dust-lang/src/chunk.rs

@@ -4,56 +4,58 @@
 //! 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::fmt::{self, Debug, Display, Formatter};
+use std::{
+    cmp::Ordering,
+    fmt::{self, Debug, Display, Formatter},
+};
 
 use serde::{Deserialize, Serialize};
 
-use crate::{value::ConcreteValue, Disassembler, FunctionType, Instruction, Scope, Span, Type};
+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>, // TODO: Use a bool indicating whether the chunk is named. If it is, get
+    name: Option<String>,
-    r#type: FunctionType, // the name from C0.
+    pub is_poisoned: bool,
 
     instructions: Vec<(Instruction, Span)>,
-    constants: Vec<ConcreteValue>,
+    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(),
-            r#type: FunctionType {
+            current_scope: Scope::default(),
-                type_parameters: None,
+            block_index: 0,
-                value_parameters: None,
-                return_type: Box::new(Type::None),
-            },
         }
     }
 
     pub fn with_data(
         name: Option<String>,
         instructions: Vec<(Instruction, Span)>,
-        constants: Vec<ConcreteValue>,
+        constants: Vec<Value>,
         locals: Vec<Local>,
     ) -> Self {
         Self {
             name,
+            is_poisoned: false,
             instructions,
             constants,
             locals,
-            r#type: FunctionType {
+            current_scope: Scope::default(),
-                type_parameters: None,
+            block_index: 0,
-                value_parameters: None,
-                return_type: Box::new(Type::None),
-            },
         }
     }
 
@@ -61,10 +63,6 @@ impl Chunk {
         self.name.as_ref()
     }
 
-    pub fn r#type(&self) -> &FunctionType {
-        &self.r#type
-    }
-
     pub fn set_name(&mut self, name: String) {
         self.name = Some(name);
     }
@@ -77,36 +75,16 @@ impl Chunk {
         self.instructions.is_empty()
     }
 
-    pub fn constants(&self) -> &Vec<ConcreteValue> {
+    pub fn constants(&self) -> &Vec<Value> {
         &self.constants
     }
 
-    pub fn constants_mut(&mut self) -> &mut Vec<ConcreteValue> {
+    pub fn constants_mut(&mut self) -> &mut Vec<Value> {
         &mut self.constants
     }
 
-    pub fn get_constant(&self, index: u8) -> Result<&ConcreteValue, ChunkError> {
+    pub fn take_constants(self) -> Vec<Value> {
         self.constants
-            .get(index as usize)
-            .ok_or(ChunkError::ConstantIndexOutOfBounds {
-                index: index as usize,
-            })
-    }
-
-    pub fn push_or_get_constant(&mut self, value: ConcreteValue) -> u8 {
-        if let Some(index) = self
-            .constants
-            .iter()
-            .position(|constant| *constant == value)
-        {
-            index as u8
-        } else {
-            let index = self.constants.len() as u8;
-
-            self.constants.push(value);
-
-            index
-        }
     }
 
     pub fn instructions(&self) -> &Vec<(Instruction, Span)> {
@@ -147,6 +125,32 @@ impl Chunk {
             })
     }
 
+    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
@@ -155,22 +159,112 @@ impl Chunk {
         })
     }
 
-    pub fn get_constant_type(&self, constant_index: u8) -> Result<Type, ChunkError> {
+    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())
-            .ok_or(ChunkError::ConstantIndexOutOfBounds {
+    }
-                index: constant_index as usize,
+
+    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 get_local_type(&self, local_index: u8) -> Result<&Type, ChunkError> {
+    pub fn return_type(&self) -> Option<Type> {
-        self.locals
+        let returns_value = self
-            .get(local_index as usize)
+            .instructions()
-            .map(|local| &local.r#type)
+            .last()
-            .ok_or(ChunkError::LocalIndexOutOfBounds {
+            .map(|(instruction, _)| {
-                index: local_index as usize,
+                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 {
@@ -215,34 +309,79 @@ pub struct Local {
     pub identifier_index: u8,
 
     /// The expected type of the local's value.
-    pub r#type: Type,
+    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: Type, mutable: bool, scope: Scope) -> Self {
+    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 },
-    FunctionIndexOutOfBounds { index: usize },
     InstructionIndexOutOfBounds { index: usize },
     LocalIndexOutOfBounds { index: usize },
+    PoisonedChunk,
 }
 
 impl Display for ChunkError {
@@ -251,15 +390,13 @@ impl Display for ChunkError {
             ChunkError::ConstantIndexOutOfBounds { index } => {
                 write!(f, "Constant index {} out of bounds", index)
             }
-            ChunkError::FunctionIndexOutOfBounds { index } => {
-                write!(f, "Function 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

@@ -45,13 +45,13 @@ use std::env::current_exe;
 
 use colored::Colorize;
 
-use crate::{value::ConcreteValue, Chunk, Local};
+use crate::{Chunk, ConcreteValue, Local, Value};
 
 const INSTRUCTION_HEADER: [&str; 4] = [
     "Instructions",
     "------------",
-    " i  BYTECODE OPERATION             INFO               POSITION ",
+    " i  BYTECODE OPERATION             INFO               TYPE        POSITION ",
-    "--- -------- ------------- ------------------------- ----------",
+    "--- -------- ------------- -------------------- ---------------- ----------",
 ];
 
 const CONSTANT_HEADER: [&str; 4] = [
@@ -64,8 +64,8 @@ const CONSTANT_HEADER: [&str; 4] = [
 const LOCAL_HEADER: [&str; 4] = [
     "Locals",
     "------",
-    " i  IDENTIFIER       TYPE       MUTABLE  SCOPE ",
+    " i  IDENTIFIER       TYPE       MUTABLE  SCOPE  REGISTER",
-    "--- ---------- ---------------- ------- -------",
+    "--- ---------- ---------------- ------- ------- --------",
 ];
 
 /// Builder that constructs a human-readable representation of a chunk.
@@ -222,16 +222,7 @@ impl<'a> Disassembler<'a> {
             .map(|identifier| identifier.to_string())
             .unwrap_or_else(|| {
                 current_exe()
-                    .map(|path| {
+                    .map(|path| path.to_string_lossy().to_string())
-                        let path_string = path.to_string_lossy();
-                        let file_name = path_string
-                            .split('/')
-                            .last()
-                            .map(|slice| slice.to_string())
-                            .unwrap_or(path_string.to_string());
-
-                        file_name
-                    })
                     .unwrap_or("Chunk Disassembly".to_string())
             });
 
@@ -254,7 +245,10 @@ impl<'a> Disassembler<'a> {
             self.chunk.len(),
             self.chunk.constants().len(),
             self.chunk.locals().len(),
-            self.chunk.r#type().return_type
+            self.chunk
+                .return_type()
+                .map(|r#type| r#type.to_string())
+                .unwrap_or("none".to_string())
         );
 
         self.push(&info_line, true, false, true, true);
@@ -268,10 +262,23 @@ impl<'a> Disassembler<'a> {
             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 =
+            let instruction_display = format!(
-                format!("{index:^3} {bytecode:>8} {operation:13} {info:<25} {position:10}");
+                "{index:^3} {bytecode:>8} {operation:13} {info:^20} {type_display:^16} {position:10}"
+            );
 
             self.push_details(&instruction_display);
         }
@@ -288,6 +295,7 @@ impl<'a> Disassembler<'a> {
                 identifier_index,
                 r#type,
                 scope,
+                register_index,
                 is_mutable: mutable,
             },
         ) in self.chunk.locals().iter().enumerate()
@@ -298,9 +306,20 @@ impl<'a> Disassembler<'a> {
                 .get(*identifier_index as usize)
                 .map(|value| value.to_string())
                 .unwrap_or_else(|| "unknown".to_string());
-            let type_display = r#type.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}"
+                "{index:^3} {identifier_display:10} {type_display:16} {mutable:7} {scope:7} {register_index:8}"
             );
 
             self.push_details(&local_display);
@@ -313,19 +332,6 @@ impl<'a> Disassembler<'a> {
         }
 
         for (index, value) in self.chunk.constants().iter().enumerate() {
-            if let ConcreteValue::Function(function) = value {
-                let function_disassembly = function
-                    .chunk()
-                    .disassembler()
-                    .styled(self.styled)
-                    .indent(self.indent + 1)
-                    .disassemble();
-
-                self.output.push_str(&function_disassembly);
-
-                continue;
-            }
-
             let value_display = {
                 let value_string = value.to_string();
 
@@ -338,6 +344,17 @@ impl<'a> Disassembler<'a> {
             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);

dust-lang/src/formatter.rs

@@ -101,13 +101,13 @@ impl<'src> Formatter<'src> {
                 String(string) => {
                     self.push_colored(string.magenta());
                 }
-                LeftBrace => {
+                LeftCurlyBrace => {
                     self.next_line.push_str(self.current_token.as_str());
                     self.commit_line(LineKind::OpenBlock);
 
                     self.indent += 1;
                 }
-                RightBrace => {
+                RightCurlyBrace => {
                     self.commit_line(LineKind::CloseBlock);
                     self.next_line.push_str(self.current_token.as_str());
 

dust-lang/src/function.rs

@@ -1,63 +0,0 @@
-use std::fmt::{self, Display, Formatter};
-
-use serde::{Deserialize, Serialize};
-
-use crate::{Chunk, Type};
-
-#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Serialize, Deserialize)]
-pub struct Function {
-    chunk: Chunk,
-}
-
-impl Function {
-    pub fn new(chunk: Chunk) -> Self {
-        Self { chunk }
-    }
-
-    pub fn chunk(&self) -> &Chunk {
-        &self.chunk
-    }
-
-    pub fn r#type(&self) -> Type {
-        Type::Function(self.chunk.r#type().clone())
-    }
-
-    pub fn as_borrowed(&self) -> FunctionBorrowed {
-        FunctionBorrowed::new(&self.chunk)
-    }
-}
-
-impl Display for Function {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "{}", self.chunk.r#type())
-    }
-}
-
-#[derive(Clone, Copy, Debug, Eq, PartialEq, PartialOrd, Ord)]
-pub struct FunctionBorrowed<'a> {
-    chunk: &'a Chunk,
-}
-
-impl<'a> FunctionBorrowed<'a> {
-    pub fn new(chunk: &'a Chunk) -> Self {
-        Self { chunk }
-    }
-
-    pub fn chunk(&self) -> &Chunk {
-        self.chunk
-    }
-
-    pub fn r#type(&self) -> Type {
-        Type::Function(self.chunk.r#type().clone())
-    }
-
-    pub fn to_owned(&self) -> Function {
-        Function::new(self.chunk.clone())
-    }
-}
-
-impl<'a> Display for FunctionBorrowed<'a> {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "{}", self.chunk.r#type())
-    }
-}

dust-lang/src/instruction.rs

@@ -362,18 +362,6 @@ impl Instruction {
         self
     }
 
-    pub fn returns_or_panics(&self) -> bool {
-        match self.operation() {
-            Operation::Return => true,
-            Operation::CallNative => {
-                let native_function = NativeFunction::from(self.b());
-
-                matches!(native_function, NativeFunction::Panic)
-            }
-            _ => false,
-        }
-    }
-
     pub fn yields_value(&self) -> bool {
         match self.operation() {
             Operation::Add
@@ -392,12 +380,43 @@ impl Instruction {
             Operation::CallNative => {
                 let native_function = NativeFunction::from(self.b());
 
-                *native_function.r#type().return_type != Type::None
+                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() {
@@ -610,7 +629,7 @@ impl Instruction {
                 let mut output = String::new();
                 let native_function_name = native_function.as_str();
 
-                if *native_function.r#type().return_type != Type::None {
+                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));
@@ -657,13 +676,13 @@ mod tests {
 
     #[test]
     fn r#move() {
-        let mut instruction = Instruction::r#move(4, 1);
+        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(), 4);
+        assert_eq!(instruction.a(), 0);
         assert_eq!(instruction.b(), 1);
         assert!(instruction.b_is_constant());
         assert!(instruction.b_is_constant());
@@ -690,13 +709,13 @@ mod tests {
 
     #[test]
     fn load_constant() {
-        let mut instruction = Instruction::load_constant(4, 1, true);
+        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(), 4);
+        assert_eq!(instruction.a(), 0);
         assert_eq!(instruction.b(), 1);
         assert!(instruction.b_is_constant());
         assert!(instruction.b_is_constant());
@@ -705,10 +724,10 @@ mod tests {
 
     #[test]
     fn load_list() {
-        let instruction = Instruction::load_list(4, 1);
+        let instruction = Instruction::load_list(0, 1);
 
         assert_eq!(instruction.operation(), Operation::LoadList);
-        assert_eq!(instruction.a(), 4);
+        assert_eq!(instruction.a(), 0);
         assert_eq!(instruction.b(), 1);
     }
 
@@ -722,12 +741,12 @@ mod tests {
 
     #[test]
     fn declare_local() {
-        let mut instruction = Instruction::define_local(4, 1, true);
+        let mut instruction = Instruction::define_local(0, 1, true);
 
         instruction.set_b_is_constant();
 
         assert_eq!(instruction.operation(), Operation::DefineLocal);
-        assert_eq!(instruction.a(), 4);
+        assert_eq!(instruction.a(), 0);
         assert_eq!(instruction.b(), 1);
         assert_eq!(instruction.c(), true as u8);
         assert!(instruction.b_is_constant());
@@ -735,26 +754,26 @@ mod tests {
 
     #[test]
     fn add() {
-        let mut instruction = Instruction::add(1, 1, 4);
+        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(), 4);
+        assert_eq!(instruction.c(), 0);
         assert!(instruction.b_is_constant());
     }
 
     #[test]
     fn subtract() {
-        let mut instruction = Instruction::subtract(4, 1, 2);
+        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(), 4);
+        assert_eq!(instruction.a(), 0);
         assert_eq!(instruction.b(), 1);
         assert_eq!(instruction.c(), 2);
         assert!(instruction.b_is_constant());
@@ -763,13 +782,13 @@ mod tests {
 
