_u8, "length", true),
+    // (Prepend, 19_u8, "prepend", false),
+    // (Replace, 20_u8, "replace", false),
+    // (Set, 21_u8, "set", false),
+    // (StartsWith, 22_u8, "starts_with", true),
+    // (Slice, 23_u8, "slice", true),
+    // (Sort, 24_u8, "sort", false),
+    // (Split, 25_u8, "split", true),
+
+    // // List
+    // (Flatten, 26_u8, "flatten", false),
+    // (Join, 27_u8, "join", true),
+    // (Map, 28_u8, "map", true),
+    // (Reduce, 29_u8, "reduce", true),
+    // (Remove, 30_u8, "remove", false),
+    // (Reverse, 31_u8, "reverse", false),
+    // (Unzip, 32_u8, "unzip", true),
+    // (Zip, 33_u8, "zip", true),
+
+    // // String
+    // (Bytes, 34_u8, "bytes", true),
+    // (CharAt, 35_u8, "char_at", true),
+    // (CharCodeAt, 36_u8, "char_code_at", true),
+    // (Chars, 37_u8, "chars", true),
+    // (Format, 38_u8, "format", true),
+    // (Repeat, 39_u8, "repeat", true),
+    // (SplitAt, 40_u8, "split_at", true),
+    // (SplitLines, 41_u8, "split_lines", true),
+    // (SplitWhitespace, 42_u8, "split_whitespace", true),
+    // (ToLowerCase, 43_u8, "to_lower_case", true),
+    // (ToUpperCase, 44_u8, "to_upper_case", true),
+    // (Trim, 45_u8, "trim", true),
+    // (TrimEnd, 46_u8, "trim_end", true),
+    // (TrimStart, 47_u8, "trim_start", true),
+
+    // // I/O
+    // // Read
+    // (Read, 48_u8, "read", true),
+    // (ReadFile, 49_u8, "read_file", true),
+    (
+        ReadLine,
+        50_u8,
+        "read_line",
+        FunctionType {
+            type_parameters: None,
+            value_parameters: None,
+            return_type: Some(Box::new(Type::String { length: None }))
+        }
+    ),
+    // (ReadTo, 51_u8, "read_to", false),
+    // (ReadUntil, 52_u8, "read_until", true),
+    // // Write
+    // (AppendFile, 53_u8, "append_file", false),
+    // (PrependFile, 54_u8, "prepend_file", false),
+    (
+        Write,
+        55_u8,
+        "write",
+        FunctionType {
+            type_parameters: None,
+            value_parameters: Some(vec![(0, Type::String { length: None })]),
+            return_type: None
+        }
+    ),
+    // (WriteFile, 56_u8, "write_file", false),
+    (
+        WriteLine,
+        57_u8,
+        "write_line",
+        FunctionType {
+            type_parameters: None,
+            value_parameters: Some(vec![(0, Type::String { length: None })]),
+            return_type: None
+        }
+    )
+
+    // // Random
+    // (Random, 58_u8, "random", true),
+    // (RandomInRange, 59_u8, "random_in_range", true)
+}
+
+impl NativeFunction {
+    pub fn call(
+        &self,
+        instruction: Instruction,
+        vm: &Vm,
+        position: Span,
+    ) -> Result<Option<Value>, VmError> {
+        let to_register = instruction.a();
+        let argument_count = instruction.c();
+
+        let return_value = match self {
+            NativeFunction::Panic => {
+                let message = if argument_count == 0 {
+                    None
+                } else {
+                    let mut message = String::new();
+
+                    for argument_index in 0..argument_count {
+                        if argument_index != 0 {
+                            message.push(' ');
+                        }
+
+                        let argument = vm.open_register(argument_index, position)?;
+
+                        message.push_str(&argument.to_string());
+                    }
+
+                    Some(message)
+                };
+
+                return Err(VmError::NativeFunction(NativeFunctionError::Panic {
+                    message,
+                    position,
+                }));
+            }
+
+            // Type conversion
+            NativeFunction::ToString => {
+                let mut string = String::new();
+
+                for argument_index in 0..argument_count {
+                    let argument = vm.open_register(argument_index, position)?;
+
+                    string.push_str(&argument.to_string());
+                }
+
+                Some(Value::Concrete(ConcreteValue::String(string)))
+            }
+
+            // I/O
+            NativeFunction::ReadLine => {
+                let mut buffer = String::new();
+
+                stdin().read_line(&mut buffer).map_err(|io_error| {
+                    VmError::NativeFunction(NativeFunctionError::Io {
+                        error: io_error.kind(),
+                        position,
+                    })
+                })?;
+
+                buffer = buffer.trim_end_matches('\n').to_string();
+
+                Some(Value::Concrete(ConcreteValue::String(buffer)))
+            }
+            NativeFunction::Write => {
+                let to_register = instruction.a();
+                let mut stdout = stdout();
+                let map_err = |io_error: io::Error| {
+                    VmError::NativeFunction(NativeFunctionError::Io {
+                        error: io_error.kind(),
+                        position,
+                    })
+                };
+
+                let first_argument = to_register.saturating_sub(argument_count);
+                let last_argument = to_register.saturating_sub(1);
+
+                for argument_index in first_argument..=last_argument {
+                    if argument_index != first_argument {
+                        stdout.write(b" ").map_err(map_err)?;
+                    }
+
+                    let argument_string = vm.open_register(argument_index, position)?.to_string();
+
+                    stdout
+                        .write_all(argument_string.as_bytes())
+                        .map_err(map_err)?;
+                }
+
+                None
+            }
+            NativeFunction::WriteLine => {
+                let mut stdout = stdout();
+                let map_err = |io_error: io::Error| {
+                    VmError::NativeFunction(NativeFunctionError::Io {
+                        error: io_error.kind(),
+                        position,
+                    })
+                };
+
+                let first_index = to_register.saturating_sub(argument_count);
+                let arguments = vm.open_nonempty_registers(first_index..to_register, position)?;
+
+                for (index, argument) in arguments.into_iter().enumerate() {
+                    if index != 0 {
+                        stdout.write(b" ").map_err(map_err)?;
+                    }
+
+                    if let Value::Concrete(ConcreteValue::String(string)) = argument {
+                        let bytes = string.as_bytes();
+
+                        stdout.write_all(bytes).map_err(map_err)?;
+                    } else {
+                        let bytes = argument.to_string().into_bytes();
+
+                        stdout.write_all(&bytes).map_err(map_err)?;
+                    }
+                }
+
+                stdout.write(b"\n").map_err(map_err)?;
+
+                None
+            }
+            _ => todo!(),
+        };
+
+        Ok(return_value)
+    }
+}
+
+impl Display for NativeFunction {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "{}", self.as_str())
+    }
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum NativeFunctionError {
+    ExpectedArgumentCount {
+        expected: usize,
+        found: usize,
+        position: Span,
+    },
+    Panic {
+        message: Option<String>,
+        position: Span,
+    },
+    Parse {
+        error: string::ParseError,
+        position: Span,
+    },
+    Io {
+        error: io::ErrorKind,
+        position: Span,
+    },
+}
+
+impl AnnotatedError for NativeFunctionError {
+    fn title() -> &'static str {
+        "Native Function Error"
+    }
+
+    fn description(&self) -> &'static str {
+        match self {
+            NativeFunctionError::ExpectedArgumentCount { .. } => {
+                "Expected a different number of arguments"
+            }
+            NativeFunctionError::Panic { .. } => "Explicit panic",
+            NativeFunctionError::Parse { .. } => "Failed to parse value",
+            NativeFunctionError::Io { .. } => "I/O error",
+        }
+    }
+
+    fn details(&self) -> Option<String> {
+        match self {
+            NativeFunctionError::ExpectedArgumentCount {
+                expected, found, ..
+            } => Some(format!("Expected {} arguments, found {}", expected, found)),
+            NativeFunctionError::Panic { message, .. } => message.clone(),
+            NativeFunctionError::Parse { error, .. } => Some(format!("{}", error)),
+            NativeFunctionError::Io { error, .. } => Some(format!("{}", error)),
+        }
+    }
+
+    fn position(&self) -> Span {
+        match self {
+            NativeFunctionError::ExpectedArgumentCount { position, .. } => *position,
+            NativeFunctionError::Panic { position, .. } => *position,
+            NativeFunctionError::Parse { position, .. } => *position,
+            NativeFunctionError::Io { position, .. } => *position,
+        }
+    }
+}

dust-lang/src/operation.rs

@@ -0,0 +1,110 @@
+//! Part of an [Instruction][crate::Instruction], which can be executed by the Dust virtual machine.
+//!
+//! !!! Warning !!!
+//! The byte values of the operations matter. The seventh and eighth bits must be zero so that the
+//! [Instruction][crate::Instruction] type can use them as flags.
+
+use std::fmt::{self, Display, Formatter};
+
+macro_rules! define_operation {
+    ($(($name:ident, $byte:literal, $str:expr, $type:expr)),*) => {
+        /// Part of an [Instruction][crate::Instruction], which can be executed by the Dust virtual machine.)
+        ///
+        /// See the [module-level documentation](index.html) for more information.
+        #[derive(Clone, Copy, Debug, PartialEq)]
+        pub enum Operation {
+            $(
+                $name = $byte as isize,
+            )*
+        }
+
+        impl From<u8> for Operation {
+            fn from(byte: u8) -> Self {
+                match byte {
+                    $(
+                        $byte => Operation::$name,
+                    )*
+                    _ => {
+                        if cfg!(test) {
+                            panic!("Invalid operation byte: {}", byte)
+                        } else {
+                            Operation::Return
+                        }
+                    }
+                }
+            }
+        }
+
+        impl From<Operation> for u8 {
+            fn from(operation: Operation) -> Self {
+                match operation {
+                    $(
+                        Operation::$name => $byte,
+                    )*
+                }
+            }
+        }
+
+        impl Display for Operation {
+            fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+                match self {
+                    $(
+                        Operation::$name => write!(f, "{}", $str),
+                    )*
+                }
+            }
+        }
+    }
+}
+
+define_operation! {
+    (Move, 0b0000_0000, "MOVE", None),
+    (Close, 0b000_0001, "CLOSE", None),
+    (LoadBoolean, 0b0000_0010, "LOAD_BOOLEAN", None),
+    (LoadConstant, 0b0000_0011, "LOAD_CONSTANT", None),
+    (LoadList, 0b0000_0100, "LOAD_LIST", None),
+    (LoadSelf, 0b0000_0101, "LOAD_SELF", None),
+    (DefineLocal, 0b0000_0110, "DEFINE_LOCAL", None),
+    (GetLocal, 0b0000_0111, "GET_LOCAL", None),
+    (SetLocal, 0b0000_1000, "SET_LOCAL", None),
+    (Add, 0b0000_1001, "ADD", None),
+    (Subtract, 0b0000_1010, "SUBTRACT", None),
+    (Multiply, 0b0000_1011, "MULTIPLY", None),
+    (Divide, 0b0000_1100, "DIVIDE", None),
+    (Modulo, 0b0000_1101, "MODULO", None),
+    (Test, 0b0000_1110, "TEST", None),
+    (TestSet, 0b0000_1111, "TEST_SET", None),
+    (Equal, 0b0001_0000, "EQUAL", None),
+    (Less, 0b0001_0001, "LESS", None),
+    (LessEqual, 0b0001_0010, "LESS_EQUAL", None),
+    (Negate, 0b0001_0011, "NEGATE", None),
+    (Not, 0b0001_0100, "NOT", None),
+    (Jump, 0b0001_0101, "JUMP", None),
+    (Call, 0b0001_0110, "CALL", None),
+    (CallNative, 0b0001_0111, "CALL_NATIVE", None),
+    (Return, 0b0001_1000, "RETURN", None)
+}
+
+impl Operation {
+    pub fn is_math(&self) -> bool {
+        matches!(
+            self,
+            Operation::Add
+                | Operation::Subtract
+                | Operation::Multiply
+                | Operation::Divide
+                | Operation::Modulo
+        )
+    }
+
+    pub fn is_comparison(&self) -> bool {
+        matches!(
+            self,
+            Operation::Equal | Operation::Less | Operation::LessEqual
+        )
+    }
+
+    pub fn is_test(&self) -> bool {
+        matches!(self, Operation::Test | Operation::TestSet)
+    }
+}

dust-lang/src/optimizer.rs

@@ -0,0 +1,96 @@
+//! Tools used by the compiler to optimize a chunk's bytecode.
+use std::{iter::Map, slice::Iter};
+
+use crate::{Instruction, Operation, Span};
+
+type MapToOperation = fn(&(Instruction, Span)) -> Operation;
+
+type OperationIter<'iter> = Map<Iter<'iter, (Instruction, Span)>, MapToOperation>;
+
+/// Performs optimizations on a subset of instructions.
+pub fn optimize(instructions: &mut [(Instruction, Span)]) -> usize {
+    Optimizer::new(instructions).optimize()
+}
+
+/// An instruction optimizer that mutably borrows instructions from a chunk.
+#[derive(Debug, Eq, PartialEq, PartialOrd, Ord)]
+pub struct Optimizer<'chunk> {
+    instructions: &'chunk mut [(Instruction, Span)],
+}
+
+impl<'chunk> Optimizer<'chunk> {
+    /// Creates a new optimizer with a mutable reference to some of a chunk's instructions.
+    pub fn new(instructions: &'chunk mut [(Instruction, Span)]) -> Self {
+        Self { instructions }
+    }
+
+    /// Potentially mutates the instructions to optimize them.
+    pub fn optimize(&mut self) -> usize {
+        let mut optimizations = 0;
+
+        if matches!(
+            self.get_operations(),
+            Some([
+                Operation::Equal | Operation::Less | Operation::LessEqual,
+                Operation::Jump,
+                Operation::LoadBoolean | Operation::LoadConstant,
+                Operation::LoadBoolean | Operation::LoadConstant,
+            ])
+        ) {
+            self.optimize_comparison();
+
+            optimizations += 1;
+        }
+
+        optimizations
+    }
+
+    /// Optimizes a comparison operation.
+    ///
+    /// The instructions must be in the following order:
+    ///     - `Operation::Equal | Operation::Less | Operation::LessEqual`
+    ///     - `Operation::Jump`
+    ///     - `Operation::LoadBoolean | Operation::LoadConstant`
+    ///     - `Operation::LoadBoolean | Operation::LoadConstant`
+    fn optimize_comparison(&mut self) {
+        log::debug!("Optimizing comparison");
+
+        let first_loader_register = {
+            let first_loader = &mut self.instructions[2].0;
+
+            first_loader.set_c_to_boolean(true);
+            first_loader.a()
+        };
+
+        let second_loader = &mut self.instructions[3].0;
+        let mut second_loader_new = Instruction::with_operation(second_loader.operation());
+
+        second_loader_new.set_a(first_loader_register);
+        second_loader_new.set_b(second_loader.b());
+        second_loader_new.set_c(second_loader.c());
+        second_loader_new.set_b_to_boolean(second_loader.b_is_constant());
+        second_loader_new.set_c_to_boolean(second_loader.c_is_constant());
+
+        *second_loader = second_loader_new;
+    }
+
+    fn operations_iter(&self) -> OperationIter {
+        self.instructions
+            .iter()
+            .map(|(instruction, _)| instruction.operation())
+    }
+
+    fn get_operations<const COUNT: usize>(&self) -> Option<[Operation; COUNT]> {
+        if self.instructions.len() < COUNT {
+            return None;
+        }
+
+        let mut n_operations = [Operation::Return; COUNT];
+
+        for (nth, operation) in n_operations.iter_mut().zip(self.operations_iter()) {
+            *nth = operation;
+        }
+
+        Some(n_operations)
+    }
+}

dust-lang/src/token.rs

@@ -0,0 +1,642 @@
+//! Token, TokenOwned and TokenKind types.
+use std::fmt::{self, Display, Formatter};
+
+use serde::{Deserialize, Serialize};
+
+macro_rules! define_tokens {
+    ($($variant:ident $(($data_type:ty))?),+ $(,)?) => {
+        /// Source token.
+        ///
+        /// This is a borrowed type, i.e. some variants contain references to the source text.
+        #[derive(Debug, Clone, Copy, Eq, PartialEq, PartialOrd, Ord, Default, Serialize, Deserialize)]
+        pub enum Token<'src> {
+            #[default]
+            Eof,
+            $(
+                $variant $(($data_type))?,
+            )*
+        }
+
+        #[derive(Debug, PartialEq, Clone)]
+        /// Data-less representation of a source token.
+        ///
+        /// If a [Token] borrows from the source text, its TokenKind omits the data.
+        pub enum TokenKind {
+            Eof,
+            $(
+                $variant,
+            )*
+        }
+    };
+}
+
+define_tokens! {
+    // Hard-coded values
+    Boolean(&'src str),
+    Byte(&'src str),
+    Character(char),
+    Float(&'src str),
+    Identifier(&'src str),
+    Integer(&'src str),
+    String(&'src str),
+
+    // Keywords
+    Async,
+    Bool,
+    Break,
+    Else,
+    FloatKeyword,
+    Fn,
+    If,
+    Int,
+    Let,
+    Loop,
+    Map,
+    Mut,
+    Return,
+    Str,
+    Struct,
+    While,
+
+    // Symbols
+    ArrowThin,
+    BangEqual,
+    Bang,
+    Colon,
+    Comma,
+    Dot,
+    DoubleAmpersand,
+    DoubleDot,
+    DoubleEqual,
+    DoublePipe,
+    Equal,
+    Greater,
+    GreaterEqual,
+    LeftCurlyBrace,
+    LeftParenthesis,
+    LeftSquareBrace,
+    Less,
+    LessEqual,
+    Minus,
+    MinusEqual,
+    Percent,
+    PercentEqual,
+    Plus,
+    PlusEqual,
+    RightCurlyBrace,
+    RightParenthesis,
+    RightSquareBrace,
+    Semicolon,
+    Slash,
+    SlashEqual,
+    Star,
+    StarEqual,
+}
+
+impl<'src> Token<'src> {
+    #[allow(clippy::len_without_is_empty)]
+    pub fn len(&self) -> usize {
+        match self {
+            Token::Eof => 0,
+            Token::Boolean(text) => text.len(),
+            Token::Byte(_) => 3,
+            Token::Character(_) => 3,
+            Token::Float(text) => text.len(),
+            Token::Identifier(text) => text.len(),
+            Token::Integer(text) => text.len(),
+            Token::String(text) => text.len() + 2,
+            Token::Async => 5,
+            Token::ArrowThin => 2,
+            Token::Bool => 4,
+            Token::Break => 5,
+            Token::Else => 4,
+            Token::FloatKeyword => 5,
+            Token::Fn => 2,
+            Token::If => 2,
+            Token::Int => 3,
+            Token::Let => 3,
+            Token::Loop => 4,
+            Token::Map => 3,
+            Token::Mut => 3,
+            Token::Str => 3,
+            Token::Struct => 6,
+            Token::While => 5,
+            Token::BangEqual => 2,
+            Token::Bang => 1,
+            Token::Colon => 1,
+            Token::Comma => 1,
+            Token::Dot => 1,
+            Token::DoubleAmpersand => 2,
+            Token::DoubleDot => 2,
+            Token::DoubleEqual => 2,
+            Token::DoublePipe => 2,
+            Token::Equal => 1,
+            Token::Greater => 1,
+            Token::GreaterEqual => 2,
+            Token::LeftCurlyBrace => 1,
+            Token::LeftParenthesis => 1,
+            Token::LeftSquareBrace => 1,
+            Token::Less => 1,
+            Token::LessEqual => 2,
+            Token::Minus => 1,
+            Token::MinusEqual => 2,
+            Token::Percent => 1,
+            Token::PercentEqual => 2,
+            Token::Plus => 1,
+            Token::PlusEqual => 2,
+            Token::Return => 6,
+            Token::RightCurlyBrace => 1,
+            Token::RightParenthesis => 1,
+            Token::RightSquareBrace => 1,
+            Token::Semicolon => 1,
+            Token::Slash => 1,
+            Token::SlashEqual => 2,
+            Token::Star => 1,
+            Token::StarEqual => 2,
+        }
+    }
+
+    pub fn as_str(&self) -> &str {
+        match self {
+            Token::Eof => "",
+            Token::Boolean(text) => text,
+            Token::Byte(text) => text,
+            Token::Character(_) => "character token",
+            Token::Float(text) => text,
+            Token::Identifier(text) => text,
+            Token::Integer(text) => text,
+            Token::String(text) => text,
+            Token::Async => "async",
+            Token::ArrowThin => "->",
+            Token::Bool => "bool",
+            Token::Break => "break",
+            Token::Else => "else",
+            Token::FloatKeyword => "float",
+            Token::Fn => "fn",
+            Token::If => "if",
+            Token::Int => "int",
+            Token::Let => "let",
+            Token::Loop => "loop",
+            Token::Map => "map",
+            Token::Mut => "mut",
+            Token::Str => "str",
+            Token::Struct => "struct",
+            Token::While => "while",
+            Token::BangEqual => "!=",
+            Token::Bang => "!",
+            Token::Colon => ":",
+            Token::Comma => ",",
+            Token::Dot => ".",
+            Token::DoubleAmpersand => "&&",
+            Token::DoubleDot => "..",
+            Token::DoubleEqual => "==",
+            Token::DoublePipe => "||",
+            Token::Equal => "=",
+            Token::Greater => ">",
+            Token::GreaterEqual => ">=",
+            Token::LeftCurlyBrace => "{",
+            Token::LeftParenthesis => "(",
+            Token::LeftSquareBrace => "[",
+            Token::Less => "<",
+            Token::LessEqual => "<=",
+            Token::Minus => "-",
+            Token::MinusEqual => "-=",
+            Token::Percent => "%",
+            Token::PercentEqual => "%=",
+            Token::Plus => "+",
+            Token::PlusEqual => "+=",
+            Token::Return => "return",
+            Token::RightCurlyBrace => "}",
+            Token::RightParenthesis => ")",
+            Token::RightSquareBrace => "]",
+            Token::Semicolon => ";",
+            Token::Slash => "/",
+            Token::SlashEqual => "/=",
+            Token::Star => "*",
+            Token::StarEqual => "*=",
+        }
+    }
+
+    pub fn to_owned(&self) -> TokenOwned {
+        match self {
+            Token::ArrowThin => TokenOwned::ArrowThin,
+            Token::Async => TokenOwned::Async,
+            Token::BangEqual => TokenOwned::BangEqual,
+            Token::Bang => TokenOwned::Bang,
+            Token::Bool => TokenOwned::Bool,
+            Token::Boolean(boolean) => TokenOwned::Boolean(boolean.to_string()),
+            Token::Break => TokenOwned::Break,
+            Token::Byte(byte) => TokenOwned::Byte(byte.to_string()),
+            Token::Character(character) => TokenOwned::Character(*character),
+            Token::Colon => TokenOwned::Colon,
+            Token::Comma => TokenOwned::Comma,
+            Token::Dot => TokenOwned::Dot,
+            Token::DoubleAmpersand => TokenOwned::DoubleAmpersand,
+            Token::DoubleDot => TokenOwned::DoubleDot,
+            Token::DoubleEqual => TokenOwned::DoubleEqual,
+            Token::DoublePipe => TokenOwned::DoublePipe,
+            Token::Else => TokenOwned::Else,
+            Token::Eof => TokenOwned::Eof,
+            Token::Equal => TokenOwned::Equal,
+            Token::Float(float) => TokenOwned::Float(float.to_string()),
+            Token::FloatKeyword => TokenOwned::FloatKeyword,
+            Token::Fn => TokenOwned::Fn,
+            Token::Greater => TokenOwned::Greater,
+            Token::GreaterEqual => TokenOwned::GreaterOrEqual,
+            Token::Identifier(text) => TokenOwned::Identifier(text.to_string()),
+            Token::If => TokenOwned::If,
+            Token::Int => TokenOwned::Int,
+            Token::Integer(integer) => TokenOwned::Integer(integer.to_string()),
+            Token::LeftCurlyBrace => TokenOwned::LeftCurlyBrace,
+            Token::LeftParenthesis => TokenOwned::LeftParenthesis,
+            Token::LeftSquareBrace => TokenOwned::LeftSquareBrace,
+            Token::Let => TokenOwned::Let,
+            Token::Less => TokenOwned::Less,
+            Token::LessEqual => TokenOwned::LessOrEqual,
+            Token::Loop => TokenOwned::Loop,
+            Token::Map => TokenOwned::Map,
+            Token::Minus => TokenOwned::Minus,
+            Token::MinusEqual => TokenOwned::MinusEqual,
+            Token::Mut => TokenOwned::Mut,
+            Token::Percent => TokenOwned::Percent,
+            Token::PercentEqual => TokenOwned::PercentEqual,
+            Token::Plus => TokenOwned::Plus,
+            Token::PlusEqual => TokenOwned::PlusEqual,
+            Token::Return => TokenOwned::Return,
+            Token::RightCurlyBrace => TokenOwned::RightCurlyBrace,
+            Token::RightParenthesis => TokenOwned::RightParenthesis,
+            Token::RightSquareBrace => TokenOwned::RightSquareBrace,
+            Token::Semicolon => TokenOwned::Semicolon,
+            Token::Star => TokenOwned::Star,
+            Token::StarEqual => TokenOwned::StarEqual,
+            Token::Slash => TokenOwned::Slash,
+            Token::SlashEqual => TokenOwned::SlashEqual,
+            Token::String(text) => TokenOwned::String(text.to_string()),
+            Token::Str => TokenOwned::Str,
+            Token::Struct => TokenOwned::Struct,
+            Token::While => TokenOwned::While,
+        }
+    }
+
+    pub fn kind(&self) -> TokenKind {
+        match self {
+            Token::ArrowThin => TokenKind::ArrowThin,
+            Token::Async => TokenKind::Async,
+            Token::BangEqual => TokenKind::BangEqual,
+            Token::Bang => TokenKind::Bang,
+            Token::Bool => TokenKind::Bool,
+            Token::Boolean(_) => TokenKind::Boolean,
+            Token::Break => TokenKind::Break,
+            Token::Byte(_) => TokenKind::Byte,
+            Token::Character(_) => TokenKind::Character,
+            Token::Colon => TokenKind::Colon,
+            Token::Comma => TokenKind::Comma,
+            Token::Dot => TokenKind::Dot,
+            Token::DoubleAmpersand => TokenKind::DoubleAmpersand,
+            Token::DoubleDot => TokenKind::DoubleDot,
+            Token::DoubleEqual => TokenKind::DoubleEqual,
+            Token::DoublePipe => TokenKind::DoublePipe,
+            Token::Else => TokenKind::Else,
+            Token::Eof => TokenKind::Eof,
+            Token::Equal => TokenKind::Equal,
+            Token::Float(_) => TokenKind::Float,
+            Token::FloatKeyword => TokenKind::FloatKeyword,
+            Token::Fn => TokenKind::Fn,
+            Token::Greater => TokenKind::Greater,
+            Token::GreaterEqual => TokenKind::GreaterEqual,
+            Token::Identifier(_) => TokenKind::Identifier,
+            Token::If => TokenKind::If,
+            Token::Int => TokenKind::Int,
+            Token::Integer(_) => TokenKind::Integer,
+            Token::LeftCurlyBrace => TokenKind::LeftCurlyBrace,
+            Token::LeftParenthesis => TokenKind::LeftParenthesis,
+            Token::LeftSquareBrace => TokenKind::LeftSquareBrace,
+            Token::Let => TokenKind::Let,
+            Token::Less => TokenKind::Less,
+            Token::LessEqual => TokenKind::LessEqual,
+            Token::Loop => TokenKind::Loop,
+            Token::Map => TokenKind::Map,
+            Token::Minus => TokenKind::Minus,
+            Token::MinusEqual => TokenKind::MinusEqual,
+            Token::Mut => TokenKind::Mut,
+            Token::Percent => TokenKind::Percent,
+            Token::PercentEqual => TokenKind::PercentEqual,
+            Token::Plus => TokenKind::Plus,
+            Token::PlusEqual => TokenKind::PlusEqual,
+            Token::Return => TokenKind::Return,
+            Token::RightCurlyBrace => TokenKind::RightCurlyBrace,
+            Token::RightParenthesis => TokenKind::RightParenthesis,
+            Token::RightSquareBrace => TokenKind::RightSquareBrace,
+            Token::Semicolon => TokenKind::Semicolon,
+            Token::Star => TokenKind::Star,
+            Token::StarEqual => TokenKind::StarEqual,
+            Token::Slash => TokenKind::Slash,
+            Token::SlashEqual => TokenKind::SlashEqual,
+            Token::Str => TokenKind::Str,
+            Token::String(_) => TokenKind::String,
+            Token::Struct => TokenKind::Struct,
+            Token::While => TokenKind::While,
+        }
+    }
+
+    /// Returns true if the token yields a value, begins an expression or is an expression operator.
+    pub fn is_expression(&self) -> bool {
+        matches!(
+            self,
+            Token::Boolean(_)
+                | Token::Byte(_)
+                | Token::Character(_)
+                | Token::Float(_)
+                | Token::Identifier(_)
+                | Token::Integer(_)
+                | Token::String(_)
+                | Token::Break
+                | Token::If
+                | Token::Return
+                | Token::Map
+                | Token::Loop
+                | Token::Struct
+                | Token::BangEqual
+                | Token::DoubleAmpersand
+                | Token::DoubleEqual
+                | Token::DoublePipe
+                | Token::Equal
+                | Token::Greater
+                | Token::GreaterEqual
+                | Token::LeftCurlyBrace
+                | Token::LeftParenthesis
+                | Token::LeftSquareBrace
+                | Token::Less
+                | Token::LessEqual
+                | Token::Minus
+                | Token::MinusEqual
+                | Token::Percent
+                | Token::PercentEqual
+                | Token::Plus
+                | Token::PlusEqual
+                | Token::Slash
+                | Token::SlashEqual
+                | Token::Star
+                | Token::StarEqual
+        )
+    }
+}
+
+impl<'src> Display for Token<'src> {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        match self {
+            Token::ArrowThin => write!(f, "->"),
+            Token::Async => write!(f, "async"),
+            Token::BangEqual => write!(f, "!="),
+            Token::Bang => write!(f, "!"),
+            Token::Bool => write!(f, "bool"),
+            Token::Boolean(value) => write!(f, "{value}"),
+            Token::Break => write!(f, "break"),
+            Token::Byte(value) => write!(f, "{value}"),
+            Token::Character(value) => write!(f, "{value}"),
+            Token::Colon => write!(f, ":"),
+            Token::Comma => write!(f, ","),
+            Token::Dot => write!(f, "."),
+            Token::DoubleAmpersand => write!(f, "&&"),
+            Token::DoubleDot => write!(f, ".."),
+            Token::DoubleEqual => write!(f, "=="),
+            Token::DoublePipe => write!(f, "||"),
+            Token::Else => write!(f, "else"),
+            Token::Eof => write!(f, "EOF"),
+            Token::Equal => write!(f, "="),
+            Token::Float(value) => write!(f, "{value}"),
+            Token::FloatKeyword => write!(f, "float"),
+            Token::Fn => write!(f, "fn"),
+            Token::Greater => write!(f, ">"),
+            Token::GreaterEqual => write!(f, ">="),
+            Token::Identifier(value) => write!(f, "{value}"),
+            Token::If => write!(f, "if"),
+            Token::Int => write!(f, "int"),
+            Token::Integer(value) => write!(f, "{value}"),
+            Token::LeftCurlyBrace => write!(f, "{{"),
+            Token::LeftParenthesis => write!(f, "("),
+            Token::LeftSquareBrace => write!(f, "["),
+            Token::Let => write!(f, "let"),
+            Token::Less => write!(f, "<"),
+            Token::LessEqual => write!(f, "<="),
+            Token::Loop => write!(f, "loop"),
+            Token::Map => write!(f, "map"),
+            Token::Minus => write!(f, "-"),
+            Token::MinusEqual => write!(f, "-="),
+            Token::Mut => write!(f, "mut"),
+            Token::Percent => write!(f, "%"),
+            Token::PercentEqual => write!(f, "%="),
+            Token::Plus => write!(f, "+"),
+            Token::PlusEqual => write!(f, "+="),
+            Token::Return => write!(f, "return"),
+            Token::RightCurlyBrace => write!(f, "}}"),
+            Token::RightParenthesis => write!(f, ")"),
+            Token::RightSquareBrace => write!(f, "]"),
+            Token::Semicolon => write!(f, ";"),
+            Token::Slash => write!(f, "/"),
+            Token::SlashEqual => write!(f, "/="),
+            Token::Star => write!(f, "*"),
+            Token::StarEqual => write!(f, "*="),
+            Token::Str => write!(f, "str"),
+            Token::String(value) => write!(f, "{value}"),
+            Token::Struct => write!(f, "struct"),
+            Token::While => write!(f, "while"),
+        }
+    }
+}
+
+/// Owned representation of a source token.
+///
+/// If a [Token] borrows from the source text, its TokenOwned omits the data.
+#[derive(Debug, PartialEq, Clone)]
+pub enum TokenOwned {
+    Eof,
+
+    Identifier(String),
+
+    // Hard-coded values
+    Boolean(String),
+    Byte(String),
+    Character(char),
+    Float(String),
+    Integer(String),
+    String(String),
+
+    // Keywords
+    Async,
+    Bool,
+    Break,
+    Else,
+    FloatKeyword,
+    Fn,
+    If,
+    Int,
+    Let,
+    Loop,
+    Map,
+    Mut,
+    Return,
+    Str,
+    While,
+
+    // Symbols
+    ArrowThin,
+    Bang,
+    BangEqual,
+    Colon,
+    Comma,
+    Dot,
+    DoubleAmpersand,
+    DoubleDot,
+    DoubleEqual,
+    DoublePipe,
+    Equal,
+    Greater,
+    GreaterOrEqual,
+    LeftCurlyBrace,
+    LeftParenthesis,
+    LeftSquareBrace,
+    Less,
+    LessOrEqual,
+    Minus,
+    MinusEqual,
+    Percent,
+    PercentEqual,
+    Plus,
+    PlusEqual,
+    RightCurlyBrace,
+    RightParenthesis,
+    RightSquareBrace,
+    Semicolon,
+    Star,
+    StarEqual,
+    Struct,
+    Slash,
+    SlashEqual,
+}
+
+impl Display for TokenOwned {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        match self {
+            TokenOwned::ArrowThin => Token::ArrowThin.fmt(f),
+            TokenOwned::Async => Token::Async.fmt(f),
+            TokenOwned::Bang => Token::Bang.fmt(f),
+            TokenOwned::BangEqual => Token::BangEqual.fmt(f),
+            TokenOwned::Bool => Token::Bool.fmt(f),
+            TokenOwned::Boolean(boolean) => Token::Boolean(boolean).fmt(f),
+            TokenOwned::Break => Token::Break.fmt(f),
+            TokenOwned::Byte(byte) => Token::Byte(byte).fmt(f),
+            TokenOwned::Character(character) => Token::Character(*character).fmt(f),
+            TokenOwned::Colon => Token::Colon.fmt(f),
+            TokenOwned::Comma => Token::Comma.fmt(f),
+            TokenOwned::Dot => Token::Dot.fmt(f),
+            TokenOwned::DoubleAmpersand => Token::DoubleAmpersand.fmt(f),
+            TokenOwned::DoubleDot => Token::DoubleDot.fmt(f),
+            TokenOwned::DoubleEqual => Token::DoubleEqual.fmt(f),
+            TokenOwned::DoublePipe => Token::DoublePipe.fmt(f),
+            TokenOwned::Else => Token::Else.fmt(f),
+            TokenOwned::Eof => Token::Eof.fmt(f),
+            TokenOwned::Equal => Token::Equal.fmt(f),
+            TokenOwned::Float(float) => Token::Float(float).fmt(f),
+            TokenOwned::FloatKeyword => Token::FloatKeyword.fmt(f),
+            TokenOwned::Fn => Token::Fn.fmt(f),
+            TokenOwned::Greater => Token::Greater.fmt(f),
+            TokenOwned::GreaterOrEqual => Token::GreaterEqual.fmt(f),
+            TokenOwned::Identifier(text) => Token::Identifier(text).fmt(f),
+            TokenOwned::If => Token::If.fmt(f),
+            TokenOwned::Int => Token::Int.fmt(f),
+            TokenOwned::Integer(integer) => Token::Integer(integer).fmt(f),
+            TokenOwned::LeftCurlyBrace => Token::LeftCurlyBrace.fmt(f),
+            TokenOwned::LeftParenthesis => Token::LeftParenthesis.fmt(f),
+            TokenOwned::LeftSquareBrace => Token::LeftSquareBrace.fmt(f),
+            TokenOwned::Let => Token::Let.fmt(f),
+            TokenOwned::Less => Token::Less.fmt(f),
+            TokenOwned::LessOrEqual => Token::LessEqual.fmt(f),
+            TokenOwned::Loop => Token::Loop.fmt(f),
+            TokenOwned::Map => Token::Map.fmt(f),
+            TokenOwned::Minus => Token::Minus.fmt(f),
+            TokenOwned::MinusEqual => Token::MinusEqual.fmt(f),
+            TokenOwned::Mut => Token::Mut.fmt(f),
+            TokenOwned::Percent => Token::Percent.fmt(f),
+            TokenOwned::PercentEqual => Token::PercentEqual.fmt(f),
+            TokenOwned::Plus => Token::Plus.fmt(f),
+            TokenOwned::PlusEqual => Token::PlusEqual.fmt(f),
+            TokenOwned::Return => Token::Return.fmt(f),
+            TokenOwned::RightCurlyBrace => Token::RightCurlyBrace.fmt(f),
+            TokenOwned::RightParenthesis => Token::RightParenthesis.fmt(f),
+            TokenOwned::RightSquareBrace => Token::RightSquareBrace.fmt(f),
+            TokenOwned::Semicolon => Token::Semicolon.fmt(f),
+            TokenOwned::Star => Token::Star.fmt(f),
+            TokenOwned::StarEqual => Token::StarEqual.fmt(f),
+            TokenOwned::Slash => Token::Slash.fmt(f),
+            TokenOwned::SlashEqual => Token::SlashEqual.fmt(f),
+            TokenOwned::Str => Token::Str.fmt(f),
+            TokenOwned::String(string) => Token::String(string).fmt(f),
+            TokenOwned::Struct => Token::Struct.fmt(f),
+            TokenOwned::While => Token::While.fmt(f),
+        }
+    }
+}
+
+impl Display for TokenKind {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        match self {
+            TokenKind::ArrowThin => Token::ArrowThin.fmt(f),
+            TokenKind::Async => Token::Async.fmt(f),
+            TokenKind::Bang => Token::Bang.fmt(f),
+            TokenKind::BangEqual => Token::BangEqual.fmt(f),
+            TokenKind::Bool => Token::Bool.fmt(f),
+            TokenKind::Boolean => write!(f, "boolean value"),
+            TokenKind::Break => Token::Break.fmt(f),
+            TokenKind::Byte => write!(f, "byte value"),
+            TokenKind::Character => write!(f, "character value"),
+            TokenKind::Colon => Token::Colon.fmt(f),
+            TokenKind::Comma => Token::Comma.fmt(f),
+            TokenKind::Dot => Token::Dot.fmt(f),
+            TokenKind::DoubleAmpersand => Token::DoubleAmpersand.fmt(f),
+            TokenKind::DoubleDot => Token::DoubleDot.fmt(f),
+            TokenKind::DoubleEqual => Token::DoubleEqual.fmt(f),
+            TokenKind::DoublePipe => Token::DoublePipe.fmt(f),
+            TokenKind::Else => Token::Else.fmt(f),
+            TokenKind::Eof => Token::Eof.fmt(f),
+            TokenKind::Equal => Token::Equal.fmt(f),
+            TokenKind::Float => write!(f, "float value"),
+            TokenKind::FloatKeyword => Token::FloatKeyword.fmt(f),
+            TokenKind::Fn => Token::Fn.fmt(f),
+            TokenKind::Greater => Token::Greater.fmt(f),
+            TokenKind::GreaterEqual => Token::GreaterEqual.fmt(f),
+            TokenKind::Identifier => write!(f, "identifier"),
+            TokenKind::If => Token::If.fmt(f),
+            TokenKind::Int => Token::Int.fmt(f),
+            TokenKind::Integer => write!(f, "integer value"),
+            TokenKind::LeftCurlyBrace => Token::LeftCurlyBrace.fmt(f),
+            TokenKind::LeftParenthesis => Token::LeftParenthesis.fmt(f),
+            TokenKind::LeftSquareBrace => Token::LeftSquareBrace.fmt(f),
+            TokenKind::Let => Token::Let.fmt(f),
+            TokenKind::Less => Token::Less.fmt(f),
+            TokenKind::LessEqual => Token::LessEqual.fmt(f),
+            TokenKind::Loop => Token::Loop.fmt(f),
+            TokenKind::Map => Token::Map.fmt(f),
+            TokenKind::Minus => Token::Minus.fmt(f),
+            TokenKind::MinusEqual => Token::MinusEqual.fmt(f),
+            TokenKind::Mut => Token::Mut.fmt(f),
+            TokenKind::Percent => Token::Percent.fmt(f),
+            TokenKind::PercentEqual => Token::PercentEqual.fmt(f),
+            TokenKind::Plus => Token::Plus.fmt(f),
+            TokenKind::PlusEqual => Token::PlusEqual.fmt(f),
+            TokenKind::Return => Token::Return.fmt(f),
+            TokenKind::RightCurlyBrace => Token::RightCurlyBrace.fmt(f),
+            TokenKind::RightParenthesis => Token::RightParenthesis.fmt(f),
+            TokenKind::RightSquareBrace => Token::RightSquareBrace.fmt(f),
+            TokenKind::Semicolon => Token::Semicolon.fmt(f),
+            TokenKind::Star => Token::Star.fmt(f),
+            TokenKind::StarEqual => Token::StarEqual.fmt(f),
+            TokenKind::Str => Token::Str.fmt(f),
+            TokenKind::Slash => Token::Slash.fmt(f),
+            TokenKind::SlashEqual => Token::SlashEqual.fmt(f),
+            TokenKind::String => write!(f, "string value"),
+            TokenKind::Struct => Token::Struct.fmt(f),
+            TokenKind::While => Token::While.fmt(f),
+        }
+    }
+}