     #[test]
     fn multiply() {
-        let mut instruction = Instruction::multiply(4, 1, 2);
+        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(), 4);
+        assert_eq!(instruction.a(), 0);
         assert_eq!(instruction.b(), 1);
         assert_eq!(instruction.c(), 2);
         assert!(instruction.b_is_constant());
@@ -778,13 +797,13 @@ mod tests {
 
     #[test]
     fn divide() {
-        let mut instruction = Instruction::divide(4, 1, 2);
+        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(), 4);
+        assert_eq!(instruction.a(), 0);
         assert_eq!(instruction.b(), 1);
         assert_eq!(instruction.c(), 2);
         assert!(instruction.b_is_constant());
@@ -827,13 +846,13 @@ mod tests {
 
     #[test]
     fn negate() {
-        let mut instruction = Instruction::negate(4, 1);
+        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(), 4);
+        assert_eq!(instruction.a(), 0);
         assert_eq!(instruction.b(), 1);
         assert!(instruction.b_is_constant());
         assert!(instruction.b_is_constant());
@@ -841,13 +860,13 @@ mod tests {
 
     #[test]
     fn not() {
-        let mut instruction = Instruction::not(4, 1);
+        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(), 4);
+        assert_eq!(instruction.a(), 0);
         assert_eq!(instruction.b(), 1);
         assert!(instruction.b_is_constant());
         assert!(instruction.b_is_constant());

dust-lang/src/lexer.rs

@@ -41,10 +41,11 @@ pub fn lex<'tokens, 'src: 'tokens>(
             error: CompileError::Lex(error),
             source,
         })?;
+        let is_eof = matches!(token, Token::Eof);
 
         tokens.push((token, span));
 
-        if lexer.is_eof() {
+        if is_eof {
             break;
         }
     }
@@ -59,7 +60,6 @@ pub fn lex<'tokens, 'src: 'tokens>(
 pub struct Lexer<'src> {
     source: &'src str,
     position: usize,
-    is_eof: bool,
 }
 
 impl<'src> Lexer<'src> {
@@ -68,7 +68,6 @@ impl<'src> Lexer<'src> {
         Lexer {
             source,
             position: 0,
-            is_eof: false,
         }
     }
 
@@ -77,7 +76,7 @@ impl<'src> Lexer<'src> {
     }
 
     pub fn is_eof(&self) -> bool {
-        self.is_eof
+        self.position >= self.source.len()
     }
 
     pub fn skip_to(&mut self, position: usize) {
@@ -88,19 +87,272 @@ impl<'src> Lexer<'src> {
     pub fn next_token(&mut self) -> Result<(Token<'src>, Span), LexError> {
         self.skip_whitespace();
 
-        let (token, span) = if let Some(character) = self.peek_char() {
+        let (token, span) = if let Some(c) = self.peek_char() {
-            let lexer = LexRule::from(&character).lexer;
+            match c {
+                '0'..='9' => self.lex_numeric()?,
+                '-' => {
+                    let second_char = self.peek_second_char();
 
-            lexer(self)?
+                    if let Some('=') = second_char {
+                        self.position += 2;
+
+                        (Token::MinusEqual, Span(self.position - 2, self.position))
+                    } else if let Some('>') = second_char {
+                        self.position += 2;
+
+                        (Token::ArrowThin, Span(self.position - 2, self.position))
+                    } else if let Some('0'..='9') = second_char {
+                        self.lex_numeric()?
+                    } else if "-Infinity" == self.peek_chars(9) {
+                        self.position += 9;
+
+                        (
+                            Token::Float("-Infinity"),
+                            Span(self.position - 9, self.position),
+                        )
+                    } else {
+                        self.position += 1;
+
+                        (Token::Minus, Span(self.position - 1, self.position))
+                    }
+                }
+                'a'..='z' | 'A'..='Z' => self.lex_alphanumeric()?,
+                '"' => self.lex_string()?,
+                '\'' => {
+                    self.position += 1;
+
+                    if let Some(c) = self.peek_char() {
+                        self.position += 1;
+
+                        let peek = self.peek_char();
+
+                        if let Some('\'') = peek {
+                            self.position += 1;
+
+                            (Token::Character(c), Span(self.position - 3, self.position))
+                        } else {
+                            return Err(LexError::ExpectedCharacter {
+                                expected: '\'',
+                                actual: peek.unwrap_or('\0'),
+                                position: self.position,
+                            });
+                        }
+                    } else {
+                        return Err(LexError::UnexpectedEndOfFile {
+                            position: self.position,
+                        });
+                    }
+                }
+                '+' => {
+                    if let Some('=') = self.peek_second_char() {
+                        self.position += 2;
+
+                        (Token::PlusEqual, Span(self.position - 2, self.position))
+                    } else {
+                        self.position += 1;
+
+                        (Token::Plus, Span(self.position - 1, self.position))
+                    }
+                }
+                '*' => {
+                    if let Some('=') = self.peek_second_char() {
+                        self.position += 2;
+
+                        (Token::StarEqual, Span(self.position - 2, self.position))
+                    } else {
+                        self.position += 1;
+
+                        (Token::Star, Span(self.position - 1, self.position))
+                    }
+                }
+                '(' => {
+                    self.position += 1;
+
+                    (
+                        Token::LeftParenthesis,
+                        Span(self.position - 1, self.position),
+                    )
+                }
+                ')' => {
+                    self.position += 1;
+
+                    (
+                        Token::RightParenthesis,
+                        Span(self.position - 1, self.position),
+                    )
+                }
+                '=' => {
+                    if let Some('=') = self.peek_second_char() {
+                        self.position += 2;
+
+                        (Token::DoubleEqual, Span(self.position - 2, self.position))
+                    } else {
+                        self.position += 1;
+
+                        (Token::Equal, Span(self.position - 1, self.position))
+                    }
+                }
+                '[' => {
+                    self.position += 1;
+
+                    (
+                        Token::LeftSquareBrace,
+                        Span(self.position - 1, self.position),
+                    )
+                }
+                ']' => {
+                    self.position += 1;
+
+                    (
+                        Token::RightSquareBrace,
+                        Span(self.position - 1, self.position),
+                    )
+                }
+                ',' => {
+                    self.position += 1;
+
+                    (Token::Comma, Span(self.position - 1, self.position))
+                }
+                '.' => {
+                    if let Some('.') = self.peek_second_char() {
+                        self.position += 2;
+
+                        (Token::DoubleDot, Span(self.position - 2, self.position))
+                    } else {
+                        self.position += 1;
+
+                        (Token::Dot, Span(self.position - 1, self.position))
+                    }
+                }
+                '>' => {
+                    if let Some('=') = self.peek_second_char() {
+                        self.position += 2;
+
+                        (Token::GreaterEqual, Span(self.position - 2, self.position))
+                    } else {
+                        self.position += 1;
+
+                        (Token::Greater, Span(self.position - 1, self.position))
+                    }
+                }
+                '<' => {
+                    if let Some('=') = self.peek_second_char() {
+                        self.position += 2;
+
+                        (Token::LessEqual, Span(self.position - 2, self.position))
+                    } else {
+                        self.position += 1;
+
+                        (Token::Less, Span(self.position - 1, self.position))
+                    }
+                }
+                '{' => {
+                    self.position += 1;
+
+                    (
+                        Token::LeftCurlyBrace,
+                        Span(self.position - 1, self.position),
+                    )
+                }
+                '}' => {
+                    self.position += 1;
+
+                    (
+                        Token::RightCurlyBrace,
+                        Span(self.position - 1, self.position),
+                    )
+                }
+                '/' => {
+                    if let Some('=') = self.peek_second_char() {
+                        self.position += 2;
+
+                        (Token::SlashEqual, Span(self.position - 2, self.position))
+                    } else {
+                        self.position += 1;
+
+                        (Token::Slash, Span(self.position - 1, self.position))
+                    }
+                }
+                '%' => {
+                    self.position += 1;
+
+                    (Token::Percent, Span(self.position - 1, self.position))
+                }
+                '&' => {
+                    if let Some('&') = self.peek_second_char() {
+                        self.position += 2;
+
+                        (
+                            Token::DoubleAmpersand,
+                            Span(self.position - 2, self.position),
+                        )
+                    } else {
+                        self.position += 1;
+
+                        return Err(LexError::UnexpectedCharacter {
+                            actual: c,
+                            position: self.position,
+                        });
+                    }
+                }
+                ';' => {
+                    self.position += 1;
+
+                    (Token::Semicolon, Span(self.position - 1, self.position))
+                }
+                '|' => {
+                    if let Some('|') = self.peek_second_char() {
+                        self.position += 2;
+
+                        (Token::DoublePipe, Span(self.position - 2, self.position))
+                    } else {
+                        self.position += 1;
+
+                        return Err(LexError::UnexpectedCharacter {
+                            actual: c,
+                            position: self.position,
+                        });
+                    }
+                }
+                '!' => {
+                    self.position += 1;
+
+                    if let Some('=') = self.peek_char() {
+                        self.position += 1;
+
+                        (Token::BangEqual, Span(self.position - 2, self.position))
+                    } else {
+                        (Token::Bang, Span(self.position - 1, self.position))
+                    }
+                }
+                ':' => {
+                    self.position += 1;
+
+                    (Token::Colon, Span(self.position - 1, self.position))
+                }
+                _ => {
+                    return Err(LexError::UnexpectedCharacter {
+                        actual: c,
+                        position: self.position,
+                    });
+                }
+            }
         } else {
-            self.is_eof = true;
-
             (Token::Eof, Span(self.position, self.position))
         };
 
         Ok((token, span))
     }
 
+    /// Peek at the next token without consuming the source.
+    pub fn peek_token(&mut self) -> Result<(Token<'src>, Span), LexError> {
+        let token = self.next_token()?;
+
+        self.position -= token.0.len();
+
+        Ok(token)
+    }
+
     /// Progress to the next character.
     fn next_char(&mut self) -> Option<char> {
         if let Some(c) = self.source[self.position..].chars().next() {
@@ -255,7 +507,7 @@ impl<'src> Lexer<'src> {
     }
 
     /// Lex an identifier token.
-    fn lex_keyword_or_identifier(&mut self) -> Result<(Token<'src>, Span), LexError> {
+    fn lex_alphanumeric(&mut self) -> Result<(Token<'src>, Span), LexError> {
         let start_pos = self.position;
 
         while let Some(c) = self.peek_char() {
@@ -312,410 +564,6 @@ impl<'src> Lexer<'src> {
 