dust-lang/src/type.rs

@@ -0,0 +1,659 @@
+//! Value types and conflict handling.
+use std::{
+    cmp::Ordering,
+    collections::HashMap,
+    fmt::{self, Display, Formatter},
+};
+
+use serde::{Deserialize, Serialize};
+
+/// Description of a kind of value.
+#[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
+pub enum Type {
+    Any,
+    Boolean,
+    Byte,
+    Character,
+    Enum(EnumType),
+    Float,
+    Function(FunctionType),
+    Generic {
+        identifier_index: u8,
+        concrete_type: Option<Box<Type>>,
+    },
+    Integer,
+    List {
+        item_type: Box<Type>,
+        length: usize,
+    },
+    ListEmpty,
+    ListOf {
+        item_type: Box<Type>,
+    },
+    Map {
+        pairs: HashMap<u8, Type>,
+    },
+    Number,
+    Range {
+        r#type: RangeableType,
+    },
+    String {
+        length: Option<usize>,
+    },
+    Struct(StructType),
+    Tuple {
+        fields: Option<Vec<Type>>,
+    },
+}
+
+impl Type {
+    /// Returns a concrete type, either the type itself or the concrete type of a generic type.
+    pub fn concrete_type(&self) -> &Type {
+        if let Type::Generic {
+            concrete_type: Some(concrete_type),
+            ..
+        } = self
+        {
+            concrete_type.concrete_type()
+        } else {
+            self
+        }
+    }
+
+    /// Checks that the type is compatible with another type.
+    pub fn check(&self, other: &Type) -> Result<(), TypeConflict> {
+        match (self.concrete_type(), other.concrete_type()) {
+            (Type::Any, _)
+            | (_, Type::Any)
+            | (Type::Boolean, Type::Boolean)
+            | (Type::Byte, Type::Byte)
+            | (Type::Character, Type::Character)
+            | (Type::Float, Type::Float)
+            | (Type::Integer, Type::Integer)
+            | (Type::String { .. }, Type::String { .. }) => return Ok(()),
+            (
+                Type::Generic {
+                    concrete_type: left,
+                    ..
+                },
+                Type::Generic {
+                    concrete_type: right,
+                    ..
+                },
+            ) => match (left, right) {
+                (Some(left), Some(right)) => {
+                    if left.check(right).is_ok() {
+                        return Ok(());
+                    }
+                }
+                (None, None) => {
+                    return Ok(());
+                }
+                _ => {}
+            },
+            (Type::Generic { concrete_type, .. }, other)
+            | (other, Type::Generic { concrete_type, .. }) => {
+                if let Some(concrete_type) = concrete_type {
+                    if other == concrete_type.as_ref() {
+                        return Ok(());
+                    }
+                }
+            }
+            (Type::Struct(left_struct_type), Type::Struct(right_struct_type)) => {
+                if left_struct_type == right_struct_type {
+                    return Ok(());
+                }
+            }
+            (
+                Type::List {
+                    item_type: left_type,
+                    length: left_length,
+                },
+                Type::List {
+                    item_type: right_type,
+                    length: right_length,
+                },
+            ) => {
+                if left_length != right_length {
+                    return Err(TypeConflict {
+                        actual: other.clone(),
+                        expected: self.clone(),
+                    });
+                }
+
+                if left_type.check(right_type).is_err() {
+                    return Err(TypeConflict {
+                        actual: other.clone(),
+                        expected: self.clone(),
+                    });
+                }
+
+                return Ok(());
+            }
+            (
+                Type::ListOf {
+                    item_type: left_type,
+                },
+                Type::ListOf {
+                    item_type: right_type,
+                },
+            ) => {
+                if left_type.check(right_type).is_err() {
+                    return Err(TypeConflict {
+                        actual: other.clone(),
+                        expected: self.clone(),
+                    });
+                }
+            }
+            (
+                Type::List {
+                    item_type: list_item_type,
+                    ..
+                },
+                Type::ListOf {
+                    item_type: list_of_item_type,
+                },
+            )
+            | (
+                Type::ListOf {
+                    item_type: list_of_item_type,
+                },
+                Type::List {
+                    item_type: list_item_type,
+                    ..
+                },
+            ) => {
+                // TODO: This is a hack, remove it.
+                if let Type::Any = **list_of_item_type {
+                    return Ok(());
+                }
+
+                if list_item_type.check(list_of_item_type).is_err() {
+                    return Err(TypeConflict {
+                        actual: other.clone(),
+                        expected: self.clone(),
+                    });
+                }
+            }
+            (
+                Type::Function(FunctionType {
+                    type_parameters: left_type_parameters,
+                    value_parameters: left_value_parameters,
+                    return_type: left_return,
+                }),
+                Type::Function(FunctionType {
+                    type_parameters: right_type_parameters,
+                    value_parameters: right_value_parameters,
+                    return_type: right_return,
+                }),
+            ) => {
+                if left_return != right_return
+                    || left_type_parameters != right_type_parameters
+                    || left_value_parameters != right_value_parameters
+                {
+                    return Err(TypeConflict {
+                        actual: other.clone(),
+                        expected: self.clone(),
+                    });
+                }
+
+                return Ok(());
+            }
+            (Type::Range { r#type: left_type }, Type::Range { r#type: right_type }) => {
+                if left_type == right_type {
+                    return Ok(());
+                }
+            }
+            (Type::Number, Type::Number | Type::Integer | Type::Float)
+            | (Type::Integer | Type::Float, Type::Number) => {
+                return Ok(());
+            }
+            _ => {}
+        }
+
+        Err(TypeConflict {
+            actual: other.clone(),
+            expected: self.clone(),
+        })
+    }
+}
+
+impl Display for Type {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        match self {
+            Type::Any => write!(f, "any"),
+            Type::Boolean => write!(f, "bool"),
+            Type::Byte => write!(f, "byte"),
+            Type::Character => write!(f, "char"),
+            Type::Enum(EnumType { name, .. }) => write!(f, "{name}"),
+            Type::Float => write!(f, "float"),
+            Type::Function(function_type) => write!(f, "{function_type}"),
+            Type::Generic { concrete_type, .. } => {
+                match concrete_type.clone().map(|r#box| *r#box) {
+                    Some(Type::Generic {
+                        identifier_index: identifier,
+                        ..
+                    }) => write!(f, "{identifier}"),
+                    Some(concrete_type) => write!(f, "implied to be {concrete_type}"),
+                    None => write!(f, "unknown"),
+                }
+            }
+            Type::Integer => write!(f, "int"),
+            Type::List { item_type, length } => write!(f, "[{item_type}; {length}]"),
+            Type::ListEmpty => write!(f, "[]"),
+            Type::ListOf { item_type } => write!(f, "[{item_type}]"),
+            Type::Map { pairs } => {
+                write!(f, "map ")?;
+
+                write!(f, "{{")?;
+
+                for (index, (key, value)) in pairs.iter().enumerate() {
+                    write!(f, "{key}: {value}")?;
+
+                    if index != pairs.len() - 1 {
+                        write!(f, ", ")?;
+                    }
+                }
+
+                write!(f, "}}")
+            }
+            Type::Number => write!(f, "num"),
+            Type::Range { r#type } => write!(f, "{type} range"),
+            Type::String { .. } => write!(f, "str"),
+            Type::Struct(struct_type) => write!(f, "{struct_type}"),
+            Type::Tuple { fields } => {
+                if let Some(fields) = fields {
+                    write!(f, "(")?;
+
+                    for (index, r#type) in fields.iter().enumerate() {
+                        write!(f, "{type}")?;
+
+                        if index != fields.len() - 1 {
+                            write!(f, ", ")?;
+                        }
+                    }
+
+                    write!(f, ")")
+                } else {
+                    write!(f, "tuple")
+                }
+            }
+        }
+    }
+}
+
+impl PartialOrd for Type {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for Type {
+    fn cmp(&self, other: &Self) -> Ordering {
+        match (self, other) {
+            (Type::Any, Type::Any) => Ordering::Equal,
+            (Type::Any, _) => Ordering::Greater,
+            (Type::Boolean, Type::Boolean) => Ordering::Equal,
+            (Type::Boolean, _) => Ordering::Greater,
+            (Type::Byte, Type::Byte) => Ordering::Equal,
+            (Type::Byte, _) => Ordering::Greater,
+            (Type::Character, Type::Character) => Ordering::Equal,
+            (Type::Character, _) => Ordering::Greater,
+            (Type::Enum(left_enum), Type::Enum(right_enum)) => left_enum.cmp(right_enum),
+            (Type::Enum(_), _) => Ordering::Greater,
+            (Type::Float, Type::Float) => Ordering::Equal,
+            (Type::Float, _) => Ordering::Greater,
+            (Type::Function(left_function), Type::Function(right_function)) => {
+                left_function.cmp(right_function)
+            }
+            (Type::Function(_), _) => Ordering::Greater,
+            (Type::Generic { .. }, Type::Generic { .. }) => Ordering::Equal,
+            (Type::Generic { .. }, _) => Ordering::Greater,
+            (Type::Integer, Type::Integer) => Ordering::Equal,
+            (Type::Integer, _) => Ordering::Greater,
+            (
+                Type::List {
+                    item_type: left_item_type,
+                    length: left_length,
+                },
+                Type::List {
+                    item_type: right_item_type,
+                    length: right_length,
+                },
+            ) => {
+                if left_length == right_length {
+                    left_item_type.cmp(right_item_type)
+                } else {
+                    left_length.cmp(right_length)
+                }
+            }
+            (Type::List { .. }, _) => Ordering::Greater,
+            (Type::ListEmpty, Type::ListEmpty) => Ordering::Equal,
+            (Type::ListEmpty, _) => Ordering::Greater,
+            (
+                Type::ListOf {
+                    item_type: left_item_type,
+                },
+                Type::ListOf {
+                    item_type: right_item_type,
+                },
+            ) => left_item_type.cmp(right_item_type),
+            (Type::ListOf { .. }, _) => Ordering::Greater,
+            (Type::Map { pairs: left_pairs }, Type::Map { pairs: right_pairs }) => {
+                left_pairs.iter().cmp(right_pairs.iter())
+            }
+            (Type::Map { .. }, _) => Ordering::Greater,
+            (Type::Number, Type::Number) => Ordering::Equal,
+            (Type::Number, _) => Ordering::Greater,
+            (Type::Range { r#type: left_type }, Type::Range { r#type: right_type }) => {
+                left_type.cmp(right_type)
+            }
+            (Type::Range { .. }, _) => Ordering::Greater,
+            (Type::String { length: left }, Type::String { length: right }) => left.cmp(right),
+            (Type::String { .. }, _) => Ordering::Greater,
+            (Type::Struct(left_struct), Type::Struct(right_struct)) => {
+                left_struct.cmp(right_struct)
+            }
+            (Type::Struct(_), _) => Ordering::Greater,
+
+            (Type::Tuple { fields: left }, Type::Tuple { fields: right }) => left.cmp(right),
+            (Type::Tuple { .. }, _) => Ordering::Greater,
+        }
+    }
+}
+
+#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Serialize, Deserialize)]
+pub struct FunctionType {
+    pub type_parameters: Option<Vec<u8>>,
+    pub value_parameters: Option<Vec<(u8, Type)>>,
+    pub return_type: Option<Box<Type>>,
+}
+
+impl Display for FunctionType {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        write!(f, "fn ")?;
+
+        if let Some(type_parameters) = &self.type_parameters {
+            write!(f, "<")?;
+
+            for (index, type_parameter) in type_parameters.iter().enumerate() {
+                if index > 0 {
+                    write!(f, ", ")?;
+                }
+
+                write!(f, "{type_parameter}")?;
+            }
+
+            write!(f, ">")?;
+        }
+
+        write!(f, "(")?;
+
+        if let Some(value_parameters) = &self.value_parameters {
+            for (index, (identifier, r#type)) in value_parameters.iter().enumerate() {
+                if index > 0 {
+                    write!(f, ", ")?;
+                }
+
+                write!(f, "{identifier}: {type}")?;
+            }
+        }
+
+        write!(f, ")")?;
+
+        if let Some(return_type) = &self.return_type {
+            write!(f, " -> {return_type}")?;
+        }
+
+        Ok(())
+    }
+}
+
+#[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
+pub enum StructType {
+    Unit { name: u8 },
+    Tuple { name: u8, fields: Vec<Type> },
+    Fields { name: u8, fields: HashMap<u8, Type> },
+}
+
+impl StructType {
+    pub fn name(&self) -> u8 {
+        match self {
+            StructType::Unit { name } => *name,
+            StructType::Tuple { name, .. } => *name,
+            StructType::Fields { name, .. } => *name,
+        }
+    }
+}
+
+impl Display for StructType {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        match self {
+            StructType::Unit { name } => write!(f, "{name}"),
+            StructType::Tuple { name, fields } => {
+                write!(f, "{name}(")?;
+
+                for (index, field) in fields.iter().enumerate() {
+                    write!(f, "{field}")?;
+
+                    if index != fields.len() - 1 {
+                        write!(f, ", ")?;
+                    }
+                }
+
+                write!(f, ")")
+            }
+            StructType::Fields { name, fields } => {
+                write!(f, "{name} {{")?;
+
+                for (index, (identifier, r#type)) in fields.iter().enumerate() {
+                    write!(f, "{identifier}: {type}")?;
+
+                    if index != fields.len() - 1 {
+                        write!(f, ", ")?;
+                    }
+                }
+
+                write!(f, "}}")
+            }
+        }
+    }
+}
+
+impl PartialOrd for StructType {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for StructType {
+    fn cmp(&self, other: &Self) -> Ordering {
+        match (self, other) {
+            (StructType::Unit { name: left_name }, StructType::Unit { name: right_name }) => {
+                left_name.cmp(right_name)
+            }
+            (StructType::Unit { .. }, _) => Ordering::Greater,
+            (
+                StructType::Tuple {
+                    name: left_name,
+                    fields: left_fields,
+                },
+                StructType::Tuple {
+                    name: right_name,
+                    fields: right_fields,
+                },
+            ) => {
+                let name_cmp = left_name.cmp(right_name);
+
+                if name_cmp == Ordering::Equal {
+                    left_fields.cmp(right_fields)
+                } else {
+                    name_cmp
+                }
+            }
+            (StructType::Tuple { .. }, _) => Ordering::Greater,
+            (
+                StructType::Fields {
+                    name: left_name,
+                    fields: left_fields,
+                },
+                StructType::Fields {
+                    name: right_name,
+                    fields: right_fields,
+                },
+            ) => {
+                let name_cmp = left_name.cmp(right_name);
+
+                if name_cmp == Ordering::Equal {
+                    let len_cmp = left_fields.len().cmp(&right_fields.len());
+
+                    if len_cmp == Ordering::Equal {
+                        left_fields.iter().cmp(right_fields.iter())
+                    } else {
+                        len_cmp
+                    }
+                } else {
+                    name_cmp
+                }
+            }
+            (StructType::Fields { .. }, _) => Ordering::Greater,
+        }
+    }
+}
+
+#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Serialize, Deserialize)]
+pub struct EnumType {
+    pub name: u8,
+    pub variants: Vec<StructType>,
+}
+
+impl Display for EnumType {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        let EnumType { name, variants } = self;
+
+        write!(f, "enum {name} {{ ")?;
+
+        for (index, variant) in variants.iter().enumerate() {
+            write!(f, "{variant}")?;
+
+            if index != self.variants.len() - 1 {
+                write!(f, ", ")?;
+            }
+        }
+
+        write!(f, " }}")
+    }
+}
+
+#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Serialize, Deserialize)]
+pub enum RangeableType {
+    Byte,
+    Character,
+    Float,
+    Integer,
+}
+
+impl Display for RangeableType {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        match self {
+            RangeableType::Byte => Type::Byte.fmt(f),
+            RangeableType::Character => Type::Character.fmt(f),
+            RangeableType::Float => Type::Float.fmt(f),
+            RangeableType::Integer => Type::Integer.fmt(f),
+        }
+    }
+}
+
+#[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
+pub struct TypeConflict {
+    pub expected: Type,
+    pub actual: Type,
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn check_type_any() {
+        let foo = Type::Any;
+        let bar = Type::Any;
+
+        foo.check(&bar).unwrap();
+    }
+
+    #[test]
+    fn check_type_boolean() {
+        let foo = Type::Boolean;
+        let bar = Type::Boolean;
+
+        foo.check(&bar).unwrap();
+    }
+
+    #[test]
+    fn check_type_byte() {
+        let foo = Type::Byte;
+        let bar = Type::Byte;
+
+        foo.check(&bar).unwrap();
+    }
+
+    #[test]
+    fn check_type_character() {
+        let foo = Type::Character;
+        let bar = Type::Character;
+
+        foo.check(&bar).unwrap();
+    }
+
+    #[test]
+    fn errors() {
+        let foo = Type::Integer;
+        let bar = Type::String { length: None };
+
+        assert_eq!(
+            foo.check(&bar),
+            Err(TypeConflict {
+                actual: bar.clone(),
+                expected: foo.clone()
+            })
+        );
+        assert_eq!(
+            bar.check(&foo),
+            Err(TypeConflict {
+                actual: foo.clone(),
+                expected: bar.clone()
+            })
+        );
+
+        let types = [
+            Type::Boolean,
+            Type::Float,
+            Type::Integer,
+            Type::List {
+                item_type: Box::new(Type::Integer),
+                length: 42,
+            },
+            Type::Range {
+                r#type: RangeableType::Integer,
+            },
+            Type::String { length: None },
+        ];
+
+        for left in types.clone() {
+            for right in types.clone() {
+                if left == right {
+                    continue;
+                }
+
+                assert_eq!(
+                    left.check(&right),
+                    Err(TypeConflict {
+                        actual: right.clone(),
+                        expected: left.clone()
+                    })
+                );
+            }
+        }
+    }
+}

dust-lang/src/value.rs

@@ -0,0 +1,767 @@
+//! Dust value representation
+//!
+//! # Examples
+//!
+//! Each type of value has a corresponding method for instantiation:
+//!
+//! ```
+//! # use dust_lang::Value;
+//! let boolean = Value::boolean(true);
+//! let float = Value::float(3.14);
+//! let integer = Value::integer(42);
+//! let string = Value::string("Hello, world!");
+//! ```
+//!
+//! Values have a type, which can be retrieved using the `r#type` method:
+//!
+//! ```
+//! # use dust_lang::*;
+//! let value = Value::integer(42);
+//!
+//! assert_eq!(value.r#type(), Type::Integer);
+//! ```
+use std::{
+    cmp::Ordering,
+    fmt::{self, Debug, Display, Formatter},
+    ops::{Range, RangeInclusive},
+};
+
+use serde::{Deserialize, Serialize};
+
+use crate::{Chunk, FunctionType, RangeableType, Type};
+
+/// Dust value representation
+///
+/// See the [module-level documentation][self] for more.
+#[derive(Debug, Eq, PartialEq, PartialOrd, Ord, Serialize, Deserialize)]
+pub enum Value {
+    Concrete(ConcreteValue),
+    Abstract(AbstractValue),
+}
+
+impl Value {
+    pub fn boolean(value: bool) -> Self {
+        Value::Concrete(ConcreteValue::Boolean(value))
+    }
+
+    pub fn byte(value: u8) -> Self {
+        Value::Concrete(ConcreteValue::Byte(value))
+    }
+
+    pub fn character(value: char) -> Self {
+        Value::Concrete(ConcreteValue::Character(value))
+    }
+
+    pub fn float(value: f64) -> Self {
+        Value::Concrete(ConcreteValue::Float(value))
+    }
+
+    pub fn function(body: Chunk, r#type: FunctionType) -> Self {
+        Value::Concrete(ConcreteValue::Function(Function {
+            chunk: body,
+            r#type: Type::Function(r#type),
+        }))
+    }
+
+    pub fn integer<T: Into<i64>>(into_i64: T) -> Self {
+        Value::Concrete(ConcreteValue::Integer(into_i64.into()))
+    }
+
+    pub fn list<T: Into<Vec<Value>>>(items: T) -> Self {
+        Value::Concrete(ConcreteValue::List(items.into()))
+    }
+
+    pub fn abstract_list(start: u8, end: u8, item_type: Type) -> Self {
+        Value::Abstract(AbstractValue::List {
+            start,
+            end,
+            item_type,
+        })
+    }
+
+    pub fn string<T: ToString>(to_string: T) -> Self {
+        Value::Concrete(ConcreteValue::String(to_string.to_string()))
+    }
+
+    pub fn as_string(&self) -> Option<&String> {
+        if let Value::Concrete(ConcreteValue::String(string)) = self {
+            Some(string)
+        } else {
+            None
+        }
+    }
+
+    pub fn is_function(&self) -> bool {
+        matches!(self, Value::Concrete(ConcreteValue::Function(_)))
+    }
+
+    pub fn r#type(&self) -> Type {
+        match self {
+            Value::Concrete(data) => data.r#type(),
+            Value::Abstract(AbstractValue::List {
+                start,
+                end,
+                item_type,
+            }) => {
+                let length = (end - start + 1) as usize;
+
+                Type::List {
+                    length,
+                    item_type: Box::new(item_type.clone()),
+                }
+            }
+        }
+    }
+
+    pub fn add(&self, other: &Value) -> Result<Value, ValueError> {
+        use ConcreteValue::*;
+        use Value::*;
+
+        let sum = match (self, other) {
+            (Concrete(Byte(left)), Concrete(Byte(right))) => {
+                Value::byte(left.saturating_add(*right))
+            }
+            (Concrete(Float(left)), Concrete(Float(right))) => Value::float(left + right),
+            (Concrete(Integer(left)), Concrete(Integer(right))) => {
+                Value::integer(left.saturating_add(*right))
+            }
+            (Concrete(String(left)), Concrete(String(right))) => {
+                Value::string(format!("{}{}", left, right))
+            }
+            _ => return Err(ValueError::CannotAdd(self.clone(), other.clone())),
+        };
+
+        Ok(sum)
+    }
+
+    pub fn subtract(&self, other: &Value) -> Result<Value, ValueError> {
+        use ConcreteValue::*;
+        use Value::*;
+
+        let different = match (self, other) {
+            (Concrete(Byte(left)), Concrete(Byte(right))) => {
+                Value::byte(left.saturating_sub(*right))
+            }
+            (Concrete(Float(left)), Concrete(Float(right))) => Value::float(left - right),
+            (Concrete(Integer(left)), Concrete(Integer(right))) => {
+                Value::integer(left.saturating_sub(*right))
+            }
+            _ => return Err(ValueError::CannotSubtract(self.clone(), other.clone())),
+        };
+
+        Ok(different)
+    }
+
+    pub fn multiply(&self, other: &Value) -> Result<Value, ValueError> {
+        use ConcreteValue::*;
+        use Value::*;
+
+        let product = match (self, other) {
+            (Concrete(Byte(left)), Concrete(Byte(right))) => {
+                Value::byte(left.saturating_mul(*right))
+            }
+            (Concrete(Float(left)), Concrete(Float(right))) => Value::float(left * right),
+            (Concrete(Integer(left)), Concrete(Integer(right))) => {
+                Value::integer(left.saturating_mul(*right))
+            }
+            _ => return Err(ValueError::CannotAdd(self.clone(), other.clone())),
+        };
+
+        Ok(product)
+    }
+
+    pub fn divide(&self, other: &Value) -> Result<Value, ValueError> {
+        use ConcreteValue::*;
+        use Value::*;
+
+        let product = match (self, other) {
+            (Concrete(Byte(left)), Concrete(Byte(right))) => {
+                Value::byte(left.saturating_div(*right))
+            }
+            (Concrete(Float(left)), Concrete(Float(right))) => Value::float(left / right),
+            (Concrete(Integer(left)), Concrete(Integer(right))) => {
+                Value::integer(left.saturating_div(*right))
+            }
+            _ => return Err(ValueError::CannotDivide(self.clone(), other.clone())),
+        };
+
+        Ok(product)
+    }
+
+    pub fn modulo(&self, other: &Value) -> Result<Value, ValueError> {
+        use ConcreteValue::*;
+        use Value::*;
+
+        let product = match (self, other) {
+            (Concrete(Byte(left)), Concrete(Byte(right))) => Value::byte(left % right),
+            (Concrete(Float(left)), Concrete(Float(right))) => Value::float(left % right),
+            (Concrete(Integer(left)), Concrete(Integer(right))) => Value::integer(left % right),
+            _ => return Err(ValueError::CannotModulo(self.clone(), other.clone())),
+        };
+
+        Ok(product)
+    }
+
+    pub fn less_than(&self, other: &Value) -> Result<Value, ValueError> {
+        let (left, right) = match (self, other) {
+            (Value::Concrete(left), Value::Concrete(right)) => (left, right),
+            _ => return Err(ValueError::CannotCompare(self.clone(), other.clone())),
+        };
+
+        Ok(Value::boolean(left < right))
+    }
+
+    pub fn less_than_or_equal(&self, other: &Value) -> Result<Value, ValueError> {
+        let (left, right) = match (self, other) {
+            (Value::Concrete(left), Value::Concrete(right)) => (left, right),
+            _ => return Err(ValueError::CannotCompare(self.clone(), other.clone())),
+        };
+
+        Ok(Value::boolean(left <= right))
+    }
+
+    pub fn equal(&self, other: &Value) -> Result<Value, ValueError> {
+        let (left, right) = match (self, other) {
+            (Value::Concrete(left), Value::Concrete(right)) => (left, right),
+            _ => return Err(ValueError::CannotCompare(self.clone(), other.clone())),
+        };
+
+        Ok(Value::boolean(left == right))
+    }
+
+    pub fn negate(&self) -> Result<Value, ValueError> {
+        use ConcreteValue::*;
+        use Value::*;
+
+        let negated = match self {
+            Concrete(Integer(integer)) => Value::integer(-integer),
+            Concrete(Float(float)) => Value::float(-float),
+            _ => return Err(ValueError::CannotNot(self.clone())),
+        };
+
+        Ok(negated)
+    }
+
+    pub fn not(&self) -> Result<Value, ValueError> {
+        use ConcreteValue::*;
+        use Value::*;
+
+        let not = match self {
+            Concrete(Boolean(boolean)) => Value::boolean(!boolean),
+            Concrete(Byte(byte)) => Value::byte(!byte),
+            Concrete(Integer(integer)) => Value::integer(!integer),
+            _ => return Err(ValueError::CannotNot(self.clone())),
+        };
+
+        Ok(not)
+    }
+}
+
+impl From<bool> for Value {
+    fn from(value: bool) -> Self {
+        Value::boolean(value)
+    }
+}
+
+impl From<u8> for Value {
+    fn from(value: u8) -> Self {
+        Value::byte(value)
+    }
+}
+
+impl From<char> for Value {
+    fn from(value: char) -> Self {
+        Value::character(value)
+    }
+}
+
+impl From<f64> for Value {
+    fn from(value: f64) -> Self {
+        Value::float(value)
+    }
+}
+
+impl From<i32> for Value {
+    fn from(value: i32) -> Self {
+        Value::integer(value as i64)
+    }
+}
+
+impl From<i64> for Value {
+    fn from(value: i64) -> Self {
+        Value::integer(value)
+    }
+}
+
+impl From<String> for Value {
+    fn from(value: String) -> Self {
+        Value::string(value)
+    }
+}
+
+impl From<&str> for Value {
+    fn from(str: &str) -> Self {
+        Value::string(str)
+    }
+}
+
+impl Clone for Value {
+    fn clone(&self) -> Self {
+        log::trace!("Cloning value {self}");
+
+        match self {
+            Value::Abstract(object) => Value::Abstract(object.clone()),
+            Value::Concrete(concrete) => Value::Concrete(concrete.clone()),
+        }
+    }
+}
+
+impl Display for Value {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        match self {
+            Value::Abstract(object) => write!(f, "{object}"),
+            Value::Concrete(concrete) => write!(f, "{concrete}"),
+        }
+    }
+}
+
+/// Value representation that can be resolved to a concrete value by the VM.
+#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize)]
+pub enum AbstractValue {
+    List { start: u8, end: u8, item_type: Type },
+}
+
+impl Display for AbstractValue {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        match self {
+            AbstractValue::List { start, end, .. } => {
+                write!(f, "List [R{}..=R{}]", start, end)
+            }
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Deserialize, Serialize)]
+pub enum ConcreteValue {
+    Boolean(bool),
+    Byte(u8),
+    Character(char),
+    Float(f64),
+    Function(Function),
+    Integer(i64),
+    List(Vec<Value>),
+    Range(RangeValue),
+    String(String),
+}
+
+impl ConcreteValue {
+    pub fn r#type(&self) -> Type {
+        match self {
+            ConcreteValue::Boolean(_) => Type::Boolean,
+            ConcreteValue::Byte(_) => Type::Byte,
+            ConcreteValue::Character(_) => Type::Character,
+            ConcreteValue::Float(_) => Type::Float,
+            ConcreteValue::Function(Function { r#type, .. }) => r#type.clone(),
+            ConcreteValue::Integer(_) => Type::Integer,
+            ConcreteValue::List(list) => Type::List {
+                item_type: list
+                    .first()
+                    .map(|value| Box::new(value.r#type()))
+                    .unwrap_or_else(|| Box::new(Type::Any)),
+                length: list.len(),
+            },
+            ConcreteValue::Range(range) => range.r#type(),
+            ConcreteValue::String(string) => Type::String {
+                length: Some(string.len()),
+            },
+        }
+    }
+
+    pub fn is_rangeable(&self) -> bool {
+        matches!(
+            self,
+            ConcreteValue::Integer(_)
+                | ConcreteValue::Float(_)
+                | ConcreteValue::Character(_)
+                | ConcreteValue::Byte(_)
+        )
+    }
+}
+
+impl Display for ConcreteValue {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        match self {
+            ConcreteValue::Boolean(boolean) => write!(f, "{boolean}"),
+            ConcreteValue::Byte(byte) => write!(f, "0x{byte:02x}"),
+            ConcreteValue::Character(character) => write!(f, "{character}"),
+            ConcreteValue::Float(float) => {
+                write!(f, "{float}")?;
+
+                if float.fract() == 0.0 {
+                    write!(f, ".0")?;
+                }
+
+                Ok(())
+            }
+            ConcreteValue::Function(Function { r#type, .. }) => {
+                write!(f, "{}", r#type)
+            }
+            ConcreteValue::Integer(integer) => write!(f, "{integer}"),
+            ConcreteValue::List(items) => {
+                write!(f, "[")?;
+
+                for (index, item) in items.iter().enumerate() {
+                    if index > 0 {
+                        write!(f, ", ")?;
+                    }
+
+                    write!(f, "{item}")?;
+                }
+
+                write!(f, "]")
+            }
+            ConcreteValue::Range(range_value) => {
+                write!(f, "{range_value}")
+            }
+            ConcreteValue::String(string) => write!(f, "{string}"),
+        }
+    }
+}
+
+impl Eq for ConcreteValue {}
+
+impl PartialOrd for ConcreteValue {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for ConcreteValue {
+    fn cmp(&self, other: &Self) -> Ordering {
+        match (self, other) {
+            (ConcreteValue::Boolean(left), ConcreteValue::Boolean(right)) => left.cmp(right),
+            (ConcreteValue::Boolean(_), _) => Ordering::Greater,
+            (ConcreteValue::Byte(left), ConcreteValue::Byte(right)) => left.cmp(right),
+            (ConcreteValue::Byte(_), _) => Ordering::Greater,
+            (ConcreteValue::Character(left), ConcreteValue::Character(right)) => left.cmp(right),
+            (ConcreteValue::Character(_), _) => Ordering::Greater,
+            (ConcreteValue::Float(left), ConcreteValue::Float(right)) => {
+                if left.is_nan() && right.is_nan() {
+                    Ordering::Equal
+                } else if left.is_nan() {
+                    Ordering::Less
+                } else if right.is_nan() {
+                    Ordering::Greater
+                } else {
+                    left.partial_cmp(right).unwrap()
+                }
+            }
+            (ConcreteValue::Float(_), _) => Ordering::Greater,
+            (ConcreteValue::Function(left), ConcreteValue::Function(right)) => left.cmp(right),
+            (ConcreteValue::Function(_), _) => Ordering::Greater,
+            (ConcreteValue::Integer(left), ConcreteValue::Integer(right)) => left.cmp(right),
+            (ConcreteValue::Integer(_), _) => Ordering::Greater,
+            (ConcreteValue::List(left), ConcreteValue::List(right)) => left.cmp(right),
+            (ConcreteValue::List(_), _) => Ordering::Greater,
+            (ConcreteValue::Range(left), ConcreteValue::Range(right)) => left.cmp(right),
+            (ConcreteValue::Range(_), _) => Ordering::Greater,
+            (ConcreteValue::String(left), ConcreteValue::String(right)) => left.cmp(right),
+            (ConcreteValue::String(_), _) => Ordering::Greater,
+        }
+    }
+}
+
+#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Serialize, Deserialize)]
+pub struct Function {
+    chunk: Chunk,
+    r#type: Type,
+}
+
+impl Function {
+    pub fn new(chunk: Chunk, r#type: Type) -> Self {
+        Self { chunk, r#type }
+    }
+
+    pub fn chunk(&self) -> &Chunk {
+        &self.chunk
+    }
+
+    pub fn chunk_mut(&mut self) -> &mut Chunk {
+        &mut self.chunk
+    }
+
+    pub fn take_chunk(self) -> Chunk {
+        self.chunk
+    }
+
+    pub fn r#type(&self) -> &Type {
+        &self.r#type
+    }
+}
+
+impl Display for Function {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "{}", self.r#type)
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub enum RangeValue {
+    ByteRange(Range<u8>),
+    ByteRangeInclusive(RangeInclusive<u8>),
+    CharacterRange(Range<char>),
+    CharacterRangeInclusive(RangeInclusive<char>),
+    FloatRange(Range<f64>),
+    FloatRangeInclusive(RangeInclusive<f64>),
+    IntegerRange(Range<i64>),
+    IntegerRangeInclusive(RangeInclusive<i64>),
+}
+
+impl RangeValue {
+    pub fn r#type(&self) -> Type {
+        let inner_type = match self {
+            RangeValue::ByteRange(_) => RangeableType::Byte,
+            RangeValue::ByteRangeInclusive(_) => RangeableType::Byte,
+            RangeValue::CharacterRange(_) => RangeableType::Character,
+            RangeValue::CharacterRangeInclusive(_) => RangeableType::Character,
+            RangeValue::FloatRange(_) => RangeableType::Float,
+            RangeValue::FloatRangeInclusive(_) => RangeableType::Float,
+            RangeValue::IntegerRange(_) => RangeableType::Integer,
+            RangeValue::IntegerRangeInclusive(_) => RangeableType::Integer,
+        };
+
+        Type::Range { r#type: inner_type }
+    }
+}
+
+impl From<Range<u8>> for RangeValue {
+    fn from(range: Range<u8>) -> Self {
+        RangeValue::ByteRange(range)
+    }
+}
+
+impl From<RangeInclusive<u8>> for RangeValue {
+    fn from(range: RangeInclusive<u8>) -> Self {
+        RangeValue::ByteRangeInclusive(range)
+    }
+}
+
+impl From<Range<char>> for RangeValue {
+    fn from(range: Range<char>) -> Self {
+        RangeValue::CharacterRange(range)
+    }
+}
+
+impl From<RangeInclusive<char>> for RangeValue {
+    fn from(range: RangeInclusive<char>) -> Self {
+        RangeValue::CharacterRangeInclusive(range)
+    }
+}
+
+impl From<Range<f64>> for RangeValue {
+    fn from(range: Range<f64>) -> Self {
+        RangeValue::FloatRange(range)
+    }
+}
+
+impl From<RangeInclusive<f64>> for RangeValue {
+    fn from(range: RangeInclusive<f64>) -> Self {
+        RangeValue::FloatRangeInclusive(range)
+    }
+}
+
+impl From<Range<i32>> for RangeValue {
+    fn from(range: Range<i32>) -> Self {
+        RangeValue::IntegerRange(range.start as i64..range.end as i64)
+    }
+}
+
+impl From<RangeInclusive<i32>> for RangeValue {
+    fn from(range: RangeInclusive<i32>) -> Self {
+        RangeValue::IntegerRangeInclusive(*range.start() as i64..=*range.end() as i64)
+    }
+}
+
+impl From<Range<i64>> for RangeValue {
+    fn from(range: Range<i64>) -> Self {
+        RangeValue::IntegerRange(range)
+    }
+}
+
+impl From<RangeInclusive<i64>> for RangeValue {
+    fn from(range: RangeInclusive<i64>) -> Self {
+        RangeValue::IntegerRangeInclusive(range)
+    }
+}
+
+impl Display for RangeValue {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        match self {
+            RangeValue::ByteRange(range) => write!(f, "{}..{}", range.start, range.end),
+            RangeValue::ByteRangeInclusive(range) => {
+                write!(f, "{}..={}", range.start(), range.end())
+            }
+            RangeValue::CharacterRange(range) => write!(f, "{}..{}", range.start, range.end),
+            RangeValue::CharacterRangeInclusive(range) => {
+                write!(f, "{}..={}", range.start(), range.end())
+            }
+            RangeValue::FloatRange(range) => write!(f, "{}..{}", range.start, range.end),
+            RangeValue::FloatRangeInclusive(range) => {
+                write!(f, "{}..={}", range.start(), range.end())
+            }
+            RangeValue::IntegerRange(range) => write!(f, "{}..{}", range.start, range.end),
+            RangeValue::IntegerRangeInclusive(range) => {
+                write!(f, "{}..={}", range.start(), range.end())
+            }
+        }
+    }
+}
+
+impl Eq for RangeValue {}
+
+impl PartialOrd for RangeValue {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for RangeValue {
+    fn cmp(&self, other: &Self) -> Ordering {
+        match (self, other) {
+            (RangeValue::ByteRange(left), RangeValue::ByteRange(right)) => {
+                let start_cmp = left.start.cmp(&right.start);
+
+                if start_cmp != Ordering::Equal {
+                    start_cmp
+                } else {
+                    left.end.cmp(&right.end)
+                }
+            }
+            (RangeValue::ByteRange(_), _) => Ordering::Greater,
+            (RangeValue::ByteRangeInclusive(left), RangeValue::ByteRangeInclusive(right)) => {
+                let start_cmp = left.start().cmp(right.start());
+
+                if start_cmp != Ordering::Equal {
+                    start_cmp
+                } else {
+                    left.end().cmp(right.end())
+                }
+            }
+            (RangeValue::ByteRangeInclusive(_), _) => Ordering::Greater,
+            (RangeValue::CharacterRange(left), RangeValue::CharacterRange(right)) => {
+                let start_cmp = left.start.cmp(&right.start);
+
+                if start_cmp != Ordering::Equal {
+                    start_cmp
+                } else {
+                    left.end.cmp(&right.end)
+                }
+            }
+            (RangeValue::CharacterRange(_), _) => Ordering::Greater,
+            (
+                RangeValue::CharacterRangeInclusive(left),
+                RangeValue::CharacterRangeInclusive(right),
+            ) => {
+                let start_cmp = left.start().cmp(right.start());
+
+                if start_cmp != Ordering::Equal {
+                    start_cmp
+                } else {
+                    left.end().cmp(right.end())
+                }
+            }
+            (RangeValue::CharacterRangeInclusive(_), _) => Ordering::Greater,
+            (RangeValue::FloatRange(left), RangeValue::FloatRange(right)) => {
+                let start_cmp = left.start.to_bits().cmp(&right.start.to_bits());
+
+                if start_cmp != Ordering::Equal {
+                    start_cmp
+                } else {
+                    left.end.to_bits().cmp(&right.end.to_bits())
+                }
+            }
+            (RangeValue::FloatRange(_), _) => Ordering::Greater,
+            (RangeValue::FloatRangeInclusive(left), RangeValue::FloatRangeInclusive(right)) => {
+                let start_cmp = left.start().to_bits().cmp(&right.start().to_bits());
+
+                if start_cmp != Ordering::Equal {
+                    start_cmp
+                } else {
+                    left.end().to_bits().cmp(&right.end().to_bits())
+                }
+            }
+            (RangeValue::FloatRangeInclusive(_), _) => Ordering::Greater,
+            (RangeValue::IntegerRange(left), RangeValue::IntegerRange(right)) => {
+                let start_cmp = left.start.cmp(&right.start);
+
+                if start_cmp != Ordering::Equal {
+                    start_cmp
+                } else {
+                    left.end.cmp(&right.end)
+                }
+            }
+            (RangeValue::IntegerRange(_), _) => Ordering::Greater,
+            (RangeValue::IntegerRangeInclusive(left), RangeValue::IntegerRangeInclusive(right)) => {
+                let start_cmp = left.start().cmp(right.start());
+
+                if start_cmp != Ordering::Equal {
+                    start_cmp
+                } else {
+                    left.end().cmp(right.end())
+                }
+            }
+            (RangeValue::IntegerRangeInclusive(_), _) => Ordering::Greater,
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum ValueError {
+    CannotAdd(Value, Value),
+    CannotAnd(Value, Value),
+    CannotCompare(Value, Value),
+    CannotDivide(Value, Value),
+    CannotModulo(Value, Value),
+    CannotMultiply(Value, Value),
+    CannotNegate(Value),
+    CannotNot(Value),
+    CannotSubtract(Value, Value),
+    CannotOr(Value, Value),
+}
+
+impl Display for ValueError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        match self {
+            ValueError::CannotAdd(left, right) => {
+                write!(f, "Cannot add {left} and {right}")
+            }
+            ValueError::CannotAnd(left, right) => {
+                write!(f, "Cannot use logical AND operation on {left} and {right}")
+            }
+            ValueError::CannotCompare(left, right) => {
+                write!(f, "Cannot compare {left} and {right}")
+            }
+            ValueError::CannotDivide(left, right) => {
+                write!(f, "Cannot divide {left} by {right}")
+            }
+            ValueError::CannotModulo(left, right) => {
+                write!(f, "Cannot use modulo operation on {left} and {right}")
+            }
+            ValueError::CannotMultiply(left, right) => {
+                write!(f, "Cannot multiply {left} by {right}")
+            }
+            ValueError::CannotNegate(value) => {
+                write!(f, "Cannot negate {value}")
+            }
+            ValueError::CannotNot(value) => {
+                write!(f, "Cannot use logical NOT operation on {value}")
+            }
+            ValueError::CannotSubtract(left, right) => {
+                write!(f, "Cannot subtract {right} from {left}")
+            }
+            ValueError::CannotOr(left, right) => {
+                write!(f, "Cannot use logical OR operation on {left} and {right}")
+            }
+        }
+    }
+}

dust-lang/src/vm.rs

@@ -0,0 +1,765 @@
+//! Virtual machine and errors
+use std::{
+    cmp::Ordering,
+    fmt::{self, Display, Formatter},
+    ops::Range,
+};
+
+use crate::{
+    compile, value::ConcreteValue, AnnotatedError, Chunk, ChunkError, DustError, FunctionType,
+    Instruction, Local, NativeFunction, NativeFunctionError, Operation, Span, Type, Value,
+    ValueError,
+};
+
+pub fn run(source: &str) -> Result<Option<Value>, DustError> {
+    let mut chunk = compile(source)?;
+    let mut vm = Vm::new(&mut chunk, None);
+
+    vm.run()
+        .map(|option| option.cloned())
+        .map_err(|error| DustError::Runtime { error, source })
+}
+
+pub fn run_and_display_output(source: &str) {
+    match run(source) {
+        Ok(Some(value)) => println!("{}", value),
+        Ok(None) => {}
+        Err(error) => eprintln!("{}", error.report()),
+    }
+}
+
+/// Dust virtual machine.
+///
+/// See the [module-level documentation](index.html) for more information.
+#[derive(Debug, Eq, PartialEq)]
+pub struct Vm<'chunk, 'parent> {
+    ip: usize,
+    chunk: &'chunk mut Chunk,
+    stack: Vec<Register>,
+    last_assigned_register: Option<u8>,
+    parent: Option<&'parent Vm<'chunk, 'parent>>,
+}
+
+impl<'chunk, 'parent> Vm<'chunk, 'parent> {
+    const STACK_LIMIT: usize = u16::MAX as usize;
+
+    pub fn new(chunk: &'chunk mut Chunk, parent: Option<&'parent Vm<'chunk, 'parent>>) -> Self {
+        Self {
+            ip: 0,
+            chunk,
+            stack: Vec::new(),
+            last_assigned_register: None,
+            parent,
+        }
+    }
+
+    pub fn run(&mut self) -> Result<Option<&Value>, VmError> {
+        // DRY helper to get constant or register values for binary operations
+        fn get_arguments<'a>(
+            vm: &'a mut Vm,
+            instruction: Instruction,
+            position: Span,
+        ) -> Result<(&'a Value, &'a Value), VmError> {
+            let left = if instruction.b_is_constant() {
+                vm.get_constant(instruction.b(), position)?
+            } else {
+                vm.open_register(instruction.b(), position)?
+            };
+            let right = if instruction.c_is_constant() {
+                vm.get_constant(instruction.c(), position)?
+            } else {
+                vm.open_register(instruction.c(), position)?
+            };
+
+            Ok((left, right))
+        }
+
+        while let Ok((instruction, position)) = self.read(Span(0, 0)).copied() {
+            log::info!(
+                "{} | {} | {} | {}",
+                self.ip - 1,
+                position,
+                instruction.operation(),
+                instruction.disassembly_info(self.chunk)
+            );
+
+            match instruction.operation() {
+                Operation::Move => {
+                    let to_register = instruction.a();
+                    let from_register = instruction.b();
+                    let from_register_has_value = self
+                        .stack
+                        .get(from_register as usize)
+                        .is_some_and(|register| !matches!(register, Register::Empty));
+
+                    if from_register_has_value {
+                        self.set_register(
+                            to_register,
+                            Register::StackPointer(from_register),
+                            position,
+                        )?;
+                    }
+                }
+                Operation::Close => {
+                    let from_register = instruction.b();
+                    let to_register = instruction.c();
+
+                    if self.stack.len() < to_register as usize {
+                        return Err(VmError::StackUnderflow { position });
+                    }
+
+                    for register_index in from_register..to_register {
+                        self.stack[register_index as usize] = Register::Empty;
+                    }
+                }
+                Operation::LoadBoolean => {
+                    let to_register = instruction.a();
+                    let boolean = instruction.b_as_boolean();
+                    let jump = instruction.c_as_boolean();
+                    let value = Value::boolean(boolean);
+
+                    self.set_register(to_register, Register::Value(value), position)?;
+
+                    if jump {
+                        self.ip += 1;
+                    }
+                }
+                Operation::LoadConstant => {
+                    let to_register = instruction.a();
+                    let from_constant = instruction.b();
+                    let jump = instruction.c_as_boolean();
+
+                    self.set_register(
+                        to_register,
+                        Register::ConstantPointer(from_constant),
+                        position,
+                    )?;
+
+                    if jump {
+                        self.ip += 1
+                    }
+                }
+                Operation::LoadList => {
+                    let to_register = instruction.a();
+                    let start_register = instruction.b();
+                    let item_type = (start_register..to_register)
+                        .find_map(|register_index| {
+                            if let Ok(value) = self.open_register(register_index, position) {
+                                Some(value.r#type())
+                            } else {
+                                None
+                            }
+                        })
+                        .unwrap_or(Type::Any);
+                    let value = Value::abstract_list(start_register, to_register, item_type);
+
+                    self.set_register(to_register, Register::Value(value), position)?;
+                }
+                Operation::LoadSelf => {
+                    let to_register = instruction.a();
+                    let value = Value::function(
+                        self.chunk.clone(),
+                        FunctionType {
+                            type_parameters: None,
+                            value_parameters: None,
+                            return_type: None,
+                        },
+                    );
+
+                    self.set_register(to_register, Register::Value(value), position)?;
+                }
+                Operation::DefineLocal => {
+                    let from_register = instruction.a();
+                    let to_local = instruction.b();
+
+                    self.define_local(to_local, from_register, position)?;
+                }
+                Operation::GetLocal => {
+                    let to_register = instruction.a();
+                    let local_index = instruction.b();
+                    let local = self.get_local(local_index, position)?;
+
+                    self.set_register(
+                        to_register,
+                        Register::StackPointer(local.register_index),
+                        position,
+                    )?;
+                }
+                Operation::SetLocal => {
+                    let register = instruction.a();
+                    let local_index = instruction.b();
+
+                    self.define_local(local_index, register, position)?;
+                }
+                Operation::Add => {
+                    let to_register = instruction.a();
+                    let (left, right) = get_arguments(self, instruction, position)?;
+                    let sum = left
+                        .add(right)
+                        .map_err(|error| VmError::Value { error, position })?;
+
+                    self.set_register(to_register, Register::Value(sum), position)?;
+                }
+                Operation::Subtract => {
+                    let to_register = instruction.a();
+                    let (left, right) = get_arguments(self, instruction, position)?;
+                    let difference = left
+                        .subtract(right)
+                        .map_err(|error| VmError::Value { error, position })?;
+
+                    self.set_register(to_register, Register::Value(difference), position)?;
+                }
+                Operation::Multiply => {
+                    let to_register = instruction.a();
+                    let (left, right) = get_arguments(self, instruction, position)?;
+                    let product = left
+                        .multiply(right)
+                        .map_err(|error| VmError::Value { error, position })?;
+
+                    self.set_register(to_register, Register::Value(product), position)?;
+                }
+                Operation::Divide => {
+                    let to_register = instruction.a();
+                    let (left, right) = get_arguments(self, instruction, position)?;
+                    let quotient = left
+                        .divide(right)
+                        .map_err(|error| VmError::Value { error, position })?;
+
+                    self.set_register(to_register, Register::Value(quotient), position)?;
+                }
+                Operation::Modulo => {
+                    let to_register = instruction.a();
+                    let (left, right) = get_arguments(self, instruction, position)?;
+                    let remainder = left
+                        .modulo(right)
+                        .map_err(|error| VmError::Value { error, position })?;
+
+                    self.set_register(to_register, Register::Value(remainder), position)?;
+                }
+                Operation::Test => {
+                    let register = instruction.a();
+                    let test_value = instruction.c_as_boolean();
+                    let value = self.open_register(register, position)?;
+                    let boolean = if let Value::Concrete(ConcreteValue::Boolean(boolean)) = value {
+                        *boolean
+                    } else {
+                        return Err(VmError::ExpectedBoolean {
+                            found: value.clone(),
+                            position,
+                        });
+                    };
+
+                    if boolean != test_value {
+                        self.ip += 1;
+                    }
+                }
+                Operation::TestSet => todo!(),
+                Operation::Equal => {
+                    debug_assert_eq!(
+                        self.get_instruction(self.ip, position)?.0.operation(),
+                        Operation::Jump
+                    );
+
+                    let (left, right) = get_arguments(self, instruction, position)?;
+                    let equal_result = left
+                        .equal(right)
+                        .map_err(|error| VmError::Value { error, position })?;
+                    let boolean =
+                        if let Value::Concrete(ConcreteValue::Boolean(boolean)) = equal_result {
+                            boolean
+                        } else {
+                            return Err(VmError::ExpectedBoolean {
+                                found: equal_result.clone(),
+                                position,
+                            });
+                        };
+                    let compare_to = instruction.a_as_boolean();
+
+                    if boolean == compare_to {
+                        self.ip += 1;
+                    } else {
+                        let (jump, _) = self.get_instruction(self.ip, position)?;
+                        let jump_distance = jump.a();
+                        let is_positive = jump.b_as_boolean();
+                        let new_ip = if is_positive {
+                            self.ip + jump_distance as usize
+                        } else {
+                            self.ip - jump_distance as usize
+                        };
+
+                        self.ip = new_ip;
+                    }
+                }
+                Operation::Less => {
+                    debug_assert_eq!(
+                        self.get_instruction(self.ip, position)?.0.operation(),
+                        Operation::Jump
+                    );
+
+                    let (left, right) = get_arguments(self, instruction, position)?;
+                    let less_result = left
+                        .less_than(right)
+                        .map_err(|error| VmError::Value { error, position })?;
+                    let boolean =
+                        if let Value::Concrete(ConcreteValue::Boolean(boolean)) = less_result {
+                            boolean
+                        } else {
+                            return Err(VmError::ExpectedBoolean {
+                                found: less_result.clone(),
+                                position,
+                            });
+                        };
+                    let compare_to = instruction.a_as_boolean();
+
+                    if boolean == compare_to {
+                        self.ip += 1;
+                    } else {
+                        let jump = self.get_instruction(self.ip, position)?.0;
+                        let jump_distance = jump.a();
+                        let is_positive = jump.b_as_boolean();
+                        let new_ip = if is_positive {
+                            self.ip + jump_distance as usize
+                        } else {
+                            self.ip - jump_distance as usize
+                        };
+
+                        self.ip = new_ip;
+                    }
+                }
+                Operation::LessEqual => {
+                    debug_assert_eq!(
+                        self.get_instruction(self.ip, position)?.0.operation(),
+                        Operation::Jump
+                    );
+
+                    let (left, right) = get_arguments(self, instruction, position)?;
+                    let less_or_equal_result = left
+                        .less_than_or_equal(right)
+                        .map_err(|error| VmError::Value { error, position })?;
+                    let boolean = if let Value::Concrete(ConcreteValue::Boolean(boolean)) =
+                        less_or_equal_result
+                    {
+                        boolean
+                    } else {
+                        return Err(VmError::ExpectedBoolean {
+                            found: less_or_equal_result.clone(),
+                            position,
+                        });
+                    };
+                    let compare_to = instruction.a_as_boolean();
+
+                    if boolean == compare_to {
+                        self.ip += 1;
+                    } else {
+                        let jump = self.get_instruction(self.ip, position)?.0;
+                        let jump_distance = jump.a();
+                        let is_positive = jump.b_as_boolean();
+                        let new_ip = if is_positive {
+                            self.ip + jump_distance as usize
+                        } else {
+                            self.ip - jump_distance as usize
+                        };
+
+                        self.ip = new_ip;
+                    }
+                }
+                Operation::Negate => {
+                    let value = if instruction.b_is_constant() {
+                        self.get_constant(instruction.b(), position)?
+                    } else {
+                        self.open_register(instruction.b(), position)?
+                    };
+                    let negated = value
+                        .negate()
+                        .map_err(|error| VmError::Value { error, position })?;
+
+                    self.set_register(instruction.a(), Register::Value(negated), position)?;
+                }
+                Operation::Not => {
+                    let value = if instruction.b_is_constant() {
+                        self.get_constant(instruction.b(), position)?
+                    } else {
+                        self.open_register(instruction.b(), position)?
+                    };
+                    let not = value
+                        .not()
+                        .map_err(|error| VmError::Value { error, position })?;
+
+                    self.set_register(instruction.a(), Register::Value(not), position)?;
+                }
+                Operation::Jump => {
+                    let jump_distance = instruction.b();
+                    let is_positive = instruction.c_as_boolean();
+                    let new_ip = if is_positive {
+                        self.ip + jump_distance as usize
+                    } else {
+                        self.ip - jump_distance as usize - 1
+                    };
+                    self.ip = new_ip;
+                }
+                Operation::Call => {
+                    let to_register = instruction.a();
+                    let function_register = instruction.b();
+                    let argument_count = instruction.c();
+                    let value = self.open_register(function_register, position)?.clone();
+                    let mut function =
+                        if let Value::Concrete(ConcreteValue::Function(function)) = value {
+                            function
+                        } else {
+                            return Err(VmError::ExpectedFunction {
+                                found: value,
+                                position,
+                            });
+                        };
+                    let mut function_vm = Vm::new(function.chunk_mut(), Some(self));
+                    let first_argument_index = function_register + 1;
+
+                    for argument_index in
+                        first_argument_index..first_argument_index + argument_count
+                    {
+                        let top_of_stack = function_vm.stack.len() as u8;
+
+                        function_vm.set_register(
+                            top_of_stack,
+                            Register::ParentStackPointer(argument_index),
+                            position,
+                        )?
+                    }
+
+                    let return_value = function_vm.run()?.cloned();
+
+                    if let Some(value) = return_value {
+                        self.set_register(to_register, Register::Value(value), position)?;
+                    }
+                }
+                Operation::CallNative => {
+                    let native_function = NativeFunction::from(instruction.b());
+                    let return_value = native_function.call(instruction, self, position)?;
+
+                    if let Some(value) = return_value {
+                        let to_register = instruction.a();
+
+                        self.set_register(to_register, Register::Value(value), position)?;
+                    }
+                }
+                Operation::Return => {
+                    let should_return_value = instruction.b_as_boolean();
+
+                    if !should_return_value {
+                        return Ok(None);
+                    }
+
+                    let return_value = if let Some(register_index) = self.last_assigned_register {
+                        self.open_register(register_index, position)?
+                    } else {
+                        return Err(VmError::StackUnderflow { position });
+                    };
+
+                    return Ok(Some(return_value));
+                }
+            }
+        }
+
+        Ok(None)
+    }
+
+    fn set_register(
+        &mut self,
+        to_register: u8,
+        register: Register,
+        position: Span,
+    ) -> Result<(), VmError> {
+        self.last_assigned_register = Some(to_register);
+
+        let length = self.stack.len();
+        let to_register = to_register as usize;
+
+        if length == Self::STACK_LIMIT {
+            return Err(VmError::StackOverflow { position });
+        }
+
+        match to_register.cmp(&length) {
+            Ordering::Less => {
+                log::trace!("Change R{to_register} to {register}");
+
+                self.stack[to_register] = register;
+
+                Ok(())
+            }
+            Ordering::Equal => {
+                log::trace!("Set R{to_register} to {register}");
+
+                self.stack.push(register);
+
+                Ok(())
+            }
+            Ordering::Greater => {
+                let difference = to_register - length;
+
+                for index in 0..difference {
+                    log::trace!("Set R{index} to {register}");
+
+                    self.stack.push(Register::Empty);
+                }
+
+                log::trace!("Set R{to_register} to {register}");
+
+                self.stack.push(register);
+
+                Ok(())
+            }
+        }
+    }
+
+    fn get_constant(&self, index: u8, position: Span) -> Result<&Value, VmError> {
+        self.chunk
+            .get_constant(index)
+            .map_err(|error| VmError::Chunk { error, position })
+    }
+
+    pub fn open_register(&self, register_index: u8, position: Span) -> Result<&Value, VmError> {
+        let register_index = register_index as usize;
+        let register =
+            self.stack
+                .get(register_index)
+                .ok_or_else(|| VmError::RegisterIndexOutOfBounds {
+                    index: register_index,
+                    position,
+                })?;
+
+        match register {
+            Register::Value(value) => Ok(value),
+            Register::StackPointer(register_index) => self.open_register(*register_index, position),
+            Register::ConstantPointer(constant_index) => {
+                self.get_constant(*constant_index, position)
+            }
+            Register::ParentStackPointer(register_index) => {
+                let parent = self
+                    .parent
+                    .as_ref()
+                    .ok_or(VmError::ExpectedParent { position })?;
+
+                parent.open_register(*register_index, position)
+            }
+            Register::ParentConstantPointer(constant_index) => {
+                let parent = self
+                    .parent
+                    .as_ref()
+                    .ok_or(VmError::ExpectedParent { position })?;
+
+                parent.get_constant(*constant_index, position)
+            }
+            Register::Empty => Err(VmError::EmptyRegister {
+                index: register_index,
+                position,
+            }),
+        }
+    }
+
+    pub fn open_nonempty_registers(
+        &self,
+        register_index_range: Range<u8>,
+        position: Span,
+    ) -> Result<Vec<&Value>, VmError> {
+        let mut values = Vec::with_capacity(register_index_range.len());
+
+        for register_index in register_index_range.clone() {
+            let register_index = register_index as usize;
+            let register = self.stack.get(register_index).ok_or_else(|| {
+                VmError::RegisterIndexOutOfBounds {
+                    index: register_index,
+                    position,
+                }
+            })?;
+
+            let value = match register {
+                Register::Value(value) => value,
+                Register::StackPointer(register_index) => {
+                    self.open_register(*register_index, position)?
+                }
+                Register::ConstantPointer(constant_index) => {
+                    self.get_constant(*constant_index, position)?
+                }
+                Register::ParentStackPointer(register_index) => {
+                    let parent = self
+                        .parent
+                        .as_ref()
+                        .ok_or(VmError::ExpectedParent { position })?;
+
+                    parent.open_register(*register_index, position)?
+                }
+                Register::ParentConstantPointer(constant_index) => {
+                    let parent = self
+                        .parent
+                        .as_ref()
+                        .ok_or(VmError::ExpectedParent { position })?;
+
+                    parent.get_constant(*constant_index, position)?
+                }
+                Register::Empty => continue,
+            };
+
+            values.push(value);
+        }
+
+        if values.is_empty() {
+            Err(VmError::EmptyRegisters {
+                indexes: register_index_range,
+                position,
+            })
+        } else {
+            Ok(values)
+        }
+    }
+
+    fn read(&mut self, position: Span) -> Result<&(Instruction, Span), VmError> {
+        self.chunk
+            .expect_not_poisoned()
+            .map_err(|error| VmError::Chunk { error, position })?;
+
+        let max_ip = self.chunk.len() - 1;
+
+        if self.ip > max_ip {
+            return self.get_instruction(max_ip, position);
+        } else {
+            self.ip += 1;
+        }
+
+        self.get_instruction(self.ip - 1, position)
+    }
+
+    fn define_local(
+        &mut self,
+        local_index: u8,
+        register_index: u8,
+        position: Span,
+    ) -> Result<(), VmError> {
+        let local = self
+            .chunk
+            .get_local_mut(local_index)
+            .map_err(|error| VmError::Chunk { error, position })?;
+
+        log::debug!("Define local L{}", local_index);
+
+        local.register_index = register_index;
+
+        Ok(())
+    }
+
+    fn get_local(&self, local_index: u8, position: Span) -> Result<&Local, VmError> {
+        self.chunk
+            .get_local(local_index)
+            .map_err(|error| VmError::Chunk { error, position })
+    }
+
+    fn get_instruction(
+        &self,
+        index: usize,
+        position: Span,
+    ) -> Result<&(Instruction, Span), VmError> {
+        self.chunk
+            .get_instruction(index)
+            .map_err(|error| VmError::Chunk { error, position })
+    }
+}
+
+#[derive(Debug, Eq, PartialEq)]
+enum Register {
+    Empty,
+    Value(Value),
+    StackPointer(u8),
+    ConstantPointer(u8),
+    ParentStackPointer(u8),
+    ParentConstantPointer(u8),
+}
+
+impl Display for Register {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        match self {
+            Self::Empty => write!(f, "empty"),
+            Self::Value(value) => write!(f, "{}", value),
+            Self::StackPointer(index) => write!(f, "R{}", index),
+            Self::ConstantPointer(index) => write!(f, "C{}", index),
+            Self::ParentStackPointer(index) => write!(f, "PR{}", index),
+            Self::ParentConstantPointer(index) => write!(f, "PC{}", index),
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub enum VmError {
+    // Stack errors
+    StackOverflow { position: Span },
+    StackUnderflow { position: Span },
+
+    // Register errors
+    EmptyRegister { index: usize, position: Span },
+    EmptyRegisters { indexes: Range<u8>, position: Span },
+    RegisterIndexOutOfBounds { index: usize, position: Span },
+
+    // Execution errors
+    ExpectedBoolean { found: Value, position: Span },
+    ExpectedFunction { found: Value, position: Span },
+    ExpectedParent { position: Span },
+
+    // Wrappers for foreign errors
+    Chunk { error: ChunkError, position: Span },
+    NativeFunction(NativeFunctionError),
+    Value { error: ValueError, position: Span },
+}
+
+impl AnnotatedError for VmError {
+    fn title() -> &'static str {
+        "Runtime Error"
+    }
+
+    fn description(&self) -> &'static str {
+        match self {
+            Self::Chunk { .. } => "Chunk error",
+            Self::EmptyRegister { .. } => "Empty register",
+            Self::EmptyRegisters { .. } => "Empty registers",
+            Self::ExpectedBoolean { .. } => "Expected boolean",
+            Self::ExpectedFunction { .. } => "Expected function",
+            Self::ExpectedParent { .. } => "Expected parent",
+            Self::NativeFunction(error) => error.description(),
+            Self::RegisterIndexOutOfBounds { .. } => "Register index out of bounds",
+            Self::StackOverflow { .. } => "Stack overflow",
+            Self::StackUnderflow { .. } => "Stack underflow",
+            Self::Value { .. } => "Value error",
+        }
+    }
+
+    fn details(&self) -> Option<String> {
+        match self {
+            Self::Chunk { error, .. } => Some(error.to_string()),
+            Self::EmptyRegister { index, .. } => Some(format!("Register R{index} is empty")),
+            Self::EmptyRegisters { indexes: range, .. } => Some(format!(
+                "Registers R{} to R{} are empty",
+                range.start, range.end
+            )),
+            Self::ExpectedFunction { found, .. } => Some(format!("{found} is not a function")),
+            Self::RegisterIndexOutOfBounds { index, .. } => {
+                Some(format!("Register {index} does not exist"))
+            }
+            Self::NativeFunction(error) => error.details(),
+            Self::Value { error, .. } => Some(error.to_string()),
+            _ => None,
+        }
+    }
+
+    fn position(&self) -> Span {
+        match self {
+            Self::Chunk { position, .. } => *position,
+            Self::EmptyRegister { position, .. } => *position,
+            Self::EmptyRegisters { position, .. } => *position,
+            Self::ExpectedBoolean { position, .. } => *position,
+            Self::ExpectedFunction { position, .. } => *position,
+            Self::ExpectedParent { position } => *position,
+            Self::NativeFunction(error) => error.position(),
+            Self::RegisterIndexOutOfBounds { position, .. } => *position,
+            Self::StackOverflow { position } => *position,
+            Self::StackUnderflow { position } => *position,
+            Self::Value { position, .. } => *position,
+        }
+    }
+}

dust-lang/tests/basic.rs

@@ -0,0 +1,66 @@
+use dust_lang::*;
+
+#[test]
+fn constant() {
+    let source = "42";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_constant(0, 0, false), Span(0, 2)),
+                (Instruction::r#return(true), Span(2, 2))
+            ],
+            vec![Value::integer(42)],
+            vec![]
+        ))
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(42))));
+}
+
+#[test]
+fn empty() {
+    let source = "";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![(Instruction::r#return(false), Span(0, 0))],
+            vec![],
+            vec![]
+        ))
+    );
+    assert_eq!(run(source), Ok(None));
+}
+
+#[test]
+fn parentheses_precedence() {
+    let source = "(1 + 2) * 3";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::add(0, 0, 1)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(3, 4)
+                ),
+                (
+                    *Instruction::multiply(1, 0, 2).set_c_is_constant(),
+                    Span(8, 9)
+                ),
+                (Instruction::r#return(true), Span(11, 11)),
+            ],
+            vec![Value::integer(1), Value::integer(2), Value::integer(3)],
+            vec![]
+        ))
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(9))));
+}

dust-lang/tests/comparison.rs

@@ -0,0 +1,169 @@
+use dust_lang::*;
+
+#[test]
+fn equal() {
+    let source = "1 == 2";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::equal(true, 0, 1)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(2, 4)
+                ),
+                (Instruction::jump(1, true), Span(2, 4)),
+                (Instruction::load_boolean(0, true, true), Span(2, 4)),
+                (Instruction::load_boolean(0, false, false), Span(2, 4)),
+                (Instruction::r#return(true), Span(6, 6)),
+            ],
+            vec![Value::integer(1), Value::integer(2)],
+            vec![]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::boolean(false))));
+}
+
+#[test]
+fn greater() {
+    let source = "1 > 2";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::less_equal(false, 0, 1)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(2, 3)
+                ),
+                (Instruction::jump(1, true), Span(2, 3)),
+                (Instruction::load_boolean(0, true, true), Span(2, 3)),
+                (Instruction::load_boolean(0, false, false), Span(2, 3)),
+                (Instruction::r#return(true), Span(5, 5)),
+            ],
+            vec![Value::integer(1), Value::integer(2)],
+            vec![]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::boolean(false))));
+}
+
+#[test]
+fn greater_than_or_equal() {
+    let source = "1 >= 2";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::less(false, 0, 1)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(2, 4)
+                ),
+                (Instruction::jump(1, true), Span(2, 4)),
+                (Instruction::load_boolean(0, true, true), Span(2, 4)),
+                (Instruction::load_boolean(0, false, false), Span(2, 4)),
+                (Instruction::r#return(true), Span(6, 6)),
+            ],
+            vec![Value::integer(1), Value::integer(2)],
+            vec![]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::boolean(false))));
+}
+
+#[test]
+fn less_than() {
+    let source = "1 < 2";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::less(true, 0, 1)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(2, 3)
+                ),
+                (Instruction::jump(1, true), Span(2, 3)),
+                (Instruction::load_boolean(0, true, true), Span(2, 3)),
+                (Instruction::load_boolean(0, false, false), Span(2, 3)),
+                (Instruction::r#return(true), Span(5, 5)),
+            ],
+            vec![Value::integer(1), Value::integer(2)],
+            vec![]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::boolean(true))));
+}
+
+#[test]
+fn less_than_or_equal() {
+    let source = "1 <= 2";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::less_equal(true, 0, 1)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(2, 4)
+                ),
+                (Instruction::jump(1, true), Span(2, 4)),
+                (Instruction::load_boolean(0, true, true), Span(2, 4)),
+                (Instruction::load_boolean(0, false, false), Span(2, 4)),
+                (Instruction::r#return(true), Span(6, 6)),
+            ],
+            vec![Value::integer(1), Value::integer(2)],
+            vec![]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::boolean(true))));
+}
+
+#[test]
+fn not_equal() {
+    let source = "1 != 2";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::equal(false, 0, 1)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(2, 4)
+                ),
+                (Instruction::jump(1, true), Span(2, 4)),
+                (Instruction::load_boolean(0, true, true), Span(2, 4)),
+                (Instruction::load_boolean(0, false, false), Span(2, 4)),
+                (Instruction::r#return(true), Span(6, 6)),
+            ],
+            vec![Value::integer(1), Value::integer(2)],
+            vec![]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::boolean(true))));
+}

dust-lang/tests/control_flow.rs

@@ -0,0 +1,420 @@
+use dust_lang::*;
+
+#[test]
+fn equality_assignment_long() {
+    let source = "let a = if 4 == 4 { true } else { false }; a";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::equal(true, 0, 0)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(13, 15)
+                ),
+                (Instruction::jump(1, true), Span(18, 19)),
+                (Instruction::load_boolean(0, true, true), Span(20, 24)),
+                (Instruction::load_boolean(0, false, false), Span(34, 39)),
+                (Instruction::define_local(0, 0, false), Span(4, 5)),
+                (Instruction::get_local(1, 0), Span(43, 44)),
+                (Instruction::r#return(true), Span(44, 44)),
+            ],
+            vec![Value::integer(4), Value::string("a")],
+            vec![Local::new(
+                1,
+                None,
+                false,
+                Scope {
+                    depth: 0,
+                    block_index: 0
+                },
+                0
+            )]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::boolean(true))));
+}
+
+#[test]
+fn equality_assignment_short() {
+    let source = "let a = 4 == 4 a";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::equal(true, 0, 0)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(10, 12)
+                ),
+                (Instruction::jump(1, true), Span(10, 12)),
+                (Instruction::load_boolean(0, true, true), Span(10, 12)),
+                (Instruction::load_boolean(0, false, false), Span(10, 12)),
+                (Instruction::define_local(0, 0, false), Span(4, 5)),
+                (Instruction::get_local(1, 0), Span(15, 16)),
+                (Instruction::r#return(true), Span(16, 16)),
+            ],
+            vec![Value::integer(4), Value::string("a")],
+            vec![Local::new(1, None, false, Scope::default(), 0)]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::boolean(true))));
+}
+
+#[test]
+fn if_else_assigment_false() {
+    let source = r#"
+        let a = if 4 == 3 {
+            1; 2; 3; 4;
+            panic()
+        } else {
+            1; 2; 3; 4;
+            42
+        };
+        a"#;
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::equal(true, 0, 1)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(22, 24)
+                ),
+                (Instruction::jump(6, true), Span(27, 28)),
+                (Instruction::load_constant(0, 2, false), Span(41, 42)),
+                (Instruction::load_constant(1, 3, false), Span(44, 45)),
+                (Instruction::load_constant(2, 1, false), Span(47, 48)),
+                (Instruction::load_constant(3, 0, false), Span(50, 51)),
+                (
+                    Instruction::call_native(4, NativeFunction::Panic, 0),
+                    Span(65, 72)
+                ),
+                (Instruction::jump(5, true), Span(138, 139)),
+                (Instruction::load_constant(5, 2, false), Span(102, 103)),
+                (Instruction::load_constant(6, 3, false), Span(105, 106)),
+                (Instruction::load_constant(7, 1, false), Span(108, 109)),
+                (Instruction::load_constant(8, 0, false), Span(111, 112)),
+                (Instruction::load_constant(9, 4, false), Span(126, 128)),
+                (Instruction::r#move(9, 4), Span(138, 139)),
+                (Instruction::define_local(9, 0, false), Span(13, 14)),
+                (Instruction::get_local(10, 0), Span(148, 149)),
+                (Instruction::r#return(true), Span(149, 149)),
+            ],
+            vec![
+                Value::integer(4),
+                Value::integer(3),
+                Value::integer(1),
+                Value::integer(2),
+                Value::integer(42),
+                Value::string("a")
+            ],
+            vec![Local::new(5, None, false, Scope::default(), 0)]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(42))));
+}
+
+#[test]
+fn if_else_assigment_true() {
+    let source = r#"
+        let a = if 4 == 4 {
+            1; 2; 3; 4;
+            42
+        } else {
+            1; 2; 3; 4;
+            panic()
+        };
+        a"#;
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::equal(true, 0, 0)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(22, 24)
+                ),
+                (Instruction::jump(6, true), Span(27, 28)),
+                (Instruction::load_constant(0, 1, false), Span(41, 42)),
+                (Instruction::load_constant(1, 2, false), Span(44, 45)),
+                (Instruction::load_constant(2, 3, false), Span(47, 48)),
+                (Instruction::load_constant(3, 0, false), Span(50, 51)),
+                (Instruction::load_constant(4, 4, false), Span(65, 67)),
+                (Instruction::jump(5, true), Span(138, 139)),
+                (Instruction::load_constant(5, 1, false), Span(97, 98)),
+                (Instruction::load_constant(6, 2, false), Span(100, 101)),
+                (Instruction::load_constant(7, 3, false), Span(103, 104)),
+                (Instruction::load_constant(8, 0, false), Span(106, 107)),
+                (
+                    Instruction::call_native(9, NativeFunction::Panic, 0),
+                    Span(121, 128)
+                ),
+                (Instruction::r#move(9, 4), Span(138, 139)),
+                (Instruction::define_local(9, 0, false), Span(13, 14)),
+                (Instruction::get_local(10, 0), Span(148, 149)),
+                (Instruction::r#return(true), Span(149, 149)),
+            ],
+            vec![
+                Value::integer(4),
+                Value::integer(1),
+                Value::integer(2),
+                Value::integer(3),
+                Value::integer(42),
+                Value::string("a")
+            ],
+            vec![Local::new(5, None, false, Scope::default(), 0)]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(42))));
+}
+
+#[test]
+fn if_else_complex() {
+    let source = "
+        if 1 == 1 {
+            1; 2; 3; 4;
+        } else {
+            1; 2; 3; 4;
+        }";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::equal(true, 0, 0)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(14, 16)
+                ),
+                (Instruction::jump(5, true), Span(19, 20)),
+                (Instruction::load_constant(0, 0, false), Span(33, 34)),
+                (Instruction::load_constant(1, 1, false), Span(36, 37)),
+                (Instruction::load_constant(2, 2, false), Span(39, 40)),
+                (Instruction::load_constant(3, 3, false), Span(42, 43)),
+                (Instruction::jump(4, true), Span(95, 95)),
+                (Instruction::load_constant(4, 0, false), Span(74, 75)),
+                (Instruction::load_constant(5, 1, false), Span(77, 78)),
+                (Instruction::load_constant(6, 2, false), Span(80, 81)),
+                (Instruction::load_constant(7, 3, false), Span(83, 84)),
+                (Instruction::r#move(7, 3), Span(95, 95)),
+                (Instruction::r#return(false), Span(95, 95)),
+            ],
+            vec![
+                Value::integer(1),
+                Value::integer(2),
+                Value::integer(3),
+                Value::integer(4),
+            ],
+            vec![]
+        ))
+    );
+
+    assert_eq!(run(source), Ok(None));
+}
+
+// #[test]
+// fn if_else_nested() {
+//     let source = r#"
+//         if 0 == 1 {
+//             if 0 == 2 {
+//                 1;
+//             } else {
+//                 2;
+//             }
+//         } else {
+//             if 0 == 3 {
+//                 3;
+//             } else {
+//                 4;
+//             }
+//         }"#;
+
+//     assert_eq!(
+//         parse(source),
+//         Ok(Chunk::with_data(
+//             None,
+//             vec![
+//                 (
+//                     *Instruction::equal(true, 0, 1)
+//                         .set_b_is_constant()
+//                         .set_c_is_constant(),
+//                     Span(14, 16)
+//                 ),
+//                 (Instruction::jump(7, true), Span(14, 16)),
+//                 (
+//                     *Instruction::equal(true, 0, 2)
+//                         .set_b_is_constant()
+//                         .set_c_is_constant(),
+//                     Span(38, 41)
+//                 ),
+//                 (Instruction::jump(3, true), Span(38, 41)),
+//                 (Instruction::load_constant(0, 1, false), Span(61, 62)),
+//                 (Instruction::jump(1, true1), Span(95, 95)),
+//                 (
+//                     *Instruction::equal(true, 0, 3)
+//                         .set_b_is_constant()
+//                         .set_c_is_constant(),
+//                     Span(77, 79)
+//                 ),
+//                 (Instruction::jump(3, true), Span(77, 79)),
+//                 (Instruction::load_constant(0, 2, false), Span(94, 95)),
+//                 (Instruction::jump(1, true1), Span(95, 95)),
+//                 (Instruction::load_constant(0, 3, false), Span(114, 115)),
+//                 (Instruction::jump(1, true1), Span(95, 95)),
+//                 (Instruction::load_constant(0, 4, false), Span(134, 135)),
+//                 (Instruction::r#return(true), Span(146, 146)),
+//             ],
+//             vec![
+//                 Value::integer(0),
+//                 Value::integer(1),
+//                 Value::integer(0),
+//                 Value::integer(2),
+//                 Value::integer(1),
+//                 Value::integer(0),
+//                 Value::integer(3),
+//                 Value::integer(3),
+//                 Value::integer(4)
+//             ],
+//             vec![]
+//         ))
+//     );
+
+//     assert_eq!(run(source), Ok(Some(Value::integer(4))));
+// }
+
+#[test]
+fn if_else_false() {
+    let source = "if 1 == 2 { panic() } else { 42 }";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::equal(true, 0, 1)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(5, 7)
+                ),
+                (Instruction::jump(1, true), Span(10, 11)),
+                (
+                    Instruction::call_native(0, NativeFunction::Panic, 0),
+                    Span(12, 19)
+                ),
+                (Instruction::load_constant(1, 2, true), Span(29, 31)),
+                (Instruction::r#move(1, 0), Span(33, 33)),
+                (Instruction::r#return(true), Span(33, 33)),
+            ],
+            vec![Value::integer(1), Value::integer(2), Value::integer(42)],
+            vec![]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(42))));
+}
+
+#[test]
+fn if_else_true() {
+    let source = "if 1 == 1 { 42 } else { panic() }";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::equal(true, 0, 0)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(5, 7)
+                ),
+                (Instruction::jump(1, true), Span(10, 11)),
+                (Instruction::load_constant(0, 1, true), Span(12, 14)),
+                (
+                    Instruction::call_native(1, NativeFunction::Panic, 0),
+                    Span(24, 31)
+                ),
+                (Instruction::r#move(1, 0), Span(33, 33)),
+                (Instruction::r#return(true), Span(33, 33))
+            ],
+            vec![Value::integer(1), Value::integer(42)],
+            vec![]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(42))));
+}
+
+#[test]
+fn if_false() {
+    let source = "if 1 == 2 { 2 }";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::equal(true, 0, 1)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(5, 7)
+                ),
+                (Instruction::jump(1, true), Span(10, 11)),
+                (Instruction::load_constant(0, 1, false), Span(12, 13)),
+                (Instruction::r#return(false), Span(15, 15))
+            ],
+            vec![Value::integer(1), Value::integer(2)],
+            vec![]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(None));
+}
+
+#[test]
+fn if_true() {
+    let source = "if 1 == 1 { 2 }";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::equal(true, 0, 0)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(5, 7)
+                ),
+                (Instruction::jump(1, true), Span(10, 11)),
+                (Instruction::load_constant(0, 1, false), Span(12, 13)),
+                (Instruction::r#return(false), Span(15, 15))
+            ],
+            vec![Value::integer(1), Value::integer(2)],
+            vec![]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(None));
+}

dust-lang/tests/functions.rs

@@ -0,0 +1,126 @@
+use dust_lang::*;
+
+#[test]
+fn function() {
+    let source = "fn(a: int, b: int) -> int { a + b }";
+
+    assert_eq!(
+        run(source),
+        Ok(Some(Value::function(
+            Chunk::with_data(
+                None,
+                vec![
+                    (Instruction::add(2, 0, 1), Span(30, 31)),
+                    (Instruction::r#return(true), Span(35, 35)),
+                ],
+                vec![Value::string("a"), Value::string("b"),],
+                vec![
+                    Local::new(0, Some(Type::Integer), false, Scope::default(), 0),
+                    Local::new(1, Some(Type::Integer), false, Scope::default(), 1)
+                ]
+            ),
+            FunctionType {
+                type_parameters: None,
+                value_parameters: Some(vec![(0, Type::Integer), (1, Type::Integer)]),
+                return_type: Some(Box::new(Type::Integer)),
+            }
+        )))
+    );
+}
+
+#[test]
+fn function_call() {
+    let source = "fn(a: int, b: int) -> int { a + b }(1, 2)";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_constant(0, 0, false), Span(0, 36)),
+                (Instruction::load_constant(1, 1, false), Span(36, 37)),
+                (Instruction::load_constant(2, 2, false), Span(39, 40)),
+                (Instruction::call(3, 0, 2), Span(35, 41)),
+                (Instruction::r#return(true), Span(41, 41)),
+            ],
+            vec![
+                Value::function(
+                    Chunk::with_data(
+                        None,
+                        vec![
+                            (Instruction::add(2, 0, 1), Span(30, 31)),
+                            (Instruction::r#return(true), Span(35, 36)),
+                        ],
+                        vec![Value::string("a"), Value::string("b"),],
+                        vec![
+                            Local::new(0, Some(Type::Integer), false, Scope::default(), 0),
+                            Local::new(1, Some(Type::Integer), false, Scope::default(), 1)
+                        ]
+                    ),
+                    FunctionType {
+                        type_parameters: None,
+                        value_parameters: Some(vec![(0, Type::Integer), (1, Type::Integer)]),
+                        return_type: Some(Box::new(Type::Integer)),
+                    }
+                ),
+                Value::integer(1),
+                Value::integer(2)
+            ],
+            vec![]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(3))));
+}
+
+#[test]
+fn function_declaration() {
+    let source = "fn add (a: int, b: int) -> int { a + b }";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_constant(0, 1, false), Span(0, 40)),
+                (Instruction::define_local(0, 0, false), Span(3, 6)),
+                (Instruction::r#return(false), Span(40, 40))
+            ],
+            vec![
+                Value::string("add"),
+                Value::function(
+                    Chunk::with_data(
+                        None,
+                        vec![
+                            (Instruction::add(2, 0, 1), Span(35, 36)),
+                            (Instruction::r#return(true), Span(40, 40)),
+                        ],
+                        vec![Value::string("a"), Value::string("b")],
+                        vec![
+                            Local::new(0, Some(Type::Integer), false, Scope::default(), 0),
+                            Local::new(1, Some(Type::Integer), false, Scope::default(), 1)
+                        ]
+                    ),
+                    FunctionType {
+                        type_parameters: None,
+                        value_parameters: Some(vec![(0, Type::Integer), (1, Type::Integer)]),
+                        return_type: Some(Box::new(Type::Integer)),
+                    },
+                )
+            ],
+            vec![Local::new(
+                0,
+                Some(Type::Function(FunctionType {
+                    type_parameters: None,
+                    value_parameters: Some(vec![(0, Type::Integer), (1, Type::Integer)]),
+                    return_type: Some(Box::new(Type::Integer)),
+                })),
+                false,
+                Scope::default(),
+                0
+            ),],
+        )),
+    );
+
+    assert_eq!(run(source), Ok(None));
+}