         Ok((Token::String(text), Span(start_pos, self.position)))
     }
-
-    fn lex_char(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_position = self.position;
-
-        self.next_char();
-
-        let char = self.source[self.position..].chars().next().unwrap();
-
-        self.next_char();
-
-        if self.peek_char() == Some('\'') {
-            self.next_char();
-        } else {
-            return Err(LexError::ExpectedCharacter {
-                expected: '\'',
-                actual: self.peek_char().unwrap_or('\0'),
-                position: self.position,
-            });
-        }
-
-        let end_position = self.position;
-
-        Ok((Token::Character(char), Span(start_position, end_position)))
-    }
-
-    fn lex_plus(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        if let Some('=') = self.peek_char() {
-            self.next_char();
-
-            Ok((Token::PlusEqual, Span(start_pos, self.position)))
-        } else {
-            Ok((Token::Plus, Span(start_pos, self.position)))
-        }
-    }
-
-    fn lex_minus(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_position = self.position;
-
-        if self
-            .peek_second_char()
-            .is_some_and(|char| char.is_ascii_digit())
-        {
-            return self.lex_numeric();
-        }
-
-        self.next_char();
-
-        if let Some('=') = self.peek_char() {
-            self.next_char();
-
-            return Ok((Token::MinusEqual, Span(start_position, self.position)));
-        }
-
-        if let Some('>') = self.peek_char() {
-            self.next_char();
-
-            return Ok((Token::ArrowThin, Span(start_position, self.position)));
-        }
-
-        if self.peek_chars(8) == "Infinity" {
-            self.position += 8;
-
-            return Ok((
-                Token::Float("-Infinity"),
-                Span(start_position, self.position),
-            ));
-        }
-
-        Ok((Token::Minus, Span(start_position, self.position)))
-    }
-
-    fn lex_star(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        if let Some('=') = self.peek_char() {
-            self.next_char();
-
-            Ok((Token::StarEqual, Span(start_pos, self.position)))
-        } else {
-            Ok((Token::Star, Span(start_pos, self.position)))
-        }
-    }
-
-    fn lex_slash(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        if let Some('=') = self.peek_char() {
-            self.next_char();
-
-            Ok((Token::SlashEqual, Span(start_pos, self.position)))
-        } else {
-            Ok((Token::Slash, Span(start_pos, self.position)))
-        }
-    }
-
-    fn lex_percent(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        if let Some('=') = self.peek_char() {
-            self.next_char();
-
-            Ok((Token::PercentEqual, Span(start_pos, self.position)))
-        } else {
-            Ok((Token::Percent, Span(start_pos, self.position)))
-        }
-    }
-
-    fn lex_unexpected(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        Err(LexError::UnexpectedCharacter {
-            actual: self.peek_char().unwrap_or('\0'),
-            position: self.position,
-        })
-    }
-
-    fn lex_exclamation_mark(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        if let Some('=') = self.peek_char() {
-            self.next_char();
-
-            Ok((Token::BangEqual, Span(start_pos, self.position)))
-        } else {
-            Ok((Token::Bang, Span(start_pos, self.position)))
-        }
-    }
-
-    fn lex_equal(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        if let Some('=') = self.peek_char() {
-            self.next_char();
-
-            Ok((Token::DoubleEqual, Span(start_pos, self.position)))
-        } else {
-            Ok((Token::Equal, Span(start_pos, self.position)))
-        }
-    }
-
-    fn lex_less_than(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        if let Some('=') = self.peek_char() {
-            self.next_char();
-
-            Ok((Token::LessEqual, Span(start_pos, self.position)))
-        } else {
-            Ok((Token::Less, Span(start_pos, self.position)))
-        }
-    }
-
-    fn lex_greater_than(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        if let Some('=') = self.peek_char() {
-            self.next_char();
-
-            Ok((Token::GreaterEqual, Span(start_pos, self.position)))
-        } else {
-            Ok((Token::Greater, Span(start_pos, self.position)))
-        }
-    }
-
-    fn lex_ampersand(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        let peek_char = self.peek_char();
-
-        if let Some('&') = peek_char {
-            self.next_char();
-
-            Ok((Token::DoubleAmpersand, Span(start_pos, self.position)))
-        } else if peek_char.is_none() {
-            Err(LexError::UnexpectedEndOfFile {
-                position: self.position,
-            })
-        } else {
-            Err(LexError::ExpectedCharacter {
-                expected: '&',
-                actual: self.peek_char().unwrap(),
-                position: self.position,
-            })
-        }
-    }
-
-    fn lex_pipe(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        let peek_char = self.peek_char();
-
-        if let Some('|') = peek_char {
-            self.next_char();
-
-            Ok((Token::DoublePipe, Span(start_pos, self.position)))
-        } else if peek_char.is_none() {
-            Err(LexError::UnexpectedEndOfFile {
-                position: self.position,
-            })
-        } else {
-            Err(LexError::ExpectedCharacter {
-                expected: '&',
-                actual: self.peek_char().unwrap(),
-                position: self.position,
-            })
-        }
-    }
-
-    fn lex_left_parenthesis(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        Ok((Token::LeftParenthesis, Span(start_pos, self.position)))
-    }
-
-    fn lex_right_parenthesis(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        Ok((Token::RightParenthesis, Span(start_pos, self.position)))
-    }
-
-    fn lex_left_bracket(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        Ok((Token::LeftBracket, Span(start_pos, self.position)))
-    }
-
-    fn lex_right_bracket(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        Ok((Token::RightBracket, Span(start_pos, self.position)))
-    }
-
-    fn lex_left_brace(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        Ok((Token::LeftBrace, Span(start_pos, self.position)))
-    }
-
-    fn lex_right_brace(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        Ok((Token::RightBrace, Span(start_pos, self.position)))
-    }
-
-    fn lex_semicolon(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        Ok((Token::Semicolon, Span(start_pos, self.position)))
-    }
-
-    fn lex_colon(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        Ok((Token::Colon, Span(start_pos, self.position)))
-    }
-
-    fn lex_comma(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        Ok((Token::Comma, Span(start_pos, self.position)))
-    }
-
-    fn lex_dot(&mut self) -> Result<(Token<'src>, Span), LexError> {
-        let start_pos = self.position;
-
-        self.next_char();
-
-        if let Some('.') = self.peek_char() {
-            self.next_char();
-
-            Ok((Token::DoubleDot, Span(start_pos, self.position)))
-        } else {
-            Ok((Token::Dot, Span(start_pos, self.position)))
-        }
-    }
-}
-
-type LexerFn<'src> = fn(&mut Lexer<'src>) -> Result<(Token<'src>, Span), LexError>;
-
-pub struct LexRule<'src> {
-    lexer: LexerFn<'src>,
-}
-
-impl<'src> From<&char> for LexRule<'src> {
-    fn from(char: &char) -> Self {
-        match char {
-            '0'..='9' => LexRule {
-                lexer: Lexer::lex_numeric,
-            },
-            char if char.is_alphabetic() => LexRule {
-                lexer: Lexer::lex_keyword_or_identifier,
-            },
-            '"' => LexRule {
-                lexer: Lexer::lex_string,
-            },
-            '\'' => LexRule {
-                lexer: Lexer::lex_char,
-            },
-            '+' => LexRule {
-                lexer: Lexer::lex_plus,
-            },
-            '-' => LexRule {
-                lexer: Lexer::lex_minus,
-            },
-            '*' => LexRule {
-                lexer: Lexer::lex_star,
-            },
-            '/' => LexRule {
-                lexer: Lexer::lex_slash,
-            },
-            '%' => LexRule {
-                lexer: Lexer::lex_percent,
-            },
-            '!' => LexRule {
-                lexer: Lexer::lex_exclamation_mark,
-            },
-            '=' => LexRule {
-                lexer: Lexer::lex_equal,
-            },
-            '<' => LexRule {
-                lexer: Lexer::lex_less_than,
-            },
-            '>' => LexRule {
-                lexer: Lexer::lex_greater_than,
-            },
-            '&' => LexRule {
-                lexer: Lexer::lex_ampersand,
-            },
-            '|' => LexRule {
-                lexer: Lexer::lex_pipe,
-            },
-            '(' => LexRule {
-                lexer: Lexer::lex_left_parenthesis,
-            },
-            ')' => LexRule {
-                lexer: Lexer::lex_right_parenthesis,
-            },
-            '[' => LexRule {
-                lexer: Lexer::lex_left_bracket,
-            },
-            ']' => LexRule {
-                lexer: Lexer::lex_right_bracket,
-            },
-            '{' => LexRule {
-                lexer: Lexer::lex_left_brace,
-            },
-            '}' => LexRule {
-                lexer: Lexer::lex_right_brace,
-            },
-            ';' => LexRule {
-                lexer: Lexer::lex_semicolon,
-            },
-            ':' => LexRule {
-                lexer: Lexer::lex_colon,
-            },
-            ',' => LexRule {
-                lexer: Lexer::lex_comma,
-            },
-            '.' => LexRule {
-                lexer: Lexer::lex_dot,
-            },
-            _ => LexRule {
-                lexer: Lexer::lex_unexpected,
-            },
-        }
-    }
 }
 
 #[derive(Debug, PartialEq, Clone)]
@@ -845,7 +693,7 @@ mod tests {
             lex(input),
             Ok(vec![
                 (Token::Map, Span(0, 3)),
-                (Token::LeftBrace, Span(4, 5)),
+                (Token::LeftCurlyBrace, Span(4, 5)),
                 (Token::Identifier("x"), Span(6, 7)),
                 (Token::Equal, Span(8, 9)),
                 (Token::String("1"), Span(10, 13)),
@@ -857,7 +705,7 @@ mod tests {
                 (Token::Identifier("z"), Span(22, 23)),
                 (Token::Equal, Span(24, 25)),
                 (Token::Float("3.0"), Span(26, 29)),
-                (Token::RightBrace, Span(30, 31)),
+                (Token::RightCurlyBrace, Span(30, 31)),
                 (Token::Eof, Span(31, 31)),
             ])
         );
@@ -921,7 +769,7 @@ mod tests {
             Ok(vec![
                 (Token::Struct, Span(0, 6)),
                 (Token::Identifier("FooBar"), Span(7, 13)),
-                (Token::LeftBrace, Span(14, 15)),
+                (Token::LeftCurlyBrace, Span(14, 15)),
                 (Token::Identifier("foo"), Span(16, 19)),
                 (Token::Colon, Span(19, 20)),
                 (Token::Int, Span(21, 24)),
@@ -929,7 +777,7 @@ mod tests {
                 (Token::Identifier("bar"), Span(26, 29)),
                 (Token::Colon, Span(29, 30)),
                 (Token::FloatKeyword, Span(31, 36)),
-                (Token::RightBrace, Span(37, 38)),
+                (Token::RightCurlyBrace, Span(37, 38)),
                 (Token::Eof, Span(38, 38))
             ])
         );
@@ -942,16 +790,16 @@ mod tests {
         assert_eq!(
             lex(input),
             Ok(vec![
-                (Token::LeftBracket, Span(0, 1)),
+                (Token::LeftSquareBrace, Span(0, 1)),
                 (Token::Integer("1"), Span(1, 2)),
                 (Token::Comma, Span(2, 3)),
                 (Token::Integer("2"), Span(4, 5)),
                 (Token::Comma, Span(5, 6)),
                 (Token::Integer("3"), Span(7, 8)),
-                (Token::RightBracket, Span(8, 9)),
+                (Token::RightSquareBrace, Span(8, 9)),
-                (Token::LeftBracket, Span(9, 10)),
+                (Token::LeftSquareBrace, Span(9, 10)),
                 (Token::Integer("1"), Span(10, 11)),
-                (Token::RightBracket, Span(11, 12)),
+                (Token::RightSquareBrace, Span(11, 12)),
                 (Token::Eof, Span(12, 12)),
             ])
         )
@@ -964,13 +812,13 @@ mod tests {
         assert_eq!(
             lex(input),
             Ok(vec![
-                (Token::LeftBracket, Span(0, 1)),
+                (Token::LeftSquareBrace, Span(0, 1)),
                 (Token::Integer("1"), Span(1, 2)),
                 (Token::Comma, Span(2, 3)),
                 (Token::Integer("2"), Span(4, 5)),
                 (Token::Comma, Span(5, 6)),
                 (Token::Integer("3"), Span(7, 8)),
-                (Token::RightBracket, Span(8, 9)),
+                (Token::RightSquareBrace, Span(8, 9)),
                 (Token::Eof, Span(9, 9)),
             ])
         )
@@ -983,7 +831,7 @@ mod tests {
         assert_eq!(
             lex(input),
             Ok(vec![
-                (Token::LeftBrace, Span(0, 1)),
+                (Token::LeftCurlyBrace, Span(0, 1)),
                 (Token::Identifier("a"), Span(1, 2)),
                 (Token::Equal, Span(3, 4)),
                 (Token::Integer("1"), Span(5, 6)),
@@ -995,7 +843,7 @@ mod tests {
                 (Token::Identifier("c"), Span(15, 16)),
                 (Token::Equal, Span(17, 18)),
                 (Token::Integer("3"), Span(19, 20)),
-                (Token::RightBrace, Span(20, 21)),
+                (Token::RightCurlyBrace, Span(20, 21)),
                 (Token::Dot, Span(21, 22)),
                 (Token::Identifier("c"), Span(22, 23)),
                 (Token::Eof, Span(23, 23)),
@@ -1064,15 +912,15 @@ mod tests {
                 (Token::Identifier("x"), Span(3, 4)),
                 (Token::Less, Span(5, 6)),
                 (Token::Integer("10"), Span(7, 9)),
-                (Token::LeftBrace, Span(10, 11)),
+                (Token::LeftCurlyBrace, Span(10, 11)),
                 (Token::Identifier("x"), Span(12, 13)),
                 (Token::Plus, Span(14, 15)),
                 (Token::Integer("1"), Span(16, 17)),
-                (Token::RightBrace, Span(18, 19)),
+                (Token::RightCurlyBrace, Span(18, 19)),
                 (Token::Else, Span(20, 24)),
-                (Token::LeftBrace, Span(25, 26)),
+                (Token::LeftCurlyBrace, Span(25, 26)),
                 (Token::Identifier("x"), Span(27, 28)),
-                (Token::RightBrace, Span(29, 30)),
+                (Token::RightCurlyBrace, Span(29, 30)),
                 (Token::Eof, Span(30, 30)),
             ])
         )
@@ -1089,11 +937,11 @@ mod tests {
                 (Token::Identifier("x"), Span(6, 7)),
                 (Token::Less, Span(8, 9)),
                 (Token::Integer("10"), Span(10, 12)),
-                (Token::LeftBrace, Span(13, 14)),
+                (Token::LeftCurlyBrace, Span(13, 14)),
                 (Token::Identifier("x"), Span(15, 16)),
                 (Token::PlusEqual, Span(17, 19)),
                 (Token::Integer("1"), Span(20, 21)),
-                (Token::RightBrace, Span(22, 23)),
+                (Token::RightCurlyBrace, Span(22, 23)),
                 (Token::Eof, Span(23, 23)),
             ])
         )
@@ -1136,7 +984,7 @@ mod tests {
         assert_eq!(
             lex(input),
             Ok(vec![
-                (Token::LeftBrace, Span(0, 1)),
+                (Token::LeftCurlyBrace, Span(0, 1)),
                 (Token::Identifier("x"), Span(2, 3)),
                 (Token::Equal, Span(4, 5)),
                 (Token::Integer("42"), Span(6, 8)),
@@ -1144,7 +992,7 @@ mod tests {
                 (Token::Identifier("y"), Span(10, 11)),
                 (Token::Equal, Span(12, 13)),
                 (Token::String("foobar"), Span(14, 22)),
-                (Token::RightBrace, Span(23, 24)),
+                (Token::RightCurlyBrace, Span(23, 24)),
                 (Token::Eof, Span(24, 24)),
             ])
         )
@@ -1485,8 +1333,8 @@ mod tests {
         assert_eq!(
             lex(input),
             Ok(vec![
-                (Token::LeftBracket, Span(0, 1)),
+                (Token::LeftSquareBrace, Span(0, 1)),
-                (Token::RightBracket, Span(1, 2)),
+                (Token::RightSquareBrace, Span(1, 2)),
                 (Token::Eof, Span(2, 2)),
             ])
         )

dust-lang/src/lib.rs

@@ -5,33 +5,29 @@ pub mod compiler;
 pub mod disassembler;
 pub mod dust_error;
 pub mod formatter;
-pub mod function;
 pub mod instruction;
 pub mod lexer;
 pub mod native_function;
 pub mod operation;
 pub mod optimizer;
-pub mod scope;
 pub mod token;
 pub mod r#type;
 pub mod value;
 pub mod vm;
 
-pub use crate::chunk::{Chunk, ChunkError, Local};
+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::function::{Function, FunctionBorrowed};
 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::Optimizer;
+pub use crate::optimizer::{optimize, Optimizer};
-pub use crate::r#type::{EnumType, FunctionType, StructType, Type, TypeConflict};
+pub use crate::r#type::{EnumType, FunctionType, RangeableType, StructType, Type, TypeConflict};
-pub use crate::scope::Scope;
+pub use crate::token::{Token, TokenKind, TokenOwned};
-pub use crate::token::{output_token_list, Token, TokenKind, TokenOwned};
+pub use crate::value::{ConcreteValue, Function, Value, ValueError};
-pub use crate::value::{ConcreteValue, Value, ValueError};
 pub use crate::vm::{run, Vm, VmError};
 
 use std::fmt::Display;

dust-lang/src/native_function.rs

@@ -2,20 +2,20 @@
 //!
 //! 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.
-mod logic;
-
 use std::{
     fmt::{self, Display, Formatter},
-    io::{self},
+    io::{self, stdin, stdout, Write},
     string::{self},
 };
 
 use serde::{Deserialize, Serialize};
 
-use crate::{AnnotatedError, ConcreteValue, FunctionType, Instruction, Span, Type, Vm, VmError};
+use crate::{
+    AnnotatedError, ConcreteValue, FunctionType, Instruction, Span, Type, Value, Vm, VmError,
+};
 
 macro_rules! define_native_function {
-    ($(($name:ident, $byte:literal, $str:expr, $type:expr, $function:expr)),*) => {
+    ($(($name:ident, $byte:literal, $str:expr, $type:expr)),*) => {
         /// A dust-native function.
         ///
         /// See the [module-level documentation](index.html) for more information.
@@ -27,19 +27,6 @@ macro_rules! define_native_function {
         }
 
         impl NativeFunction {
-            pub fn call(
-                &self,
-                vm: &mut Vm,
-                instruction: Instruction,
-                span: Span
-            ) -> Result<Option<ConcreteValue>, VmError> {
-                match self {
-                    $(
-                        NativeFunction::$name => $function(vm, instruction, span),
-                    )*
-                }
-            }
-
             pub fn as_str(&self) -> &'static str {
                 match self {
                     $(
@@ -69,7 +56,7 @@ macro_rules! define_native_function {
             pub fn returns_value(&self) -> bool {
                 match self {
                     $(
-                        NativeFunction::$name => *$type.return_type != Type::None,
+                        NativeFunction::$name => $type.return_type.is_some(),
                     )*
                 }
             }
@@ -104,25 +91,18 @@ macro_rules! define_native_function {
     };
 }
 
-impl Display for NativeFunction {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "{}", self.as_str())
-    }
-}
-
 define_native_function! {
     // Assertion
-    // (
+    (
-    //     Assert,
+        Assert,
-    //     0_u8,
+        0_u8,
-    //     "assert",
+        "assert",
-    //     FunctionType {
+        FunctionType {
-    //         type_parameters: None,
+            type_parameters: None,
-    //         value_parameters: None,
+            value_parameters: None,
-    //         return_type: Box::new(Type::None)
+            return_type: None
-    //     },
+        }
-    //     assert
+    ),
-    // ),
     // (AssertEqual, 1_u8, "assert_equal", false),
     // (AssertNotEqual, 2_u8, "assert_not_equal", false),
     (
@@ -132,9 +112,8 @@ define_native_function! {
         FunctionType {
             type_parameters: None,
             value_parameters: None,
-            return_type: Box::new(Type::None)
+            return_type: Some(Box::new(Type::Any))
-        },
+        }
-        logic::panic
     ),
 
     // // Type conversion
@@ -149,9 +128,8 @@ define_native_function! {
         FunctionType {
             type_parameters: None,
             value_parameters: Some(vec![(0, Type::Any)]),
-            return_type: Box::new(Type::String { length: None })
+            return_type: Some(Box::new(Type::String { length: None }))
-        },
+        }
-        logic::to_string
     ),
 
     // // List and string
@@ -210,9 +188,8 @@ define_native_function! {
         FunctionType {
             type_parameters: None,
             value_parameters: None,
-            return_type: Box::new(Type::String { length: None })
+            return_type: Some(Box::new(Type::String { length: None }))
-        },
+        }
-        logic::read_line
     ),
     // (ReadTo, 51_u8, "read_to", false),
     // (ReadUntil, 52_u8, "read_until", true),
@@ -226,9 +203,8 @@ define_native_function! {
         FunctionType {
             type_parameters: None,
             value_parameters: Some(vec![(0, Type::String { length: None })]),
-            return_type: Box::new(Type::None)
+            return_type: None
-        },
+        }
-        logic::write
     ),
     // (WriteFile, 56_u8, "write_file", false),
     (
@@ -238,9 +214,8 @@ define_native_function! {
         FunctionType {
             type_parameters: None,
             value_parameters: Some(vec![(0, Type::String { length: None })]),
-            return_type: Box::new(Type::None)
+            return_type: None
-        },
+        }
-        logic::write_line
     )
 
     // // Random
@@ -248,6 +223,142 @@ define_native_function! {
     // (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 {

dust-lang/src/native_function/logic.rs

@@ -1,157 +0,0 @@
-use std::io::{self, stdout, Write};
-
-use crate::{ConcreteValue, Instruction, NativeFunctionError, Span, Value, Vm, VmError};
-
-pub fn panic(
-    vm: &Vm,
-    instruction: Instruction,
-    position: Span,
-) -> Result<Option<ConcreteValue>, VmError> {
-    let argument_count = instruction.c();
-    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)
-    };
-
-    Err(VmError::NativeFunction(NativeFunctionError::Panic {
-        message,
-        position,
-    }))
-}
-
-pub fn to_string(
-    vm: &Vm,
-    instruction: Instruction,
-    position: Span,
-) -> Result<Option<ConcreteValue>, VmError> {
-    let argument_count = instruction.c();
-
-    if argument_count != 1 {
-        return Err(VmError::NativeFunction(
-            NativeFunctionError::ExpectedArgumentCount {
-                expected: 1,
-                found: argument_count as usize,
-                position,
-            },
-        ));
-    }
-
-    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());
-    }
-
-    Ok(Some(ConcreteValue::String(string)))
-}
-
-pub fn read_line(
-    _: &Vm,
-    instruction: Instruction,
-    position: Span,
-) -> Result<Option<ConcreteValue>, VmError> {
-    let argument_count = instruction.c();
-
-    if argument_count != 0 {
-        return Err(VmError::NativeFunction(
-            NativeFunctionError::ExpectedArgumentCount {
-                expected: 0,
-                found: argument_count as usize,
-                position,
-            },
-        ));
-    }
-
-    let mut buffer = String::new();
-
-    match io::stdin().read_line(&mut buffer) {
-        Ok(_) => Ok(Some(ConcreteValue::String(
-            buffer.trim_end_matches('\n').to_string(),
-        ))),
-        Err(error) => Err(VmError::NativeFunction(NativeFunctionError::Io {
-            error: error.kind(),
-            position,
-        })),
-    }
-}
-
-pub fn write(
-    vm: &Vm,
-    instruction: Instruction,
-    position: Span,
-) -> Result<Option<ConcreteValue>, VmError> {
-    let to_register = instruction.a();
-    let argument_count = instruction.c();
-    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);
-
-    for argument_index in first_argument..to_register {
-        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)?;
-    }
-
-    Ok(None)
-}
-
-pub fn write_line(
-    vm: &Vm,
-    instruction: Instruction,
-    position: Span,
-) -> Result<Option<ConcreteValue>, VmError> {
-    let to_register = instruction.a();
-    let argument_count = instruction.c();
-    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);
-
-    for argument_index in first_argument..to_register {
-        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)?;
-    }
-
-    stdout.write(b"\n").map_err(map_err)?;
-
-    Ok(None)
-}

dust-lang/src/optimizer.rs

@@ -1,41 +1,34 @@
-//! Tool used by the compiler to optimize a chunk's bytecode.
+//! Tools used by the compiler to optimize a chunk's bytecode.
+use std::{iter::Map, slice::Iter};
 
 use crate::{Instruction, Operation, Span};
 
-/// An instruction optimizer that mutably borrows instructions from a chunk.
+type MapToOperation = fn(&(Instruction, Span)) -> Operation;
-#[derive(Debug, Eq, PartialEq, PartialOrd, Ord)]
+
-pub struct Optimizer<'a> {
+type OperationIter<'iter> = Map<Iter<'iter, (Instruction, Span)>, MapToOperation>;
-    instructions: &'a mut Vec<(Instruction, Span)>,
+
+/// Performs optimizations on a subset of instructions.
+pub fn optimize(instructions: &mut [(Instruction, Span)]) -> usize {
+    Optimizer::new(instructions).optimize()
 }
 
-impl<'a> Optimizer<'a> {
+/// 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: &'a mut Vec<(Instruction, Span)>) -> Self {
+    pub fn new(instructions: &'chunk mut [(Instruction, Span)]) -> Self {
         Self { instructions }
     }
 
-    /// Optimizes a comparison operation.
+    /// Potentially mutates the instructions to optimize them.
-    ///
+    pub fn optimize(&mut self) -> usize {
-    /// Comparison instructions (which are always followed by a JUMP) can be optimized when the
+        let mut optimizations = 0;
-    /// next instructions are two constant or boolean loaders. The first loader is set to skip an
+
-    /// instruction if it is run while the second loader is modified to use the first's register.
+        if matches!(
-    /// This makes the following two code snippets compile to the same bytecode:
-    ///
-    /// ```dust
-    /// 4 == 4
-    /// ```
-    ///
-    /// ```dust
-    /// if 4 == 4 { true } else { false }
-    /// ```
-    ///
-    /// The instructions must be in the following order:
-    ///     - `Operation::Equal | Operation::Less | Operation::LessEqual`
-    ///     - `Operation::Jump`
-    ///     - `Operation::LoadBoolean | Operation::LoadConstant`
-    ///     - `Operation::LoadBoolean | Operation::LoadConstant`
-    pub fn optimize_comparison(&mut self) -> bool {
-        if !matches!(
             self.get_operations(),
             Some([
                 Operation::Equal | Operation::Less | Operation::LessEqual,
@@ -44,9 +37,22 @@ impl<'a> Optimizer<'a> {
                 Operation::LoadBoolean | Operation::LoadConstant,
             ])
         ) {
-            return false;
+            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 = {
@@ -66,30 +72,12 @@ impl<'a> Optimizer<'a> {
         second_loader_new.set_c_to_boolean(second_loader.c_is_constant());
 
         *second_loader = second_loader_new;
-
-        true
     }
 
-    pub fn optimize_set_local(&mut self) -> bool {
+    fn operations_iter(&self) -> OperationIter {
-        if !matches!(
+        self.instructions
-            self.get_operations(),
+            .iter()
-            Some([
+            .map(|(instruction, _)| instruction.operation())
-                Operation::Add
-                    | Operation::Subtract
-                    | Operation::Multiply
-                    | Operation::Divide
-                    | Operation::Modulo,
-                Operation::SetLocal,
-            ])
-        ) {
-            return false;
-        }
-
-        log::debug!("Optimizing set local");
-
-        self.instructions.pop();
-
-        true
     }
 
     fn get_operations<const COUNT: usize>(&self) -> Option<[Operation; COUNT]> {
@@ -99,12 +87,7 @@ impl<'a> Optimizer<'a> {
 
         let mut n_operations = [Operation::Return; COUNT];
 
-        for (nth, operation) in n_operations.iter_mut().rev().zip(
+        for (nth, operation) in n_operations.iter_mut().zip(self.operations_iter()) {
-            self.instructions
-                .iter()
-                .rev()
-                .map(|(instruction, _)| instruction.operation()),
-        ) {
             *nth = operation;
         }
 

dust-lang/src/scope.rs

@@ -1,59 +0,0 @@
-//! Scope, a type that represents the locality of a variable.
-use std::{
-    cmp::Ordering,
-    fmt::{self, Display, Formatter},
-};
-
-use serde::{Deserialize, Serialize};
-
-/// 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,
-        }
-    }
-
-    #[inline]
-    pub fn begin(&mut self, block_index: u8) {
-        self.block_index = block_index;
-        self.depth += 1;
-    }
-
-    #[inline]
-    pub fn end(&mut self) {
-        self.depth -= 1;
-
-        if self.depth == 0 {
-            self.block_index = 0;
-        } else {
-            self.block_index -= 1;
-        }
-    }
-}
-
-impl Display for Scope {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "({}, {})", self.depth, self.block_index)
-    }
-}

dust-lang/src/token.rs

@@ -1,30 +1,8 @@
 //! Token, TokenOwned and TokenKind types.
-use std::{
+use std::fmt::{self, Display, Formatter};
-    fmt::{self, Display, Formatter},
-    io::Write,
-};
 
 use serde::{Deserialize, Serialize};
 