dust-lang/tests/lists.rs

@@ -0,0 +1,127 @@
+use dust_lang::*;
+
+#[test]
+fn empty_list() {
+    let source = "[]";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_list(0, 0), Span(0, 2)),
+                (Instruction::r#return(true), Span(2, 2)),
+            ],
+            vec![],
+            vec![]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::abstract_list(0, 0, Type::Any))));
+}
+
+#[test]
+fn list() {
+    let source = "[1, 2, 3]";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_constant(0, 0, false), Span(1, 2)),
+                (Instruction::load_constant(1, 1, false), Span(4, 5)),
+                (Instruction::load_constant(2, 2, false), Span(7, 8)),
+                (Instruction::load_list(3, 0), Span(0, 9)),
+                (Instruction::r#return(true), Span(9, 9)),
+            ],
+            vec![Value::integer(1), Value::integer(2), Value::integer(3)],
+            vec![]
+        )),
+    );
+
+    assert_eq!(
+        run(source),
+        Ok(Some(Value::abstract_list(0, 3, Type::Integer)))
+    );
+}
+
+#[test]
+fn list_with_complex_expression() {
+    let source = "[1, 2 + 3 - 4 * 5]";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_constant(0, 0, false), Span(1, 2)),
+                (
+                    *Instruction::add(1, 1, 2)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(6, 7)
+                ),
+                (
+                    *Instruction::multiply(2, 3, 4)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(14, 15)
+                ),
+                (Instruction::subtract(3, 1, 2), Span(10, 11)),
+                (Instruction::close(1, 3), Span(17, 18)),
+                (Instruction::load_list(4, 0), Span(0, 18)),
+                (Instruction::r#return(true), Span(18, 18)),
+            ],
+            vec![
+                Value::integer(1),
+                Value::integer(2),
+                Value::integer(3),
+                Value::integer(4),
+                Value::integer(5)
+            ],
+            vec![]
+        )),
+    );
+
+    assert_eq!(
+        run(source),
+        Ok(Some(Value::abstract_list(0, 4, Type::Integer)))
+    );
+}
+
+#[test]
+fn list_with_simple_expression() {
+    let source = "[1, 2 + 3, 4]";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_constant(0, 0, false), Span(1, 2)),
+                (
+                    *Instruction::add(1, 1, 2)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(6, 7)
+                ),
+                (Instruction::load_constant(2, 3, false), Span(11, 12)),
+                (Instruction::load_list(3, 0), Span(0, 13)),
+                (Instruction::r#return(true), Span(13, 13)),
+            ],
+            vec![
+                Value::integer(1),
+                Value::integer(2),
+                Value::integer(3),
+                Value::integer(4),
+            ],
+            vec![]
+        )),
+    );
+
+    assert_eq!(
+        run(source),
+        Ok(Some(Value::abstract_list(0, 3, Type::Integer)))
+    );
+}

dust-lang/tests/logic.rs

@@ -0,0 +1,77 @@
+use dust_lang::*;
+
+#[test]
+fn and() {
+    let source = "true && false";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_boolean(0, true, false), Span(0, 4)),
+                (Instruction::test(0, false), Span(5, 7)),
+                (Instruction::jump(1, true), Span(5, 7)),
+                (Instruction::load_boolean(1, false, false), Span(8, 13)),
+                (Instruction::r#return(true), Span(13, 13)),
+            ],
+            vec![],
+            vec![]
+        ))
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::boolean(false))));
+}
+
+#[test]
+fn or() {
+    let source = "true || false";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_boolean(0, true, false), Span(0, 4)),
+                (Instruction::test(0, true), Span(5, 7)),
+                (Instruction::jump(1, true), Span(5, 7)),
+                (Instruction::load_boolean(1, false, false), Span(8, 13)),
+                (Instruction::r#return(true), Span(13, 13)),
+            ],
+            vec![],
+            vec![]
+        ))
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::boolean(true))));
+}
+
+#[test]
+fn variable_and() {
+    let source = "let a = true; let b = false; a && b";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_boolean(0, true, false), Span(8, 12)),
+                (Instruction::define_local(0, 0, false), Span(4, 5)),
+                (Instruction::load_boolean(1, false, false), Span(22, 27)),
+                (Instruction::define_local(1, 1, false), Span(18, 19)),
+                (Instruction::get_local(2, 0), Span(29, 30)),
+                (Instruction::test(2, false), Span(31, 33)),
+                (Instruction::jump(1, true), Span(31, 33)),
+                (Instruction::get_local(3, 1), Span(34, 35)),
+                (Instruction::r#return(true), Span(35, 35)),
+            ],
+            vec![Value::string("a"), Value::string("b"),],
+            vec![
+                Local::new(0, None, false, Scope::default(), 0),
+                Local::new(1, None, false, Scope::default(), 1),
+            ]
+        ))
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::boolean(false))));
+}

dust-lang/tests/loops.rs

@@ -0,0 +1,35 @@
+use dust_lang::*;
+
+#[test]
+fn r#while() {
+    let source = "let mut x = 0; while x < 5 { x = x + 1 } x";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_constant(0, 0, false), Span(12, 13)),
+                (Instruction::define_local(0, 0, true), Span(8, 9)),
+                (
+                    *Instruction::less(true, 0, 2).set_c_is_constant(),
+                    Span(23, 24)
+                ),
+                (Instruction::jump(2, true), Span(41, 42)),
+                (*Instruction::add(0, 0, 3).set_c_is_constant(), Span(39, 40)),
+                (Instruction::jump(3, false), Span(41, 42)),
+                (Instruction::get_local(1, 0), Span(41, 42)),
+                (Instruction::r#return(true), Span(42, 42)),
+            ],
+            vec![
+                Value::integer(0),
+                Value::string("x"),
+                Value::integer(5),
+                Value::integer(1),
+            ],
+            vec![Local::new(1, None, true, Scope::default(), 0),]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(5))));
+}

dust-lang/tests/math.rs

@@ -0,0 +1,324 @@
+use dust_lang::*;
+
+#[test]
+fn add() {
+    let source = "1 + 2";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::add(0, 0, 1)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(2, 3)
+                ),
+                (Instruction::r#return(true), Span(5, 5))
+            ],
+            vec![Value::integer(1), Value::integer(2)],
+            vec![]
+        ))
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(3))));
+}
+
+#[test]
+fn add_assign() {
+    let source = "let mut a = 1; a += 2; a";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_constant(0, 0, false), Span(12, 13)),
+                (Instruction::define_local(0, 0, true), Span(8, 9)),
+                (*Instruction::add(0, 0, 2).set_c_is_constant(), Span(17, 19)),
+                (Instruction::get_local(1, 0), Span(23, 24)),
+                (Instruction::r#return(true), Span(24, 24))
+            ],
+            vec![Value::integer(1), Value::string("a"), Value::integer(2)],
+            vec![Local::new(1, None, true, Scope::default(), 0)]
+        ))
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(3))));
+}
+
+#[test]
+fn add_assign_expects_mutable_variable() {
+    let source = "1 += 2";
+
+    assert_eq!(
+        compile(source),
+        Err(DustError::Compile {
+            error: CompileError::ExpectedMutableVariable {
+                found: Token::Integer("1").to_owned(),
+                position: Span(0, 1)
+            },
+            source
+        })
+    );
+}
+
+// #[test]
+// fn add_expects_integer_float_or_string() {
+//     let source = "true + false";
+
+//     assert_eq!(
+//         parse(source),
+//         Err(DustError::Parse {
+//             error: ParseError::ExpectedIntegerFloatOrString {
+//                 found: Token::True,
+//                 position: Span(0, 3)
+//             },
+//             source
+//         })
+//     );
+// }
+
+#[test]
+fn divide() {
+    let source = "2 / 2";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::divide(0, 0, 0)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(2, 3)
+                ),
+                (Instruction::r#return(true), Span(5, 5))
+            ],
+            vec![Value::integer(2)],
+            vec![]
+        ))
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(1))));
+}
+
+#[test]
+fn divide_assign() {
+    let source = "let mut a = 2; a /= 2; a";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_constant(0, 0, false), Span(12, 13)),
+                (Instruction::define_local(0, 0, true), Span(8, 9)),
+                (
+                    *Instruction::divide(0, 0, 0).set_c_is_constant(),
+                    Span(17, 19)
+                ),
+                (Instruction::get_local(1, 0), Span(23, 24)),
+                (Instruction::r#return(true), Span(24, 24))
+            ],
+            vec![Value::integer(2), Value::string("a")],
+            vec![Local::new(1, None, true, Scope::default(), 0)]
+        ))
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(1))));
+}
+
+#[test]
+fn divide_assign_expects_mutable_variable() {
+    let source = "1 -= 2";
+
+    assert_eq!(
+        compile(source),
+        Err(DustError::Compile {
+            error: CompileError::ExpectedMutableVariable {
+                found: Token::Integer("1").to_owned(),
+                position: Span(0, 1)
+            },
+            source
+        })
+    );
+}
+
+#[test]
+fn math_operator_precedence() {
+    let source = "1 + 2 - 3 * 4 / 5";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::add(0, 0, 1)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(2, 3)
+                ),
+                (
+                    *Instruction::multiply(1, 2, 3)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(10, 11)
+                ),
+                (
+                    *Instruction::divide(2, 1, 4).set_c_is_constant(),
+                    Span(14, 15)
+                ),
+                (Instruction::subtract(3, 0, 2), Span(6, 7)),
+                (Instruction::r#return(true), Span(17, 17)),
+            ],
+            vec![
+                Value::integer(1),
+                Value::integer(2),
+                Value::integer(3),
+                Value::integer(4),
+                Value::integer(5),
+            ],
+            vec![]
+        ))
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(1))));
+}
+
+#[test]
+fn multiply() {
+    let source = "1 * 2";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::multiply(0, 0, 1)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(2, 3)
+                ),
+                (Instruction::r#return(true), Span(5, 5)),
+            ],
+            vec![Value::integer(1), Value::integer(2)],
+            vec![]
+        ))
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(2))));
+}
+
+#[test]
+fn multiply_assign() {
+    let source = "let mut a = 2; a *= 3 a";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_constant(0, 0, false), Span(12, 13)),
+                (Instruction::define_local(0, 0, true), Span(8, 9)),
+                (
+                    *Instruction::multiply(0, 0, 2).set_c_is_constant(),
+                    Span(17, 19)
+                ),
+                (Instruction::get_local(1, 0), Span(22, 23)),
+                (Instruction::r#return(true), Span(23, 23))
+            ],
+            vec![Value::integer(2), Value::string("a"), Value::integer(3)],
+            vec![Local::new(1, None, true, Scope::default(), 0),]
+        ))
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(6))));
+}
+
+#[test]
+fn multiply_assign_expects_mutable_variable() {
+    let source = "1 *= 2";
+
+    assert_eq!(
+        compile(source),
+        Err(DustError::Compile {
+            error: CompileError::ExpectedMutableVariable {
+                found: Token::Integer("1").to_owned(),
+                position: Span(0, 1)
+            },
+            source
+        })
+    );
+}
+
+#[test]
+fn subtract() {
+    let source = "1 - 2";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (
+                    *Instruction::subtract(0, 0, 1)
+                        .set_b_is_constant()
+                        .set_c_is_constant(),
+                    Span(2, 3)
+                ),
+                (Instruction::r#return(true), Span(5, 5)),
+            ],
+            vec![Value::integer(1), Value::integer(2)],
+            vec![]
+        ))
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(-1))));
+}
+
+#[test]
+fn subtract_assign() {
+    let source = "let mut x = 42; x -= 2; x";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_constant(0, 0, false), Span(12, 14)),
+                (Instruction::define_local(0, 0, true), Span(8, 9)),
+                (
+                    *Instruction::subtract(0, 0, 2).set_c_is_constant(),
+                    Span(18, 20)
+                ),
+                (Instruction::get_local(1, 0), Span(24, 25)),
+                (Instruction::r#return(true), Span(25, 25)),
+            ],
+            vec![Value::integer(42), Value::string("x"), Value::integer(2)],
+            vec![Local::new(1, None, true, Scope::default(), 0)]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(40))));
+}
+
+#[test]
+fn subtract_assign_expects_mutable_variable() {
+    let source = "1 -= 2";
+
+    assert_eq!(
+        compile(source),
+        Err(DustError::Compile {
+            error: CompileError::ExpectedMutableVariable {
+                found: Token::Integer("1").to_owned(),
+                position: Span(0, 1)
+            },
+            source
+        })
+    );
+}

dust-lang/tests/native_functions.rs

@@ -0,0 +1,59 @@
+use dust_lang::*;
+
+#[test]
+fn panic() {
+    let source = "panic(\"Goodbye world!\", 42)";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_constant(0, 0, false), Span(6, 22)),
+                (Instruction::load_constant(1, 1, false), Span(24, 26)),
+                (
+                    Instruction::call_native(2, NativeFunction::Panic, 2),
+                    Span(0, 27)
+                ),
+                (Instruction::r#return(true), Span(27, 27))
+            ],
+            vec![Value::string("Goodbye world!"), Value::integer(42)],
+            vec![]
+        )),
+    );
+
+    assert_eq!(
+        run(source),
+        Err(DustError::Runtime {
+            error: VmError::NativeFunction(NativeFunctionError::Panic {
+                message: Some("Goodbye world! 42".to_string()),
+                position: Span(0, 27)
+            }),
+            source
+        })
+    )
+}
+
+#[test]
+fn to_string() {
+    let source = "to_string(42)";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_constant(0, 0, false), Span(10, 12)),
+                (
+                    Instruction::call_native(1, NativeFunction::ToString, 1),
+                    Span(0, 13)
+                ),
+                (Instruction::r#return(true), Span(13, 13))
+            ],
+            vec![Value::integer(42)],
+            vec![]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::string("42"))))
+}

dust-lang/tests/scopes.rs

@@ -0,0 +1,244 @@
+use dust_lang::*;
+
+#[test]
+fn allow_access_to_parent_scope() {
+    let source = r#"
+        let x = 1;
+        {
+            x
+        }
+    "#;
+
+    assert_eq!(run(source), Ok(Some(Value::integer(1))));
+}
+
+#[test]
+fn block_scope() {
+    let source = "
+        let a = 0;
+        {
+            let b = 42;
+            {
+                let c = 1;
+            }
+            let d = 2;
+        }
+        let e = 1;
+    ";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_constant(0, 0, false), Span(17, 18)),
+                (Instruction::define_local(0, 0, false), Span(13, 14)),
+                (Instruction::load_constant(1, 2, false), Span(50, 52)),
+                (Instruction::define_local(1, 1, false), Span(46, 47)),
+                (Instruction::load_constant(2, 4, false), Span(92, 93)),
+                (Instruction::define_local(2, 2, false), Span(88, 89)),
+                (Instruction::load_constant(3, 6, false), Span(129, 130)),
+                (Instruction::define_local(3, 3, false), Span(125, 126)),
+                (Instruction::load_constant(4, 4, false), Span(158, 159)),
+                (Instruction::define_local(4, 4, false), Span(154, 155)),
+                (Instruction::r#return(false), Span(165, 165))
+            ],
+            vec![
+                Value::integer(0),
+                Value::string("a"),
+                Value::integer(42),
+                Value::string("b"),
+                Value::integer(1),
+                Value::string("c"),
+                Value::integer(2),
+                Value::string("d"),
+                Value::string("e"),
+            ],
+            vec![
+                Local::new(1, None, false, Scope::new(0, 0), 0),
+                Local::new(3, None, false, Scope::new(1, 1), 1),
+                Local::new(5, None, false, Scope::new(2, 2), 2),
+                Local::new(7, None, false, Scope::new(1, 1), 3),
+                Local::new(8, None, false, Scope::new(0, 0), 4),
+            ]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(None));
+}
+
+#[test]
+fn multiple_block_scopes() {
+    let source = "
+        let a = 0;
+        {
+            let b = 42;
+            {
+                let c = 1;
+            }
+            let d = 2;
+        }
+        let q = 42;
+        {
+            let b = 42;
+            {
+                let c = 1;
+            }
+            let d = 2;
+        }
+        let e = 1;
+    ";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_constant(0, 0, false), Span(17, 18)),
+                (Instruction::define_local(0, 0, false), Span(13, 14)),
+                (Instruction::load_constant(1, 2, false), Span(50, 52)),
+                (Instruction::define_local(1, 1, false), Span(46, 47)),
+                (Instruction::load_constant(2, 4, false), Span(92, 93)),
+                (Instruction::define_local(2, 2, false), Span(88, 89)),
+                (Instruction::load_constant(3, 6, false), Span(129, 130)),
+                (Instruction::define_local(3, 3, false), Span(125, 126)),
+                (Instruction::load_constant(4, 2, false), Span(158, 160)),
+                (Instruction::define_local(4, 4, false), Span(154, 155)),
+                (Instruction::load_constant(5, 2, false), Span(192, 194)),
+                (Instruction::define_local(5, 5, false), Span(188, 189)),
+                (Instruction::load_constant(6, 4, false), Span(234, 235)),
+                (Instruction::define_local(6, 6, false), Span(230, 231)),
+                (Instruction::load_constant(7, 6, false), Span(271, 272)),
+                (Instruction::define_local(7, 7, false), Span(267, 268)),
+                (Instruction::load_constant(8, 4, false), Span(300, 301)),
+                (Instruction::define_local(8, 8, false), Span(296, 297)),
+                (Instruction::r#return(false), Span(307, 307))
+            ],
+            vec![
+                Value::integer(0),
+                Value::string("a"),
+                Value::integer(42),
+                Value::string("b"),
+                Value::integer(1),
+                Value::string("c"),
+                Value::integer(2),
+                Value::string("d"),
+                Value::string("q"),
+                Value::string("e"),
+            ],
+            vec![
+                Local::new(1, None, false, Scope::new(0, 0), 0),
+                Local::new(3, None, false, Scope::new(1, 1), 1),
+                Local::new(5, None, false, Scope::new(2, 2), 2),
+                Local::new(7, None, false, Scope::new(1, 1), 3),
+                Local::new(8, None, false, Scope::new(0, 0), 4),
+                Local::new(3, None, false, Scope::new(1, 3), 5),
+                Local::new(5, None, false, Scope::new(2, 4), 6),
+                Local::new(7, None, false, Scope::new(1, 3), 7),
+                Local::new(9, None, false, Scope::new(0, 0), 8),
+            ]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(None));
+}
+
+#[test]
+fn disallow_access_to_child_scope() {
+    let source = r#"
+        {
+            let x = 1;
+        }
+        x
+    "#;
+
+    assert_eq!(
+        run(source),
+        Err(DustError::Compile {
+            error: CompileError::VariableOutOfScope {
+                identifier: "x".to_string(),
+                position: Span(52, 53),
+                variable_scope: Scope::new(1, 1),
+                access_scope: Scope::new(0, 0),
+            },
+            source
+        })
+    );
+}
+
+#[test]
+fn disallow_access_to_child_scope_nested() {
+    let source = r#"
+        {
+            {
+                let x = 1;
+            }
+            x
+        }
+    "#;
+
+    assert_eq!(
+        run(source),
+        Err(DustError::Compile {
+            error: CompileError::VariableOutOfScope {
+                identifier: "x".to_string(),
+                position: Span(78, 79),
+                variable_scope: Scope::new(2, 2),
+                access_scope: Scope::new(1, 1),
+            },
+            source
+        })
+    );
+}
+
+#[test]
+fn disallow_access_to_sibling_scope() {
+    let source = r#"
+        {
+            let x = 1;
+        }
+        {
+            x
+        }
+    "#;
+
+    assert_eq!(
+        run(source),
+        Err(DustError::Compile {
+            error: CompileError::VariableOutOfScope {
+                identifier: "x".to_string(),
+                variable_scope: Scope::new(1, 1),
+                access_scope: Scope::new(1, 2),
+                position: Span(66, 67),
+            },
+            source
+        })
+    );
+}
+
+#[test]
+fn disallow_access_to_sibling_scope_nested() {
+    let source = r#"
+        {
+            {
+                let x = 1;
+            }
+            {
+                x
+            }
+        }
+    "#;
+
+    assert_eq!(
+        run(source),
+        Err(DustError::Compile {
+            error: CompileError::VariableOutOfScope {
+                identifier: "x".to_string(),
+                variable_scope: Scope::new(2, 2),
+                access_scope: Scope::new(2, 3),
+                position: Span(96, 97),
+            },
+            source
+        })
+    );
+}

dust-lang/tests/unary_operations.rs

@@ -0,0 +1,42 @@
+use dust_lang::*;
+
+#[test]
+fn negate() {
+    let source = "-(42)";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (*Instruction::negate(0, 0).set_b_is_constant(), Span(0, 1)),
+                (Instruction::r#return(true), Span(5, 5)),
+            ],
+            vec![Value::integer(42)],
+            vec![]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(-42))));
+}
+
+#[test]
+fn not() {
+    let source = "!true";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_boolean(0, true, false), Span(1, 5)),
+                (Instruction::not(1, 0), Span(0, 1)),
+                (Instruction::r#return(true), Span(5, 5)),
+            ],
+            vec![],
+            vec![]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::boolean(false))));
+}

dust-lang/tests/variables.rs

@@ -0,0 +1,63 @@
+use dust_lang::*;
+
+#[test]
+fn define_local() {
+    let source = "let x = 42;";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_constant(0, 0, false), Span(8, 10)),
+                (Instruction::define_local(0, 0, false), Span(4, 5)),
+                (Instruction::r#return(false), Span(11, 11))
+            ],
+            vec![Value::integer(42), Value::string("x")],
+            vec![Local::new(1, None, false, Scope::default(), 0)]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(None));
+}
+
+#[test]
+fn let_statement_expects_identifier() {
+    let source = "let 1 = 2";
+
+    assert_eq!(
+        compile(source),
+        Err(DustError::Compile {
+            error: CompileError::ExpectedToken {
+                expected: TokenKind::Identifier,
+                found: Token::Integer("1").to_owned(),
+                position: Span(4, 5)
+            },
+            source
+        })
+    );
+}
+
+#[test]
+fn set_local() {
+    let source = "let mut x = 41; x = 42; x";
+
+    assert_eq!(
+        compile(source),
+        Ok(Chunk::with_data(
+            None,
+            vec![
+                (Instruction::load_constant(0, 0, false), Span(12, 14)),
+                (Instruction::define_local(0, 0, true), Span(8, 9)),
+                (Instruction::load_constant(1, 2, false), Span(20, 22)),
+                (Instruction::set_local(1, 0), Span(16, 17)),
+                (Instruction::get_local(2, 0), Span(24, 25)),
+                (Instruction::r#return(true), Span(25, 25)),
+            ],
+            vec![Value::integer(41), Value::string("x"), Value::integer(42)],
+            vec![Local::new(1, None, true, Scope::default(), 0)]
+        )),
+    );
+
+    assert_eq!(run(source), Ok(Some(Value::integer(42))));
+}

dust-shell/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "dust-shell"
+version = "0.1.0"
+authors.workspace = true
+edition.workspace = true
+license.workspace = true
+readme.workspace = true
+repository.workspace = true
+
+[dependencies]
+clap = { version = "4.5.14", features = ["derive"] }
+colored = "2.1.0"
+dust-lang = { path = "../dust-lang" }
+env_logger = "0.11.5"
+log = "0.4.22"

dust-shell/src/main.rs

@@ -0,0 +1,138 @@
+use std::{fs::read_to_string, io::Write};
+
+use clap::Parser;
+use colored::Colorize;
+use dust_lang::{compile, format, run};
+use log::{Level, LevelFilter};
+
+#[derive(Parser)]
+struct Cli {
+    /// Source code sent via command line
+    #[arg(short, long)]
+    command: Option<String>,
+
+    /// Whether to output formatted source code
+    #[arg(short, long)]
+    format: bool,
+
+    /// Whether to output line numbers in formatted source code
+    #[arg(long)]
+    format_line_numbers: Option<bool>,
+
+    /// Whether to output colors in formatted source code
+    #[arg(long)]
+    format_colored: Option<bool>,
+
+    /// Whether to output the disassembled chunk
+    #[arg(short, long)]
+    parse: bool,
+
+    /// Whether to style the disassembled chunk
+    #[arg(long)]
+    style_disassembly: Option<bool>,
+
+    /// Log level
+    #[arg(short, long)]
+    log: Option<LevelFilter>,
+
+    /// Path to a source code file
+    path: Option<String>,
+}
+
+fn main() {
+    let args = Cli::parse();
+    let mut logger = env_logger::builder();
+
+    logger.format(|buf, record| {
+        let level_display = match record.level() {
+            Level::Info => "INFO".bold().white(),
+            Level::Debug => "DEBUG".bold().blue(),
+            Level::Warn => "WARN".bold().yellow(),
+            Level::Error => "ERROR".bold().red(),
+            Level::Trace => "TRACE".bold().purple(),
+        };
+        let module = record
+            .module_path()
+            .map(|path| path.split("::").last().unwrap_or(path))
+            .unwrap_or("unknown")
+            .dimmed();
+        let display = format!("{level_display:5} {module:^6} {args}", args = record.args());
+
+        writeln!(buf, "{display}")
+    });
+
+    if let Some(level) = args.log {
+        logger.filter_level(level).init();
+    } else {
+        logger.parse_env("DUST_LOG").init();
+    }
+
+    let source = if let Some(path) = &args.path {
+        &read_to_string(path).expect("Failed to read file")
+    } else if let Some(command) = &args.command {
+        command
+    } else {
+        eprintln!("No input provided");
+
+        return;
+    };
+
+    if args.format {
+        let line_numbers = args.format_line_numbers.unwrap_or(true);
+        let colored = args.format_colored.unwrap_or(true);
+
+        log::info!("Formatting source");
+
+        match format(source, line_numbers, colored) {
+            Ok(formatted) => println!("{}", formatted),
+            Err(error) => {
+                eprintln!("{}", error.report());
+            }
+        }
+    }
+
+    if args.parse {
+        let styled = args.style_disassembly.unwrap_or(true);
+
+        log::info!("Parsing source");
+
+        match compile(source) {
+            Ok(chunk) => {
+                let disassembly = chunk
+                    .disassembler()
+                    .source(source)
+                    .styled(styled)
+                    .disassemble();
+
+                println!("{}", disassembly);
+            }
+            Err(error) => {
+                eprintln!("{}", error.report());
+            }
+        }
+    }
+
+    if args.format || args.parse {
+        return;
+    }
+
+    match run(source) {
+        Ok(Some(value)) => println!("{}", value),
+        Ok(None) => {}
+        Err(error) => {
+            eprintln!("{}", error.report());
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use clap::CommandFactory;
+
+    use super::*;
+
+    #[test]
+    fn verify_cli() {
+        Cli::command().debug_assert();
+    }
+}

examples/assets/count.js

@@ -0,0 +1,5 @@
+var i = 0;
+
+while (i < 10000) {
+  i++;
+}

examples/assets/data.json

@@ -0,0 +1,6 @@
+[
+    { "name": "Sammy", "type": "shark", "clams": 5 },
+    { "name": "Bubbles", "type": "orca", "clams": 3 },
+    { "name": "Splish", "type": "dolphin", "clams": 2 },
+    { "name": "Splash", "type": "dolphin", "clams": 2 }
+]

examples/assets/fibonacci.js

@@ -0,0 +1,11 @@
+function fib(n) {
+  if (n <= 0) {
+    return 0;
+  } else if (n === 1) {
+    return 1;
+  } else {
+    return fib(n - 1) + fib(n - 2);
+  }
+}
+
+console.log(fib(25));

examples/async.ds

@@ -1,19 +0,0 @@
-create_random_numbers = (count <int>) <none> {
-	numbers = []
-
-	while length(numbers) < count {
-		numbers += random:integer()
-	}
-
-	output("Made " + length(numbers) + " numbers.")
-}
-
-output("This will print first.")
-
-async {
-	create_random_numbers(1000)
- 	create_random_numbers(100)
-	create_random_numbers(10)
-}
-
-output("This will print last.")

examples/async_commands.ds

@@ -1,17 +0,0 @@
-async {
-	{
-		^echo 'Starting 1...'
-		^sleep 1
-		^echo 'Finished 1.'
-	}
-	{
-		^echo 'Starting 2...'
-		^sleep 2
-		^echo 'Finished 2.'
-	}
-	{
-		^echo 'Starting 3...'
-		^sleep 3
-		^echo 'Finished 3.'
-	}
-}

examples/async_count.ds

@@ -0,0 +1,21 @@
+count_slowly = fn (
+	multiplier: int,
+) {
+	i = 0
+
+	while i < 10 {
+		sleep_time = i * multiplier;
+
+		thread.sleep(sleep_time)
+		thread.write_line(i as str)
+
+		i += 1
+	}
+}
+
+async {
+	count_slowly(50)
+	count_slowly(100)
+	count_slowly(200)
+	count_slowly(250)
+}

examples/async_download.ds

@@ -1,20 +0,0 @@
-cast_len = 0
-characters_len = 0
-episodes_len = 0
-
-async {	
-	{
-		cast = download("https://api.sampleapis.com/futurama/cast")
-		cast_len = length(from_json(cast))		
-	}
-	{
-		characters = download("https://api.sampleapis.com/futurama/characters")	
-		characters_len = length(from_json(characters))
-	}
-	{
-		episodes = download("https://api.sampleapis.com/futurama/episodes")
-		episodes_len = length(from_json(episodes))
-	}
-}
-
-output ([cast_len, characters_len, episodes_len])

examples/clue_solver.ds

@@ -1,53 +0,0 @@
-cards = {
-	rooms = ['Library' 'Kitchen' 'Conservatory']
-	suspects = ['White' 'Green' 'Scarlett']
-	weapons = ['Rope' 'Lead_Pipe' 'Knife']
-}
-
-is_ready_to_solve = (cards <map>) <bool> {
-	(length(cards:suspects) == 1)
-	&& (length(cards:rooms) == 1)
-	&& (length(cards:weapons) == 1)
-}
-
-remove_card = (cards <map>, opponent_card <str>) <none> {
-	cards:rooms -= opponent_card
-	cards:suspects -= opponent_card
-	cards:weapons -= opponent_card
-}
-
-make_guess = (cards <map>, current_room <str>) <none> {
-	if is_ready_to_solve(cards) {
-		output(
-			'I accuse '
-			+ cards:suspects:0
-			+ ' in the ' 
-			+ cards:rooms:0  
-			+ ' with the ' 
-			+ cards:weapons:0 
-			+ '!'
-		)
-	} else {
-		output(
-			'I question '
-			+ random:from(cards:suspects)
-			+ ' in the '
-			+ current_room
-			+ ' with the '
-			+ random:from(cards:weapons)
-			+ '.'
-		)
-	}
-}
-
-take_turn = (cards <map>, opponent_card <str>, current_room <str>) <none> {
-	remove_card(cards opponent_card)
-	make_guess(cards current_room)
-}
-
-take_turn(cards 'Rope' 'Kitchen')
-take_turn(cards 'Library' 'Kitchen')
-take_turn(cards 'Conservatory' 'Kitchen')
-take_turn(cards 'White' 'Kitchen')
-take_turn(cards 'Green' 'Kitchen')
-take_turn(cards 'Knife' 'Kitchen')

examples/count.ds

@@ -0,0 +1,5 @@
+let mut i = 0;
+
+while i < 10000 {
+    i += 1;
+}

examples/download.ds

@@ -1,10 +0,0 @@
-raw_data = download("https://api.sampleapis.com/futurama/cast")
-cast_data = from_json(raw_data)
-
-names = []
-
-for cast_member in cast_data {
-	names += cast_member:name
-}
-
-assert_equal("Billy West", names:0)

examples/fibonacci.ds

@@ -1,9 +1,8 @@
-fib = (i <int>) <int> {
+fn fib (n: int) -> int {
-	if i <= 1 {
+    if n <= 0 { return 0 }
-		1
+    if n == 1 { return 1 }
-	} else {
+
-		fib(i - 1) + fib(i - 2)
+    fib(n - 1) + fib(n - 2)
-	}
 }
 
-fib(8)
+write_line(fib(25))

examples/fizzbuzz.ds

@@ -1,18 +1,20 @@
-count = 1
+let mut count = 1
 
 while count <= 15 {
-	divides_by_3 = count % 3 == 0
+	let divides_by_3 = count % 3 == 0
-	divides_by_5 = count % 5 == 0
+	let divides_by_5 = count % 5 == 0
 
-	if divides_by_3 && divides_by_5 { 
+	let output = if divides_by_3 && divides_by_5 {
-		output('fizzbuzz')
+		"fizzbuzz"
 	} else if divides_by_3 {
-		output('fizz')
+		"fizz"
 	} else if divides_by_5 {
-		output('buzz')
+		"buzz"
 	} else {
-		output(count)
+		to_string(count)
 	}
 
+	write_line(output)
+
 	count += 1
 }

examples/guessing_game.ds

@@ -0,0 +1,19 @@
+write_line("Guess the number.")
+
+let secret_number = random(0..100);
+
+loop {
+	write_line("Input your guess.")
+
+	let input = io.read_line();
+	let guess = int.parse(input);
+
+	if guess < secret_number {
+		io.write_line("Too low!")
+	} else if guess > secret_number {
+		io.write_line("Too high!")
+	} else {
+		io.write_line("You win!")
+		break
+	}
+}

examples/hello_world.ds

@@ -1 +1,6 @@
-output('Hello, world!')
+write_line("Hello, world!")
+write_line("Enter your name...")
+
+let name = read_line()
+
+write_line("Hello " + name + "!")

examples/jq_data.ds

@@ -1,12 +0,0 @@
-data = json:parse(fs:read_file('examples/assets/jq_data.json'))
-
-new_data = []
-
-for commit_data in data {	
-	new_data += {
-		message = commit_data:commit:message
-		name = commit_data:commit:committer:name
-	}
-}
-
-new_data

examples/json_length.ds

@@ -0,0 +1,4 @@
+input = fs.read_file('examples/assets/data.json')
+data = json.parse(input)
+
+length(data)

examples/random.ds

@@ -1,13 +0,0 @@
-stuff = [
-	random:integer()
-	random:integer()
-	random:integer()
-	random:float()
-	random:float()
-	random:float()
-	random:boolean()
-	random:boolean()
-	random:boolean()
-]
-
-random:from(stuff)

examples/sea_creatures.ds

@@ -1,19 +0,0 @@
-raw_data = fs:read_file('examples/assets/seaCreatures.json')
-sea_creatures = json:parse(raw_data)
-
-data = {
-	creatures = []
-	total_clams = 0
-	dolphin_clams = 0
-}
-
-for creature in sea_creatures {
-	data:creatures += creature:name
-	data:total_clams += creature:clams
-
-	if creature:type == 'dolphin' {
-		data:dolphin_clams += creature:clams
-	}
-}
-
-data

examples/type_inference.ds

@@ -0,0 +1,20 @@
+// This function returns its argument.
+foo = fn <T>(x: T) -> T { x }
+
+// Use turbofish to supply type information.
+bar = foo::<str>("hi")
+
+// Use type annotation
+baz: str = foo("hi")
+
+// The `json.parse` function takes a string and returns the specified type
+
+// Use turbofish
+x = json.parse::<int>("1")
+
+// Use type annotation
+x: int = json.parse("1")
+
+x: int = {
+	json.parse("1")
+}

scripts/bench.fish

@@ -1,35 +0,0 @@
-#!/usr/bin/fish
-# This script is has the following prerequisites (aside from fish):
-# - hyperfine
-# - dust (can be installed with "cargo install dust-lang")
-# - jq
-# - nodejs
-# - nushell
-# - dielectron.json (can be downloaded from https://opendata.cern.ch/record/304)
-
-hyperfine \
-      --shell none \
-      --parameter-list data_path examples/assets/seaCreatures.json \
-      --warmup 3 \
-      "dust -c 'length(json:parse(input))' -p {data_path}" \
-      "jq 'length' {data_path}" \
-      "node --eval \"require('node:fs').readFile('{data_path}', (err, data)=>{console.log(JSON.parse(data).length)})\"" \
-      "nu -c 'open {data_path} | length'"
-
-hyperfine \
-      --shell none \
-      --parameter-list data_path examples/assets/jq_data.json \
-      --warmup 3 \
-      "dust -c 'length(json:parse(input))' -p {data_path}" \
-      "jq 'length' {data_path}" \
-      "node --eval \"require('node:fs').readFile('{data_path}', (err, data)=>{console.log(JSON.parse(data).length)})\"" \
-      "nu -c 'open {data_path} | length'"
-
-hyperfine \
-      --shell none \
-      --parameter-list data_path dielectron.json \
-      --warmup 3 \
-      "dust -c 'length(json:parse(input))' -p {data_path}" \
-      "jq 'length' {data_path}" \
-      "node --eval \"require('node:fs').readFile('{data_path}', (err, data)=>{console.log(JSON.parse(data).length)})\"" \
-      "nu -c 'open {data_path} | length'"

scripts/build_debug.fish

@@ -1,8 +0,0 @@
-#!/usr/bin/fish
-# Build the project in debug mode.
-
-cd tree-sitter-dust/
-tree-sitter generate --debug-build --no-bindings
-
-cd ..
-cargo build

scripts/build_release.fish

@@ -1,8 +0,0 @@
-#!/bin/fish
-# Build the project in release mode.
-
-cd tree-sitter-dust/
-tree-sitter generate --no-bindings
-
-cd ..
-cargo build --release

scripts/test.fish

@@ -1,9 +0,0 @@
-#!/usr/bin/fish
-# Build the project in debug mode.
-
-cd tree-sitter-dust/
-tree-sitter generate --debug-build --no-bindings
-tree-sitter test
-
-cd ..
-cargo test

src/abstract_tree/as.rs

@@ -1,123 +0,0 @@
-use serde::{Deserialize, Serialize};
-use tree_sitter::Node;
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Expression, Format, List, SourcePosition, Type, Value,
-};
-
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct As {
-    expression: Expression,
-    r#type: Type,
-    position: SourcePosition,
-}
-
-impl AbstractTree for As {
-    fn from_syntax(node: Node, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("as", node)?;
-
-        let expression_node = node.child(0).unwrap();
-        let expression = Expression::from_syntax(expression_node, source, context)?;
-
-        let type_node = node.child(2).unwrap();
-        let r#type = Type::from_syntax(type_node, source, context)?;
-
-        Ok(As {
-            expression,
-            r#type,
-            position: SourcePosition::from(node.range()),
-        })
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        Ok(self.r#type.clone())
-    }
-
-    fn validate(&self, _source: &str, context: &Context) -> Result<(), ValidationError> {
-        let initial_type = self.expression.expected_type(context)?;
-
-        if let Type::List(item_type) = &self.r#type {
-            match &initial_type {
-                Type::List(expected_item_type) => {
-                    if !item_type.accepts(&expected_item_type) {
-                        return Err(ValidationError::TypeCheck {
-                            expected: self.r#type.clone(),
-                            actual: initial_type.clone(),
-                            position: self.position,
-                        });
-                    }
-                }
-                Type::String => {
-                    if let Type::String = item_type.as_ref() {
-                    } else {
-                        return Err(ValidationError::ConversionImpossible {
-                            initial_type,
-                            target_type: self.r#type.clone(),
-                        });
-                    }
-                }
-
-                Type::Any => {
-                    // Do no validation when converting from "any" to a list.
-                    // This effectively defers to runtime behavior, potentially
-                    // causing a runtime error.
-                }
-                _ => {
-                    return Err(ValidationError::ConversionImpossible {
-                        initial_type,
-                        target_type: self.r#type.clone(),
-                    })
-                }
-            }
-        }
-
-        Ok(())
-    }
-
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        let value = self.expression.run(source, context)?;
-        let converted_value = if let Type::List(_) = self.r#type {
-            match value {
-                Value::List(list) => Value::List(list),
-                Value::String(string) => {
-                    let chars = string
-                        .chars()
-                        .map(|char| Value::String(char.to_string()))
-                        .collect();
-
-                    Value::List(List::with_items(chars))
-                }
-                _ => {
-                    return Err(RuntimeError::ConversionImpossible {
-                        from: value.r#type()?,
-                        to: self.r#type.clone(),
-                        position: self.position.clone(),
-                    });
-                }
-            }
-        } else if let Type::Integer = self.r#type {
-            match value {
-                Value::Integer(integer) => Value::Integer(integer),
-                Value::Float(float) => Value::Integer(float as i64),
-                _ => {
-                    return Err(RuntimeError::ConversionImpossible {
-                        from: value.r#type()?,
-                        to: self.r#type.clone(),
-                        position: self.position.clone(),
-                    })
-                }
-            }
-        } else {
-            todo!()
-        };
-
-        Ok(converted_value)
-    }
-}
-
-impl Format for As {
-    fn format(&self, _output: &mut String, _indent_level: u8) {
-        todo!()
-    }
-}