-use crate::Span;
-
-pub fn output_token_list<W: Write>(tokens: &[(Token, Span)], writer: &mut W) {
-    const HEADER: [&str; 2] = [
-        "TOKEN        KIND       POSITION  ",
-        "------------ ---------- ----------",
-    ];
-
-    writeln!(writer, "{}", HEADER[0]).unwrap();
-    writeln!(writer, "{}", HEADER[1]).unwrap();
-
-    for (token, position) in tokens {
-        let kind = token.kind().to_string();
-        let token = token.to_string();
-
-        writeln!(writer, "{token:<12} {kind:<10} {position}").unwrap();
-    }
-}
-
 macro_rules! define_tokens {
     ($($variant:ident $(($data_type:ty))?),+ $(,)?) => {
         /// Source token.
@@ -94,9 +72,9 @@ define_tokens! {
     Equal,
     Greater,
     GreaterEqual,
-    LeftBrace,
+    LeftCurlyBrace,
-    LeftBracket,
     LeftParenthesis,
+    LeftSquareBrace,
     Less,
     LessEqual,
     Minus,
@@ -105,9 +83,9 @@ define_tokens! {
     PercentEqual,
     Plus,
     PlusEqual,
-    RightBrace,
+    RightCurlyBrace,
-    RightBracket,
     RightParenthesis,
+    RightSquareBrace,
     Semicolon,
     Slash,
     SlashEqual,
@@ -155,9 +133,9 @@ impl<'src> Token<'src> {
             Token::Equal => 1,
             Token::Greater => 1,
             Token::GreaterEqual => 2,
-            Token::LeftBrace => 1,
+            Token::LeftCurlyBrace => 1,
             Token::LeftParenthesis => 1,
-            Token::LeftBracket => 1,
+            Token::LeftSquareBrace => 1,
             Token::Less => 1,
             Token::LessEqual => 2,
             Token::Minus => 1,
@@ -167,9 +145,9 @@ impl<'src> Token<'src> {
             Token::Plus => 1,
             Token::PlusEqual => 2,
             Token::Return => 6,
-            Token::RightBrace => 1,
+            Token::RightCurlyBrace => 1,
             Token::RightParenthesis => 1,
-            Token::RightBracket => 1,
+            Token::RightSquareBrace => 1,
             Token::Semicolon => 1,
             Token::Slash => 1,
             Token::SlashEqual => 2,
@@ -216,9 +194,9 @@ impl<'src> Token<'src> {
             Token::Equal => "=",
             Token::Greater => ">",
             Token::GreaterEqual => ">=",
-            Token::LeftBrace => "{",
+            Token::LeftCurlyBrace => "{",
             Token::LeftParenthesis => "(",
-            Token::LeftBracket => "[",
+            Token::LeftSquareBrace => "[",
             Token::Less => "<",
             Token::LessEqual => "<=",
             Token::Minus => "-",
@@ -228,9 +206,9 @@ impl<'src> Token<'src> {
             Token::Plus => "+",
             Token::PlusEqual => "+=",
             Token::Return => "return",
-            Token::RightBrace => "}",
+            Token::RightCurlyBrace => "}",
             Token::RightParenthesis => ")",
-            Token::RightBracket => "]",
+            Token::RightSquareBrace => "]",
             Token::Semicolon => ";",
             Token::Slash => "/",
             Token::SlashEqual => "/=",
@@ -269,9 +247,9 @@ impl<'src> Token<'src> {
             Token::If => TokenOwned::If,
             Token::Int => TokenOwned::Int,
             Token::Integer(integer) => TokenOwned::Integer(integer.to_string()),
-            Token::LeftBrace => TokenOwned::LeftCurlyBrace,
+            Token::LeftCurlyBrace => TokenOwned::LeftCurlyBrace,
             Token::LeftParenthesis => TokenOwned::LeftParenthesis,
-            Token::LeftBracket => TokenOwned::LeftSquareBrace,
+            Token::LeftSquareBrace => TokenOwned::LeftSquareBrace,
             Token::Let => TokenOwned::Let,
             Token::Less => TokenOwned::Less,
             Token::LessEqual => TokenOwned::LessOrEqual,
@@ -285,9 +263,9 @@ impl<'src> Token<'src> {
             Token::Plus => TokenOwned::Plus,
             Token::PlusEqual => TokenOwned::PlusEqual,
             Token::Return => TokenOwned::Return,
-            Token::RightBrace => TokenOwned::RightCurlyBrace,
+            Token::RightCurlyBrace => TokenOwned::RightCurlyBrace,
             Token::RightParenthesis => TokenOwned::RightParenthesis,
-            Token::RightBracket => TokenOwned::RightSquareBrace,
+            Token::RightSquareBrace => TokenOwned::RightSquareBrace,
             Token::Semicolon => TokenOwned::Semicolon,
             Token::Star => TokenOwned::Star,
             Token::StarEqual => TokenOwned::StarEqual,
@@ -330,9 +308,9 @@ impl<'src> Token<'src> {
             Token::If => TokenKind::If,
             Token::Int => TokenKind::Int,
             Token::Integer(_) => TokenKind::Integer,
-            Token::LeftBrace => TokenKind::LeftBrace,
+            Token::LeftCurlyBrace => TokenKind::LeftCurlyBrace,
             Token::LeftParenthesis => TokenKind::LeftParenthesis,
-            Token::LeftBracket => TokenKind::LeftBracket,
+            Token::LeftSquareBrace => TokenKind::LeftSquareBrace,
             Token::Let => TokenKind::Let,
             Token::Less => TokenKind::Less,
             Token::LessEqual => TokenKind::LessEqual,
@@ -346,9 +324,9 @@ impl<'src> Token<'src> {
             Token::Plus => TokenKind::Plus,
             Token::PlusEqual => TokenKind::PlusEqual,
             Token::Return => TokenKind::Return,
-            Token::RightBrace => TokenKind::RightBrace,
+            Token::RightCurlyBrace => TokenKind::RightCurlyBrace,
             Token::RightParenthesis => TokenKind::RightParenthesis,
-            Token::RightBracket => TokenKind::RightBracket,
+            Token::RightSquareBrace => TokenKind::RightSquareBrace,
             Token::Semicolon => TokenKind::Semicolon,
             Token::Star => TokenKind::Star,
             Token::StarEqual => TokenKind::StarEqual,
@@ -385,9 +363,9 @@ impl<'src> Token<'src> {
                 | Token::Equal
                 | Token::Greater
                 | Token::GreaterEqual
-                | Token::LeftBrace
+                | Token::LeftCurlyBrace
                 | Token::LeftParenthesis
-                | Token::LeftBracket
+                | Token::LeftSquareBrace
                 | Token::Less
                 | Token::LessEqual
                 | Token::Minus
@@ -435,9 +413,9 @@ impl<'src> Display for Token<'src> {
             Token::If => write!(f, "if"),
             Token::Int => write!(f, "int"),
             Token::Integer(value) => write!(f, "{value}"),
-            Token::LeftBrace => write!(f, "{{"),
+            Token::LeftCurlyBrace => write!(f, "{{"),
             Token::LeftParenthesis => write!(f, "("),
-            Token::LeftBracket => write!(f, "["),
+            Token::LeftSquareBrace => write!(f, "["),
             Token::Let => write!(f, "let"),
             Token::Less => write!(f, "<"),
             Token::LessEqual => write!(f, "<="),
@@ -451,9 +429,9 @@ impl<'src> Display for Token<'src> {
             Token::Plus => write!(f, "+"),
             Token::PlusEqual => write!(f, "+="),
             Token::Return => write!(f, "return"),
-            Token::RightBrace => write!(f, "}}"),
+            Token::RightCurlyBrace => write!(f, "}}"),
             Token::RightParenthesis => write!(f, ")"),
-            Token::RightBracket => write!(f, "]"),
+            Token::RightSquareBrace => write!(f, "]"),
             Token::Semicolon => write!(f, ";"),
             Token::Slash => write!(f, "/"),
             Token::SlashEqual => write!(f, "/="),
@@ -568,9 +546,9 @@ impl Display for TokenOwned {
             TokenOwned::If => Token::If.fmt(f),
             TokenOwned::Int => Token::Int.fmt(f),
             TokenOwned::Integer(integer) => Token::Integer(integer).fmt(f),
-            TokenOwned::LeftCurlyBrace => Token::LeftBrace.fmt(f),
+            TokenOwned::LeftCurlyBrace => Token::LeftCurlyBrace.fmt(f),
             TokenOwned::LeftParenthesis => Token::LeftParenthesis.fmt(f),
-            TokenOwned::LeftSquareBrace => Token::LeftBracket.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),
@@ -584,9 +562,9 @@ impl Display for TokenOwned {
             TokenOwned::Plus => Token::Plus.fmt(f),
             TokenOwned::PlusEqual => Token::PlusEqual.fmt(f),
             TokenOwned::Return => Token::Return.fmt(f),
-            TokenOwned::RightCurlyBrace => Token::RightBrace.fmt(f),
+            TokenOwned::RightCurlyBrace => Token::RightCurlyBrace.fmt(f),
             TokenOwned::RightParenthesis => Token::RightParenthesis.fmt(f),
-            TokenOwned::RightSquareBrace => Token::RightBracket.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),
@@ -608,10 +586,10 @@ impl Display for TokenKind {
             TokenKind::Bang => Token::Bang.fmt(f),
             TokenKind::BangEqual => Token::BangEqual.fmt(f),
             TokenKind::Bool => Token::Bool.fmt(f),
-            TokenKind::Boolean => write!(f, "boolean"),
+            TokenKind::Boolean => write!(f, "boolean value"),
             TokenKind::Break => Token::Break.fmt(f),
-            TokenKind::Byte => write!(f, "byte"),
+            TokenKind::Byte => write!(f, "byte value"),
-            TokenKind::Character => write!(f, "character"),
+            TokenKind::Character => write!(f, "character value"),
             TokenKind::Colon => Token::Colon.fmt(f),
             TokenKind::Comma => Token::Comma.fmt(f),
             TokenKind::Dot => Token::Dot.fmt(f),
@@ -622,7 +600,7 @@ impl Display for TokenKind {
             TokenKind::Else => Token::Else.fmt(f),
             TokenKind::Eof => Token::Eof.fmt(f),
             TokenKind::Equal => Token::Equal.fmt(f),
-            TokenKind::Float => write!(f, "float"),
+            TokenKind::Float => write!(f, "float value"),
             TokenKind::FloatKeyword => Token::FloatKeyword.fmt(f),
             TokenKind::Fn => Token::Fn.fmt(f),
             TokenKind::Greater => Token::Greater.fmt(f),
@@ -630,10 +608,10 @@ impl Display for TokenKind {
             TokenKind::Identifier => write!(f, "identifier"),
             TokenKind::If => Token::If.fmt(f),
             TokenKind::Int => Token::Int.fmt(f),
-            TokenKind::Integer => write!(f, "integer"),
+            TokenKind::Integer => write!(f, "integer value"),
-            TokenKind::LeftBrace => Token::LeftBrace.fmt(f),
+            TokenKind::LeftCurlyBrace => Token::LeftCurlyBrace.fmt(f),
             TokenKind::LeftParenthesis => Token::LeftParenthesis.fmt(f),
-            TokenKind::LeftBracket => Token::LeftBracket.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),
@@ -647,16 +625,16 @@ impl Display for TokenKind {
             TokenKind::Plus => Token::Plus.fmt(f),
             TokenKind::PlusEqual => Token::PlusEqual.fmt(f),
             TokenKind::Return => Token::Return.fmt(f),
-            TokenKind::RightBrace => Token::RightBrace.fmt(f),
+            TokenKind::RightCurlyBrace => Token::RightCurlyBrace.fmt(f),
             TokenKind::RightParenthesis => Token::RightParenthesis.fmt(f),
-            TokenKind::RightBracket => Token::RightBracket.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"),
+            TokenKind::String => write!(f, "string value"),
             TokenKind::Struct => Token::Struct.fmt(f),
             TokenKind::While => Token::While.fmt(f),
         }

dust-lang/src/type.rs

@@ -33,12 +33,10 @@ pub enum Type {
     Map {
         pairs: HashMap<u8, Type>,
     },
-    None,
     Number,
     Range {
-        r#type: Box<Type>,
+        r#type: RangeableType,
     },
-    SelfChunk,
     String {
         length: Option<usize>,
     },
@@ -72,7 +70,6 @@ impl Type {
             | (Type::Character, Type::Character)
             | (Type::Float, Type::Float)
             | (Type::Integer, Type::Integer)
-            | (Type::None, Type::None)
             | (Type::String { .. }, Type::String { .. }) => return Ok(()),
             (
                 Type::Generic {
@@ -260,10 +257,8 @@ impl Display for Type {
 
                 write!(f, "}}")
             }
-            Type::None => write!(f, "none"),
             Type::Number => write!(f, "num"),
             Type::Range { r#type } => write!(f, "{type} range"),
-            Type::SelfChunk => write!(f, "self"),
             Type::String { .. } => write!(f, "str"),
             Type::Struct(struct_type) => write!(f, "{struct_type}"),
             Type::Tuple { fields } => {
@@ -348,16 +343,12 @@ impl Ord for Type {
                 left_pairs.iter().cmp(right_pairs.iter())
             }
             (Type::Map { .. }, _) => Ordering::Greater,
-            (Type::None, Type::None) => Ordering::Equal,
-            (Type::None, _) => 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::SelfChunk, Type::SelfChunk) => Ordering::Equal,
-            (Type::SelfChunk, _) => 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)) => {
@@ -375,7 +366,7 @@ impl Ord for Type {
 pub struct FunctionType {
     pub type_parameters: Option<Vec<u8>>,
     pub value_parameters: Option<Vec<(u8, Type)>>,
-    pub return_type: Box<Type>,
+    pub return_type: Option<Box<Type>>,
 }
 
 impl Display for FunctionType {
@@ -410,8 +401,8 @@ impl Display for FunctionType {
 
         write!(f, ")")?;
 
-        if *self.return_type != Type::None {
+        if let Some(return_type) = &self.return_type {
-            write!(f, " -> {}", self.return_type)?;
+            write!(f, " -> {return_type}")?;
         }
 
         Ok(())
@@ -554,8 +545,115 @@ impl Display for EnumType {
     }
 }
 
+#[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/vm.rs

@@ -1,22 +1,22 @@
 //! Virtual machine and errors
 use std::{
     cmp::Ordering,
-    collections::HashMap,
     fmt::{self, Display, Formatter},
-    mem::replace,
+    ops::Range,
-    rc::Weak,
 };
 
 use crate::{
-    compile, value::ConcreteValue, AnnotatedError, Chunk, ChunkError, DustError, FunctionBorrowed,
+    compile, value::ConcreteValue, AnnotatedError, Chunk, ChunkError, DustError, FunctionType,
-    Instruction, NativeFunction, NativeFunctionError, Operation, Span, Type, Value, ValueError,
+    Instruction, Local, NativeFunction, NativeFunctionError, Operation, Span, Type, Value,
+    ValueError,
 };
 
-pub fn run(source: &str) -> Result<Option<ConcreteValue>, DustError> {
+pub fn run(source: &str) -> Result<Option<Value>, DustError> {
-    let chunk = compile(source)?;
+    let mut chunk = compile(source)?;
-    let mut vm = Vm::new(&chunk, None);
+    let mut vm = Vm::new(&mut chunk, None);
 
     vm.run()
+        .map(|option| option.cloned())
         .map_err(|error| DustError::Runtime { error, source })
 }
 