src/abstract_tree/assignment.rs

@@ -1,182 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    context::Context,
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, AssignmentOperator, Format, Function, Identifier, SourcePosition, Statement,
-    SyntaxNode, Type, TypeSpecification, Value,
-};
-
-/// Variable assignment, including add-assign and subtract-assign operations.
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct Assignment {
-    identifier: Identifier,
-    type_specification: Option<TypeSpecification>,
-    operator: AssignmentOperator,
-    statement: Statement,
-    syntax_position: SourcePosition,
-}
-
-impl AbstractTree for Assignment {
-    fn from_syntax(
-        syntax_node: SyntaxNode,
-        source: &str,
-        context: &Context,
-    ) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("assignment", syntax_node)?;
-
-        let child_count = syntax_node.child_count();
-
-        let identifier_node = syntax_node.child(0).unwrap();
-        let identifier = Identifier::from_syntax(identifier_node, source, context)?;
-
-        let type_node = syntax_node.child(1).unwrap();
-        let type_specification = if type_node.kind() == "type_specification" {
-            Some(TypeSpecification::from_syntax(type_node, source, context)?)
-        } else {
-            None
-        };
-
-        let operator_node = syntax_node.child(child_count - 2).unwrap();
-        let operator = AssignmentOperator::from_syntax(operator_node, source, context)?;
-
-        let statement_node = syntax_node.child(child_count - 1).unwrap();
-        let statement = Statement::from_syntax(statement_node, source, context)?;
-
-        Ok(Assignment {
-            identifier,
-            type_specification,
-            operator,
-            statement,
-            syntax_position: syntax_node.range().into(),
-        })
-    }
-
-    fn validate(&self, source: &str, context: &Context) -> Result<(), ValidationError> {
-        if let AssignmentOperator::Equal = self.operator {
-            let r#type = if let Some(definition) = &self.type_specification {
-                definition.inner().clone()
-            } else {
-                self.statement.expected_type(context)?
-            };
-
-            context.set_type(self.identifier.clone(), r#type)?;
-        }
-
-        if let Some(type_specification) = &self.type_specification {
-            match self.operator {
-                AssignmentOperator::Equal => {
-                    let expected = type_specification.inner();
-                    let actual = self.statement.expected_type(context)?;
-
-                    if !expected.accepts(&actual) {
-                        return Err(ValidationError::TypeCheck {
-                            expected: expected.clone(),
-                            actual,
-                            position: self.syntax_position,
-                        });
-                    }
-                }
-                AssignmentOperator::PlusEqual => {
-                    if let Type::List(expected) = type_specification.inner() {
-                        let actual = self.identifier.expected_type(context)?;
-
-                        if !expected.accepts(&actual) {
-                            return Err(ValidationError::TypeCheck {
-                                expected: expected.as_ref().clone(),
-                                actual,
-                                position: self.syntax_position,
-                            });
-                        }
-                    } else {
-                        let expected = type_specification.inner();
-                        let actual = self.identifier.expected_type(context)?;
-
-                        if !expected.accepts(&actual) {
-                            return Err(ValidationError::TypeCheck {
-                                expected: expected.clone(),
-                                actual,
-                                position: self.syntax_position,
-                            });
-                        }
-                    }
-                }
-                AssignmentOperator::MinusEqual => todo!(),
-            }
-        } else {
-            match self.operator {
-                AssignmentOperator::Equal => {}
-                AssignmentOperator::PlusEqual => {
-                    if let Type::List(expected) = self.identifier.expected_type(context)? {
-                        let actual = self.statement.expected_type(context)?;
-
-                        if !expected.accepts(&actual) {
-                            return Err(ValidationError::TypeCheck {
-                                expected: expected.as_ref().clone(),
-                                actual,
-                                position: self.syntax_position,
-                            });
-                        }
-                    }
-                }
-                AssignmentOperator::MinusEqual => todo!(),
-            }
-        }
-
-        self.statement.validate(source, context)?;
-
-        Ok(())
-    }
-
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        let right = self.statement.run(source, context)?;
-
-        let new_value = match self.operator {
-            AssignmentOperator::PlusEqual => {
-                let left = self.identifier.run(source, context)?;
-
-                left.add(right, self.syntax_position)?
-            }
-            AssignmentOperator::MinusEqual => {
-                if let Some(left) = context.get_value(&self.identifier)? {
-                    left.subtract(right, self.syntax_position)?
-                } else {
-                    return Err(RuntimeError::ValidationFailure(
-                        ValidationError::VariableIdentifierNotFound(self.identifier.clone()),
-                    ));
-                }
-            }
-            AssignmentOperator::Equal => right,
-        };
-
-        if let Value::Function(Function::ContextDefined(function_node)) = &new_value {
-            function_node
-                .context()
-                .set_value(self.identifier.clone(), new_value.clone())?;
-        }
-
-        context.set_value(self.identifier.clone(), new_value)?;
-
-        Ok(Value::none())
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        Ok(Type::None)
-    }
-}
-
-impl Format for Assignment {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        self.identifier.format(output, indent_level);
-
-        if let Some(type_specification) = &self.type_specification {
-            type_specification.format(output, indent_level);
-        }
-
-        output.push(' ');
-        self.operator.format(output, indent_level);
-        output.push(' ');
-
-        self.statement.format(output, 0);
-    }
-}

src/abstract_tree/assignment_operator.rs

@@ -1,62 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Format, SyntaxNode, Type, Value,
-};
-
-/// Operators that be used in an assignment statement.
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub enum AssignmentOperator {
-    Equal,
-    PlusEqual,
-    MinusEqual,
-}
-
-impl AbstractTree for AssignmentOperator {
-    fn from_syntax(
-        node: SyntaxNode,
-        _source: &str,
-        _context: &Context,
-    ) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("assignment_operator", node)?;
-
-        let operator_node = node.child(0).unwrap();
-        let operator = match operator_node.kind() {
-            "=" => AssignmentOperator::Equal,
-            "+=" => AssignmentOperator::PlusEqual,
-            "-=" => AssignmentOperator::MinusEqual,
-            _ => {
-                return Err(SyntaxError::UnexpectedSyntaxNode {
-                    expected: "=, += or -=".to_string(),
-                    actual: operator_node.kind().to_string(),
-                    position: node.range().into(),
-                })
-            }
-        };
-
-        Ok(operator)
-    }
-
-    fn run(&self, _source: &str, _context: &Context) -> Result<Value, RuntimeError> {
-        Ok(Value::none())
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        Ok(Type::None)
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        Ok(())
-    }
-}
-
-impl Format for AssignmentOperator {
-    fn format(&self, output: &mut String, _indent_level: u8) {
-        match self {
-            AssignmentOperator::Equal => output.push('='),
-            AssignmentOperator::PlusEqual => output.push_str("+="),
-            AssignmentOperator::MinusEqual => output.push_str("-="),
-        }
-    }
-}

src/abstract_tree/block.rs

@@ -1,170 +0,0 @@
-use std::{
-    fmt::{self, Formatter},
-    sync::RwLock,
-};
-
-use rayon::prelude::*;
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    error::{rw_lock_error::RwLockError, RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Format, Statement, SyntaxNode, Type, Value,
-};
-
-/// Abstract representation of a block.
-///
-/// A block is almost identical to the root except that it must have curly
-/// braces and can optionally be asynchronous. A block evaluates to the value of
-/// its final statement but an async block will short-circuit if a statement
-/// results in an error. Note that this will be the first statement to encounter
-/// an error at runtime, not necessarilly the first statement as they are
-/// written.
-#[derive(Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct Block {
-    is_async: bool,
-    contains_return: bool,
-    statements: Vec<Statement>,
-}
-
-impl Block {
-    pub fn contains_return(&self) -> bool {
-        self.contains_return
-    }
-}
-
-impl AbstractTree for Block {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("block", node)?;
-
-        let first_child = node.child(0).unwrap();
-        let is_async = first_child.kind() == "async";
-        let mut contains_return = false;
-
-        let statement_count = if is_async {
-            node.child_count() - 3
-        } else {
-            node.child_count() - 2
-        };
-        let mut statements = Vec::with_capacity(statement_count);
-        let block_context = Context::with_variables_from(context)?;
-
-        for index in 1..node.child_count() - 1 {
-            let child_node = node.child(index).unwrap();
-
-            if child_node.kind() == "statement" {
-                let statement = Statement::from_syntax(child_node, source, &block_context)?;
-
-                if statement.is_return() {
-                    contains_return = true;
-                }
-
-                statements.push(statement);
-            }
-        }
-
-        Ok(Block {
-            is_async,
-            contains_return,
-            statements,
-        })
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        for statement in &self.statements {
-            statement.validate(_source, _context)?;
-        }
-
-        Ok(())
-    }
-
-    fn run(&self, _source: &str, _context: &Context) -> Result<Value, RuntimeError> {
-        if self.is_async {
-            let statements = &self.statements;
-            let final_result = RwLock::new(Ok(Value::none()));
-
-            statements
-                .into_par_iter()
-                .enumerate()
-                .find_map_first(|(index, statement)| {
-                    let result = statement.run(_source, _context);
-                    let should_return = if self.contains_return {
-                        statement.is_return()
-                    } else {
-                        index == statements.len() - 1
-                    };
-
-                    if should_return {
-                        let get_write_lock = final_result.write();
-
-                        match get_write_lock {
-                            Ok(mut final_result) => {
-                                *final_result = result;
-                                None
-                            }
-                            Err(_error) => Some(Err(RuntimeError::RwLock(RwLockError))),
-                        }
-                    } else {
-                        None
-                    }
-                })
-                .unwrap_or(final_result.into_inner().map_err(|_| RwLockError)?)
-        } else {
-            for (index, statement) in self.statements.iter().enumerate() {
-                if statement.is_return() {
-                    return statement.run(_source, _context);
-                }
-
-                if index == self.statements.len() - 1 {
-                    return statement.run(_source, _context);
-                }
-            }
-
-            Ok(Value::none())
-        }
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        for (index, statement) in self.statements.iter().enumerate() {
-            if statement.is_return() {
-                return statement.expected_type(_context);
-            }
-
-            if index == self.statements.len() - 1 {
-                return statement.expected_type(_context);
-            }
-        }
-
-        Ok(Type::None)
-    }
-}
-
-impl Format for Block {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        if self.is_async {
-            output.push_str("async {\n");
-        } else {
-            output.push_str("{\n");
-        }
-
-        for (index, statement) in self.statements.iter().enumerate() {
-            if index > 0 {
-                output.push('\n');
-            }
-
-            statement.format(output, indent_level + 1);
-        }
-
-        output.push('\n');
-        Block::indent(output, indent_level);
-        output.push('}');
-    }
-}
-
-impl fmt::Debug for Block {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        f.debug_struct("Block")
-            .field("is_async", &self.is_async)
-            .field("statements", &self.statements)
-            .finish()
-    }
-}

src/abstract_tree/command.rs

@@ -1,75 +0,0 @@
-use std::process;
-
-use serde::{Deserialize, Serialize};
-use tree_sitter::Node as SyntaxNode;
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Format, Type, Value,
-};
-
-/// An external program invokation.
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct Command {
-    command_text: String,
-    command_arguments: Vec<String>,
-}
-
-impl AbstractTree for Command {
-    fn from_syntax(
-        node: SyntaxNode,
-        source: &str,
-        _context: &Context,
-    ) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("command", node)?;
-
-        let command_text_node = node.child(1).unwrap();
-        let command_text = source[command_text_node.byte_range()].to_string();
-
-        let mut command_arguments = Vec::new();
-
-        for index in 2..node.child_count() {
-            let text_node = node.child(index).unwrap();
-            let mut text = source[text_node.byte_range()].to_string();
-
-            if (text.starts_with('\'') && text.ends_with('\''))
-                || (text.starts_with('"') && text.ends_with('"'))
-                || (text.starts_with('`') && text.ends_with('`'))
-            {
-                text = text[1..text.len() - 1].to_string();
-            }
-
-            command_arguments.push(text);
-        }
-
-        Ok(Command {
-            command_text,
-            command_arguments,
-        })
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        Ok(Type::String)
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        todo!()
-    }
-
-    fn run(&self, _source: &str, _context: &Context) -> Result<Value, RuntimeError> {
-        let output = process::Command::new(&self.command_text)
-            .args(&self.command_arguments)
-            .spawn()?
-            .wait_with_output()?
-            .stdout;
-        let string = String::from_utf8(output)?;
-
-        Ok(Value::String(string))
-    }
-}
-
-impl Format for Command {
-    fn format(&self, _output: &mut String, _indent_level: u8) {
-        todo!()
-    }
-}

src/abstract_tree/enum_defintion.rs

@@ -1,83 +0,0 @@
-use serde::{Deserialize, Serialize};
-use tree_sitter::Node as SyntaxNode;
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, EnumInstance, Format, Identifier, Type, TypeDefinition, Value,
-};
-
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct EnumDefinition {
-    identifier: Identifier,
-    variants: Vec<(Identifier, Option<Type>)>,
-}
-
-impl EnumDefinition {
-    pub fn new(identifier: Identifier, variants: Vec<(Identifier, Option<Type>)>) -> Self {
-        Self {
-            identifier,
-            variants,
-        }
-    }
-
-    pub fn instantiate(&self, variant: Identifier, content: Option<Value>) -> EnumInstance {
-        EnumInstance::new(self.identifier.clone(), variant, content)
-    }
-
-    pub fn identifier(&self) -> &Identifier {
-        &self.identifier
-    }
-}
-
-impl AbstractTree for EnumDefinition {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("enum_definition", node)?;
-
-        let identifier_node = node.child(1).unwrap();
-        let identifier = Identifier::from_syntax(identifier_node, source, context)?;
-
-        let mut variants = Vec::new();
-        let mut current_identifier = None;
-
-        for index in 3..node.child_count() - 1 {
-            let child = node.child(index).unwrap();
-
-            if child.kind() == "identifier" {
-                current_identifier = Some(Identifier::from_syntax(child, source, context)?);
-            }
-
-            if let Some(identifier) = &current_identifier {
-                if child.kind() == "type" {
-                    let r#type = Type::from_syntax(child, source, context)?;
-
-                    variants.push((identifier.clone(), Some(r#type)));
-                }
-            }
-        }
-
-        Ok(EnumDefinition {
-            identifier,
-            variants,
-        })
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        Ok(Type::None)
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        Ok(())
-    }
-
-    fn run(&self, _source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        context.set_definition(self.identifier.clone(), TypeDefinition::Enum(self.clone()))?;
-
-        Ok(Value::none())
-    }
-}
-
-impl Format for EnumDefinition {
-    fn format(&self, _output: &mut String, _indent_level: u8) {
-        todo!()
-    }
-}

src/abstract_tree/enum_pattern.rs

@@ -1,70 +0,0 @@
-use serde::{Deserialize, Serialize};
-use tree_sitter::Node as SyntaxNode;
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Format, Identifier, Type, Value,
-};
-
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct EnumPattern {
-    name: Identifier,
-    variant: Identifier,
-    inner_identifier: Option<Identifier>,
-}
-
-impl EnumPattern {
-    pub fn name(&self) -> &Identifier {
-        &self.name
-    }
-
-    pub fn variant(&self) -> &Identifier {
-        &self.variant
-    }
-
-    pub fn inner_identifier(&self) -> &Option<Identifier> {
-        &self.inner_identifier
-    }
-}
-
-impl AbstractTree for EnumPattern {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("enum_pattern", node)?;
-
-        let enum_name_node = node.child(0).unwrap();
-        let name = Identifier::from_syntax(enum_name_node, source, context)?;
-
-        let enum_variant_node = node.child(2).unwrap();
-        let variant = Identifier::from_syntax(enum_variant_node, source, context)?;
-
-        let inner_identifier = if let Some(child) = node.child(4) {
-            Some(Identifier::from_syntax(child, source, context)?)
-        } else {
-            None
-        };
-
-        Ok(EnumPattern {
-            name,
-            variant,
-            inner_identifier,
-        })
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        Ok(Type::None)
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        Ok(())
-    }
-
-    fn run(&self, _source: &str, _context: &Context) -> Result<Value, RuntimeError> {
-        Ok(Value::none())
-    }
-}
-
-impl Format for EnumPattern {
-    fn format(&self, _output: &mut String, _indent_level: u8) {
-        todo!()
-    }
-}

src/abstract_tree/expression.rs

@@ -1,120 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    value_node::ValueNode,
-    AbstractTree, As, Command, Context, Format, FunctionCall, Identifier, Index, Logic, Math,
-    SyntaxNode, Type, Value,
-};
-
-/// Abstract representation of an expression statement.
-///
-/// Unlike statements, which can involve complex logic, an expression is
-/// expected to evaluate to a value. However, an expression can still contain
-/// nested statements and may evaluate to an empty value.
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub enum Expression {
-    Value(ValueNode),
-    Identifier(Identifier),
-    Index(Box<Index>),
-    Math(Box<Math>),
-    Logic(Box<Logic>),
-    FunctionCall(Box<FunctionCall>),
-    Command(Command),
-    As(Box<As>),
-}
-
-impl AbstractTree for Expression {
-    fn from_syntax(
-        node: SyntaxNode,
-        source: &str,
-        _context: &Context,
-    ) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("expression", node)?;
-
-        let child = if node.child(0).unwrap().is_named() {
-            node.child(0).unwrap()
-        } else {
-            node.child(1).unwrap()
-        };
-
-        let expression = match child.kind() {
-            "as" => Expression::As(Box::new(As::from_syntax(child, source, _context)?)),
-            "value" => Expression::Value(ValueNode::from_syntax(child, source, _context)?),
-            "identifier" => {
-                Expression::Identifier(Identifier::from_syntax(child, source, _context)?)
-            }
-            "index" => Expression::Index(Box::new(Index::from_syntax(child, source, _context)?)),
-            "math" => Expression::Math(Box::new(Math::from_syntax(child, source, _context)?)),
-            "logic" => Expression::Logic(Box::new(Logic::from_syntax(child, source, _context)?)),
-            "function_call" => Expression::FunctionCall(Box::new(FunctionCall::from_syntax(
-                child, source, _context,
-            )?)),
-            "command" => Expression::Command(Command::from_syntax(child, source, _context)?),
-            _ => {
-                return Err(SyntaxError::UnexpectedSyntaxNode {
-                    expected: "value, identifier, index, math, logic, function call, as or command"
-                        .to_string(),
-                    actual: child.kind().to_string(),
-                    position: node.range().into(),
-                })
-            }
-        };
-
-        Ok(expression)
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        match self {
-            Expression::Value(value_node) => value_node.expected_type(_context),
-            Expression::Identifier(identifier) => identifier.expected_type(_context),
-            Expression::Math(math) => math.expected_type(_context),
-            Expression::Logic(logic) => logic.expected_type(_context),
-            Expression::FunctionCall(function_call) => function_call.expected_type(_context),
-            Expression::Index(index) => index.expected_type(_context),
-            Expression::Command(command) => command.expected_type(_context),
-            Expression::As(r#as) => r#as.expected_type(_context),
-        }
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        match self {
-            Expression::Value(value_node) => value_node.validate(_source, _context),
-            Expression::Identifier(identifier) => identifier.validate(_source, _context),
-            Expression::Math(math) => math.validate(_source, _context),
-            Expression::Logic(logic) => logic.validate(_source, _context),
-            Expression::FunctionCall(function_call) => function_call.validate(_source, _context),
-            Expression::Index(index) => index.validate(_source, _context),
-            Expression::Command(command) => command.validate(_source, _context),
-            Expression::As(r#as) => r#as.validate(_source, _context),
-        }
-    }
-
-    fn run(&self, _source: &str, _context: &Context) -> Result<Value, RuntimeError> {
-        match self {
-            Expression::Value(value_node) => value_node.run(_source, _context),
-            Expression::Identifier(identifier) => identifier.run(_source, _context),
-            Expression::Math(math) => math.run(_source, _context),
-            Expression::Logic(logic) => logic.run(_source, _context),
-            Expression::FunctionCall(function_call) => function_call.run(_source, _context),
-            Expression::Index(index) => index.run(_source, _context),
-            Expression::Command(command) => command.run(_source, _context),
-            Expression::As(r#as) => r#as.run(_source, _context),
-        }
-    }
-}
-
-impl Format for Expression {
-    fn format(&self, _output: &mut String, _indent_level: u8) {
-        match self {
-            Expression::Value(value_node) => value_node.format(_output, _indent_level),
-            Expression::Identifier(identifier) => identifier.format(_output, _indent_level),
-            Expression::Math(math) => math.format(_output, _indent_level),
-            Expression::Logic(logic) => logic.format(_output, _indent_level),
-            Expression::FunctionCall(function_call) => function_call.format(_output, _indent_level),
-            Expression::Index(index) => index.format(_output, _indent_level),
-            Expression::Command(command) => command.format(_output, _indent_level),
-            Expression::As(r#as) => r#as.format(_output, _indent_level),
-        }
-    }
-}

src/abstract_tree/for.rs

@@ -1,143 +0,0 @@
-use rayon::prelude::*;
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Block, Context, Expression, Format, Identifier, SourcePosition, SyntaxNode, Type,
-    Value,
-};
-
-/// Abstract representation of a for loop statement.
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct For {
-    is_async: bool,
-    item_id: Identifier,
-    collection: Expression,
-    block: Block,
-    source_position: SourcePosition,
-
-    #[serde(skip)]
-    context: Context,
-}
-
-impl AbstractTree for For {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("for", node)?;
-
-        let for_node = node.child(0).unwrap();
-        let is_async = match for_node.kind() {
-            "for" => false,
-            "async for" => true,
-            _ => {
-                return Err(SyntaxError::UnexpectedSyntaxNode {
-                    expected: "for or async for".to_string(),
-                    actual: for_node.kind().to_string(),
-                    position: node.range().into(),
-                })
-            }
-        };
-
-        let identifier_node = node.child(1).unwrap();
-        let identifier = Identifier::from_syntax(identifier_node, source, context)?;
-
-        let expression_node = node.child(3).unwrap();
-        let expression = Expression::from_syntax(expression_node, source, context)?;
-
-        let loop_context = Context::with_variables_from(context)?;
-
-        let item_node = node.child(4).unwrap();
-        let item = Block::from_syntax(item_node, source, &loop_context)?;
-
-        Ok(For {
-            is_async,
-            item_id: identifier,
-            collection: expression,
-            block: item,
-            source_position: SourcePosition::from(node.range()),
-            context: loop_context,
-        })
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        Ok(Type::None)
-    }
-
-    fn validate(&self, _source: &str, context: &Context) -> Result<(), ValidationError> {
-        self.collection.validate(_source, context)?;
-
-        let collection_type = self.collection.expected_type(context)?;
-        let item_type = if let Type::List(item_type) = collection_type {
-            item_type.as_ref().clone()
-        } else if let Type::Range = collection_type {
-            Type::Integer
-        } else {
-            return Err(ValidationError::TypeCheck {
-                expected: Type::Collection,
-                actual: collection_type,
-                position: self.source_position,
-            });
-        };
-        let key = self.item_id.clone();
-
-        self.context.inherit_all_from(context)?;
-        self.context.set_type(key, item_type)?;
-        self.item_id.validate(_source, &self.context)?;
-        self.block.validate(_source, &self.context)
-    }
-
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        self.context.inherit_all_from(context)?;
-
-        let expression_run = self.collection.run(source, context)?;
-        let key = &self.item_id;
-
-        if let Value::Range(range) = expression_run {
-            if self.is_async {
-                range.into_par_iter().try_for_each(|integer| {
-                    self.context
-                        .set_value(key.clone(), Value::Integer(integer))?;
-                    self.block.run(source, &self.context).map(|_value| ())
-                })?;
-            } else {
-                for i in range {
-                    self.context.set_value(key.clone(), Value::Integer(i))?;
-                    self.block.run(source, &self.context)?;
-                }
-            }
-
-            return Ok(Value::none());
-        }
-
-        if let Value::List(list) = &expression_run {
-            if self.is_async {
-                list.items()?.par_iter().try_for_each(|value| {
-                    self.context.set_value(key.clone(), value.clone())?;
-                    self.block.run(source, &self.context).map(|_value| ())
-                })?;
-            } else {
-                for value in list.items()?.iter() {
-                    self.context.set_value(key.clone(), value.clone())?;
-                    self.block.run(source, &self.context)?;
-                }
-            }
-        }
-
-        Ok(Value::none())
-    }
-}
-
-impl Format for For {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        if self.is_async {
-            output.push_str("async for ");
-        } else {
-            output.push_str("for ");
-        }
-
-        self.item_id.format(output, indent_level);
-        output.push_str(" in ");
-        self.collection.format(output, indent_level);
-        output.push(' ');
-        self.block.format(output, indent_level);
-    }
-}

src/abstract_tree/function_call.rs

@@ -1,202 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    built_in_functions::Callable,
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Expression, Format, Function, FunctionExpression, SourcePosition,
-    SyntaxNode, Type, Value,
-};
-
-/// A function being invoked and the arguments it is being passed.
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct FunctionCall {
-    function_expression: FunctionExpression,
-    arguments: Vec<Expression>,
-    syntax_position: SourcePosition,
-}
-
-impl FunctionCall {
-    /// Returns a new FunctionCall.
-    pub fn new(
-        function_expression: FunctionExpression,
-        arguments: Vec<Expression>,
-        syntax_position: SourcePosition,
-    ) -> Self {
-        Self {
-            function_expression,
-            arguments,
-            syntax_position,
-        }
-    }
-}
-
-impl AbstractTree for FunctionCall {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("function_call", node)?;
-
-        let function_node = node.child(0).unwrap();
-        let function_expression = FunctionExpression::from_syntax(function_node, source, context)?;
-
-        let mut arguments = Vec::new();
-
-        for index in 2..node.child_count() - 1 {
-            let child = node.child(index).unwrap();
-
-            if child.is_named() {
-                let expression = Expression::from_syntax(child, source, context)?;
-
-                arguments.push(expression);
-            }
-        }
-
-        Ok(FunctionCall {
-            function_expression,
-            arguments,
-            syntax_position: node.range().into(),
-        })
-    }
-
-    fn expected_type(&self, context: &Context) -> Result<Type, ValidationError> {
-        match &self.function_expression {
-            FunctionExpression::Identifier(identifier) => {
-                let identifier_type = identifier.expected_type(context)?;
-
-                if let Type::Function {
-                    parameter_types: _,
-                    return_type,
-                } = &identifier_type
-                {
-                    Ok(*return_type.clone())
-                } else {
-                    Ok(identifier_type)
-                }
-            }
-            FunctionExpression::FunctionCall(function_call) => function_call.expected_type(context),
-            FunctionExpression::Value(value_node) => {
-                let value_type = value_node.expected_type(context)?;
-
-                if let Type::Function { return_type, .. } = value_type {
-                    Ok(*return_type)
-                } else {
-                    Ok(value_type)
-                }
-            }
-            FunctionExpression::Index(index) => {
-                let index_type = index.expected_type(context)?;
-
-                if let Type::Function { return_type, .. } = index_type {
-                    Ok(*return_type)
-                } else {
-                    Ok(index_type)
-                }
-            }
-        }
-    }
-
-    fn validate(&self, _source: &str, context: &Context) -> Result<(), ValidationError> {
-        self.function_expression.validate(_source, context)?;
-
-        let function_expression_type = self.function_expression.expected_type(context)?;
-
-        let parameter_types = if let Type::Function {
-            parameter_types, ..
-        } = function_expression_type
-        {
-            parameter_types
-        } else {
-            return Err(ValidationError::TypeCheckExpectedFunction {
-                actual: function_expression_type,
-                position: self.syntax_position,
-            });
-        };
-
-        if self.arguments.len() != parameter_types.len() {
-            return Err(ValidationError::ExpectedFunctionArgumentAmount {
-                expected: parameter_types.len(),
-                actual: self.arguments.len(),
-                position: self.syntax_position,
-            });
-        }
-
-        for (index, expression) in self.arguments.iter().enumerate() {
-            expression.validate(_source, context)?;
-
-            if let Some(expected) = parameter_types.get(index) {
-                let actual = expression.expected_type(context)?;
-
-                if !expected.accepts(&actual) {
-                    return Err(ValidationError::TypeCheck {
-                        expected: expected.clone(),
-                        actual,
-                        position: self.syntax_position,
-                    });
-                }
-            }
-        }
-
-        Ok(())
-    }
-
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        let value = match &self.function_expression {
-            FunctionExpression::Identifier(identifier) => {
-                if let Some(value) = context.get_value(identifier)? {
-                    value.clone()
-                } else {
-                    return Err(RuntimeError::ValidationFailure(
-                        ValidationError::VariableIdentifierNotFound(identifier.clone()),
-                    ));
-                }
-            }
-            FunctionExpression::FunctionCall(function_call) => {
-                function_call.run(source, context)?
-            }
-            FunctionExpression::Value(value_node) => value_node.run(source, context)?,
-            FunctionExpression::Index(index) => index.run(source, context)?,
-        };
-        let function = value.as_function()?;
-
-        match function {
-            Function::BuiltIn(built_in_function) => {
-                let mut arguments = Vec::with_capacity(self.arguments.len());
-
-                for expression in &self.arguments {
-                    let value = expression.run(source, context)?;
-
-                    arguments.push(value);
-                }
-
-                built_in_function.call(&arguments, source, context)
-            }
-            Function::ContextDefined(function_node) => {
-                let call_context = Context::with_variables_from(function_node.context())?;
-
-                call_context.inherit_from(context)?;
-
-                let parameter_expression_pairs =
-                    function_node.parameters().iter().zip(self.arguments.iter());
-
-                for (identifier, expression) in parameter_expression_pairs {
-                    let value = expression.run(source, context)?;
-
-                    call_context.set_value(identifier.clone(), value)?;
-                }
-
-                function_node.body().run(source, &call_context)
-            }
-        }
-    }
-}
-
-impl Format for FunctionCall {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        self.function_expression.format(output, indent_level);
-        output.push('(');
-
-        for expression in &self.arguments {
-            expression.format(output, indent_level);
-        }
-
-        output.push(')');
-    }
-}

src/abstract_tree/function_expression.rs

@@ -1,91 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Format, FunctionCall, Identifier, Index, SyntaxNode, Type, Value,
-    ValueNode,
-};
-
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub enum FunctionExpression {
-    Identifier(Identifier),
-    FunctionCall(Box<FunctionCall>),
-    Value(ValueNode),
-    Index(Index),
-}
-
-impl AbstractTree for FunctionExpression {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("function_expression", node)?;
-
-        let first_child = node.child(0).unwrap();
-        let child = if first_child.is_named() {
-            first_child
-        } else {
-            node.child(1).unwrap()
-        };
-
-        let function_expression = match child.kind() {
-            "identifier" => {
-                FunctionExpression::Identifier(Identifier::from_syntax(child, source, context)?)
-            }
-
-            "function_call" => FunctionExpression::FunctionCall(Box::new(
-                FunctionCall::from_syntax(child, source, context)?,
-            )),
-            "value" => FunctionExpression::Value(ValueNode::from_syntax(child, source, context)?),
-            "index" => FunctionExpression::Index(Index::from_syntax(child, source, context)?),
-            _ => {
-                return Err(SyntaxError::UnexpectedSyntaxNode {
-                    expected: "identifier, function call, value or index".to_string(),
-                    actual: child.kind().to_string(),
-                    position: node.range().into(),
-                })
-            }
-        };
-
-        Ok(function_expression)
-    }
-
-    fn expected_type(&self, context: &Context) -> Result<Type, ValidationError> {
-        match self {
-            FunctionExpression::Identifier(identifier) => identifier.expected_type(context),
-            FunctionExpression::FunctionCall(function_call) => function_call.expected_type(context),
-            FunctionExpression::Value(value_node) => value_node.expected_type(context),
-            FunctionExpression::Index(index) => index.expected_type(context),
-        }
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        match self {
-            FunctionExpression::Identifier(identifier) => identifier.validate(_source, _context),
-            FunctionExpression::FunctionCall(function_call) => {
-                function_call.validate(_source, _context)
-            }
-            FunctionExpression::Value(value_node) => value_node.validate(_source, _context),
-            FunctionExpression::Index(index) => index.validate(_source, _context),
-        }
-    }
-
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        match self {
-            FunctionExpression::Identifier(identifier) => identifier.run(source, context),
-            FunctionExpression::FunctionCall(function_call) => function_call.run(source, context),
-            FunctionExpression::Value(value_node) => value_node.run(source, context),
-            FunctionExpression::Index(index) => index.run(source, context),
-        }
-    }
-}
-
-impl Format for FunctionExpression {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        match self {
-            FunctionExpression::Value(value_node) => value_node.format(output, indent_level),
-            FunctionExpression::Identifier(identifier) => identifier.format(output, indent_level),
-            FunctionExpression::FunctionCall(function_call) => {
-                function_call.format(output, indent_level)
-            }
-            FunctionExpression::Index(index) => index.format(output, indent_level),
-        }
-    }
-}

src/abstract_tree/function_node.rs

@@ -1,179 +0,0 @@
-use std::fmt::{self, Display, Formatter};
-
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Block, Context, Format, Function, Identifier, SourcePosition, SyntaxNode, Type,
-    TypeSpecification, Value,
-};
-
-#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, PartialOrd, Ord)]
-pub struct FunctionNode {
-    parameters: Vec<Identifier>,
-    body: Block,
-    r#type: Type,
-    syntax_position: SourcePosition,
-
-    #[serde(skip)]
-    context: Context,
-}
-
-impl FunctionNode {
-    pub fn parameters(&self) -> &Vec<Identifier> {
-        &self.parameters
-    }
-
-    pub fn body(&self) -> &Block {
-        &self.body
-    }
-
-    pub fn r#type(&self) -> &Type {
-        &self.r#type
-    }
-
-    pub fn syntax_position(&self) -> &SourcePosition {
-        &self.syntax_position
-    }
-
-    pub fn context(&self) -> &Context {
-        &self.context
-    }
-
-    pub fn return_type(&self) -> &Type {
-        match &self.r#type {
-            Type::Function {
-                parameter_types: _,
-                return_type,
-            } => return_type.as_ref(),
-            _ => &Type::None,
-        }
-    }
-}
-
-impl AbstractTree for FunctionNode {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("function", node)?;
-
-        let child_count = node.child_count();
-        let mut parameters = Vec::new();
-        let mut parameter_types = Vec::new();
-
-        for index in 1..child_count - 3 {
-            let child = node.child(index).unwrap();
-
-            if child.kind() == "identifier" {
-                let identifier = Identifier::from_syntax(child, source, context)?;
-
-                parameters.push(identifier);
-            }
-
-            if child.kind() == "type_specification" {
-                let type_specification = TypeSpecification::from_syntax(child, source, context)?;
-
-                parameter_types.push(type_specification.take_inner());
-            }
-        }
-
-        let return_type_node = node.child(child_count - 2).unwrap();
-        let return_type = TypeSpecification::from_syntax(return_type_node, source, context)?;
-
-        let function_context = Context::with_variables_from(context)?;
-
-        let body_node = node.child(child_count - 1).unwrap();
-        let body = Block::from_syntax(body_node, source, &function_context)?;
-
-        let r#type = Type::function(parameter_types, return_type.take_inner());
-        let syntax_position = node.range().into();
-
-        Ok(FunctionNode {
-            parameters,
-            body,
-            r#type,
-            syntax_position,
-            context: function_context,
-        })
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        Ok(self.r#type().clone())
-    }
-
-    fn validate(&self, source: &str, context: &Context) -> Result<(), ValidationError> {
-        if let Type::Function {
-            parameter_types,
-            return_type,
-        } = &self.r#type
-        {
-            self.context.inherit_from(context)?;
-
-            for (parameter, r#type) in self.parameters.iter().zip(parameter_types.iter()) {
-                self.context.set_type(parameter.clone(), r#type.clone())?;
-            }
-
-            let actual = self.body.expected_type(&self.context)?;
-
-            if !return_type.accepts(&actual) {
-                return Err(ValidationError::TypeCheck {
-                    expected: return_type.as_ref().clone(),
-                    actual,
-                    position: self.syntax_position,
-                });
-            }
-
-            self.body.validate(source, &self.context)?;
-
-            Ok(())
-        } else {
-            Err(ValidationError::TypeCheckExpectedFunction {
-                actual: self.r#type.clone(),
-                position: self.syntax_position,
-            })
-        }
-    }
-
-    fn run(&self, _source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        self.context.inherit_from(context)?;
-
-        let self_as_value = Value::Function(Function::ContextDefined(self.clone()));
-
-        Ok(self_as_value)
-    }
-}
-
-impl Format for FunctionNode {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        let (parameter_types, return_type) = if let Type::Function {
-            parameter_types,
-            return_type,
-        } = &self.r#type
-        {
-            (parameter_types, return_type)
-        } else {
-            return;
-        };
-
-        output.push('(');
-
-        for (identifier, r#type) in self.parameters.iter().zip(parameter_types.iter()) {
-            identifier.format(output, indent_level);
-            output.push_str(" <");
-            r#type.format(output, indent_level);
-            output.push('>');
-        }
-
-        output.push_str(") <");
-        return_type.format(output, indent_level);
-        output.push_str("> ");
-        self.body.format(output, indent_level);
-    }
-}
-
-impl Display for FunctionNode {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        let mut string = String::new();
-
-        self.format(&mut string, 0);
-        f.write_str(&string)
-    }
-}

src/abstract_tree/identifier.rs

@@ -1,167 +0,0 @@
-use std::{
-    fmt::{self, Display, Formatter},
-    sync::Arc,
-};
-
-use serde::{de::Visitor, Deserialize, Serialize};
-
-use crate::{
-    built_in_identifiers::all_built_in_identifiers,
-    built_in_values::all_built_in_values,
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Format, SyntaxNode, Type, Value,
-};
-
-/// A string by which a variable is known to a context.
-///
-/// Every variable is a key-value pair. An identifier holds the key part of that
-/// pair. Its inner value can be used to retrieve a Value instance from a Map.
-#[derive(Debug, Clone, Eq, PartialEq, PartialOrd, Ord, Hash)]
-pub struct Identifier(Arc<String>);
-
-impl Identifier {
-    pub fn new(key: &str) -> Self {
-        for built_in_identifier in all_built_in_identifiers() {
-            let identifier = built_in_identifier.get();
-
-            if &key == identifier.inner().as_ref() {
-                return identifier.clone();
-            }
-        }
-
-        Identifier(Arc::new(key.to_string()))
-    }
-
-    pub fn from_raw_parts(arc: Arc<String>) -> Self {
-        Identifier(arc)
-    }
-
-    pub fn inner(&self) -> &Arc<String> {
-        &self.0
-    }
-
-    pub fn contains(&self, string: &str) -> bool {
-        self.0.as_ref() == string
-    }
-}
-
-impl AbstractTree for Identifier {
-    fn from_syntax(
-        node: SyntaxNode,
-        source: &str,
-        _context: &Context,
-    ) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("identifier", node)?;
-
-        let text = &source[node.byte_range()];
-
-        debug_assert!(!text.is_empty());
-
-        Ok(Identifier::new(text))
-    }
-
-    fn validate(&self, _source: &str, context: &Context) -> Result<(), ValidationError> {
-        let variable_exists = context.add_allowance(self)?;
-
-        if variable_exists {
-            Ok(())
-        } else {
-            for built_in_value in all_built_in_values() {
-                if built_in_value.name() == self.inner().as_ref() {
-                    return Ok(());
-                }
-            }
-
-            Err(ValidationError::VariableIdentifierNotFound(self.clone()))
-        }
-    }
-
-    fn expected_type(&self, context: &Context) -> Result<Type, ValidationError> {
-        if let Some(r#type) = context.get_type(self)? {
-            Ok(r#type)
-        } else {
-            for built_in_value in all_built_in_values() {
-                if built_in_value.name() == self.inner().as_ref() {
-                    return Ok(built_in_value.get().r#type()?);
-                }
-            }
-
-            Err(ValidationError::VariableIdentifierNotFound(self.clone()))
-        }
-    }
-
-    fn run(&self, _source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        if let Some(value) = context.get_value(self)? {
-            return Ok(value);
-        } else {
-            for built_in_value in all_built_in_values() {
-                if built_in_value.name() == self.inner().as_ref() {
-                    return Ok(built_in_value.get().clone());
-                }
-            }
-        }
-
-        Err(RuntimeError::ValidationFailure(
-            ValidationError::VariableIdentifierNotFound(self.clone()),
-        ))
-    }
-}
-
-impl Format for Identifier {
-    fn format(&self, output: &mut String, _indent_level: u8) {
-        output.push_str(&self.0);
-    }
-}
-
-impl From<String> for Identifier {
-    fn from(value: String) -> Self {
-        Identifier::from_raw_parts(Arc::new(value))
-    }
-}
-
-impl From<&str> for Identifier {
-    fn from(value: &str) -> Self {
-        Identifier::new(value)
-    }
-}
-
-impl Display for Identifier {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "{}", self.0)
-    }
-}
-
-impl Serialize for Identifier {
-    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    where
-        S: serde::Serializer,
-    {
-        serializer.serialize_str(self.0.as_ref())
-    }
-}
-
-impl<'de> Deserialize<'de> for Identifier {
-    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
-    where
-        D: serde::Deserializer<'de>,
-    {
-        deserializer.deserialize_string(IdentifierVisitor)
-    }
-}
-
-struct IdentifierVisitor;
-
-impl<'de> Visitor<'de> for IdentifierVisitor {
-    type Value = Identifier;
-
-    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
-        formatter.write_str("valid UFT-8 sequence")
-    }
-
-    fn visit_string<E>(self, v: String) -> Result<Self::Value, E>
-    where
-        E: serde::de::Error,
-    {
-        Ok(Identifier(Arc::new(v)))
-    }
-}

src/abstract_tree/if_else.rs

@@ -1,160 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Block, Context, Expression, Format, SourcePosition, SyntaxNode, Type, Value,
-};
-
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct IfElse {
-    if_expression: Expression,
-    if_block: Block,
-    else_if_expressions: Vec<Expression>,
-    else_if_blocks: Vec<Block>,
-    else_block: Option<Block>,
-    source_position: SourcePosition,
-}
-
-impl AbstractTree for IfElse {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        let if_expression_node = node.child(0).unwrap().child(1).unwrap();
-        let if_expression = Expression::from_syntax(if_expression_node, source, context)?;
-
-        let if_block_node = node.child(0).unwrap().child(2).unwrap();
-        let if_block = Block::from_syntax(if_block_node, source, context)?;
-
-        let child_count = node.child_count();
-        let mut else_if_expressions = Vec::new();
-        let mut else_if_blocks = Vec::new();
-        let mut else_block = None;
-
-        for index in 1..child_count {
-            let child = node.child(index).unwrap();
-
-            if child.kind() == "else_if" {
-                let expression_node = child.child(1).unwrap();
-                let expression = Expression::from_syntax(expression_node, source, context)?;
-
-                else_if_expressions.push(expression);
-
-                let block_node = child.child(2).unwrap();
-                let block = Block::from_syntax(block_node, source, context)?;
-
-                else_if_blocks.push(block);
-            }
-
-            if child.kind() == "else" {
-                let else_node = child.child(1).unwrap();
-                else_block = Some(Block::from_syntax(else_node, source, context)?);
-            }
-        }
-
-        Ok(IfElse {
-            if_expression,
-            if_block,
-            else_if_expressions,
-            else_if_blocks,
-            else_block,
-            source_position: SourcePosition::from(node.range()),
-        })
-    }
-
-    fn expected_type(&self, context: &Context) -> Result<Type, ValidationError> {
-        self.if_block.expected_type(context)
-    }
-
-    fn validate(&self, _source: &str, context: &Context) -> Result<(), ValidationError> {
-        self.if_expression.validate(_source, context)?;
-        self.if_block.validate(_source, context)?;
-
-        let expected = self.if_block.expected_type(context)?;
-        let else_ifs = self
-            .else_if_expressions
-            .iter()
-            .zip(self.else_if_blocks.iter());
-
-        for (expression, block) in else_ifs {
-            expression.validate(_source, context)?;
-            block.validate(_source, context)?;
-
-            let actual = block.expected_type(context)?;
-
-            if !expected.accepts(&actual) {
-                return Err(ValidationError::TypeCheck {
-                    expected,
-                    actual,
-                    position: self.source_position,
-                });
-            }
-        }
-
-        if let Some(block) = &self.else_block {
-            block.validate(_source, context)?;
-
-            let actual = block.expected_type(context)?;
-
-            if !expected.accepts(&actual) {
-                return Err(ValidationError::TypeCheck {
-                    expected,
-                    actual,
-                    position: self.source_position,
-                });
-            }
-        }
-
-        Ok(())
-    }
-
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        let if_boolean = self.if_expression.run(source, context)?.as_boolean()?;
-
-        if if_boolean {
-            self.if_block.run(source, context)
-        } else {
-            let else_ifs = self
-                .else_if_expressions
-                .iter()
-                .zip(self.else_if_blocks.iter());
-
-            for (expression, block) in else_ifs {
-                let if_boolean = expression.run(source, context)?.as_boolean()?;
-
-                if if_boolean {
-                    return block.run(source, context);
-                }
-            }
-
-            if let Some(block) = &self.else_block {
-                block.run(source, context)
-            } else {
-                Ok(Value::none())
-            }
-        }
-    }
-}
-
-impl Format for IfElse {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        output.push_str("if ");
-        self.if_expression.format(output, indent_level);
-        output.push(' ');
-        self.if_block.format(output, indent_level);
-
-        let else_ifs = self
-            .else_if_expressions
-            .iter()
-            .zip(self.else_if_blocks.iter());
-
-        for (expression, block) in else_ifs {
-            output.push_str("else if ");
-            expression.format(output, indent_level);
-            output.push(' ');
-            block.format(output, indent_level);
-        }
-
-        if let Some(block) = &self.else_block {
-            output.push_str("else ");
-            block.format(output, indent_level);
-        }
-    }
-}

src/abstract_tree/index.rs

@@ -1,134 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Format, Identifier, IndexExpression, SourcePosition, SyntaxNode, Type,
-    Value,
-};
-
-/// Abstract representation of an index expression.
-///
-/// An index is a means of accessing values stored in list, maps and strings.
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct Index {
-    pub collection: IndexExpression,
-    pub index: IndexExpression,
-    source_position: SourcePosition,
-}
-
-impl AbstractTree for Index {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("index", node)?;
-
-        let collection_node = node.child(0).unwrap();
-        let collection = IndexExpression::from_syntax(collection_node, source, context)?;
-
-        let index_node = node.child(2).unwrap();
-        let index = IndexExpression::from_syntax(index_node, source, context)?;
-
-        Ok(Index {
-            collection,
-            index,
-            source_position: SourcePosition::from(node.range()),
-        })
-    }
-
-    fn expected_type(&self, context: &Context) -> Result<Type, ValidationError> {
-        match self.collection.expected_type(context)? {
-            Type::List(item_type) => Ok(*item_type.clone()),
-            Type::Map(map_types_option) => {
-                if let (Some(map_type), IndexExpression::Identifier(identifier)) =
-                    (map_types_option, &self.index)
-                {
-                    if let Some(r#type) = map_type.get(&identifier) {
-                        Ok(r#type.clone())
-                    } else {
-                        Ok(Type::Any)
-                    }
-                } else {
-                    Ok(Type::Any)
-                }
-            }
-            Type::None => Ok(Type::None),
-            r#type => Ok(r#type),
-        }
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        self.collection.validate(_source, _context)?;
-
-        let collection_type = self.collection.expected_type(_context)?;
-
-        if let (Type::Map(type_map_option), IndexExpression::Identifier(identifier)) =
-            (collection_type, &self.index)
-        {
-            if let Some(type_map) = type_map_option {
-                if !type_map.contains_key(identifier) {
-                    return Err(ValidationError::VariableIdentifierNotFound(
-                        identifier.clone(),
-                    ));
-                }
-            }
-        } else {
-            self.index.validate(_source, _context)?;
-        }
-
-        Ok(())
-    }
-
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        let value = self.collection.run(source, context)?;
-
-        match value {
-            Value::List(list) => {
-                let index = self.index.run(source, context)?.as_integer()? as usize;
-                let item = list.items()?.get(index).cloned().unwrap_or_default();
-
-                Ok(item)
-            }
-            Value::Map(map) => {
-                let map = map.inner();
-
-                let value = if let IndexExpression::Identifier(identifier) = &self.index {
-                    if let Some(value) = map.get(identifier) {
-                        value
-                    } else {
-                        return Err(RuntimeError::ValidationFailure(
-                            ValidationError::VariableIdentifierNotFound(identifier.clone()),
-                        ));
-                    }
-                } else {
-                    let index_value = self.index.run(source, context)?;
-                    let identifier = Identifier::new(index_value.as_string()?);
-
-                    if let Some(value) = map.get(&identifier) {
-                        value
-                    } else {
-                        return Err(RuntimeError::ValidationFailure(
-                            ValidationError::VariableIdentifierNotFound(identifier.clone()),
-                        ));
-                    }
-                };
-
-                Ok(value.clone())
-            }
-            Value::String(string) => {
-                let index = self.index.run(source, context)?.as_integer()? as usize;
-                let item = string.chars().nth(index).unwrap_or_default();
-
-                Ok(Value::string(item.to_string()))
-            }
-            _ => Err(RuntimeError::ValidationFailure(
-                ValidationError::ExpectedCollection { actual: value },
-            )),
-        }
-    }
-}
-
-impl Format for Index {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        self.collection.format(output, indent_level);
-        output.push(':');
-        self.index.format(output, indent_level);
-    }
-}

src/abstract_tree/index_assignment.rs

@@ -1,96 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, AssignmentOperator, Context, Format, Identifier, Index, IndexExpression,
-    SourcePosition, Statement, SyntaxNode, Type, Value,
-};
-
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct IndexAssignment {
-    index: Index,
-    operator: AssignmentOperator,
-    statement: Statement,
-    position: SourcePosition,
-}
-
-impl AbstractTree for IndexAssignment {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("index_assignment", node)?;
-
-        let index_node = node.child(0).unwrap();
-        let index = Index::from_syntax(index_node, source, context)?;
-
-        let operator_node = node.child(1).unwrap();
-        let operator = AssignmentOperator::from_syntax(operator_node, source, context)?;
-
-        let statement_node = node.child(2).unwrap();
-        let statement = Statement::from_syntax(statement_node, source, context)?;
-
-        Ok(IndexAssignment {
-            index,
-            operator,
-            statement,
-            position: node.range().into(),
-        })
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        Ok(Type::None)
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        self.index.validate(_source, _context)?;
-        self.statement.validate(_source, _context)
-    }
-
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        let _index_collection = self.index.collection.run(source, context)?;
-        let index_identifier = if let IndexExpression::Identifier(identifier) = &self.index.index {
-            identifier
-        } else {
-            let index_run = self.index.index.run(source, context)?;
-            let expected_identifier = Identifier::new(index_run.as_string()?);
-
-            return Err(RuntimeError::ValidationFailure(
-                ValidationError::VariableIdentifierNotFound(expected_identifier),
-            ));
-        };
-
-        let value = self.statement.run(source, context)?;
-
-        let new_value = match self.operator {
-            AssignmentOperator::PlusEqual => {
-                if let Some(previous_value) = context.get_value(index_identifier)? {
-                    previous_value.add(value, self.position)?
-                } else {
-                    return Err(RuntimeError::ValidationFailure(
-                        ValidationError::VariableIdentifierNotFound(index_identifier.clone()),
-                    ));
-                }
-            }
-            AssignmentOperator::MinusEqual => {
-                if let Some(previous_value) = context.get_value(index_identifier)? {
-                    previous_value.subtract(value, self.position)?
-                } else {
-                    Value::none()
-                }
-            }
-            AssignmentOperator::Equal => value,
-        };
-
-        context.set_value(index_identifier.clone(), new_value)?;
-
-        Ok(Value::none())
-    }
-}
-
-impl Format for IndexAssignment {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        self.index.format(output, indent_level);
-        output.push(' ');
-        self.operator.format(output, indent_level);
-        output.push(' ');
-        self.statement.format(output, indent_level);
-    }
-}

src/abstract_tree/index_expression.rs

@@ -1,94 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    value_node::ValueNode,
-    AbstractTree, Context, Format, FunctionCall, Identifier, Index, SyntaxNode, Type, Value,
-};
-
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub enum IndexExpression {
-    Value(ValueNode),
-    Identifier(Identifier),
-    Index(Box<Index>),
-    FunctionCall(Box<FunctionCall>),
-}
-
-impl AbstractTree for IndexExpression {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("index_expression", node)?;
-
-        let first_child = node.child(0).unwrap();
-        let child = if first_child.is_named() {
-            first_child
-        } else {
-            node.child(1).unwrap()
-        };
-
-        let abstract_node = match child.kind() {
-            "value" => IndexExpression::Value(ValueNode::from_syntax(child, source, context)?),
-            "identifier" => {
-                IndexExpression::Identifier(Identifier::from_syntax(child, source, context)?)
-            }
-            "index" => {
-                IndexExpression::Index(Box::new(Index::from_syntax(child, source, context)?))
-            }
-            "function_call" => IndexExpression::FunctionCall(Box::new(FunctionCall::from_syntax(
-                child, source, context,
-            )?)),
-            _ => {
-                return Err(SyntaxError::UnexpectedSyntaxNode {
-                    expected: "value, identifier, index or function call".to_string(),
-                    actual: child.kind().to_string(),
-                    position: node.range().into(),
-                })
-            }
-        };
-
-        Ok(abstract_node)
-    }
-
-    fn expected_type(&self, context: &Context) -> Result<Type, ValidationError> {
-        match self {
-            IndexExpression::Value(value_node) => value_node.expected_type(context),
-            IndexExpression::Identifier(identifier) => identifier.expected_type(context),
-            IndexExpression::Index(index) => index.expected_type(context),
-            IndexExpression::FunctionCall(function_call) => function_call.expected_type(context),
-        }
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        match self {
-            IndexExpression::Value(value_node) => value_node.validate(_source, _context),
-            IndexExpression::Identifier(identifier) => identifier.validate(_source, _context),
-            IndexExpression::Index(index) => index.validate(_source, _context),
-            IndexExpression::FunctionCall(function_call) => {
-                function_call.validate(_source, _context)
-            }
-        }
-    }
-
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        match self {
-            IndexExpression::Value(value_node) => value_node.run(source, context),
-            IndexExpression::Identifier(identifier) => identifier.run(source, context),
-            IndexExpression::Index(index) => index.run(source, context),
-            IndexExpression::FunctionCall(function_call) => function_call.run(source, context),
-        }
-    }
-}
-
-impl Format for IndexExpression {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        match self {
-            IndexExpression::Value(value_node) => {
-                value_node.format(output, indent_level);
-            }
-            IndexExpression::Identifier(identifier) => identifier.format(output, indent_level),
-            IndexExpression::FunctionCall(function_call) => {
-                function_call.format(output, indent_level)
-            }
-            IndexExpression::Index(index) => index.format(output, indent_level),
-        }
-    }
-}

src/abstract_tree/logic.rs

@@ -1,90 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Expression, Format, LogicOperator, SyntaxNode, Type, Value,
-};
-
-/// Abstract representation of a logic expression.
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct Logic {
-    left: Expression,
-    operator: LogicOperator,
-    right: Expression,
-}
-
-impl AbstractTree for Logic {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("logic", node)?;
-
-        let first_node = node.child(0).unwrap();
-        let (left_node, operator_node, right_node) = {
-            if first_node.is_named() {
-                (first_node, node.child(1).unwrap(), node.child(2).unwrap())
-            } else {
-                (
-                    node.child(1).unwrap(),
-                    node.child(2).unwrap(),
-                    node.child(3).unwrap(),
-                )
-            }
-        };
-        let left = Expression::from_syntax(left_node, source, context)?;
-        let operator = LogicOperator::from_syntax(operator_node, source, context)?;
-        let right = Expression::from_syntax(right_node, source, context)?;
-
-        Ok(Logic {
-            left,
-            operator,
-            right,
-        })
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        Ok(Type::Boolean)
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        self.left.validate(_source, _context)?;
-        self.right.validate(_source, _context)
-    }
-
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        let left = self.left.run(source, context)?;
-        let right = self.right.run(source, context)?;
-        let result = match self.operator {
-            LogicOperator::Equal => {
-                if let (Ok(left_num), Ok(right_num)) = (left.as_number(), right.as_number()) {
-                    left_num == right_num
-                } else {
-                    left == right
-                }
-            }
-            LogicOperator::NotEqual => {
-                if let (Ok(left_num), Ok(right_num)) = (left.as_number(), right.as_number()) {
-                    left_num != right_num
-                } else {
-                    left != right
-                }
-            }
-            LogicOperator::And => left.as_boolean()? && right.as_boolean()?,
-            LogicOperator::Or => left.as_boolean()? || right.as_boolean()?,
-            LogicOperator::Greater => left > right,
-            LogicOperator::Less => left < right,
-            LogicOperator::GreaterOrEqual => left >= right,
-            LogicOperator::LessOrEqual => left <= right,
-        };
-
-        Ok(Value::Boolean(result))
-    }
-}
-
-impl Format for Logic {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        self.left.format(output, indent_level);
-        output.push(' ');
-        self.operator.format(output, indent_level);
-        output.push(' ');
-        self.right.format(output, indent_level);
-    }
-}

src/abstract_tree/logic_operator.rs

@@ -1,76 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Format, SyntaxNode, Type, Value,
-};
-
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub enum LogicOperator {
-    Equal,
-    NotEqual,
-    And,
-    Or,
-    Greater,
-    Less,
-    GreaterOrEqual,
-    LessOrEqual,
-}
-
-impl AbstractTree for LogicOperator {
-    fn from_syntax(
-        node: SyntaxNode,
-        _source: &str,
-        _context: &Context,
-    ) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("logic_operator", node)?;
-
-        let operator_node = node.child(0).unwrap();
-        let operator = match operator_node.kind() {
-            "==" => LogicOperator::Equal,
-            "!=" => LogicOperator::NotEqual,
-            "&&" => LogicOperator::And,
-            "||" => LogicOperator::Or,
-            ">" => LogicOperator::Greater,
-            "<" => LogicOperator::Less,
-            ">=" => LogicOperator::GreaterOrEqual,
-            "<=" => LogicOperator::LessOrEqual,
-            _ => {
-                return Err(SyntaxError::UnexpectedSyntaxNode {
-                    expected: "==, !=, &&, ||, >, <, >= or <=".to_string(),
-                    actual: operator_node.kind().to_string(),
-                    position: node.range().into(),
-                })
-            }
-        };
-
-        Ok(operator)
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        Ok(Type::None)
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        Ok(())
-    }
-
-    fn run(&self, _source: &str, _context: &Context) -> Result<Value, RuntimeError> {
-        Ok(Value::none())
-    }
-}
-
-impl Format for LogicOperator {
-    fn format(&self, output: &mut String, _indent_level: u8) {
-        match self {
-            LogicOperator::Equal => output.push('='),
-            LogicOperator::NotEqual => output.push_str("!="),
-            LogicOperator::And => output.push_str("&&"),
-            LogicOperator::Or => output.push_str("||"),
-            LogicOperator::Greater => output.push('>'),
-            LogicOperator::Less => output.push('<'),
-            LogicOperator::GreaterOrEqual => output.push_str(">="),
-            LogicOperator::LessOrEqual => output.push_str("<="),
-        }
-    }
-}

src/abstract_tree/map_node.rs

@@ -1,117 +0,0 @@
-use std::collections::BTreeMap;
-
-use serde::{Deserialize, Serialize};
-use tree_sitter::Node as SyntaxNode;
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Format, Identifier, Map, SourcePosition, Statement, Type,
-    TypeSpecification, Value,
-};
-
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct MapNode {
-    properties: BTreeMap<Identifier, (Statement, Option<Type>)>,
-    position: SourcePosition,
-}
-
-impl MapNode {
-    pub fn properties(&self) -> &BTreeMap<Identifier, (Statement, Option<Type>)> {
-        &self.properties
-    }
-}
-
-impl AbstractTree for MapNode {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("map", node)?;
-
-        let mut properties = BTreeMap::new();
-        let mut current_identifier = None;
-        let mut current_type = None;
-
-        for index in 0..node.child_count() - 1 {
-            let child = node.child(index).unwrap();
-
-            if child.kind() == "identifier" {
-                current_identifier = Some(Identifier::from_syntax(child, source, context)?);
-                current_type = None;
-            }
-
-            if child.kind() == "type_specification" {
-                current_type =
-                    Some(TypeSpecification::from_syntax(child, source, context)?.take_inner());
-            }
-
-            if child.kind() == "statement" {
-                let statement = Statement::from_syntax(child, source, context)?;
-
-                if let Some(identifier) = &current_identifier {
-                    properties.insert(identifier.clone(), (statement, current_type.clone()));
-                }
-            }
-        }
-
-        Ok(MapNode {
-            properties,
-            position: SourcePosition::from(node.range()),
-        })
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        if self.properties.is_empty() {
-            return Ok(Type::Map(None));
-        }
-
-        let mut type_map = BTreeMap::new();
-
-        for (identifier, (statement, r#type_option)) in &self.properties {
-            let r#type = if let Some(r#type) = type_option {
-                r#type.clone()
-            } else {
-                statement.expected_type(_context)?
-            };
-
-            type_map.insert(identifier.clone(), r#type);
-        }
-
-        Ok(Type::Map(Some(type_map)))
-    }
-
-    fn validate(&self, _source: &str, context: &Context) -> Result<(), ValidationError> {
-        for (_key, (statement, r#type)) in &self.properties {
-            statement.validate(_source, context)?;
-
-            if let Some(expected) = r#type {
-                let actual = statement.expected_type(context)?;
-
-                if !expected.accepts(&actual) {
-                    return Err(ValidationError::TypeCheck {
-                        expected: expected.clone(),
-                        actual,
-                        position: self.position.clone(),
-                    });
-                }
-            }
-        }
-
-        Ok(())
-    }
-
-    fn run(&self, _source: &str, _context: &Context) -> Result<Value, RuntimeError> {
-        let mut map = Map::new();
-
-        for (key, (statement, _)) in &self.properties {
-            let value = statement.run(_source, _context)?;
-
-            map.set(key.clone(), value);
-        }
-
-        Ok(Value::Map(map))
-    }
-}
-
-impl Format for MapNode {
-    fn format(&self, _output: &mut String, _indent_level: u8) {
-        todo!()
-    }
-}

src/abstract_tree/match.rs

@@ -1,145 +0,0 @@
-//! Pattern matching.
-//!
-//! Note that this module is called "match" but is escaped as "r#match" because
-//! "match" is a keyword in Rust.
-use serde::{Deserialize, Serialize};
-use tree_sitter::Node as SyntaxNode;
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Expression, Format, MatchPattern, Statement, Type, Value,
-};
-
-/// Abstract representation of a match statement.
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct Match {
-    matcher: Expression,
-    options: Vec<(MatchPattern, Statement)>,
-    fallback: Option<Box<Statement>>,
-
-    #[serde(skip)]
-    context: Context,
-}
-
-impl AbstractTree for Match {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("match", node)?;
-
-        let matcher_node = node.child(1).unwrap();
-        let matcher = Expression::from_syntax(matcher_node, source, context)?;
-
-        let mut options = Vec::new();
-        let mut previous_pattern = None;
-        let mut next_statement_is_fallback = false;
-        let mut fallback = None;
-
-        for index in 2..node.child_count() {
-            let child = node.child(index).unwrap();
-
-            if child.kind() == "match_pattern" {
-                previous_pattern = Some(MatchPattern::from_syntax(child, source, context)?);
-            }
-
-            if child.kind() == "statement" {
-                let statement = Statement::from_syntax(child, source, context)?;
-
-                if next_statement_is_fallback {
-                    fallback = Some(Box::new(statement));
-                    next_statement_is_fallback = false;
-                } else if let Some(expression) = &previous_pattern {
-                    options.push((expression.clone(), statement));
-                }
-            }
-        }
-
-        Ok(Match {
-            matcher,
-            options,
-            fallback,
-            context: Context::default(),
-        })
-    }
-
-    fn expected_type(&self, context: &Context) -> Result<Type, ValidationError> {
-        let (_, first_statement) = self.options.first().unwrap();
-
-        first_statement.expected_type(context)
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        self.matcher.validate(_source, _context)?;
-
-        for (match_pattern, statement) in &self.options {
-            if let MatchPattern::EnumPattern(enum_pattern) = match_pattern {
-                if let Some(identifier) = enum_pattern.inner_identifier() {
-                    self.context.set_type(identifier.clone(), Type::Any)?;
-                }
-            }
-
-            match_pattern.validate(_source, _context)?;
-            statement.validate(_source, &self.context)?;
-        }
-
-        if let Some(statement) = &self.fallback {
-            statement.validate(_source, _context)?;
-        }
-
-        Ok(())
-    }
-
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        let matcher_value = self.matcher.run(source, context)?;
-
-        for (pattern, statement) in &self.options {
-            if let (Value::Enum(enum_instance), MatchPattern::EnumPattern(enum_pattern)) =
-                (&matcher_value, pattern)
-            {
-                if enum_instance.name() == enum_pattern.name()
-                    && enum_instance.variant() == enum_pattern.variant()
-                {
-                    let statement_context = Context::with_variables_from(context)?;
-
-                    if let (Some(identifier), Some(value)) =
-                        (enum_pattern.inner_identifier(), enum_instance.value())
-                    {
-                        statement_context.set_value(identifier.clone(), value.as_ref().clone())?;
-                    }
-
-                    return statement.run(source, &statement_context);
-                }
-            }
-            let pattern_value = pattern.run(source, context)?;
-
-            if matcher_value == pattern_value {
-                return statement.run(source, context);
-            }
-        }
-
-        if let Some(fallback) = &self.fallback {
-            fallback.run(source, context)
-        } else {
-            Ok(Value::none())
-        }
-    }
-}
-
-impl Format for Match {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        output.push_str("match ");
-        self.matcher.format(output, indent_level);
-        output.push_str(" {");
-
-        for (expression, statement) in &self.options {
-            expression.format(output, indent_level);
-            output.push_str(" => ");
-            statement.format(output, indent_level);
-        }
-
-        if let Some(statement) = &self.fallback {
-            output.push_str("* => ");
-            statement.format(output, indent_level);
-        }
-
-        output.push('}');
-    }
-}

src/abstract_tree/match_pattern.rs

@@ -1,64 +0,0 @@
-use serde::{Deserialize, Serialize};
-use tree_sitter::Node as SyntaxNode;
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, EnumPattern, Format, Type, Value, ValueNode,
-};
-
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub enum MatchPattern {
-    EnumPattern(EnumPattern),
-    Value(ValueNode),
-    Wildcard,
-}
-
-impl AbstractTree for MatchPattern {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("match_pattern", node)?;
-
-        let child = node.child(0).unwrap();
-        let pattern = match child.kind() {
-            "enum_pattern" => {
-                MatchPattern::EnumPattern(EnumPattern::from_syntax(child, source, context)?)
-            }
-            "value" => MatchPattern::Value(ValueNode::from_syntax(child, source, context)?),
-            "*" => MatchPattern::Wildcard,
-            _ => {
-                return Err(SyntaxError::UnexpectedSyntaxNode {
-                    expected: "enum pattern or value".to_string(),
-                    actual: child.kind().to_string(),
-                    position: node.range().into(),
-                })
-            }
-        };
-
-        Ok(pattern)
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        match self {
-            MatchPattern::EnumPattern(enum_pattern) => enum_pattern.expected_type(_context),
-            MatchPattern::Value(value_node) => value_node.expected_type(_context),
-            MatchPattern::Wildcard => todo!(),
-        }
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        Ok(())
-    }
-
-    fn run(&self, _source: &str, _context: &Context) -> Result<Value, RuntimeError> {
-        match self {
-            MatchPattern::EnumPattern(enum_pattern) => enum_pattern.run(_source, _context),
-            MatchPattern::Value(value_node) => value_node.run(_source, _context),
-            MatchPattern::Wildcard => todo!(),
-        }
-    }
-}
-
-impl Format for MatchPattern {
-    fn format(&self, _output: &mut String, _indent_level: u8) {
-        todo!()
-    }
-}

src/abstract_tree/math.rs

@@ -1,74 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Expression, Format, MathOperator, SourcePosition, SyntaxNode, Type,
-    Value,
-};
-
-/// Abstract representation of a math operation.
-///
-/// Dust currently supports the four basic operations and the modulo (or
-/// remainder) operator.
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct Math {
-    left: Expression,
-    operator: MathOperator,
-    right: Expression,
-    position: SourcePosition,
-}
-
-impl AbstractTree for Math {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("math", node)?;
-
-        let left_node = node.child(0).unwrap();
-        let left = Expression::from_syntax(left_node, source, context)?;
-
-        let operator_node = node.child(1).unwrap();
-        let operator = MathOperator::from_syntax(operator_node, source, context)?;
-
-        let right_node = node.child(2).unwrap();
-        let right = Expression::from_syntax(right_node, source, context)?;
-
-        Ok(Math {
-            left,
-            operator,
-            right,
-            position: node.range().into(),
-        })
-    }
-
-    fn expected_type(&self, context: &Context) -> Result<Type, ValidationError> {
-        self.left.expected_type(context)
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        self.left.validate(_source, _context)?;
-        self.right.validate(_source, _context)
-    }
-
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        let left = self.left.run(source, context)?;
-        let right = self.right.run(source, context)?;
-        let value = match self.operator {
-            MathOperator::Add => left.add(right, self.position)?,
-            MathOperator::Subtract => left.subtract(right, self.position)?,
-            MathOperator::Multiply => left.multiply(right, self.position)?,
-            MathOperator::Divide => left.divide(right, self.position)?,
-            MathOperator::Modulo => left.modulo(right, self.position)?,
-        };
-
-        Ok(value)
-    }
-}
-
-impl Format for Math {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        self.left.format(output, indent_level);
-        output.push(' ');
-        self.operator.format(output, indent_level);
-        output.push(' ');
-        self.right.format(output, indent_level);
-    }
-}

src/abstract_tree/math_operator.rs

@@ -1,67 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Format, SyntaxNode, Type, Value,
-};
-
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub enum MathOperator {
-    Add,
-    Subtract,
-    Multiply,
-    Divide,
-    Modulo,
-}
-
-impl AbstractTree for MathOperator {
-    fn from_syntax(
-        node: SyntaxNode,
-        _source: &str,
-        _context: &Context,
-    ) -> Result<Self, SyntaxError> {
-        let operator_node = node.child(0).unwrap();
-        let operator = match operator_node.kind() {
-            "+" => MathOperator::Add,
-            "-" => MathOperator::Subtract,
-            "*" => MathOperator::Multiply,
-            "/" => MathOperator::Divide,
-            "%" => MathOperator::Modulo,
-            _ => {
-                return Err(SyntaxError::UnexpectedSyntaxNode {
-                    expected: "+, -, *, / or %".to_string(),
-                    actual: operator_node.kind().to_string(),
-                    position: node.range().into(),
-                })
-            }
-        };
-
-        Ok(operator)
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        Ok(Type::None)
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        Ok(())
-    }
-
-    fn run(&self, _source: &str, _context: &Context) -> Result<Value, RuntimeError> {
-        Ok(Value::none())
-    }
-}
-
-impl Format for MathOperator {
-    fn format(&self, output: &mut String, _indent_level: u8) {
-        let char = match self {
-            MathOperator::Add => '+',
-            MathOperator::Subtract => '-',
-            MathOperator::Multiply => '*',
-            MathOperator::Divide => '/',
-            MathOperator::Modulo => '%',
-        };
-
-        output.push(char);
-    }
-}

src/abstract_tree/mod.rs

@@ -1,178 +0,0 @@
-//! Abstract, executable representations of corresponding items found in Dust
-//! source code. The types that implement [AbstractTree] are inteded to be
-//! created by an [Interpreter].
-pub mod r#as;
-pub mod assignment;
-pub mod assignment_operator;
-pub mod block;
-pub mod command;
-pub mod enum_defintion;
-pub mod enum_pattern;
-pub mod expression;
-pub mod r#for;
-pub mod function_call;
-pub mod function_expression;
-pub mod function_node;
-pub mod identifier;
-pub mod if_else;
-pub mod index;
-pub mod index_assignment;
-pub mod index_expression;
-pub mod logic;
-pub mod logic_operator;
-pub mod map_node;
-pub mod r#match;
-pub mod match_pattern;
-pub mod math;
-pub mod math_operator;
-pub mod statement;
-pub mod struct_definition;
-pub mod r#type;
-pub mod type_definition;
-pub mod type_specification;
-pub mod value_node;
-pub mod r#while;
-
-pub use {
-    assignment::*, assignment_operator::*, block::*, command::*, enum_defintion::*,
-    enum_pattern::*, expression::*, function_call::*, function_expression::*, function_node::*,
-    identifier::*, if_else::*, index::*, index_assignment::IndexAssignment, index_expression::*,
-    logic::*, logic_operator::*, map_node::*, match_pattern::*, math::*, math_operator::*, r#as::*,
-    r#for::*, r#match::*, r#type::*, r#while::*, statement::*, struct_definition::*,
-    type_definition::*, type_specification::*, value_node::*,
-};
-
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    context::Context,
-    error::{RuntimeError, SyntaxError, ValidationError},
-    SyntaxNode, Value,
-};
-
-/// A detailed report of a position in the source code string.
-#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize)]
-pub struct SourcePosition {
-    pub start_byte: usize,
-    pub end_byte: usize,
-    pub start_row: usize,
-    pub start_column: usize,
-    pub end_row: usize,
-    pub end_column: usize,
-}
-
-impl From<tree_sitter::Range> for SourcePosition {
-    fn from(range: tree_sitter::Range) -> Self {
-        SourcePosition {
-            start_byte: range.start_byte,
-            end_byte: range.end_byte,
-            start_row: range.start_point.row + 1,
-            start_column: range.start_point.column,
-            end_row: range.end_point.row + 1,
-            end_column: range.end_point.column,
-        }
-    }
-}
-
-/// Abstraction that represents a whole, executable unit of dust code.
-#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize)]
-pub struct Root {
-    statements: Vec<Statement>,
-}
-
-// TODO Change Root to use tree sitter's cursor to traverse the statements
-// instead of indexes. This will be more performant when there are a lot of
-// top-level statements in the tree.
-impl AbstractTree for Root {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("root", node)?;
-
-        let statement_count = node.child_count();
-        let mut statements = Vec::with_capacity(statement_count);
-
-        for index in 0..statement_count {
-            let statement_node = node.child(index).unwrap();
-            let statement = Statement::from_syntax(statement_node, source, context)?;
-
-            statements.push(statement);
-        }
-
-        Ok(Root { statements })
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        for statement in &self.statements {
-            statement.validate(_source, _context)?;
-        }
-
-        Ok(())
-    }
-
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        let mut value = Value::none();
-
-        for statement in &self.statements {
-            value = statement.run(source, context)?;
-
-            if statement.is_return() {
-                return Ok(value);
-            }
-        }
-
-        Ok(value)
-    }
-
-    fn expected_type(&self, context: &Context) -> Result<Type, ValidationError> {
-        self.statements.last().unwrap().expected_type(context)
-    }
-}
-
-impl Format for Root {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        for (index, statement) in self.statements.iter().enumerate() {
-            if index > 0 {
-                output.push('\n');
-            }
-            statement.format(output, indent_level);
-            output.push('\n');
-        }
-    }
-}
-
-/// This trait is implemented by the Evaluator's internal types to form an
-/// executable tree that resolves to a single value.
-pub trait AbstractTree: Sized + Format {
-    /// Interpret the syntax tree at the given node and return the abstraction.
-    /// Returns a syntax error if the source is invalid.
-    ///
-    /// This function is used to convert nodes in the Tree Sitter concrete
-    /// syntax tree into executable nodes in an abstract tree. This function is
-    /// where the tree should be traversed by accessing sibling and child nodes.
-    /// Each node in the CST should be traversed only once.
-    ///
-    /// If necessary, the source code can be accessed directly by getting the
-    /// node's byte range.
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError>;
-
-    /// Return the type of the value that this abstract node will create when
-    /// run. Returns a validation error if the tree is invalid.
-    fn expected_type(&self, context: &Context) -> Result<Type, ValidationError>;
-
-    /// Verify the type integrity of the node. Returns a validation error if the
-    /// tree is invalid.
-    fn validate(&self, source: &str, context: &Context) -> Result<(), ValidationError>;
-
-    /// Execute this node's logic and return a value. Returns a runtime error if
-    /// the node cannot resolve to a value.
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError>;
-}
-
-pub trait Format {
-    fn format(&self, output: &mut String, indent_level: u8);
-
-    fn indent(output: &mut String, indent_level: u8) {
-        for _ in 0..indent_level {
-            output.push_str("    ");
-        }
-    }
-}

src/abstract_tree/new.rs

@@ -1,45 +0,0 @@
-use serde::{Deserialize, Serialize};
-use tree_sitter::Node;
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Format, Identifier, Type, TypeSpecification, Value, ValueNode,
-};
-
-#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq, PartialOrd, Ord)]
-pub struct New {
-    identifier: Identifier,
-    properties: Vec<(Identifier, ValueNode, Option<TypeSpecification>)>,
-}
-
-impl AbstractTree for New {
-    fn from_syntax(node: Node, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        let identifier_node = node.child(1).unwrap();
-        let identifier = Identifier::from_syntax(identifier_node, source, context)?;
-
-        let properties = Vec::new();
-
-        Ok(New {
-            identifier,
-            properties,
-        })
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        todo!()
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        todo!()
-    }
-
-    fn run(&self, _source: &str, _context: &Context) -> Result<Value, RuntimeError> {
-        todo!()
-    }
-}
-
-impl Format for New {
-    fn format(&self, _output: &mut String, _indent_level: u8) {
-        todo!()
-    }
-}

src/abstract_tree/statement.rs

@@ -1,202 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Assignment, Block, Context, Expression, For, Format, IfElse, IndexAssignment,
-    Match, SyntaxNode, Type, TypeDefinition, Value, While,
-};
-
-/// Abstract representation of a statement.
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct Statement {
-    is_return: bool,
-    statement_kind: StatementKind,
-}
-
-impl Statement {
-    pub fn is_return(&self) -> bool {
-        self.is_return
-    }
-}
-
-impl AbstractTree for Statement {
-    fn from_syntax(
-        node: SyntaxNode,
-        source: &str,
-        _context: &Context,
-    ) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("statement", node)?;
-
-        let first_child = node.child(0).unwrap();
-        let mut is_return = first_child.kind() == "return" || first_child.kind() == "break";
-        let child = if is_return {
-            node.child(1).unwrap()
-        } else {
-            first_child
-        };
-
-        let statement_kind = StatementKind::from_syntax(child, source, _context)?;
-
-        if let StatementKind::Block(block) = &statement_kind {
-            if block.contains_return() {
-                is_return = true;
-            }
-        };
-
-        Ok(Statement {
-            is_return,
-            statement_kind,
-        })
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        self.statement_kind.expected_type(_context)
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        self.statement_kind.validate(_source, _context)
-    }
-
-    fn run(&self, _source: &str, _context: &Context) -> Result<Value, RuntimeError> {
-        self.statement_kind.run(_source, _context)
-    }
-}
-
-impl Format for Statement {
-    fn format(&self, _output: &mut String, _indent_level: u8) {
-        self.statement_kind.format(_output, _indent_level)
-    }
-}
-
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-enum StatementKind {
-    Assignment(Box<Assignment>),
-    Expression(Expression),
-    IfElse(Box<IfElse>),
-    Match(Match),
-    While(Box<While>),
-    Block(Box<Block>),
-    For(Box<For>),
-    IndexAssignment(Box<IndexAssignment>),
-    TypeDefinition(TypeDefinition),
-}
-
-impl AbstractTree for StatementKind {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("statement_kind", node)?;
-
-        let child = node.child(0).unwrap();
-
-        match child.kind() {
-            "assignment" => Ok(StatementKind::Assignment(Box::new(
-                Assignment::from_syntax(child, source, context)?,
-            ))),
-            "expression" => Ok(StatementKind::Expression(Expression::from_syntax(
-                child, source, context,
-            )?)),
-            "if_else" => Ok(StatementKind::IfElse(Box::new(IfElse::from_syntax(
-                child, source, context,
-            )?))),
-            "while" => Ok(StatementKind::While(Box::new(While::from_syntax(
-                child, source, context,
-            )?))),
-            "block" => Ok(StatementKind::Block(Box::new(Block::from_syntax(
-                child, source, context,
-            )?))),
-            "for" => Ok(StatementKind::For(Box::new(For::from_syntax(
-                child, source, context,
-            )?))),
-            "index_assignment" => Ok(StatementKind::IndexAssignment(Box::new(
-                IndexAssignment::from_syntax(child, source, context)?,
-            ))),
-            "match" => Ok(StatementKind::Match(Match::from_syntax(
-                child, source, context,
-            )?)),
-            "type_definition" => Ok(StatementKind::TypeDefinition(TypeDefinition::from_syntax(
-                child, source, context
-            )?)),
-            _ => Err(SyntaxError::UnexpectedSyntaxNode {
-                expected:
-                    "assignment, index assignment, expression, type_definition, block, return, if...else, while, for or match".to_string(),
-                actual: child.kind().to_string(),
-                position: node.range().into(),
-            }),
-        }
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        match self {
-            StatementKind::Assignment(assignment) => assignment.expected_type(_context),
-            StatementKind::Expression(expression) => expression.expected_type(_context),
-            StatementKind::IfElse(if_else) => if_else.expected_type(_context),
-            StatementKind::Match(r#match) => r#match.expected_type(_context),
-            StatementKind::While(r#while) => r#while.expected_type(_context),
-            StatementKind::Block(block) => block.expected_type(_context),
-            StatementKind::For(r#for) => r#for.expected_type(_context),
-            StatementKind::IndexAssignment(index_assignment) => {
-                index_assignment.expected_type(_context)
-            }
-            StatementKind::TypeDefinition(type_definition) => {
-                type_definition.expected_type(_context)
-            }
-        }
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        match self {
-            StatementKind::Assignment(assignment) => assignment.validate(_source, _context),
-            StatementKind::Expression(expression) => expression.validate(_source, _context),
-            StatementKind::IfElse(if_else) => if_else.validate(_source, _context),
-            StatementKind::Match(r#match) => r#match.validate(_source, _context),
-            StatementKind::While(r#while) => r#while.validate(_source, _context),
-            StatementKind::Block(block) => block.validate(_source, _context),
-            StatementKind::For(r#for) => r#for.validate(_source, _context),
-            StatementKind::IndexAssignment(index_assignment) => {
-                index_assignment.validate(_source, _context)
-            }
-            StatementKind::TypeDefinition(type_definition) => {
-                type_definition.validate(_source, _context)
-            }
-        }
-    }
-
-    fn run(&self, _source: &str, _context: &Context) -> Result<Value, RuntimeError> {
-        match self {
-            StatementKind::Assignment(assignment) => assignment.run(_source, _context),
-            StatementKind::Expression(expression) => expression.run(_source, _context),
-            StatementKind::IfElse(if_else) => if_else.run(_source, _context),
-            StatementKind::Match(r#match) => r#match.run(_source, _context),
-            StatementKind::While(r#while) => r#while.run(_source, _context),
-            StatementKind::Block(block) => block.run(_source, _context),
-            StatementKind::For(r#for) => r#for.run(_source, _context),
-            StatementKind::IndexAssignment(index_assignment) => {
-                index_assignment.run(_source, _context)
-            }
-            StatementKind::TypeDefinition(type_definition) => {
-                type_definition.run(_source, _context)
-            }
-        }
-    }
-}
-
-impl Format for StatementKind {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        StatementKind::indent(output, indent_level);
-
-        match self {
-            StatementKind::Assignment(assignment) => assignment.format(output, indent_level),
-            StatementKind::Expression(expression) => expression.format(output, indent_level),
-            StatementKind::IfElse(if_else) => if_else.format(output, indent_level),
-            StatementKind::Match(r#match) => r#match.format(output, indent_level),
-            StatementKind::While(r#while) => r#while.format(output, indent_level),
-            StatementKind::Block(block) => block.format(output, indent_level),
-            StatementKind::For(r#for) => r#for.format(output, indent_level),
-            StatementKind::IndexAssignment(index_assignment) => {
-                index_assignment.format(output, indent_level)
-            }
-            StatementKind::TypeDefinition(type_definition) => {
-                type_definition.format(output, indent_level)
-            }
-        }
-    }
-}