@@ -32,30 +32,48 @@ pub fn run_and_display_output(source: &str) {
 ///
 /// See the [module-level documentation](index.html) for more information.
 #[derive(Debug, Eq, PartialEq)]
-pub struct Vm<'chunk, 'parent, 'stack> {
+pub struct Vm<'chunk, 'parent> {
     ip: usize,
-    chunk: &'chunk Chunk,
+    chunk: &'chunk mut Chunk,
-    stack: Vec<Register<'stack>>,
+    stack: Vec<Register>,
-    local_definitions: HashMap<u8, u8>,
     last_assigned_register: Option<u8>,
-    parent: Option<&'parent Vm<'chunk, 'stack, 'parent>>,
+    parent: Option<&'parent Vm<'chunk, 'parent>>,
 }
 
-impl<'chunk, 'parent, 'stack: 'chunk + 'parent> Vm<'chunk, 'parent, 'stack> {
+impl<'chunk, 'parent> Vm<'chunk, 'parent> {
     const STACK_LIMIT: usize = u16::MAX as usize;
 
-    pub fn new(chunk: &'chunk Chunk, parent: Option<&'parent Vm<'chunk, 'parent, 'stack>>) -> Self {
+    pub fn new(chunk: &'chunk mut Chunk, parent: Option<&'parent Vm<'chunk, 'parent>>) -> Self {
         Self {
             ip: 0,
             chunk,
             stack: Vec::new(),
-            local_definitions: HashMap::new(),
             last_assigned_register: None,
             parent,
         }
     }
 
-    pub fn run(&'stack mut self) -> Result<Option<ConcreteValue>, VmError> {
+    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!(
                 "{} | {} | {} | {}",
@@ -98,9 +116,9 @@ impl<'chunk, 'parent, 'stack: 'chunk + 'parent> Vm<'chunk, 'parent, 'stack> {
                     let to_register = instruction.a();
                     let boolean = instruction.b_as_boolean();
                     let jump = instruction.c_as_boolean();
-                    let boolean = ConcreteValue::boolean(boolean);
+                    let value = Value::boolean(boolean);
 
-                    self.set_register(to_register, Register::Value(boolean), position)?;
+                    self.set_register(to_register, Register::Value(value), position)?;
 
                     if jump {
                         self.ip += 1;
@@ -124,103 +142,96 @@ impl<'chunk, 'parent, 'stack: 'chunk + 'parent> Vm<'chunk, 'parent, 'stack> {
                 Operation::LoadList => {
                     let to_register = instruction.a();
                     let start_register = instruction.b();
-                    let mut list = Vec::new();
+                    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);
 
-                    for register_index in start_register..to_register {
+                    self.set_register(to_register, Register::Value(value), position)?;
-                        let value = self.open_register(register_index, position)?;
-
-                        list.push(value);
-                    }
-
-                    self.set_register(to_register, Register::List(list), position)?;
                 }
                 Operation::LoadSelf => {
                     let to_register = instruction.a();
-                    let function = Value::FunctionBorrowed(FunctionBorrowed::new(self.chunk));
+                    let value = Value::function(
+                        self.chunk.clone(),
+                        FunctionType {
+                            type_parameters: None,
+                            value_parameters: None,
+                            return_type: None,
+                        },
+                    );
 
-                    // self.set_register(to_register, Register::Value(function), position)?;
+                    self.set_register(to_register, Register::Value(value), position)?;
-
-                    todo!()
                 }
                 Operation::DefineLocal => {
                     let from_register = instruction.a();
                     let to_local = instruction.b();
 
-                    self.define_local(to_local, from_register)?;
+                    self.define_local(to_local, from_register, position)?;
                 }
                 Operation::GetLocal => {
                     let to_register = instruction.a();
                     let local_index = instruction.b();
-                    let local_register = self.local_definitions.get(&local_index).copied().ok_or(
+                    let local = self.get_local(local_index, position)?;
-                        VmError::UndefinedLocal {
-                            local_index,
-                            position,
-                        },
-                    )?;
 
                     self.set_register(
                         to_register,
-                        Register::StackPointer(local_register),
+                        Register::StackPointer(local.register_index),
                         position,
                     )?;
                 }
                 Operation::SetLocal => {
-                    let from_register = instruction.a();
+                    let register = instruction.a();
-                    let to_local = instruction.b();
+                    let local_index = instruction.b();
-                    let local_register = self.local_definitions.get(&to_local).copied().ok_or(
-                        VmError::UndefinedLocal {
-                            local_index: to_local,
-                            position,
-                        },
-                    )?;
 
-                    self.set_register(
+                    self.define_local(local_index, register, position)?;
-                        local_register,
-                        Register::StackPointer(from_register),
-                        position,
-                    )?;
                 }
                 Operation::Add => {
                     let to_register = instruction.a();
-                    let (left, right) = self.get_arguments(instruction, position)?;
+                    let (left, right) = get_arguments(self, instruction, position)?;
                     let sum = left
-                        .add(&right)
+                        .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) = self.get_arguments(instruction, position)?;
+                    let (left, right) = get_arguments(self, instruction, position)?;
                     let difference = left
-                        .subtract(&right)
+                        .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) = self.get_arguments(instruction, position)?;
+                    let (left, right) = get_arguments(self, instruction, position)?;
                     let product = left
-                        .multiply(&right)
+                        .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) = self.get_arguments(instruction, position)?;
+                    let (left, right) = get_arguments(self, instruction, position)?;
                     let quotient = left
-                        .divide(&right)
+                        .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) = self.get_arguments(instruction, position)?;
+                    let (left, right) = get_arguments(self, instruction, position)?;
                     let remainder = left
-                        .modulo(&right)
+                        .modulo(right)
                         .map_err(|error| VmError::Value { error, position })?;
 
                     self.set_register(to_register, Register::Value(remainder), position)?;
@@ -229,11 +240,11 @@ impl<'chunk, 'parent, 'stack: 'chunk + 'parent> Vm<'chunk, 'parent, 'stack> {
                     let register = instruction.a();
                     let test_value = instruction.c_as_boolean();
                     let value = self.open_register(register, position)?;
-                    let boolean = if let Some(boolean) = value.as_boolean() {
+                    let boolean = if let Value::Concrete(ConcreteValue::Boolean(boolean)) = value {
-                        boolean
+                        *boolean
                     } else {
                         return Err(VmError::ExpectedBoolean {
-                            found: value.into_concrete(),
+                            found: value.clone(),
                             position,
                         });
                     };
@@ -249,26 +260,34 @@ impl<'chunk, 'parent, 'stack: 'chunk + 'parent> Vm<'chunk, 'parent, 'stack> {
                         Operation::Jump
                     );
 
-                    let compare_to = instruction.a_as_boolean();
+                    let (left, right) = get_arguments(self, instruction, position)?;
-                    let (left, right) = self.get_arguments(instruction, position)?;
                     let equal_result = left
-                        .equal(&right)
+                        .equal(right)
                         .map_err(|error| VmError::Value { error, position })?;
-                    let is_equal = if let ConcreteValue::Boolean(boolean) = equal_result {
+                    let boolean =
-                        boolean
+                        if let Value::Concrete(ConcreteValue::Boolean(boolean)) = equal_result {
-                    } else {
+                            boolean
-                        return Err(VmError::ExpectedBoolean {
+                        } else {
-                            found: equal_result.clone(),
+                            return Err(VmError::ExpectedBoolean {
-                            position,
+                                found: equal_result.clone(),
-                        });
+                                position,
-                    };
+                            });
+                        };
+                    let compare_to = instruction.a_as_boolean();
 
-                    if is_equal == compare_to {
+                    if boolean == compare_to {
                         self.ip += 1;
                     } else {
-                        let jump = self.get_instruction(self.ip, position)?.0;
+                        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.jump(jump);
+                        self.ip = new_ip;
                     }
                 }
                 Operation::Less => {
@@ -277,26 +296,34 @@ impl<'chunk, 'parent, 'stack: 'chunk + 'parent> Vm<'chunk, 'parent, 'stack> {
                         Operation::Jump
                     );
 
-                    let compare_to = instruction.a_as_boolean();
+                    let (left, right) = get_arguments(self, instruction, position)?;
-                    let (left, right) = self.get_arguments(instruction, position)?;
                     let less_result = left
-                        .less_than(&right)
+                        .less_than(right)
                         .map_err(|error| VmError::Value { error, position })?;
-                    let is_less_than = if let ConcreteValue::Boolean(boolean) = less_result {
+                    let boolean =
-                        boolean
+                        if let Value::Concrete(ConcreteValue::Boolean(boolean)) = less_result {
-                    } else {
+                            boolean
-                        return Err(VmError::ExpectedBoolean {
+                        } else {
-                            found: less_result.clone(),
+                            return Err(VmError::ExpectedBoolean {
-                            position,
+                                found: less_result.clone(),
-                        });
+                                position,
-                    };
+                            });
+                        };
+                    let compare_to = instruction.a_as_boolean();
 
-                    if is_less_than == compare_to {
+                    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.jump(jump);
+                        self.ip = new_ip;
                     }
                 }
                 Operation::LessEqual => {
@@ -305,32 +332,43 @@ impl<'chunk, 'parent, 'stack: 'chunk + 'parent> Vm<'chunk, 'parent, 'stack> {
                         Operation::Jump
                     );
 
-                    let compare_to = instruction.a_as_boolean();
+                    let (left, right) = get_arguments(self, instruction, position)?;
-                    let (left, right) = self.get_arguments(instruction, position)?;
                     let less_or_equal_result = left
-                        .less_than_or_equal(&right)
+                        .less_than_or_equal(right)
                         .map_err(|error| VmError::Value { error, position })?;
-                    let is_less_than_or_equal =
+                    let boolean = if let Value::Concrete(ConcreteValue::Boolean(boolean)) =
-                        if let ConcreteValue::Boolean(boolean) = less_or_equal_result {
+                        less_or_equal_result
-                            boolean
+                    {
-                        } else {
+                        boolean
-                            return Err(VmError::ExpectedBoolean {
+                    } else {
-                                found: less_or_equal_result.clone(),
+                        return Err(VmError::ExpectedBoolean {
-                                position,
+                            found: less_or_equal_result.clone(),
-                            });
+                            position,
-                        };
+                        });
+                    };
+                    let compare_to = instruction.a_as_boolean();
 
-                    if is_less_than_or_equal == compare_to {
+                    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.jump(jump);
+                        self.ip = new_ip;
                     }
                 }
                 Operation::Negate => {
-                    let value =
+                    let value = if instruction.b_is_constant() {
-                        self.get_argument(instruction.b(), instruction.b_is_constant(), position)?;
+                        self.get_constant(instruction.b(), position)?
+                    } else {
+                        self.open_register(instruction.b(), position)?
+                    };
                     let negated = value
                         .negate()
                         .map_err(|error| VmError::Value { error, position })?;
@@ -338,30 +376,42 @@ impl<'chunk, 'parent, 'stack: 'chunk + 'parent> Vm<'chunk, 'parent, 'stack> {
                     self.set_register(instruction.a(), Register::Value(negated), position)?;
                 }
                 Operation::Not => {
-                    let value =
+                    let value = if instruction.b_is_constant() {
-                        self.get_argument(instruction.b(), instruction.b_is_constant(), position)?;
+                        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 => self.jump(instruction),
+                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)?;
+                    let value = self.open_register(function_register, position)?.clone();
-                    let function = if let Some(function) = value.as_function() {
+                    let mut function =
-                        function
+                        if let Value::Concrete(ConcreteValue::Function(function)) = value {
-                    } else {
+                            function
-                        return Err(VmError::ExpectedFunction {
+                        } else {
-                            found: value.into_concrete(),
+                            return Err(VmError::ExpectedFunction {
-                            position,
+                                found: value,
-                        });
+                                position,
-                    };
+                            });
-                    let mut function_vm = Vm::new(function.chunk(), Some(self));
+                        };
-
+                    let mut function_vm = Vm::new(function.chunk_mut(), Some(self));
                     let first_argument_index = function_register + 1;
 
                     for argument_index in
@@ -376,7 +426,7 @@ impl<'chunk, 'parent, 'stack: 'chunk + 'parent> Vm<'chunk, 'parent, 'stack> {
                         )?
                     }
 
-                    let return_value = function_vm.run()?;
+                    let return_value = function_vm.run()?.cloned();
 
                     if let Some(value) = return_value {
                         self.set_register(to_register, Register::Value(value), position)?;
@@ -384,12 +434,12 @@ impl<'chunk, 'parent, 'stack: 'chunk + 'parent> Vm<'chunk, 'parent, 'stack> {
                 }
                 Operation::CallNative => {
                     let native_function = NativeFunction::from(instruction.b());
-                    let return_value = native_function.call(self, instruction, position)?;
+                    let return_value = native_function.call(instruction, self, position)?;
 
-                    if let Some(concrete_value) = return_value {
+                    if let Some(value) = return_value {
                         let to_register = instruction.a();
 
-                        self.set_register(to_register, Register::Value(concrete_value), position)?;
+                        self.set_register(to_register, Register::Value(value), position)?;
                     }
                 }
                 Operation::Return => {
@@ -399,12 +449,13 @@ impl<'chunk, 'parent, 'stack: 'chunk + 'parent> Vm<'chunk, 'parent, 'stack> {
                         return Ok(None);
                     }
 
-                    return if let Some(register_index) = self.last_assigned_register {
+                    let return_value = if let Some(register_index) = self.last_assigned_register {
-                        self.open_register(register_index, position)
+                        self.open_register(register_index, position)?
-                            .map(|value| Some(value.into_concrete()))
                     } else {
-                        Err(VmError::StackUnderflow { position })
+                        return Err(VmError::StackUnderflow { position });
                     };
+
+                    return Ok(Some(return_value));
                 }
             }
         }
@@ -412,149 +463,10 @@ impl<'chunk, 'parent, 'stack: 'chunk + 'parent> Vm<'chunk, 'parent, 'stack> {
         Ok(None)
     }
 