src/abstract_tree/struct_definition.rs

@@ -1,120 +0,0 @@
-use std::collections::BTreeMap;
-
-use serde::{Deserialize, Serialize};
-use tree_sitter::Node as SyntaxNode;
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Format, Identifier, Map, MapNode, Statement, StructInstance, Type,
-    TypeDefinition, TypeSpecification, Value,
-};
-
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct StructDefinition {
-    name: Identifier,
-    properties: BTreeMap<Identifier, (Option<Statement>, Type)>,
-}
-
-impl StructDefinition {
-    pub fn instantiate(
-        &self,
-        new_properties: &MapNode,
-        source: &str,
-        context: &Context,
-    ) -> Result<StructInstance, RuntimeError> {
-        let mut all_properties = Map::new();
-
-        for (key, (statement_option, _)) in &self.properties {
-            if let Some(statement) = statement_option {
-                let value = statement.run(source, context)?;
-
-                all_properties.set(key.clone(), value);
-            }
-        }
-
-        for (key, (statement, _)) in new_properties.properties() {
-            let value = statement.run(source, context)?;
-
-            all_properties.set(key.clone(), value);
-        }
-
-        Ok(StructInstance::new(self.name.clone(), all_properties))
-    }
-}
-
-impl AbstractTree for StructDefinition {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("struct_definition", node)?;
-
-        let name_node = node.child(1).unwrap();
-        let name = Identifier::from_syntax(name_node, source, context)?;
-
-        let mut properties = BTreeMap::new();
-        let mut current_identifier: Option<Identifier> = None;
-        let mut current_type: Option<Type> = None;
-        let mut current_statement = None;
-
-        for index in 2..node.child_count() - 1 {
-            let child_syntax_node = node.child(index).unwrap();
-
-            if child_syntax_node.kind() == "identifier" {
-                if current_statement.is_none() {
-                    if let (Some(identifier), Some(r#type)) = (&current_identifier, &current_type) {
-                        properties.insert(identifier.clone(), (None, r#type.clone()));
-                    }
-                }
-
-                current_type = None;
-                current_identifier =
-                    Some(Identifier::from_syntax(child_syntax_node, source, context)?);
-            }
-
-            if child_syntax_node.kind() == "type_specification" {
-                current_type = Some(
-                    TypeSpecification::from_syntax(child_syntax_node, source, context)?
-                        .take_inner(),
-                );
-            }
-
-            if child_syntax_node.kind() == "statement" {
-                current_statement =
-                    Some(Statement::from_syntax(child_syntax_node, source, context)?);
-
-                if let Some(identifier) = &current_identifier {
-                    let r#type = if let Some(r#type) = &current_type {
-                        r#type.clone()
-                    } else {
-                        Type::None
-                    };
-
-                    properties.insert(
-                        identifier.clone(),
-                        (current_statement.clone(), r#type.clone()),
-                    );
-                }
-            }
-        }
-
-        Ok(StructDefinition { name, properties })
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        Ok(Type::None)
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        Ok(())
-    }
-
-    fn run(&self, _source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        context.set_definition(self.name.clone(), TypeDefinition::Struct(self.clone()))?;
-
-        Ok(Value::none())
-    }
-}
-
-impl Format for StructDefinition {
-    fn format(&self, _output: &mut String, _indent_level: u8) {
-        todo!()
-    }
-}

src/abstract_tree/type.rs

@@ -1,341 +0,0 @@
-use std::{
-    collections::BTreeMap,
-    fmt::{self, Display, Formatter},
-};
-
-use serde::{Deserialize, Serialize};
-use tree_sitter::Node as SyntaxNode;
-
-use crate::{
-    built_in_types::BuiltInType,
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Format, Identifier, TypeSpecification, Value,
-};
-
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub enum Type {
-    Any,
-    Boolean,
-    Collection,
-    Custom {
-        name: Identifier,
-        argument: Option<Box<Type>>,
-    },
-    Float,
-    Function {
-        parameter_types: Vec<Type>,
-        return_type: Box<Type>,
-    },
-    Integer,
-    List(Box<Type>),
-    Map(Option<BTreeMap<Identifier, Type>>),
-    Number,
-    String,
-    Range,
-    None,
-}
-
-impl Type {
-    pub fn custom(name: Identifier, argument: Option<Type>) -> Self {
-        Type::Custom {
-            name,
-            argument: argument.map(|r#type| Box::new(r#type)),
-        }
-    }
-
-    pub fn option(inner_type: Option<Type>) -> Self {
-        BuiltInType::Option(inner_type).get().clone()
-    }
-
-    pub fn list(item_type: Type) -> Self {
-        Type::List(Box::new(item_type))
-    }
-
-    pub fn function(parameter_types: Vec<Type>, return_type: Type) -> Self {
-        Type::Function {
-            parameter_types,
-            return_type: Box::new(return_type),
-        }
-    }
-
-    /// Returns a boolean indicating whether is type is accepting of the other.
-    ///
-    /// The types do not need to match exactly. For example, the Any variant matches all of the
-    /// others and the Number variant accepts Number, Integer and Float.
-    pub fn accepts(&self, other: &Type) -> bool {
-        log::info!("Checking type {self} against {other}.");
-
-        match (self, other) {
-            (Type::Any, _)
-            | (_, Type::Any)
-            | (Type::Boolean, Type::Boolean)
-            | (Type::Collection, Type::Collection)
-            | (Type::Collection, Type::List(_))
-            | (Type::List(_), Type::Collection)
-            | (Type::Collection, Type::Map(_))
-            | (Type::Map(_), Type::Collection)
-            | (Type::Collection, Type::String)
-            | (Type::String, Type::Collection)
-            | (Type::Float, Type::Float)
-            | (Type::Integer, Type::Integer)
-            | (Type::Map(None), Type::Map(None))
-            | (Type::Number, Type::Number)
-            | (Type::Number, Type::Integer)
-            | (Type::Number, Type::Float)
-            | (Type::Integer, Type::Number)
-            | (Type::Float, Type::Number)
-            | (Type::String, Type::String)
-            | (Type::None, Type::None) => true,
-            (Type::Map(left_types), Type::Map(right_types)) => left_types == right_types,
-            (
-                Type::Custom {
-                    name: left_name,
-                    argument: left_argument,
-                },
-                Type::Custom {
-                    name: right_name,
-                    argument: right_argument,
-                },
-            ) => {
-                if left_name != right_name {
-                    false
-                } else {
-                    left_argument == right_argument
-                }
-            }
-            (Type::List(self_item_type), Type::List(other_item_type)) => {
-                self_item_type.accepts(&other_item_type)
-            }
-            (
-                Type::Function {
-                    parameter_types: self_parameter_types,
-                    return_type: self_return_type,
-                },
-                Type::Function {
-                    parameter_types: other_parameter_types,
-                    return_type: other_return_type,
-                },
-            ) => {
-                let parameter_type_pairs = self_parameter_types
-                    .iter()
-                    .zip(other_parameter_types.iter());
-
-                for (self_parameter_type, other_parameter_type) in parameter_type_pairs {
-                    if self_parameter_type == other_parameter_type {
-                        return false;
-                    }
-                }
-
-                self_return_type == other_return_type
-            }
-            _ => false,
-        }
-    }
-
-    pub fn is_function(&self) -> bool {
-        matches!(self, Type::Function { .. })
-    }
-
-    pub fn is_list(&self) -> bool {
-        matches!(self, Type::List(_))
-    }
-
-    pub fn is_map(&self) -> bool {
-        matches!(self, Type::Map(_))
-    }
-}
-
-impl AbstractTree for Type {
-    fn from_syntax(
-        node: SyntaxNode,
-        _source: &str,
-        context: &Context,
-    ) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("type", node)?;
-
-        let type_node = node.child(0).unwrap();
-
-        let r#type = match type_node.kind() {
-            "identifier" => {
-                let name = Identifier::from_syntax(type_node, _source, context)?;
-                let argument = if let Some(child) = node.child(2) {
-                    Some(Type::from_syntax(child, _source, context)?)
-                } else {
-                    None
-                };
-
-                Type::custom(name, argument)
-            }
-            "{" => {
-                let mut type_map = BTreeMap::new();
-                let mut previous_identifier = None;
-
-                for index in 1..node.child_count() - 1 {
-                    let child = node.child(index).unwrap();
-
-                    if let Some(identifier) = previous_identifier {
-                        let type_specification =
-                            TypeSpecification::from_syntax(child, _source, context)?;
-
-                        type_map.insert(identifier, type_specification.take_inner());
-                        previous_identifier = None;
-                    } else {
-                        previous_identifier =
-                            Some(Identifier::from_syntax(child, _source, context)?)
-                    }
-                }
-
-                Type::Map(Some(type_map))
-            }
-            "[" => {
-                let item_type_node = node.child(1).unwrap();
-                let item_type = Type::from_syntax(item_type_node, _source, context)?;
-
-                Type::List(Box::new(item_type))
-            }
-            "any" => Type::Any,
-            "bool" => Type::Boolean,
-            "collection" => Type::Collection,
-            "float" => Type::Float,
-            "(" => {
-                let child_count = node.child_count();
-                let mut parameter_types = Vec::new();
-
-                for index in 1..child_count - 2 {
-                    let child = node.child(index).unwrap();
-
-                    if child.is_named() {
-                        let parameter_type = Type::from_syntax(child, _source, context)?;
-
-                        parameter_types.push(parameter_type);
-                    }
-                }
-
-                let final_node = node.child(child_count - 1).unwrap();
-                let return_type = if final_node.is_named() {
-                    Type::from_syntax(final_node, _source, context)?
-                } else {
-                    Type::option(None)
-                };
-
-                Type::Function {
-                    parameter_types,
-                    return_type: Box::new(return_type),
-                }
-            }
-            "int" => Type::Integer,
-            "map" => Type::Map(None),
-            "num" => Type::Number,
-            "none" => Type::None,
-            "str" => Type::String,
-            _ => {
-                return Err(SyntaxError::UnexpectedSyntaxNode {
-                    expected: "any, bool, float, int, num, str, custom type, (, [ or {".to_string(),
-                    actual: type_node.kind().to_string(),
-                    position: node.range().into(),
-                })
-            }
-        };
-
-        Ok(r#type)
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        Ok(Type::None)
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        Ok(())
-    }
-
-    fn run(&self, _source: &str, _context: &Context) -> Result<Value, RuntimeError> {
-        Ok(Value::none())
-    }
-}
-
-impl Format for Type {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        match self {
-            Type::Any => output.push_str("any"),
-            Type::Boolean => output.push_str("bool"),
-            Type::Collection => output.push_str("collection"),
-            Type::Custom {
-                name: _,
-                argument: _,
-            } => todo!(),
-            Type::Float => output.push_str("float"),
-            Type::Function {
-                parameter_types,
-                return_type,
-            } => {
-                output.push('(');
-
-                for (index, parameter_type) in parameter_types.iter().enumerate() {
-                    parameter_type.format(output, indent_level);
-
-                    if index != parameter_types.len() - 1 {
-                        output.push(' ');
-                    }
-                }
-
-                output.push_str(") -> ");
-                return_type.format(output, indent_level);
-            }
-            Type::Integer => output.push_str("int"),
-            Type::List(item_type) => {
-                output.push('[');
-                item_type.format(output, indent_level);
-                output.push(']');
-            }
-            Type::Map(_) => {
-                output.push_str("map");
-            }
-            Type::None => output.push_str("Option::None"),
-            Type::Number => output.push_str("num"),
-            Type::String => output.push_str("str"),
-            Type::Range => todo!(),
-        }
-    }
-}
-
-impl Display for Type {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        match self {
-            Type::Any => write!(f, "any"),
-            Type::Boolean => write!(f, "bool"),
-            Type::Collection => write!(f, "collection"),
-            Type::Custom { name, argument } => {
-                if let Some(argument) = argument {
-                    write!(f, "{name}<{argument}>")
-                } else {
-                    write!(f, "{name}")
-                }
-            }
-            Type::Float => write!(f, "float"),
-            Type::Function {
-                parameter_types,
-                return_type,
-            } => {
-                write!(f, "(")?;
-
-                for (index, parameter_type) in parameter_types.iter().enumerate() {
-                    write!(f, "{parameter_type}")?;
-
-                    if index != parameter_types.len() - 1 {
-                        write!(f, " ")?;
-                    }
-                }
-
-                write!(f, ")")?;
-                write!(f, " -> {return_type}")
-            }
-            Type::Integer => write!(f, "int"),
-            Type::List(item_type) => write!(f, "[{item_type}]"),
-            Type::Map(_) => write!(f, "map"),
-            Type::Number => write!(f, "num"),
-            Type::None => write!(f, "none"),
-            Type::String => write!(f, "str"),
-            Type::Range => todo!(),
-        }
-    }
-}

src/abstract_tree/type_definition.rs

@@ -1,73 +0,0 @@
-use serde::{Deserialize, Serialize};
-use tree_sitter::Node as SyntaxNode;
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, EnumDefinition, Format, Identifier, StructDefinition, Type, Value,
-};
-
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub enum TypeDefinition {
-    Enum(EnumDefinition),
-    Struct(StructDefinition),
-}
-
-impl TypeDefinition {
-    pub fn identifier(&self) -> &Identifier {
-        match self {
-            TypeDefinition::Enum(enum_definition) => enum_definition.identifier(),
-            TypeDefinition::Struct(_) => todo!(),
-        }
-    }
-}
-
-impl AbstractTree for TypeDefinition {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("type_definition", node)?;
-
-        let child = node.child(0).unwrap();
-
-        match child.kind() {
-            "enum_definition" => Ok(TypeDefinition::Enum(EnumDefinition::from_syntax(
-                child, source, context,
-            )?)),
-            "struct_definition" => Ok(TypeDefinition::Struct(StructDefinition::from_syntax(
-                child, source, context,
-            )?)),
-            _ => Err(SyntaxError::UnexpectedSyntaxNode {
-                expected: "enum or struct definition".to_string(),
-                actual: child.kind().to_string(),
-                position: node.range().into(),
-            }),
-        }
-    }
-
-    fn expected_type(&self, _context: &Context) -> Result<Type, ValidationError> {
-        match self {
-            TypeDefinition::Enum(enum_definition) => enum_definition.expected_type(_context),
-            TypeDefinition::Struct(struct_definition) => struct_definition.expected_type(_context),
-        }
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        match self {
-            TypeDefinition::Enum(enum_definition) => enum_definition.validate(_source, _context),
-            TypeDefinition::Struct(struct_definition) => {
-                struct_definition.validate(_source, _context)
-            }
-        }
-    }
-
-    fn run(&self, _source: &str, _context: &Context) -> Result<Value, RuntimeError> {
-        match self {
-            TypeDefinition::Enum(enum_definition) => enum_definition.run(_source, _context),
-            TypeDefinition::Struct(struct_definition) => struct_definition.run(_source, _context),
-        }
-    }
-}
-
-impl Format for TypeDefinition {
-    fn format(&self, _output: &mut String, _indent_level: u8) {
-        todo!()
-    }
-}

src/abstract_tree/type_specification.rs

@@ -1,56 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Format, SyntaxNode, Type, Value,
-};
-
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct TypeSpecification {
-    r#type: Type,
-}
-
-impl TypeSpecification {
-    pub fn new(r#type: Type) -> Self {
-        Self { r#type }
-    }
-
-    pub fn inner(&self) -> &Type {
-        &self.r#type
-    }
-
-    pub fn take_inner(self) -> Type {
-        self.r#type
-    }
-}
-
-impl AbstractTree for TypeSpecification {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("type_specification", node)?;
-
-        let type_node = node.child(1).unwrap();
-        let r#type = Type::from_syntax(type_node, source, context)?;
-
-        Ok(TypeSpecification { r#type })
-    }
-
-    fn expected_type(&self, context: &Context) -> Result<Type, ValidationError> {
-        self.r#type.expected_type(context)
-    }
-
-    fn validate(&self, _source: &str, _context: &Context) -> Result<(), ValidationError> {
-        Ok(())
-    }
-
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        self.r#type.run(source, context)
-    }
-}
-
-impl Format for TypeSpecification {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        output.push('<');
-        self.r#type.format(output, indent_level);
-        output.push('>');
-    }
-}

src/abstract_tree/value_node.rs

@@ -1,346 +0,0 @@
-use std::{cmp::Ordering, ops::RangeInclusive};
-
-use serde::{Deserialize, Serialize};
-use tree_sitter::Node as SyntaxNode;
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Context, Expression, Format, Function, FunctionNode,
-    Identifier, List, Type, Value, TypeDefinition, MapNode,
-};
-
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq)]
-pub enum ValueNode {
-    Boolean(String),
-    Float(String),
-    Function(Function),
-    Integer(String),
-    String(String),
-    List(Vec<Expression>),
-    Map(MapNode),
-    Range(RangeInclusive<i64>),
-    Struct {
-        name: Identifier,
-        properties: MapNode,
-    },
-    Enum {
-        name: Identifier,
-        variant: Identifier,
-        expression: Option<Box<Expression>>,
-    },
-}
-
-impl AbstractTree for ValueNode {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("value", node)?;
-
-        let child = node.child(0).unwrap();
-        let value_node = match child.kind() {
-            "boolean" => ValueNode::Boolean(source[child.byte_range()].to_string()),
-            "float" => ValueNode::Float(source[child.byte_range()].to_string()),
-            "function" => {
-                let function_node = FunctionNode::from_syntax(child, source, context)?;
-
-                ValueNode::Function(Function::ContextDefined(function_node))
-            }
-            "integer" => ValueNode::Integer(source[child.byte_range()].to_string()),
-            "string" => {
-                let without_quotes = child.start_byte() + 1..child.end_byte() - 1;
-
-                ValueNode::String(source[without_quotes].to_string())
-            }
-            "list" => {
-                let mut expressions = Vec::new();
-
-                for index in 1..child.child_count() - 1 {
-                    let current_node = child.child(index).unwrap();
-
-                    if current_node.is_named() {
-                        let expression = Expression::from_syntax(current_node, source, context)?;
-
-                        expressions.push(expression);
-                    }
-                }
-
-                ValueNode::List(expressions)
-            }
-            "map" => {
-                ValueNode::Map(MapNode::from_syntax(child, source, context)?)
-            }
-            "range" => {
-                let mut split = source[child.byte_range()].split("..");
-                let start = split.next().unwrap().parse().unwrap();
-                let end = split.next().unwrap().parse().unwrap();
-
-                ValueNode::Range(start..=end)
-            }
-            "enum_instance" => {
-                let name_node = child.child(0).unwrap();
-                let name = Identifier::from_syntax(name_node, source, context)?;
-                
-                let variant_node = child.child(2).unwrap();
-                let variant = Identifier::from_syntax(variant_node, source, context)?;
-             
-                let expression = if let Some(expression_node) = child.child(4) {                
-                    Some(Box::new(Expression::from_syntax(expression_node, source, context)?))
-                } else {
-                    None
-                };
-
-                ValueNode::Enum { name, variant , expression  }                
-            }
-            "struct_instance" => {
-                let name_node = child.child(0).unwrap();
-                let name = Identifier::from_syntax(name_node, source, context)?;
-
-                let properties_node = child.child(2).unwrap();
-                let properties = MapNode::from_syntax(properties_node, source, context)?;
-
-                ValueNode::Struct
-                {
-                    name,
-                    properties
-                }
-            }
-            _ => {
-                return Err(SyntaxError::UnexpectedSyntaxNode {
-                    expected:
-                        "string, integer, float, boolean, range, list, map, option, function, struct or enum"
-                            .to_string(),
-                    actual: child.kind().to_string(),
-                    position: node.range().into(),
-                })
-            }
-        };
-
-        Ok(value_node)
-    }
-
-    fn expected_type(&self, context: &Context) -> Result<Type, ValidationError> {
-        let r#type = match self {
-            ValueNode::Boolean(_) => Type::Boolean,
-            ValueNode::Float(_) => Type::Float,
-            ValueNode::Function(function) => function.r#type(),
-            ValueNode::Integer(_) => Type::Integer,
-            ValueNode::String(_) => Type::String,
-            ValueNode::List(expressions) => {
-                let mut previous_type = None;
-
-                for expression in expressions {
-                    let expression_type = expression.expected_type(context)?;
-
-                    if let Some(previous) = previous_type {
-                        if expression_type != previous {
-                            return Ok(Type::List(Box::new(Type::Any)));
-                        }
-                    }
-
-                    previous_type = Some(expression_type);
-                }
-
-                if let Some(previous) = previous_type {
-                    Type::List(Box::new(previous))
-                } else {
-                    Type::List(Box::new(Type::Any))
-                }
-            }
-            ValueNode::Map(map_node) => map_node.expected_type(context)?,
-            ValueNode::Struct { name, .. }  => {
-                Type::Custom { name: name.clone(), argument: None }
-            }
-            ValueNode::Range(_) => Type::Range,
-            ValueNode::Enum { name, variant: _, expression } => {
-                if let Some(expression) = expression {
-                    Type::Custom {
-                        name: name.clone(),
-                        argument: Some(Box::new(expression.expected_type(context)?))
-                    }
-                } else {
-                    Type::Custom{
-                        name: name.clone(),
-                        argument: None,
-                    }
-                }
-            },
-        };
-
-        Ok(r#type)
-    }
-
-    fn validate(&self, _source: &str, context: &Context) -> Result<(), ValidationError> {
-        match self {
-            ValueNode::Function(function) => {
-                if let Function::ContextDefined(function_node) = function {
-                    function_node.validate(_source, context)?;
-                }
-            }
-            ValueNode::Map(map_node) => map_node.validate(_source, context)?,
-            _ => {},
-        }
-
-        Ok(())
-    }
-
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        let value = match self {
-            ValueNode::Boolean(value_source) => Value::Boolean(value_source.parse().unwrap()),
-            ValueNode::Float(value_source) => {
-                let float = value_source.parse()?;
-
-                Value::Float(float)
-            }
-            ValueNode::Function(function) => Value::Function(function.clone()),
-            ValueNode::Integer(value_source) => Value::Integer(value_source.parse().unwrap()),
-            ValueNode::String(value_source) => Value::string(value_source.clone()),
-            ValueNode::List(expressions) => {
-                let mut values = Vec::with_capacity(expressions.len());
-
-                for node in expressions {
-                    let value = node.run(source, context)?;
-
-                    values.push(value);
-                }
-
-                Value::List(List::with_items(values))
-            }
-            ValueNode::Map(map_node) => map_node.run(source, context)?,
-            ValueNode::Range(range) => Value::Range(range.clone()),
-            ValueNode::Struct { name, properties } => {
-                let instance = if let Some(definition) = context.get_definition(name)? {
-                    if let TypeDefinition::Struct(struct_definition) = definition {
-                        struct_definition.instantiate(properties, source, context)?
-                    } else {
-                        return Err(RuntimeError::ValidationFailure(ValidationError::ExpectedStructDefintion { actual: definition.clone() }))
-                    }
-                } else {
-                    return Err(RuntimeError::ValidationFailure(
-                        ValidationError::TypeDefinitionNotFound(name.clone())
-                    ));
-                };
-
-                Value::Struct(instance)
-
-            }
-            ValueNode::Enum { name, variant, expression } => {
-                let value = if let Some(expression) = expression {
-                    expression.run(source, context)?
-                } else {
-                    Value::none()
-                };
-                let instance = if let Some(definition) = context.get_definition(name)? {
-                    if let TypeDefinition::Enum(enum_defintion) = definition {
-                        enum_defintion.instantiate(variant.clone(), Some(value))
-                    } else {
-                        return Err(RuntimeError::ValidationFailure(
-                            ValidationError::ExpectedEnumDefintion {
-                                actual: definition.clone()
-                            }
-                        ));
-                    }
-                } else {
-                    return Err(RuntimeError::ValidationFailure(
-                        ValidationError::TypeDefinitionNotFound(name.clone())
-                    ));
-                };
-
-                Value::Enum(instance)                
-            },
-        };
-
-        Ok(value)
-    }
-}
-
-impl Format for ValueNode {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        match self {
-            ValueNode::Boolean(source) | ValueNode::Float(source) | ValueNode::Integer(source) => {
-                output.push_str(source)
-            }
-            ValueNode::String(source) => {
-                output.push('\'');
-                output.push_str(source);
-                output.push('\'');
-            }
-            ValueNode::Function(function) => function.format(output, indent_level),
-            ValueNode::List(expressions) => {
-                output.push('[');
-
-                for expression in expressions {
-                    expression.format(output, indent_level);
-                }
-
-                output.push(']');
-            }
-            ValueNode::Map(map_node) => map_node.format(output, indent_level),
-            ValueNode::Struct { name, properties } => {
-                name.format(output, indent_level);
-                properties.format(output, indent_level);
-            }
-            ValueNode::Range(_) => todo!(),
-            ValueNode::Enum { ..  } => todo!(),
-        }
-    }
-}
-
-impl Ord for ValueNode {
-    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
-        match (self, other) {
-            (ValueNode::Boolean(left), ValueNode::Boolean(right)) => left.cmp(right),
-            (ValueNode::Boolean(_), _) => Ordering::Greater,
-            (ValueNode::Float(left), ValueNode::Float(right)) => left.cmp(right),
-            (ValueNode::Float(_), _) => Ordering::Greater,
-            (ValueNode::Function(left), ValueNode::Function(right)) => left.cmp(right),
-            (ValueNode::Function(_), _) => Ordering::Greater,
-            (ValueNode::Integer(left), ValueNode::Integer(right)) => left.cmp(right),
-            (ValueNode::Integer(_), _) => Ordering::Greater,
-            (ValueNode::String(left), ValueNode::String(right)) => left.cmp(right),
-            (ValueNode::String(_), _) => Ordering::Greater,
-            (ValueNode::List(left), ValueNode::List(right)) => left.cmp(right),
-            (ValueNode::List(_), _) => Ordering::Greater,
-            (ValueNode::Map(left), ValueNode::Map(right)) => left.cmp(right),
-            (ValueNode::Map(_), _) => Ordering::Greater,
-            (ValueNode::Struct{ name: left_name, properties: left_properties }, ValueNode::Struct {name: right_name, properties: right_properties} ) => {
-                let name_cmp = left_name.cmp(right_name);
-
-                if name_cmp.is_eq() {
-                    left_properties.cmp(right_properties)
-                } else {
-                    name_cmp
-                }
-            },
-            (ValueNode::Struct {..}, _) => Ordering::Greater,
-            (
-                ValueNode::Enum {
-                    name: left_name, variant: left_variant, expression: left_expression
-                },
-                ValueNode::Enum {
-                    name: right_name, variant: right_variant, expression: right_expression
-                }
-            ) => {
-                let name_cmp = left_name.cmp(right_name);
-
-                if name_cmp.is_eq() {
-                    let variant_cmp = left_variant.cmp(right_variant);
-
-                    if variant_cmp.is_eq() {
-                        left_expression.cmp(right_expression)
-                    } else {
-                        variant_cmp
-                    }
-                } else {
-                    name_cmp
-                }
-            },
-            (ValueNode::Enum { .. }, _) => Ordering::Greater,
-            (ValueNode::Range(left), ValueNode::Range(right)) => left.clone().cmp(right.clone()),
-            (ValueNode::Range(_), _) => Ordering::Less,
-        }
-    }
-}
-
-impl PartialOrd for ValueNode {
-    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
-        Some(self.cmp(other))
-    }
-}

src/abstract_tree/while.rs

@@ -1,58 +0,0 @@
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    error::{RuntimeError, SyntaxError, ValidationError},
-    AbstractTree, Block, Context, Expression, Format, SyntaxNode, Type, Value,
-};
-
-/// Abstract representation of a while loop.
-///
-/// While executes its block repeatedly until its expression evaluates to true.
-#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq, PartialOrd, Ord)]
-pub struct While {
-    expression: Expression,
-    block: Block,
-}
-
-impl AbstractTree for While {
-    fn from_syntax(node: SyntaxNode, source: &str, context: &Context) -> Result<Self, SyntaxError> {
-        SyntaxError::expect_syntax_node("while", node)?;
-
-        let expression_node = node.child(1).unwrap();
-        let expression = Expression::from_syntax(expression_node, source, context)?;
-
-        let block_node = node.child(2).unwrap();
-        let block = Block::from_syntax(block_node, source, context)?;
-
-        Ok(While { expression, block })
-    }
-
-    fn expected_type(&self, context: &Context) -> Result<Type, ValidationError> {
-        self.block.expected_type(context)
-    }
-
-    fn validate(&self, _source: &str, context: &Context) -> Result<(), ValidationError> {
-        self.expression.validate(_source, context)?;
-        self.block.validate(_source, context)
-    }
-
-    fn run(&self, source: &str, context: &Context) -> Result<Value, RuntimeError> {
-        while self.expression.run(source, context)?.as_boolean()? {
-            self.block.run(source, context)?;
-        }
-
-        Ok(Value::none())
-    }
-}
-
-impl Format for While {
-    fn format(&self, output: &mut String, indent_level: u8) {
-        output.push('\n');
-        While::indent(output, indent_level);
-        output.push_str("while ");
-        self.expression.format(output, indent_level);
-        output.push(' ');
-        self.block.format(output, indent_level);
-        output.push('\n');
-    }
-}

src/built_in_functions/fs.rs

@@ -1,55 +0,0 @@
-use std::fs::read_to_string;
-
-use enum_iterator::{all, Sequence};
-use serde::{Deserialize, Serialize};
-
-use crate::{error::RuntimeError, Context, Type, Value};
-
-use super::Callable;
-
-pub fn fs_functions() -> impl Iterator<Item = Fs> {
-    all()
-}
-
-#[derive(Sequence, Debug, Copy, Clone, Serialize, Deserialize, PartialEq, Eq, PartialOrd, Ord)]
-pub enum Fs {
-    ReadFile,
-}
-
-impl Callable for Fs {
-    fn name(&self) -> &'static str {
-        match self {
-            Fs::ReadFile => "read_file",
-        }
-    }
-
-    fn description(&self) -> &'static str {
-        match self {
-            Fs::ReadFile => "Read the contents of a file to a string.",
-        }
-    }
-
-    fn r#type(&self) -> Type {
-        match self {
-            Fs::ReadFile => Type::function(vec![Type::String], Type::String),
-        }
-    }
-
-    fn call(
-        &self,
-        arguments: &[Value],
-        _source: &str,
-        _outer_context: &Context,
-    ) -> Result<Value, RuntimeError> {
-        match self {
-            Fs::ReadFile => {
-                RuntimeError::expect_argument_amount(self.name(), 1, arguments.len())?;
-
-                let path = arguments.first().unwrap().as_string()?;
-                let file_content = read_to_string(path.as_str())?;
-
-                Ok(Value::string(file_content))
-            }
-        }
-    }
-}

src/built_in_functions/json.rs

@@ -1,77 +0,0 @@
-use enum_iterator::Sequence;
-use serde::{Deserialize, Serialize};
-
-use crate::{error::RuntimeError, Context, Type, Value};
-
-use super::Callable;
-
-pub fn json_functions() -> impl Iterator<Item = Json> {
-    enum_iterator::all()
-}
-
-#[derive(Sequence, Debug, Copy, Clone, Serialize, Deserialize, PartialEq, Eq, PartialOrd, Ord)]
-pub enum Json {
-    Create,
-    CreatePretty,
-    Parse,
-}
-
-impl Callable for Json {
-    fn name(&self) -> &'static str {
-        match self {
-            Json::Create => "create",
-            Json::CreatePretty => "create_pretty",
-            Json::Parse => "parse",
-        }
-    }
-
-    fn description(&self) -> &'static str {
-        match self {
-            Json::Create => "Convert a value to a JSON string.",
-            Json::CreatePretty => "Convert a value to a formatted JSON string.",
-            Json::Parse => "Convert JSON to a value",
-        }
-    }
-
-    fn r#type(&self) -> Type {
-        match self {
-            Json::Create => Type::function(vec![Type::Any], Type::String),
-            Json::CreatePretty => Type::function(vec![Type::Any], Type::String),
-            Json::Parse => Type::function(vec![Type::String], Type::Any),
-        }
-    }
-
-    fn call(
-        &self,
-        arguments: &[Value],
-        _source: &str,
-        _outer_context: &Context,
-    ) -> Result<Value, RuntimeError> {
-        match self {
-            Json::Create => {
-                RuntimeError::expect_argument_amount(self.name(), 1, arguments.len())?;
-
-                let value = arguments.first().unwrap();
-                let json_string = serde_json::to_string(value)?;
-
-                Ok(Value::String(json_string))
-            }
-            Json::CreatePretty => {
-                RuntimeError::expect_argument_amount(self.name(), 1, arguments.len())?;
-
-                let value = arguments.first().unwrap();
-                let json_string = serde_json::to_string_pretty(value)?;
-
-                Ok(Value::String(json_string))
-            }
-            Json::Parse => {
-                RuntimeError::expect_argument_amount(self.name(), 1, arguments.len())?;
-
-                let json_string = arguments.first().unwrap().as_string()?;
-                let value = serde_json::from_str(json_string)?;
-
-                Ok(value)
-            }
-        }
-    }
-}

src/built_in_functions/mod.rs

@@ -1,204 +0,0 @@
-pub mod fs;
-pub mod json;
-pub mod str;
-
-use std::fmt::{self, Display, Formatter};
-
-use rand::{random, thread_rng, Rng};
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    error::{RuntimeError, ValidationError},
-    Context, EnumInstance, Format, Identifier, Type, Value,
-};
-
-use self::{fs::Fs, json::Json, str::StrFunction};
-
-pub trait Callable {
-    fn name(&self) -> &'static str;
-    fn description(&self) -> &'static str;
-    fn r#type(&self) -> Type;
-    fn call(
-        &self,
-        arguments: &[Value],
-        source: &str,
-        context: &Context,
-    ) -> Result<Value, RuntimeError>;
-}
-
-#[derive(Debug, Copy, Clone, Serialize, Deserialize, PartialEq, Eq, PartialOrd, Ord)]
-pub enum BuiltInFunction {
-    AssertEqual,
-    Fs(Fs),
-    Json(Json),
-    Length,
-    Output,
-    RandomBoolean,
-    RandomFloat,
-    RandomFrom,
-    RandomInteger,
-    String(StrFunction),
-}
-
-impl Callable for BuiltInFunction {
-    fn name(&self) -> &'static str {
-        match self {
-            BuiltInFunction::AssertEqual => "assert_equal",
-            BuiltInFunction::Fs(fs_function) => fs_function.name(),
-            BuiltInFunction::Json(json_function) => json_function.name(),
-            BuiltInFunction::Length => "length",
-            BuiltInFunction::Output => "output",
-            BuiltInFunction::RandomBoolean => "boolean",
-            BuiltInFunction::RandomFloat => "float",
-            BuiltInFunction::RandomFrom => "from",
-            BuiltInFunction::RandomInteger => "integer",
-            BuiltInFunction::String(string_function) => string_function.name(),
-        }
-    }
-
-    fn description(&self) -> &'static str {
-        match self {
-            BuiltInFunction::AssertEqual => "assert_equal",
-            BuiltInFunction::Fs(fs_function) => fs_function.description(),
-            BuiltInFunction::Json(json_function) => json_function.description(),
-            BuiltInFunction::Length => "length",
-            BuiltInFunction::Output => "output",
-            BuiltInFunction::RandomBoolean => "boolean",
-            BuiltInFunction::RandomFloat => "float",
-            BuiltInFunction::RandomFrom => "from",
-            BuiltInFunction::RandomInteger => "integer",
-            BuiltInFunction::String(string_function) => string_function.description(),
-        }
-    }
-
-    fn r#type(&self) -> Type {
-        match self {
-            BuiltInFunction::AssertEqual => Type::function(
-                vec![Type::Any, Type::Any],
-                Type::Custom {
-                    name: Identifier::new("Result"),
-                    argument: None,
-                },
-            ),
-            BuiltInFunction::Fs(fs_function) => fs_function.r#type(),
-            BuiltInFunction::Json(json_function) => json_function.r#type(),
-            BuiltInFunction::Length => Type::function(vec![Type::Collection], Type::Integer),
-            BuiltInFunction::Output => Type::function(vec![Type::Any], Type::None),
-            BuiltInFunction::RandomBoolean => Type::function(vec![], Type::Boolean),
-            BuiltInFunction::RandomFloat => Type::function(vec![], Type::Float),
-            BuiltInFunction::RandomFrom => Type::function(vec![Type::Collection], Type::Any),
-            BuiltInFunction::RandomInteger => Type::function(vec![], Type::Integer),
-            BuiltInFunction::String(string_function) => string_function.r#type(),
-        }
-    }
-
-    fn call(
-        &self,
-        arguments: &[Value],
-        _source: &str,
-        context: &Context,
-    ) -> Result<Value, RuntimeError> {
-        match self {
-            BuiltInFunction::AssertEqual => {
-                RuntimeError::expect_argument_amount(self.name(), 2, arguments.len())?;
-
-                let left = arguments.get(0).unwrap();
-                let right = arguments.get(1).unwrap();
-
-                if left == right {
-                    Ok(Value::Enum(EnumInstance::new(
-                        Identifier::new("Result"),
-                        Identifier::new("Ok"),
-                        Some(Value::none()),
-                    )))
-                } else {
-                    Err(RuntimeError::AssertEqualFailed {
-                        left: left.clone(),
-                        right: right.clone(),
-                    })
-                }
-            }
-            BuiltInFunction::Fs(fs_function) => fs_function.call(arguments, _source, context),
-            BuiltInFunction::Json(json_function) => json_function.call(arguments, _source, context),
-            BuiltInFunction::Length => {
-                RuntimeError::expect_argument_amount(self.name(), 1, arguments.len())?;
-
-                let value = arguments.first().unwrap();
-                let length = if let Ok(list) = value.as_list() {
-                    list.items()?.len()
-                } else if let Ok(map) = value.as_map() {
-                    map.inner().len()
-                } else if let Ok(str) = value.as_string() {
-                    str.chars().count()
-                } else {
-                    return Err(RuntimeError::ValidationFailure(
-                        ValidationError::ExpectedCollection {
-                            actual: value.clone(),
-                        },
-                    ));
-                };
-
-                Ok(Value::Integer(length as i64))
-            }
-            BuiltInFunction::Output => {
-                RuntimeError::expect_argument_amount(self.name(), 1, arguments.len())?;
-
-                let value = arguments.first().unwrap();
-
-                println!("{value}");
-
-                Ok(Value::none())
-            }
-            BuiltInFunction::RandomBoolean => {
-                RuntimeError::expect_argument_amount(self.name(), 0, arguments.len())?;
-
-                Ok(Value::Boolean(random()))
-            }
-            BuiltInFunction::RandomFloat => {
-                RuntimeError::expect_argument_amount(self.name(), 0, arguments.len())?;
-
-                Ok(Value::Float(random()))
-            }
-            BuiltInFunction::RandomFrom => {
-                RuntimeError::expect_argument_amount(self.name(), 1, arguments.len())?;
-
-                let value = arguments.first().unwrap();
-
-                if let Ok(list) = value.as_list() {
-                    let items = list.items()?;
-
-                    if items.len() == 0 {
-                        Ok(Value::none())
-                    } else {
-                        let random_index = thread_rng().gen_range(0..items.len());
-                        let random_value = items.get(random_index).cloned().unwrap_or_default();
-
-                        Ok(random_value)
-                    }
-                } else {
-                    todo!()
-                }
-            }
-            BuiltInFunction::RandomInteger => {
-                RuntimeError::expect_argument_amount(self.name(), 0, arguments.len())?;
-
-                Ok(Value::Integer(random()))
-            }
-            BuiltInFunction::String(string_function) => {
-                string_function.call(arguments, _source, context)
-            }
-        }
-    }
-}
-
-impl Format for BuiltInFunction {
-    fn format(&self, output: &mut String, _indent_level: u8) {
-        output.push_str(self.name());
-    }
-}
-
-impl Display for BuiltInFunction {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "{}", self.name())
-    }
-}

src/built_in_functions/str.rs

@@ -1,591 +0,0 @@
-use enum_iterator::Sequence;
-use serde::{Deserialize, Serialize};
-
-use crate::{error::RuntimeError, Context, EnumInstance, Identifier, List, Type, Value};
-
-use super::Callable;
-
-pub fn string_functions() -> impl Iterator<Item = StrFunction> {
-    enum_iterator::all()
-}
-
-#[derive(Sequence, Debug, Copy, Clone, Serialize, Deserialize, PartialEq, Eq, PartialOrd, Ord)]
-pub enum StrFunction {
-    AsBytes,
-    EndsWith,
-    Find,
-    Insert,
-    IsAscii,
-    IsEmpty,
-    Lines,
-    Matches,
-    Parse,
-    Remove,
-    ReplaceRange,
-    Retain,
-    Split,
-    SplitAt,
-    SplitInclusive,
-    SplitN,
-    SplitOnce,
-    SplitTerminator,
-    SplitWhitespace,
-    StartsWith,
-    StripPrefix,
-    ToLowercase,
-    ToUppercase,
-    Trim,
-    TrimEnd,
-    TrimEndMatches,
-    TrimMatches,
-    TrimStart,
-    TrimStartMatches,
-    Truncate,
-}
-
-impl Callable for StrFunction {
-    fn name(&self) -> &'static str {
-        match self {
-            StrFunction::AsBytes => "as_bytes",
-            StrFunction::EndsWith => "ends_with",
-            StrFunction::Find => "find",
-            StrFunction::Insert => "insert",
-            StrFunction::IsAscii => "is_ascii",
-            StrFunction::IsEmpty => "is_empty",
-            StrFunction::Lines => "lines",
-            StrFunction::Matches => "matches",
-            StrFunction::Parse => "parse",
-            StrFunction::Remove => "remove",
-            StrFunction::ReplaceRange => "replace_range",
-            StrFunction::Retain => "retain",
-            StrFunction::Split => "split",
-            StrFunction::SplitAt => "split_at",
-            StrFunction::SplitInclusive => "split_inclusive",
-            StrFunction::SplitN => "split_n",
-            StrFunction::SplitOnce => "split_once",
-            StrFunction::SplitTerminator => "split_terminator",
-            StrFunction::SplitWhitespace => "split_whitespace",
-            StrFunction::StartsWith => "starts_with",
-            StrFunction::StripPrefix => "strip_prefix",
-            StrFunction::ToLowercase => "to_lowercase",
-            StrFunction::ToUppercase => "to_uppercase",
-            StrFunction::Trim => "trim",
-            StrFunction::TrimEnd => "trim_end",
-            StrFunction::TrimEndMatches => "trim_end_matches",
-            StrFunction::TrimMatches => "trim_matches",
-            StrFunction::TrimStart => "trim_start",
-            StrFunction::TrimStartMatches => "trim_start_matches",
-            StrFunction::Truncate => "truncate",
-        }
-    }
-
-    fn description(&self) -> &'static str {
-        match self {
-            StrFunction::AsBytes => "TODO",
-            StrFunction::EndsWith => "TODO",
-            StrFunction::Find => "TODO",
-            StrFunction::Insert => "TODO",
-            StrFunction::IsAscii => "TODO",
-            StrFunction::IsEmpty => "TODO",
-            StrFunction::Lines => "TODO",
-            StrFunction::Matches => "TODO",
-            StrFunction::Parse => "TODO",
-            StrFunction::Remove => "TODO",
-            StrFunction::ReplaceRange => "TODO",
-            StrFunction::Retain => "TODO",
-            StrFunction::Split => "TODO",
-            StrFunction::SplitAt => "TODO",
-            StrFunction::SplitInclusive => "TODO",
-            StrFunction::SplitN => "TODO",
-            StrFunction::SplitOnce => "TODO",
-            StrFunction::SplitTerminator => "TODO",
-            StrFunction::SplitWhitespace => "TODO",
-            StrFunction::StartsWith => "TODO",
-            StrFunction::StripPrefix => "TODO",
-            StrFunction::ToLowercase => "TODO",
-            StrFunction::ToUppercase => "TODO",
-            StrFunction::Trim => "TODO",
-            StrFunction::TrimEnd => "TODO",
-            StrFunction::TrimEndMatches => "TODO",
-            StrFunction::TrimMatches => "TODO",
-            StrFunction::TrimStart => "TODO",
-            StrFunction::TrimStartMatches => "TODO",
-            StrFunction::Truncate => "TODO",
-        }
-    }
-
-    fn r#type(&self) -> Type {
-        match self {
-            StrFunction::AsBytes => Type::function(vec![Type::String], Type::list(Type::Integer)),
-            StrFunction::EndsWith => {
-                Type::function(vec![Type::String, Type::String], Type::Boolean)
-            }
-            StrFunction::Find => Type::function(
-                vec![Type::String, Type::String],
-                Type::option(Some(Type::Integer)),
-            ),
-            StrFunction::Insert => Type::function(
-                vec![Type::String, Type::Integer, Type::String],
-                Type::String,
-            ),
-            StrFunction::IsAscii => Type::function(vec![Type::String], Type::Boolean),
-            StrFunction::IsEmpty => Type::function(vec![Type::String], Type::Boolean),
-            StrFunction::Lines => Type::function(vec![Type::String], Type::list(Type::String)),
-            StrFunction::Matches => {
-                Type::function(vec![Type::String, Type::String], Type::list(Type::String))
-            }
-            StrFunction::Parse => Type::function(vec![Type::String], Type::Any),
-            StrFunction::Remove => Type::function(
-                vec![Type::String, Type::Integer],
-                Type::option(Some(Type::String)),
-            ),
-            StrFunction::ReplaceRange => Type::function(
-                vec![Type::String, Type::list(Type::Integer), Type::String],
-                Type::String,
-            ),
-            StrFunction::Retain => Type::function(
-                vec![
-                    Type::String,
-                    Type::function(vec![Type::String], Type::Boolean),
-                ],
-                Type::String,
-            ),
-            StrFunction::Split => {
-                Type::function(vec![Type::String, Type::String], Type::list(Type::String))
-            }
-            StrFunction::SplitAt => {
-                Type::function(vec![Type::String, Type::Integer], Type::list(Type::String))
-            }
-            StrFunction::SplitInclusive => {
-                Type::function(vec![Type::String, Type::String], Type::list(Type::String))
-            }
-            StrFunction::SplitN => Type::function(
-                vec![Type::String, Type::Integer, Type::String],
-                Type::list(Type::String),
-            ),
-            StrFunction::SplitOnce => {
-                Type::function(vec![Type::String, Type::String], Type::list(Type::String))
-            }
-            StrFunction::SplitTerminator => {
-                Type::function(vec![Type::String, Type::String], Type::list(Type::String))
-            }
-            StrFunction::SplitWhitespace => {
-                Type::function(vec![Type::String], Type::list(Type::String))
-            }
-            StrFunction::StartsWith => {
-                Type::function(vec![Type::String, Type::String], Type::Boolean)
-            }
-            StrFunction::StripPrefix => Type::function(
-                vec![Type::String, Type::String],
-                Type::option(Some(Type::String)),
-            ),
-            StrFunction::ToLowercase => Type::function(vec![Type::String], Type::String),
-            StrFunction::ToUppercase => Type::function(vec![Type::String], Type::String),
-            StrFunction::Truncate => {
-                Type::function(vec![Type::String, Type::Integer], Type::String)
-            }
-            StrFunction::Trim => Type::function(vec![Type::String], Type::String),
-            StrFunction::TrimEnd => Type::function(vec![Type::String], Type::String),
-            StrFunction::TrimEndMatches => {
-                Type::function(vec![Type::String, Type::String], Type::String)
-            }
-            StrFunction::TrimMatches => {
-                Type::function(vec![Type::String, Type::String], Type::String)
-            }
-            StrFunction::TrimStart => Type::function(vec![Type::String], Type::String),
-            StrFunction::TrimStartMatches => {
-                Type::function(vec![Type::String, Type::String], Type::String)
-            }
-        }
-    }
-
-    fn call(
-        &self,
-        arguments: &[Value],
-        _source: &str,
-        _context: &Context,
-    ) -> Result<Value, RuntimeError> {
-        let value = match self {
-            StrFunction::AsBytes => {
-                RuntimeError::expect_argument_amount(self.name(), 1, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let bytes = string
-                    .bytes()
-                    .map(|byte| Value::Integer(byte as i64))
-                    .collect();
-
-                Value::List(List::with_items(bytes))
-            }
-            StrFunction::EndsWith => {
-                RuntimeError::expect_argument_amount(self.name(), 2, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let pattern_string = arguments.get(1).unwrap().as_string()?;
-                let pattern = pattern_string.as_str();
-
-                Value::Boolean(string.ends_with(pattern))
-            }
-            StrFunction::Find => {
-                RuntimeError::expect_argument_amount(self.name(), 2, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let pattern_string = arguments.get(1).unwrap().as_string()?;
-                let pattern = pattern_string.as_str();
-                let find = string
-                    .find(pattern)
-                    .map(|index| Value::Integer(index as i64));
-
-                if let Some(index) = find {
-                    Value::Enum(EnumInstance::new(
-                        Identifier::new("Option"),
-                        Identifier::new("Some"),
-                        Some(index),
-                    ))
-                } else {
-                    Value::Enum(EnumInstance::new(
-                        Identifier::new("Option"),
-                        Identifier::new("None"),
-                        Some(Value::none()),
-                    ))
-                }
-            }
-            StrFunction::IsAscii => {
-                RuntimeError::expect_argument_amount(self.name(), 1, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-
-                Value::Boolean(string.is_ascii())
-            }
-            StrFunction::IsEmpty => {
-                RuntimeError::expect_argument_amount(self.name(), 1, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-
-                Value::Boolean(string.is_empty())
-            }
-            StrFunction::Insert => {
-                RuntimeError::expect_argument_amount(self.name(), 3, arguments.len())?;
-
-                let mut string = arguments.first().unwrap().as_string()?.clone();
-                let index = arguments.get(1).unwrap().as_integer()? as usize;
-                let insertion = arguments.get(2).unwrap().as_string()?;
-
-                string.insert_str(index, insertion);
-
-                Value::String(string)
-            }
-            StrFunction::Lines => {
-                RuntimeError::expect_argument_amount(self.name(), 1, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let lines = string
-                    .lines()
-                    .map(|line| Value::string(line.to_string()))
-                    .collect();
-
-                Value::List(List::with_items(lines))
-            }
-            StrFunction::Matches => {
-                RuntimeError::expect_argument_amount(self.name(), 2, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let pattern_string = arguments.get(1).unwrap().as_string()?;
-                let pattern = pattern_string.as_str();
-                let matches = string
-                    .matches(pattern)
-                    .map(|pattern| Value::string(pattern.to_string()))
-                    .collect();
-
-                Value::List(List::with_items(matches))
-            }
-            StrFunction::Parse => {
-                RuntimeError::expect_argument_amount(self.name(), 1, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-
-                if let Ok(integer) = string.parse::<i64>() {
-                    Value::Integer(integer)
-                } else if let Ok(float) = string.parse::<f64>() {
-                    Value::Float(float)
-                } else {
-                    Value::none()
-                }
-            }
-            StrFunction::Remove => {
-                RuntimeError::expect_argument_amount(self.name(), 2, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let index = arguments.get(1).unwrap().as_integer()? as usize;
-                let chars = string.chars().collect::<Vec<char>>();
-
-                if index < chars.len() {
-                    let new_string = chars
-                        .iter()
-                        .map(|char| char.to_string())
-                        .collect::<String>();
-
-                    Value::some(Value::string(new_string))
-                } else {
-                    Value::none()
-                }
-            }
-            StrFunction::ReplaceRange => {
-                RuntimeError::expect_argument_amount(self.name(), 3, arguments.len())?;
-
-                let mut string = arguments.first().unwrap().as_string()?.clone();
-                let range = arguments.get(1).unwrap().as_list()?.items()?;
-                let start = range[0].as_integer()? as usize;
-                let end = range[1].as_integer()? as usize;
-                let pattern = arguments.get(2).unwrap().as_string()?;
-
-                string.replace_range(start..end, pattern);
-
-                Value::String(string)
-            }
-            StrFunction::Retain => {
-                RuntimeError::expect_argument_amount(self.name(), 2, arguments.len())?;
-
-                todo!();
-
-                // let mut string = arguments.first().unwrap().as_string()?.clone();
-                // let predicate = arguments.get(1).unwrap().as_function()?;
-
-                // string.retain(|char| {
-                //     predicate
-                //         .call(&[Value::string(char)], _source, _outer_context)
-                //         .unwrap()
-                //         .as_boolean()
-                //         .unwrap()
-                // });
-
-                // Value::String(string)
-            }
-            StrFunction::Split => {
-                RuntimeError::expect_argument_amount(self.name(), 2, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let pattern_string = arguments.get(1).unwrap().as_string()?;
-                let pattern = pattern_string.as_str();
-                let sections = string
-                    .split(pattern)
-                    .map(|section| Value::string(section.to_string()))
-                    .collect();
-
-                Value::List(List::with_items(sections))
-            }
-            StrFunction::SplitAt => {
-                RuntimeError::expect_argument_amount(self.name(), 2, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let index = arguments.get(1).unwrap().as_integer()?;
-                let (left, right) = string.split_at(index as usize);
-
-                Value::List(List::with_items(vec![
-                    Value::string(left.to_string()),
-                    Value::string(right.to_string()),
-                ]))
-            }
-            StrFunction::SplitInclusive => {
-                RuntimeError::expect_argument_amount(self.name(), 2, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let pattern_string = arguments.get(1).unwrap().as_string()?;
-                let pattern = pattern_string.as_str();
-                let sections = string
-                    .split(pattern)
-                    .map(|pattern| Value::string(pattern.to_string()))
-                    .collect();
-
-                Value::List(List::with_items(sections))
-            }
-            StrFunction::SplitN => {
-                RuntimeError::expect_argument_amount(self.name(), 3, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let count = arguments.get(1).unwrap().as_integer()?;
-                let pattern_string = arguments.get(2).unwrap().as_string()?;
-                let pattern = pattern_string.as_str();
-                let sections = string
-                    .splitn(count as usize, pattern)
-                    .map(|pattern| Value::string(pattern.to_string()))
-                    .collect();
-
-                Value::List(List::with_items(sections))
-            }
-            StrFunction::SplitOnce => {
-                RuntimeError::expect_argument_amount(self.name(), 2, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let pattern_string = arguments.get(1).unwrap().as_string()?;
-                let pattern = pattern_string.as_str();
-                let sections = string.split_once(pattern).map(|(left, right)| {
-                    Value::List(List::with_items(vec![
-                        Value::string(left.to_string()),
-                        Value::string(right.to_string()),
-                    ]))
-                });
-
-                if let Some(sections) = sections {
-                    Value::some(sections)
-                } else {
-                    Value::none()
-                }
-            }
-            StrFunction::SplitTerminator => {
-                RuntimeError::expect_argument_amount(self.name(), 2, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let pattern_string = arguments.get(1).unwrap().as_string()?;
-                let pattern = pattern_string.as_str();
-                let sections = string
-                    .split_terminator(pattern)
-                    .map(|section| Value::string(section.to_string()))
-                    .collect();
-
-                Value::List(List::with_items(sections))
-            }
-            StrFunction::SplitWhitespace => {
-                RuntimeError::expect_argument_amount(self.name(), 1, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let sections = string
-                    .split_whitespace()
-                    .map(|section| Value::string(section.to_string()))
-                    .collect();
-
-                Value::List(List::with_items(sections))
-            }
-            StrFunction::StartsWith => {
-                RuntimeError::expect_argument_amount(self.name(), 2, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let pattern_string = arguments.get(1).unwrap().as_string()?;
-                let pattern = pattern_string.as_str();
-
-                Value::Boolean(string.starts_with(pattern))
-            }
-            StrFunction::StripPrefix => {
-                RuntimeError::expect_argument_amount(self.name(), 2, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let prefix_string = arguments.get(1).unwrap().as_string()?;
-                let prefix = prefix_string.as_str();
-                let stripped = string
-                    .strip_prefix(prefix)
-                    .map(|remainder| Value::string(remainder.to_string()));
-
-                if let Some(value) = stripped {
-                    Value::Enum(EnumInstance::new(
-                        Identifier::new("Option"),
-                        Identifier::new("Some"),
-                        Some(value),
-                    ))
-                } else {
-                    Value::none()
-                }
-            }
-            StrFunction::ToLowercase => {
-                RuntimeError::expect_argument_amount(self.name(), 1, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let lowercase = string.to_lowercase();
-
-                Value::string(lowercase)
-            }
-            StrFunction::ToUppercase => {
-                RuntimeError::expect_argument_amount(self.name(), 1, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let uppercase = string.to_uppercase();
-
-                Value::string(uppercase)
-            }
-            StrFunction::Trim => {
-                RuntimeError::expect_argument_amount(self.name(), 1, arguments.len())?;
-
-                let trimmed = arguments.first().unwrap().as_string()?.trim().to_string();
-
-                Value::string(trimmed)
-            }
-            StrFunction::TrimEnd => {
-                RuntimeError::expect_argument_amount(self.name(), 1, arguments.len())?;
-
-                let trimmed = arguments
-                    .first()
-                    .unwrap()
-                    .as_string()?
-                    .trim_end()
-                    .to_string();
-
-                Value::string(trimmed)
-            }
-            StrFunction::TrimEndMatches => {
-                RuntimeError::expect_argument_amount(self.name(), 2, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let pattern_string = arguments.get(1).unwrap().as_string()?;
-                let pattern = pattern_string.as_str();
-                let trimmed = string.trim_end_matches(pattern).to_string();
-
-                Value::string(trimmed)
-            }
-            StrFunction::TrimMatches => {
-                RuntimeError::expect_argument_amount(self.name(), 2, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let pattern = arguments
-                    .get(1)
-                    .unwrap()
-                    .as_string()?
-                    .chars()
-                    .collect::<Vec<char>>();
-                let trimmed = string.trim_matches(pattern.as_slice()).to_string();
-
-                Value::string(trimmed)
-            }
-            StrFunction::TrimStart => {
-                RuntimeError::expect_argument_amount(self.name(), 1, arguments.len())?;
-
-                let trimmed = arguments
-                    .first()
-                    .unwrap()
-                    .as_string()?
-                    .trim_start()
-                    .to_string();
-
-                Value::string(trimmed)
-            }
-            StrFunction::TrimStartMatches => {
-                RuntimeError::expect_argument_amount(self.name(), 2, arguments.len())?;
-
-                let string = arguments.first().unwrap().as_string()?;
-                let pattern = arguments
-                    .get(1)
-                    .unwrap()
-                    .as_string()?
-                    .chars()
-                    .collect::<Vec<char>>();
-                let trimmed = string.trim_start_matches(pattern.as_slice()).to_string();
-
-                Value::string(trimmed)
-            }
-            StrFunction::Truncate => {
-                RuntimeError::expect_argument_amount(self.name(), 2, arguments.len())?;
-
-                let input_string = arguments.first().unwrap().as_string()?;
-                let new_length = arguments.get(1).unwrap().as_integer()? as usize;
-
-                let new_string = input_string
-                    .chars()
-                    .take(new_length)
-                    .map(|char| char.to_string())
-                    .collect();
-
-                Value::String(new_string)
-            }
-        };
-
-        Ok(value)
-    }
-}

src/built_in_identifiers.rs

@@ -1,51 +0,0 @@
-use std::sync::{Arc, OnceLock};
-
-use enum_iterator::{all, Sequence};
-
-use crate::Identifier;
-
-pub fn all_built_in_identifiers() -> impl Iterator<Item = BuiltInIdentifier> {
-    all()
-}
-
-static OPTION: OnceLock<Identifier> = OnceLock::new();
-static NONE: OnceLock<Identifier> = OnceLock::new();
-static SOME: OnceLock<Identifier> = OnceLock::new();
-static RESULT: OnceLock<Identifier> = OnceLock::new();
-static OK: OnceLock<Identifier> = OnceLock::new();
-static ERROR: OnceLock<Identifier> = OnceLock::new();
-
-#[derive(Sequence, Debug)]
-pub enum BuiltInIdentifier {
-    Option,
-    None,
-    Some,
-    Result,
-    Ok,
-    Error,
-}
-
-impl BuiltInIdentifier {
-    pub fn get(&self) -> &Identifier {
-        match self {
-            BuiltInIdentifier::Option => {
-                OPTION.get_or_init(|| Identifier::from_raw_parts(Arc::new("Option".to_string())))
-            }
-            BuiltInIdentifier::None => {
-                NONE.get_or_init(|| Identifier::from_raw_parts(Arc::new("None".to_string())))
-            }
-            BuiltInIdentifier::Some => {
-                SOME.get_or_init(|| Identifier::from_raw_parts(Arc::new("Some".to_string())))
-            }
-            BuiltInIdentifier::Result => {
-                RESULT.get_or_init(|| Identifier::from_raw_parts(Arc::new("Result".to_string())))
-            }
-            BuiltInIdentifier::Ok => {
-                OK.get_or_init(|| Identifier::from_raw_parts(Arc::new("Ok".to_string())))
-            }
-            BuiltInIdentifier::Error => {
-                ERROR.get_or_init(|| Identifier::from_raw_parts(Arc::new("Error".to_string())))
-            }
-        }
-    }
-}

src/built_in_type_definitions.rs

@@ -1,56 +0,0 @@
-use std::sync::OnceLock;
-
-use enum_iterator::{all, Sequence};
-
-use crate::{
-    error::rw_lock_error::RwLockError, Context, EnumDefinition, Identifier, Type, TypeDefinition,
-};
-
-static OPTION: OnceLock<Result<TypeDefinition, RwLockError>> = OnceLock::new();
-static RESULT: OnceLock<Result<TypeDefinition, RwLockError>> = OnceLock::new();
-
-pub fn all_built_in_type_definitions() -> impl Iterator<Item = BuiltInTypeDefinition> {
-    all()
-}
-
-#[derive(Sequence)]
-pub enum BuiltInTypeDefinition {
-    Option,
-    Result,
-}
-
-impl BuiltInTypeDefinition {
-    pub fn name(&self) -> &'static str {
-        match self {
-            BuiltInTypeDefinition::Option => "Option",
-            BuiltInTypeDefinition::Result => "Result",
-        }
-    }
-
-    pub fn get(&self, _context: &Context) -> &Result<TypeDefinition, RwLockError> {
-        match self {
-            BuiltInTypeDefinition::Option => OPTION.get_or_init(|| {
-                let definition = TypeDefinition::Enum(EnumDefinition::new(
-                    Identifier::new(self.name()),
-                    vec![
-                        (Identifier::new("Some"), Some(Type::Any)),
-                        (Identifier::new("None"), None),
-                    ],
-                ));
-
-                Ok(definition)
-            }),
-            BuiltInTypeDefinition::Result => RESULT.get_or_init(|| {
-                let definition = TypeDefinition::Enum(EnumDefinition::new(
-                    Identifier::new(self.name()),
-                    vec![
-                        (Identifier::new("Ok"), Some(Type::Any)),
-                        (Identifier::new("Err"), Some(Type::Any)),
-                    ],
-                ));
-
-                Ok(definition)
-            }),
-        }
-    }
-}

src/built_in_types.rs

@@ -1,35 +0,0 @@
-use std::sync::OnceLock;
-
-use crate::{Identifier, Type};
-
-static OPTION: OnceLock<Type> = OnceLock::new();
-
-pub enum BuiltInType {
-    Option(Option<Type>),
-}
-
-impl BuiltInType {
-    pub fn name(&self) -> &'static str {
-        match self {
-            BuiltInType::Option(_) => "Option",
-        }
-    }
-
-    pub fn get(&self) -> &Type {
-        match self {
-            BuiltInType::Option(content_type) => OPTION.get_or_init(|| {
-                if let Some(content_type) = content_type {
-                    Type::Custom {
-                        name: Identifier::new("Option"),
-                        argument: Some(Box::new(content_type.clone())),
-                    }
-                } else {
-                    Type::Custom {
-                        name: Identifier::new("Option"),
-                        argument: None,
-                    }
-                }
-            }),
-        }
-    }
-}

src/built_in_values.rs

@@ -1,180 +0,0 @@
-use std::{env::args, sync::OnceLock};
-
-use enum_iterator::{all, Sequence};
-use serde::{Deserialize, Serialize};
-
-use crate::{
-    built_in_functions::{fs::fs_functions, json::json_functions, str::string_functions, Callable},
-    BuiltInFunction, EnumInstance, Function, Identifier, List, Map, Value,
-};
-
-static ARGS: OnceLock<Value> = OnceLock::new();
-static FS: OnceLock<Value> = OnceLock::new();
-static JSON: OnceLock<Value> = OnceLock::new();
-static NONE: OnceLock<Value> = OnceLock::new();
-static RANDOM: OnceLock<Value> = OnceLock::new();
-static STR: OnceLock<Value> = OnceLock::new();
-
-/// Returns the entire built-in value API.
-pub fn all_built_in_values() -> impl Iterator<Item = BuiltInValue> {
-    all()
-}
-
-/// A variable with a hard-coded key that is globally available.
-#[derive(Sequence, Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Serialize, Deserialize)]
-pub enum BuiltInValue {
-    /// The arguments used to launch the current program.
-    Args,
-
-    /// Create an error if two values are not equal.
-    AssertEqual,
-
-    /// File system tools.
-    Fs,
-
-    /// JSON format tools.
-    Json,
-
-    /// Get the length of a collection.
-    Length,
-
-    /// The absence of a value.
-    None,
-
-    /// Print a value to stdout.
-    Output,
-
-    /// Random value generators.
-    Random,
-
-    /// String utilities.
-    Str,
-}
-
-impl BuiltInValue {
-    /// Returns the hard-coded key used to identify the value.
-    pub fn name(&self) -> &'static str {
-        match self {
-            BuiltInValue::Args => "args",
-            BuiltInValue::AssertEqual => "assert_equal",
-            BuiltInValue::Fs => "fs",
-            BuiltInValue::Json => "json",
-            BuiltInValue::Length => BuiltInFunction::Length.name(),
-            BuiltInValue::None => "None",
-            BuiltInValue::Output => "output",
-            BuiltInValue::Random => "random",
-            BuiltInValue::Str => "str",
-        }
-    }
-
-    /// Returns a brief description of the value's features.
-    ///
-    /// This is used by the shell when suggesting completions.
-    pub fn description(&self) -> &'static str {
-        match self {
-            BuiltInValue::Args => "The command line arguments sent to this program.",
-            BuiltInValue::AssertEqual => "Error if the two values are not equal.",
-            BuiltInValue::Fs => "File and directory tools.",
-            BuiltInValue::Json => "JSON formatting tools.",
-            BuiltInValue::Length => BuiltInFunction::Length.description(),
-            BuiltInValue::None => "The absence of a value.",
-            BuiltInValue::Output => "output",
-            BuiltInValue::Random => "random",
-            BuiltInValue::Str => "string",
-        }
-    }
-
-    /// Returns the value by creating it or, if it has already been accessed, retrieving it from its
-    /// [OnceLock][].
-    pub fn get(&self) -> Value {
-        match self {
-            BuiltInValue::Args => ARGS
-                .get_or_init(|| {
-                    let args = args().map(|arg| Value::string(arg.to_string())).collect();
-
-                    Value::List(List::with_items(args))
-                })
-                .clone(),
-            BuiltInValue::AssertEqual => {
-                Value::Function(Function::BuiltIn(BuiltInFunction::AssertEqual))
-            }
-            BuiltInValue::Fs => FS
-                .get_or_init(|| {
-                    let mut fs_map = Map::new();
-
-                    for fs_function in fs_functions() {
-                        let key = fs_function.name();
-                        let value =
-                            Value::Function(Function::BuiltIn(BuiltInFunction::Fs(fs_function)));
-
-                        fs_map.set(Identifier::new(key), value);
-                    }
-
-                    Value::Map(fs_map)
-                })
-                .clone(),
-            BuiltInValue::Json => JSON
-                .get_or_init(|| {
-                    let mut json_map = Map::new();
-
-                    for json_function in json_functions() {
-                        let key = json_function.name();
-                        let value = Value::Function(Function::BuiltIn(BuiltInFunction::Json(
-                            json_function,
-                        )));
-
-                        json_map.set(Identifier::new(key), value);
-                    }
-
-                    Value::Map(json_map)
-                })
-                .clone(),
-            BuiltInValue::Length => Value::Function(Function::BuiltIn(BuiltInFunction::Length)),
-            BuiltInValue::None => NONE
-                .get_or_init(|| {
-                    Value::Enum(EnumInstance::new(
-                        Identifier::new("Option"),
-                        Identifier::new("None"),
-                        None,
-                    ))
-                })
-                .clone(),
-            BuiltInValue::Output => Value::Function(Function::BuiltIn(BuiltInFunction::Output)),
-            BuiltInValue::Random => RANDOM
-                .get_or_init(|| {
-                    let mut random_map = Map::new();
-
-                    for built_in_function in [
-                        BuiltInFunction::RandomBoolean,
-                        BuiltInFunction::RandomFloat,
-                        BuiltInFunction::RandomFrom,
-                        BuiltInFunction::RandomInteger,
-                    ] {
-                        let identifier = Identifier::new(built_in_function.name());
-                        let value = Value::Function(Function::BuiltIn(built_in_function));
-
-                        random_map.set(identifier, value);
-                    }
-
-                    Value::Map(random_map)
-                })
-                .clone(),
-            BuiltInValue::Str => STR
-                .get_or_init(|| {
-                    let mut str_map = Map::new();
-
-                    for string_function in string_functions() {
-                        let identifier = Identifier::new(string_function.name());
-                        let value = Value::Function(Function::BuiltIn(BuiltInFunction::String(
-                            string_function,
-                        )));
-
-                        str_map.set(identifier, value);
-                    }
-
-                    Value::Map(str_map)
-                })
-                .clone(),
-        }
-    }
-}

src/context/mod.rs

@@ -1,399 +0,0 @@
-//! A garbage-collecting execution context that stores variables and type data
-//! during the [Interpreter][crate::Interpreter]'s abstraction and execution
-//! process.
-//!
-//! ## Setting values
-//!
-//! When data is stored in a context, it can be accessed by dust source code.
-//! This allows you to insert values and type definitions before any code is
-//! interpreted.
-//!
-//! ```
-//! # use dust_lang::*;
-//! let context = Context::default();
-//!
-//! context.set_value(
-//!     "foobar".into(),
-//!     Value::String("FOOBAR".to_string())
-//! ).unwrap();
-//!
-//! interpret_with_context("output foobar", context);
-//!
-//! // Stdout: "FOOBAR"
-//! ```
-//!
-//! ## Built-in values and type definitions
-//!
-//! When looking up values and definitions, the Context will try to use one that
-//! has been explicitly set. If nothing is found, it will then check the built-
-//! in values and type definitions for a match. This means that the user can
-//! override the built-ins.
-//!
-//! ## Garbage Collection
-//!
-//! To disable garbage collection, run a Context in AllowGarbage mode.
-//!
-//! ```
-//! # use dust_lang::*;
-//! let context = Context::new(ContextMode::AllowGarbage);   
-//! ```
-//!
-//!
-//! Every item stored in a Context has a counter attached to it. You must use
-//! [Context::add_allowance][] to let the Context know not to drop the value.
-//! Every time you use [Context::get_value][] it checks the number of times it
-//! has been used and compares it to the number of allowances. If the limit
-//! has been reached, the value will be removed from the context and can no
-//! longer be found.
-mod usage_counter;
-mod value_data;
-
-pub use usage_counter::UsageCounter;
-pub use value_data::ValueData;
-
-use std::{
-    cmp::Ordering,
-    collections::BTreeMap,
-    fmt::Display,
-    sync::{Arc, RwLock, RwLockReadGuard},
-};
-
-use crate::{
-    built_in_type_definitions::all_built_in_type_definitions, built_in_values::all_built_in_values,
-    error::rw_lock_error::RwLockError, Identifier, Type, TypeDefinition, Value,
-};
-
-#[derive(Clone, Debug, PartialEq)]
-pub enum ContextMode {
-    AllowGarbage,
-    RemoveGarbage,
-}
-
-/// An execution context stores that variable and type data during the
-/// [Interpreter]'s abstraction and execution process.
-///
-/// See the [module-level docs][self] for more info.
-#[derive(Clone, Debug)]
-pub struct Context {
-    mode: ContextMode,
-    inner: Arc<RwLock<BTreeMap<Identifier, (ValueData, UsageCounter)>>>,
-}
-
-impl Context {
-    /// Return a new, empty Context.
-    pub fn new(mode: ContextMode) -> Self {
-        Self {
-            mode,
-            inner: Arc::new(RwLock::new(BTreeMap::new())),
-        }
-    }
-
-    /// Return a lock guard to the inner BTreeMap.
-    pub fn inner(
-        &self,
-    ) -> Result<RwLockReadGuard<BTreeMap<Identifier, (ValueData, UsageCounter)>>, RwLockError> {
-        Ok(self.inner.read()?)
-    }
-
-    /// Create a new context with all of the data from an existing context.
-    pub fn with_variables_from(other: &Context) -> Result<Context, RwLockError> {
-        let mut new_variables = BTreeMap::new();
-
-        for (identifier, (value_data, counter)) in other.inner.read()?.iter() {
-            let (allowances, _runtime_uses) = counter.get_counts()?;
-            let new_counter = UsageCounter::with_counts(allowances, 0);
-
-            new_variables.insert(identifier.clone(), (value_data.clone(), new_counter));
-        }
-
-        Ok(Context {
-            mode: other.mode.clone(),
-            inner: Arc::new(RwLock::new(new_variables)),
-        })
-    }
-
-    /// Modify a context to take the functions and type definitions of another.
-    ///
-    /// In the case of the conflict, the inherited value will override the previous
-    /// value.
-    pub fn inherit_from(&self, other: &Context) -> Result<(), RwLockError> {
-        let mut self_variables = self.inner.write()?;
-
-        for (identifier, (value_data, counter)) in other.inner.read()?.iter() {
-            let (allowances, _runtime_uses) = counter.get_counts()?;
-            let new_counter = UsageCounter::with_counts(allowances, 0);
-
-            if let ValueData::Value(value) = value_data {
-                if value.is_function() {
-                    self_variables.insert(identifier.clone(), (value_data.clone(), new_counter));
-                }
-            } else if let ValueData::TypeHint(r#type) = value_data {
-                if r#type.is_function() {
-                    self_variables.insert(identifier.clone(), (value_data.clone(), new_counter));
-                }
-            } else if let ValueData::TypeDefinition(_) = value_data {
-                self_variables.insert(identifier.clone(), (value_data.clone(), new_counter));
-            }
-        }
-
-        Ok(())
-    }
-
-    /// Modify a context to take all the information of another.
-    ///
-    /// In the case of the conflict, the inherited value will override the previous
-    /// value.
-    ///
-    /// ```
-    /// # use dust_lang::*;
-    /// let first_context = Context::default();
-    /// let second_context = Context::default();
-    ///
-    /// second_context.set_value(
-    ///     "Foo".into(),
-    ///     Value::String("Bar".to_string())
-    /// );
-    ///
-    /// first_context.inherit_all_from(&second_context).unwrap();
-    ///
-    /// assert_eq!(first_context, second_context);
-    /// ```
-    pub fn inherit_all_from(&self, other: &Context) -> Result<(), RwLockError> {
-        let mut self_variables = self.inner.write()?;
-
-        for (identifier, (value_data, _counter)) in other.inner.read()?.iter() {
-            self_variables.insert(
-                identifier.clone(),
-                (value_data.clone(), UsageCounter::new()),
-            );
-        }
-
-        Ok(())
-    }
-
-    /// Increment the number of allowances a variable has. Return a boolean
-    /// representing whether or not the variable was found.
-    pub fn add_allowance(&self, identifier: &Identifier) -> Result<bool, RwLockError> {
-        if let Some((_value_data, counter)) = self.inner.read()?.get(identifier) {
-            log::debug!("Adding allowance for {identifier}.");
-
-            counter.add_allowance()?;
-
-            Ok(true)
-        } else {
-            Ok(false)
-        }
-    }
-
-    /// Get a [Value] from the context.
-    pub fn get_value(&self, identifier: &Identifier) -> Result<Option<Value>, RwLockError> {
-        let (value, counter) =
-            if let Some((value_data, counter)) = self.inner.read()?.get(identifier) {
-                if let ValueData::Value(value) = value_data {
-                    (value.clone(), counter.clone())
-                } else {
-                    return Ok(None);
-                }
-            } else {
-                for built_in_value in all_built_in_values() {
-                    if built_in_value.name() == identifier.inner().as_ref() {
-                        return Ok(Some(built_in_value.get().clone()));
-                    }
-                }
-
-                return Ok(None);
-            };
-
-        counter.add_runtime_use()?;
-
-        log::debug!("Adding runtime use for {identifier}.");
-
-        let (allowances, runtime_uses) = counter.get_counts()?;
-
-        if self.mode == ContextMode::RemoveGarbage && allowances == runtime_uses {
-            self.unset(identifier)?;
-        }
-
-        Ok(Some(value))
-    }
-
-    /// Get a [Type] from the context.
-    ///
-    /// If the key matches a stored [Value], its type will be returned. It if
-    /// matches a type hint, the type hint will be returned.
-    pub fn get_type(&self, identifier: &Identifier) -> Result<Option<Type>, RwLockError> {
-        if let Some((value_data, _counter)) = self.inner.read()?.get(identifier) {
-            match value_data {
-                ValueData::Value(value) => return Ok(Some(value.r#type()?)),
-                ValueData::TypeHint(r#type) => return Ok(Some(r#type.clone())),
-                ValueData::TypeDefinition(_) => todo!(),
-            }
-        }
-
-        for built_in_value in all_built_in_values() {
-            if built_in_value.name() == identifier.inner().as_ref() {
-                return Ok(Some(built_in_value.get().r#type()?));
-            }
-        }
-
-        Ok(None)
-    }
-
-    /// Get a [TypeDefinition] from the context.
-    ///
-    /// This will also return a built-in type definition if one matches the key.
-    /// See the [module-level docs][self] for more info.
-    pub fn get_definition(
-        &self,
-        identifier: &Identifier,
-    ) -> Result<Option<TypeDefinition>, RwLockError> {
-        if let Some((value_data, _counter)) = self.inner.read()?.get(identifier) {
-            if let ValueData::TypeDefinition(definition) = value_data {
-                return Ok(Some(definition.clone()));
-            }
-        }
-
-        for built_in_definition in all_built_in_type_definitions() {
-            if built_in_definition.name() == identifier.inner().as_ref() {
-                return Ok(Some(built_in_definition.get(self).clone()?));
-            }
-        }
-
-        Ok(None)
-    }
-
-    /// Set a value to a key.
-    pub fn set_value(&self, key: Identifier, value: Value) -> Result<(), RwLockError> {
-        log::info!("Setting value: {key} = {value}");
-
-        let mut map = self.inner.write()?;
-        let old_data = map.remove(&key);
-
-        if let Some((_, old_counter)) = old_data {
-            map.insert(key, (ValueData::Value(value), old_counter.clone()));
-        } else {
-            map.insert(key, (ValueData::Value(value), UsageCounter::new()));
-        }
-
-        Ok(())
-    }
-
-    /// Set a type hint.
-    ///
-    /// This allows the interpreter to check a value's type before the value
-    /// actually exists by predicting what the abstract tree will produce.
-    pub fn set_type(&self, key: Identifier, r#type: Type) -> Result<(), RwLockError> {
-        log::info!("Setting type: {key} <{}>", r#type);
-
-        self.inner
-            .write()?
-            .insert(key, (ValueData::TypeHint(r#type), UsageCounter::new()));
-
-        Ok(())
-    }
-
-    /// Set a type definition.
-    ///
-    /// This allows defined types (i.e. structs and enums) to be instantiated
-    /// later while running the interpreter using this context.
-    pub fn set_definition(
-        &self,
-        key: Identifier,
-        definition: TypeDefinition,
-    ) -> Result<(), RwLockError> {
-        self.inner.write()?.insert(
-            key,
-            (ValueData::TypeDefinition(definition), UsageCounter::new()),
-        );
-
-        Ok(())
-    }
-
-    /// Remove a key-value pair.
-    pub fn unset(&self, key: &Identifier) -> Result<(), RwLockError> {
-        log::debug!("Dropping variable {key}.");
-
-        self.inner.write()?.remove(key);
-
-        Ok(())
-    }
-}
-
-impl Default for Context {
-    fn default() -> Self {
-        Context::new(ContextMode::RemoveGarbage)
-    }
-}
-
-impl Eq for Context {}
-
-impl PartialEq for Context {
-    fn eq(&self, other: &Self) -> bool {
-        let self_variables = self.inner().unwrap();
-        let other_variables = other.inner().unwrap();
-
-        if self_variables.len() != other_variables.len() {
-            return false;
-        }
-
-        for ((left_key, left_value_data), (right_key, right_value_data)) in
-            self_variables.iter().zip(other_variables.iter())
-        {
-            if left_key != right_key || left_value_data != right_value_data {
-                return false;
-            }
-        }
-
-        true
-    }
-}
-
-impl PartialOrd for Context {
-    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
-        Some(self.cmp(other))
-    }
-}
-
-impl Ord for Context {
-    fn cmp(&self, other: &Self) -> Ordering {
-        let left = self.inner().unwrap();
-        let right = other.inner().unwrap();
-
-        left.cmp(&right)
-    }
-}
-
-impl Display for Context {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        writeln!(f, "{{")?;
-
-        for (identifier, value_data) in self.inner.read().unwrap().iter() {
-            writeln!(f, "{identifier} {value_data:?}")?;
-        }
-
-        writeln!(f, "}}")
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use crate::*;
-
-    #[test]
-    fn drops_variables() {
-        let context = Context::default();
-
-        interpret_with_context(
-            "
-                x = 1
-                y = 2
-
-                z = x + y
-            ",
-            context.clone(),
-        )
-        .unwrap();
-
-        assert_eq!(context.inner.read().unwrap().len(), 1);
-    }
-}