-    pub(crate) fn open_register(
-        &'stack self,
-        register_index: u8,
-        position: Span,
-    ) -> Result<&'stack ConcreteValue, VmError> {
-        let register_index = register_index as usize;
-        let register =
-            self.stack
-                .get(register_index)
-                .ok_or_else(|| VmError::RegisterIndexOutOfBounds {
-                    index: register_index,
-                    position,
-                })?;
-
-        log::trace!("Open R{register_index} to {register}");
-
-        match register {
-            Register::Value(value) => Ok(value),
-            Register::List(list) => Ok(ConcreteValue::List(
-                list.into_iter()
-                    .map(|concrete_value| (*concrete_value).clone())
-                    .collect(),
-            )),
-            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.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 })?;
-                let constant = parent.get_constant(*constant_index, position)?;
-
-                Ok(constant)
-            }
-            Register::Empty => Err(VmError::EmptyRegister {
-                index: register_index,
-                position,
-            }),
-        }
-    }
-
-    fn get_concrete_from_register(
-        &'stack self,
-        register_index: u8,
-        position: Span,
-    ) -> Result<ConcreteValue, VmError> {
-        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(concrete_value) => concrete_value.clone(),
-            Register::List(list) => {
-                let items = list.into_iter().map(|value| (*value).clone()).collect();
-
-                ConcreteValue::List(items)
-            }
-            Register::StackPointer(register_index) => {
-                self.get_concrete_from_register(*register_index, position)?
-            }
-            Register::ConstantPointer(constant_pointer) => {
-                self.get_constant(*constant_pointer, position)?.clone()
-            }
-            Register::ParentStackPointer(register_index) => {
-                let parent = self.parent.ok_or(VmError::ExpectedParent { position })?;
-
-                parent.get_concrete_from_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)?.clone()
-            }
-            Register::Empty => {
-                return Err(VmError::EmptyRegister {
-                    index: register_index,
-                    position,
-                })
-            }
-        };
-
-        Ok(value)
-    }
-
-    /// DRY helper for handling JUMP instructions
-    fn jump(&mut self, jump: Instruction) {
-        let jump_distance = jump.b();
-        let is_positive = jump.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;
-    }
-
-    /// DRY helper to get a constant or register values
-    fn get_argument(
-        &'stack self,
-        index: u8,
-        is_constant: bool,
-        position: Span,
-    ) -> Result<Value<'stack>, VmError> {
-        let argument = if is_constant {
-            self.get_constant(index, position)?.as_reference_value()
-        } else {
-            self.open_register(index, position)?
-        };
-
-        Ok(argument)
-    }
-
-    /// DRY helper to get two arguments for binary operations
-    fn get_arguments(
-        &'stack self,
-        instruction: Instruction,
-        position: Span,
-    ) -> Result<(Value<'stack>, Value<'stack>), VmError> {
-        let left = self.get_argument(instruction.b(), instruction.b_is_constant(), position)?;
-        let right = self.get_argument(instruction.c(), instruction.c_is_constant(), position)?;
-
-        Ok((left, right))
-    }
-
     fn set_register(
         &mut self,
         to_register: u8,
-        register: Register<'stack>,
+        register: Register,
         position: Span,
     ) -> Result<(), VmError> {
         self.last_assigned_register = Some(to_register);
@@ -599,18 +511,145 @@ impl<'chunk, 'parent, 'stack: 'chunk + 'parent> Vm<'chunk, 'parent, 'stack> {
         }
     }
 
-    fn get_constant(&self, index: u8, position: Span) -> Result<&'chunk ConcreteValue, VmError> {
+    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> {
-        let ip = self.ip;
+        self.chunk
+            .expect_not_poisoned()
+            .map_err(|error| VmError::Chunk { error, position })?;
 
-        self.ip += 1;
+        let max_ip = self.chunk.len() - 1;
 
-        self.get_instruction(ip, position)
+        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(
@@ -622,45 +661,23 @@ impl<'chunk, 'parent, 'stack: 'chunk + 'parent> Vm<'chunk, 'parent, 'stack> {
             .get_instruction(index)
             .map_err(|error| VmError::Chunk { error, position })
     }
-
-    fn define_local(&mut self, local_index: u8, register_index: u8) -> Result<(), VmError> {
-        log::debug!("Define local L{}", local_index);
-
-        self.local_definitions.insert(local_index, register_index);
-
-        Ok(())
-    }
 }
 
 #[derive(Debug, Eq, PartialEq)]
-enum Register<'stack> {
+enum Register {
     Empty,
-    Value(ConcreteValue),
+    Value(Value),
-    List(Vec<&'stack ConcreteValue>),
     StackPointer(u8),
     ConstantPointer(u8),
     ParentStackPointer(u8),
     ParentConstantPointer(u8),
 }
 
-impl<'stack> Display for Register<'stack> {
+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::List(values) => {
-                write!(f, "[")?;
-
-                for (index, value) in values.iter().enumerate() {
-                    if index > 0 {
-                        write!(f, ", ")?;
-                    }
-
-                    write!(f, "{}", value)?;
-                }
-
-                write!(f, "]")
-            }
             Self::StackPointer(index) => write!(f, "R{}", index),
             Self::ConstantPointer(index) => write!(f, "C{}", index),
             Self::ParentStackPointer(index) => write!(f, "PR{}", index),
@@ -672,52 +689,23 @@ impl<'stack> Display for Register<'stack> {
 #[derive(Clone, Debug, PartialEq)]
 pub enum VmError {
     // Stack errors
-    StackOverflow {
+    StackOverflow { position: Span },
-        position: Span,
+    StackUnderflow { position: Span },
-    },
-    StackUnderflow {
-        position: Span,
-    },
 
     // Register errors
-    EmptyRegister {
+    EmptyRegister { index: usize, position: Span },
-        index: usize,
+    EmptyRegisters { indexes: Range<u8>, position: Span },
-        position: Span,
+    RegisterIndexOutOfBounds { index: usize, position: Span },
-    },
-    RegisterIndexOutOfBounds {
-        index: usize,
-        position: Span,
-    },
-
-    // Local errors
-    UndefinedLocal {
-        local_index: u8,
-        position: Span,
-    },
 
     // Execution errors
-    ExpectedBoolean {
+    ExpectedBoolean { found: Value, position: Span },
-        found: ConcreteValue,
+    ExpectedFunction { found: Value, position: Span },
-        position: Span,
+    ExpectedParent { position: Span },
-    },
-    ExpectedFunction {
-        found: ConcreteValue,
-        position: Span,
-    },
-    ExpectedParent {
-        position: Span,
-    },
 
     // Wrappers for foreign errors
-    Chunk {
+    Chunk { error: ChunkError, position: Span },
-        error: ChunkError,
-        position: Span,
-    },
     NativeFunction(NativeFunctionError),
-    Value {
+    Value { error: ValueError, position: Span },
-        error: ValueError,
-        position: Span,
-    },
 }
 
 impl AnnotatedError for VmError {
@@ -729,6 +717,7 @@ impl AnnotatedError for VmError {
         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",
@@ -736,7 +725,6 @@ impl AnnotatedError for VmError {
             Self::RegisterIndexOutOfBounds { .. } => "Register index out of bounds",
             Self::StackOverflow { .. } => "Stack overflow",
             Self::StackUnderflow { .. } => "Stack underflow",
-            Self::UndefinedLocal { .. } => "Undefined local",
             Self::Value { .. } => "Value error",
         }
     }
@@ -745,8 +733,11 @@ impl AnnotatedError for VmError {
         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"))
             }
@@ -760,6 +751,7 @@ impl AnnotatedError for VmError {
         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,
@@ -767,7 +759,6 @@ impl AnnotatedError for VmError {
             Self::RegisterIndexOutOfBounds { position, .. } => *position,
             Self::StackOverflow { position } => *position,
             Self::StackUnderflow { position } => *position,
-            Self::UndefinedLocal { position, .. } => *position,
             Self::Value { position, .. } => *position,
         }
     }

dust-lang/tests/basic.rs

@@ -12,12 +12,12 @@ fn constant() {
                 (Instruction::load_constant(0, 0, false), Span(0, 2)),
                 (Instruction::r#return(true), Span(2, 2))
             ],
-            vec![ValueOwned::Primitive(Primitive::Integer(42))],
+            vec![Value::integer(42)],
             vec![]
         ))
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(42))));
+    assert_eq!(run(source), Ok(Some(Value::integer(42))));
 }
 
 #[test]
@@ -57,14 +57,10 @@ fn parentheses_precedence() {
                 ),
                 (Instruction::r#return(true), Span(11, 11)),
             ],
-            vec![
+            vec![Value::integer(1), Value::integer(2), Value::integer(3)],
-                ValueOwned::integer(1),
-                ValueOwned::integer(2),
-                ValueOwned::integer(3)
-            ],
             vec![]
         ))
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(9))));
+    assert_eq!(run(source), Ok(Some(Value::integer(9))));
 }

dust-lang/tests/comparison.rs

@@ -20,12 +20,12 @@ fn equal() {
                 (Instruction::load_boolean(0, false, false), Span(2, 4)),
                 (Instruction::r#return(true), Span(6, 6)),
             ],
-            vec![ValueOwned::integer(1), ValueOwned::integer(2)],
+            vec![Value::integer(1), Value::integer(2)],
             vec![]
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::boolean(false))));
+    assert_eq!(run(source), Ok(Some(Value::boolean(false))));
 }
 
 #[test]
@@ -48,12 +48,12 @@ fn greater() {
                 (Instruction::load_boolean(0, false, false), Span(2, 3)),
                 (Instruction::r#return(true), Span(5, 5)),
             ],
-            vec![ValueOwned::integer(1), ValueOwned::integer(2)],
+            vec![Value::integer(1), Value::integer(2)],
             vec![]
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::boolean(false))));
+    assert_eq!(run(source), Ok(Some(Value::boolean(false))));
 }
 
 #[test]
@@ -76,12 +76,12 @@ fn greater_than_or_equal() {
                 (Instruction::load_boolean(0, false, false), Span(2, 4)),
                 (Instruction::r#return(true), Span(6, 6)),
             ],
-            vec![ValueOwned::integer(1), ValueOwned::integer(2)],
+            vec![Value::integer(1), Value::integer(2)],
             vec![]
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::boolean(false))));
+    assert_eq!(run(source), Ok(Some(Value::boolean(false))));
 }
 
 #[test]
@@ -104,12 +104,12 @@ fn less_than() {
                 (Instruction::load_boolean(0, false, false), Span(2, 3)),
                 (Instruction::r#return(true), Span(5, 5)),
             ],
-            vec![ValueOwned::integer(1), ValueOwned::integer(2)],
+            vec![Value::integer(1), Value::integer(2)],
             vec![]
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::boolean(true))));
+    assert_eq!(run(source), Ok(Some(Value::boolean(true))));
 }
 
 #[test]
@@ -132,12 +132,12 @@ fn less_than_or_equal() {
                 (Instruction::load_boolean(0, false, false), Span(2, 4)),
                 (Instruction::r#return(true), Span(6, 6)),
             ],
-            vec![ValueOwned::integer(1), ValueOwned::integer(2)],
+            vec![Value::integer(1), Value::integer(2)],
             vec![]
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::boolean(true))));
+    assert_eq!(run(source), Ok(Some(Value::boolean(true))));
 }
 
 #[test]
@@ -160,10 +160,10 @@ fn not_equal() {
                 (Instruction::load_boolean(0, false, false), Span(2, 4)),
                 (Instruction::r#return(true), Span(6, 6)),
             ],
-            vec![ValueOwned::integer(1), ValueOwned::integer(2)],
+            vec![Value::integer(1), Value::integer(2)],
             vec![]
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::boolean(true))));
+    assert_eq!(run(source), Ok(Some(Value::boolean(true))));
 }

dust-lang/tests/control_flow.rs

@@ -22,12 +22,21 @@ fn equality_assignment_long() {
                 (Instruction::get_local(1, 0), Span(43, 44)),
                 (Instruction::r#return(true), Span(44, 44)),
             ],
-            vec![ValueOwned::integer(4), ValueOwned::string("a")],
+            vec![Value::integer(4), Value::string("a")],
-            vec![Local::new(1, Type::Boolean, false, Scope::default(),)]
+            vec![Local::new(
+                1,
+                None,
+                false,
+                Scope {
+                    depth: 0,
+                    block_index: 0
+                },
+                0
+            )]
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::boolean(true))));
+    assert_eq!(run(source), Ok(Some(Value::boolean(true))));
 }
 
 #[test]
@@ -52,12 +61,12 @@ fn equality_assignment_short() {
                 (Instruction::get_local(1, 0), Span(15, 16)),
                 (Instruction::r#return(true), Span(16, 16)),
             ],
-            vec![ValueOwned::integer(4), ValueOwned::string("a")],
+            vec![Value::integer(4), Value::string("a")],
-            vec![Local::new(1, Type::Boolean, false, Scope::default())]
+            vec![Local::new(1, None, false, Scope::default(), 0)]
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::boolean(true))));
+    assert_eq!(run(source), Ok(Some(Value::boolean(true))));
 }
 
 #[test]
@@ -104,18 +113,18 @@ fn if_else_assigment_false() {
                 (Instruction::r#return(true), Span(149, 149)),
             ],
             vec![
-                ValueOwned::integer(4),
+                Value::integer(4),
-                ValueOwned::integer(3),
+                Value::integer(3),
-                ValueOwned::integer(1),
+                Value::integer(1),
-                ValueOwned::integer(2),
+                Value::integer(2),
-                ValueOwned::integer(42),
+                Value::integer(42),
-                ValueOwned::string("a")
+                Value::string("a")
             ],
-            vec![Local::new(5, Type::Integer, false, Scope::default())]
+            vec![Local::new(5, None, false, Scope::default(), 0)]
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(42))));
+    assert_eq!(run(source), Ok(Some(Value::integer(42))));
 }
 
 #[test]
@@ -162,18 +171,18 @@ fn if_else_assigment_true() {
                 (Instruction::r#return(true), Span(149, 149)),
             ],
             vec![
-                ValueOwned::integer(4),
+                Value::integer(4),
-                ValueOwned::integer(1),
+                Value::integer(1),
-                ValueOwned::integer(2),
+                Value::integer(2),
-                ValueOwned::integer(3),
+                Value::integer(3),
-                ValueOwned::integer(42),
+                Value::integer(42),
-                ValueOwned::string("a")
+                Value::string("a")
             ],
-            vec![Local::new(5, Type::Integer, false, Scope::default())]
+            vec![Local::new(5, None, false, Scope::default(), 0)]
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(42))));
+    assert_eq!(run(source), Ok(Some(Value::integer(42))));
 }
 
 #[test]
@@ -210,10 +219,10 @@ fn if_else_complex() {
                 (Instruction::r#return(false), Span(95, 95)),
             ],
             vec![
-                ValueOwned::integer(1),
+                Value::integer(1),
-                ValueOwned::integer(2),
+                Value::integer(2),
-                ValueOwned::integer(3),
+                Value::integer(3),
-                ValueOwned::integer(4),
+                Value::integer(4),
             ],
             vec![]
         ))
@@ -275,26 +284,26 @@ fn if_else_complex() {
 //                 (Instruction::r#return(true), Span(146, 146)),
 //             ],
 //             vec![
-//                 ValueOwned::integer(0),
+//                 Value::integer(0),
-//                 ValueOwned::integer(1),
+//                 Value::integer(1),
-//                 ValueOwned::integer(0),
+//                 Value::integer(0),
-//                 ValueOwned::integer(2),
+//                 Value::integer(2),
-//                 ValueOwned::integer(1),
+//                 Value::integer(1),
-//                 ValueOwned::integer(0),
+//                 Value::integer(0),
-//                 ValueOwned::integer(3),
+//                 Value::integer(3),
-//                 ValueOwned::integer(3),
+//                 Value::integer(3),
-//                 ValueOwned::integer(4)
+//                 Value::integer(4)
 //             ],
 //             vec![]
 //         ))
 //     );
 
-//     assert_eq!(run(source), Ok(Some(ValueOwned::integer(4))));
+//     assert_eq!(run(source), Ok(Some(Value::integer(4))));
 // }
 
 #[test]
 fn if_else_false() {
-    let source = "if 1 == 2 { panic(); 0 } else { 42 }";
+    let source = "if 1 == 2 { panic() } else { 42 }";
 
     assert_eq!(
         compile(source),
@@ -316,21 +325,17 @@ fn if_else_false() {
                 (Instruction::r#move(1, 0), Span(33, 33)),
                 (Instruction::r#return(true), Span(33, 33)),
             ],
-            vec![
+            vec![Value::integer(1), Value::integer(2), Value::integer(42)],
-                ValueOwned::integer(1),
-                ValueOwned::integer(2),
-                ValueOwned::integer(42)
-            ],
             vec![]
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(42))));
+    assert_eq!(run(source), Ok(Some(Value::integer(42))));
 }
 
 #[test]
 fn if_else_true() {
-    let source = "if 1 == 1 { 42 } else { panic(); 0 }";
+    let source = "if 1 == 1 { 42 } else { panic() }";
 
     assert_eq!(
         compile(source),
@@ -352,17 +357,17 @@ fn if_else_true() {
                 (Instruction::r#move(1, 0), Span(33, 33)),
                 (Instruction::r#return(true), Span(33, 33))
             ],
-            vec![ValueOwned::integer(1), ValueOwned::integer(42)],
+            vec![Value::integer(1), Value::integer(42)],
             vec![]
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(42))));
+    assert_eq!(run(source), Ok(Some(Value::integer(42))));
 }
 
 #[test]
 fn if_false() {
-    let source = "if 1 == 2 { panic() }";
+    let source = "if 1 == 2 { 2 }";
 
     assert_eq!(
         compile(source),
@@ -376,13 +381,10 @@ fn if_false() {
                     Span(5, 7)
                 ),
                 (Instruction::jump(1, true), Span(10, 11)),
-                (
+                (Instruction::load_constant(0, 1, false), Span(12, 13)),
-                    Instruction::call_native(0, NativeFunction::Panic, 0),
+                (Instruction::r#return(false), Span(15, 15))
-                    Span(12, 19)
-                ),
-                (Instruction::r#return(false), Span(21, 21))
             ],
-            vec![ValueOwned::integer(1), ValueOwned::integer(2)],
+            vec![Value::integer(1), Value::integer(2)],
             vec![]
         )),
     );
@@ -392,7 +394,7 @@ fn if_false() {
 
 #[test]
 fn if_true() {
-    let source = "if 1 == 1 { panic() }";
+    let source = "if 1 == 1 { 2 }";
 
     assert_eq!(
         compile(source),
@@ -406,25 +408,13 @@ fn if_true() {
                     Span(5, 7)
                 ),
                 (Instruction::jump(1, true), Span(10, 11)),
-                (
+                (Instruction::load_constant(0, 1, false), Span(12, 13)),
-                    Instruction::call_native(0, NativeFunction::Panic, 0),
+                (Instruction::r#return(false), Span(15, 15))
-                    Span(12, 19)
-                ),
-                (Instruction::r#return(false), Span(21, 21))
             ],
-            vec![ValueOwned::integer(1)],
+            vec![Value::integer(1), Value::integer(2)],
             vec![]
         )),
     );
 
-    assert_eq!(
+    assert_eq!(run(source), Ok(None));
-        run(source),
-        Err(DustError::Runtime {
-            error: VmError::NativeFunction(NativeFunctionError::Panic {
-                message: None,
-                position: Span(12, 19)
-            }),
-            source
-        })
-    );
 }

dust-lang/tests/functions.rs

@@ -6,18 +6,25 @@ fn function() {
 
     assert_eq!(
         run(source),
-        Ok(Some(ValueOwned::function(Chunk::with_data(
+        Ok(Some(Value::function(
-            None,
+            Chunk::with_data(
-            vec![
+                None,
-                (Instruction::add(2, 0, 1), Span(30, 31)),
+                vec![
-                (Instruction::r#return(true), Span(35, 35)),
+                    (Instruction::add(2, 0, 1), Span(30, 31)),
-            ],
+                    (Instruction::r#return(true), Span(35, 35)),
-            vec![ValueOwned::string("a"), ValueOwned::string("b"),],
+                ],
-            vec![
+                vec![Value::string("a"), Value::string("b"),],
-                Local::new(0, Type::Integer, false, Scope::default()),
+                vec![
-                Local::new(1, Type::Integer, false, Scope::default())
+                    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)),
+            }
+        )))
     );
 }
 
@@ -37,26 +44,33 @@ fn function_call() {
                 (Instruction::r#return(true), Span(41, 41)),
             ],
             vec![
-                ValueOwned::function(Chunk::with_data(
+                Value::function(
-                    None,
+                    Chunk::with_data(
-                    vec![
+                        None,
-                        (Instruction::add(2, 0, 1), Span(30, 31)),
+                        vec![
-                        (Instruction::r#return(true), Span(35, 36)),
+                            (Instruction::add(2, 0, 1), Span(30, 31)),
-                    ],
+                            (Instruction::r#return(true), Span(35, 36)),
-                    vec![ValueOwned::string("a"), ValueOwned::string("b"),],
+                        ],
-                    vec![
+                        vec![Value::string("a"), Value::string("b"),],
-                        Local::new(0, Type::Integer, false, Scope::default()),
+                        vec![
-                        Local::new(1, Type::Integer, false, Scope::default())
+                            Local::new(0, Some(Type::Integer), false, Scope::default(), 0),
-                    ]
+                            Local::new(1, Some(Type::Integer), false, Scope::default(), 1)
-                )),
+                        ]
-                ValueOwned::integer(1),
+                    ),
-                ValueOwned::integer(2)
+                    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(ValueOwned::integer(3))));
+    assert_eq!(run(source), Ok(Some(Value::integer(3))));
 }
 
 #[test]
@@ -73,30 +87,38 @@ fn function_declaration() {
                 (Instruction::r#return(false), Span(40, 40))
             ],
             vec![
-                ValueOwned::string("add"),
+                Value::string("add"),
-                ValueOwned::function(Chunk::with_data(
+                Value::function(
-                    None,
+                    Chunk::with_data(
-                    vec![
+                        None,
-                        (Instruction::add(2, 0, 1), Span(35, 36)),
+                        vec![
-                        (Instruction::r#return(true), Span(40, 40)),
+                            (Instruction::add(2, 0, 1), Span(35, 36)),
-                    ],
+                            (Instruction::r#return(true), Span(40, 40)),
-                    vec![ValueOwned::string("a"), ValueOwned::string("b")],
+                        ],
-                    vec![
+                        vec![Value::string("a"), Value::string("b")],
-                        Local::new(0, Type::Integer, false, Scope::default()),
+                        vec![
-                        Local::new(1, Type::Integer, false, Scope::default())
+                            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,
-                Type::Function(FunctionType {
+                Some(Type::Function(FunctionType {
                     type_parameters: None,
                     value_parameters: Some(vec![(0, Type::Integer), (1, Type::Integer)]),
-                    return_type: Box::new(Type::Integer),
+                    return_type: Some(Box::new(Type::Integer)),
-                }),
+                })),
                 false,
                 Scope::default(),
-            )],
+                0
+            ),],
         )),
     );
 

dust-lang/tests/lists.rs

@@ -17,7 +17,7 @@ fn empty_list() {
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::list([]))));
+    assert_eq!(run(source), Ok(Some(Value::abstract_list(0, 0, Type::Any))));
 }
 
 #[test]
@@ -35,22 +35,14 @@ fn list() {
                 (Instruction::load_list(3, 0), Span(0, 9)),
                 (Instruction::r#return(true), Span(9, 9)),
             ],
-            vec![
+            vec![Value::integer(1), Value::integer(2), Value::integer(3)],
-                ValueOwned::integer(1),
-                ValueOwned::integer(2),
-                ValueOwned::integer(3)
-            ],
             vec![]
         )),
     );
 
     assert_eq!(
         run(source),
-        Ok(Some(ValueOwned::list([
+        Ok(Some(Value::abstract_list(0, 3, Type::Integer)))
-            ValueOwned::integer(1),
-            ValueOwned::integer(2),
-            ValueOwned::integer(3)
-        ])))
     );
 }
 
@@ -82,11 +74,11 @@ fn list_with_complex_expression() {
                 (Instruction::r#return(true), Span(18, 18)),
             ],
             vec![
-                ValueOwned::integer(1),
+                Value::integer(1),
-                ValueOwned::integer(2),
+                Value::integer(2),
-                ValueOwned::integer(3),
+                Value::integer(3),
-                ValueOwned::integer(4),
+                Value::integer(4),
-                ValueOwned::integer(5)
+                Value::integer(5)
             ],
             vec![]
         )),
@@ -94,10 +86,7 @@ fn list_with_complex_expression() {
 
     assert_eq!(
         run(source),
-        Ok(Some(ValueOwned::list([
+        Ok(Some(Value::abstract_list(0, 4, Type::Integer)))
-            ValueOwned::integer(0),
-            ValueOwned::integer(4)
-        ])))
     );
 }
 
@@ -122,10 +111,10 @@ fn list_with_simple_expression() {
                 (Instruction::r#return(true), Span(13, 13)),
             ],
             vec![
-                ValueOwned::integer(1),
+                Value::integer(1),
-                ValueOwned::integer(2),
+                Value::integer(2),
-                ValueOwned::integer(3),
+                Value::integer(3),
-                ValueOwned::integer(4),
+                Value::integer(4),
             ],
             vec![]
         )),
@@ -133,9 +122,6 @@ fn list_with_simple_expression() {
 
     assert_eq!(
         run(source),
-        Ok(Some(ValueOwned::list([
+        Ok(Some(Value::abstract_list(0, 3, Type::Integer)))
-            ValueOwned::integer(0),
-            ValueOwned::integer(3)
-        ])))
     );
 }

dust-lang/tests/logic.rs

@@ -20,7 +20,7 @@ fn and() {
         ))
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::boolean(false))));
+    assert_eq!(run(source), Ok(Some(Value::boolean(false))));
 }
 
 #[test]
@@ -43,7 +43,7 @@ fn or() {
         ))
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::boolean(true))));
+    assert_eq!(run(source), Ok(Some(Value::boolean(true))));
 }
 
 #[test]
@@ -65,13 +65,13 @@ fn variable_and() {
                 (Instruction::get_local(3, 1), Span(34, 35)),
                 (Instruction::r#return(true), Span(35, 35)),
             ],
-            vec![ValueOwned::string("a"), ValueOwned::string("b"),],
+            vec![Value::string("a"), Value::string("b"),],
             vec![
-                Local::new(0, Type::Boolean, false, Scope::default()),
+                Local::new(0, None, false, Scope::default(), 0),
-                Local::new(1, Type::Boolean, false, Scope::default()),
+                Local::new(1, None, false, Scope::default(), 1),
             ]
         ))
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::boolean(false))));
+    assert_eq!(run(source), Ok(Some(Value::boolean(false))));
 }

dust-lang/tests/loops.rs

@@ -16,20 +16,20 @@ fn r#while() {
                     Span(23, 24)
                 ),
                 (Instruction::jump(2, true), Span(41, 42)),
-                (*Instruction::add(0, 0, 3).set_c_is_constant(), Span(35, 36)),
+                (*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![
-                ValueOwned::integer(0),
+                Value::integer(0),
-                ValueOwned::string("x"),
+                Value::string("x"),
-                ValueOwned::integer(5),
+                Value::integer(5),
-                ValueOwned::integer(1),
+                Value::integer(1),
             ],
-            vec![Local::new(1, Type::Integer, true, Scope::default())]
+            vec![Local::new(1, None, true, Scope::default(), 0),]
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(5))));
+    assert_eq!(run(source), Ok(Some(Value::integer(5))));
 }

dust-lang/tests/math.rs

@@ -17,12 +17,12 @@ fn add() {
                 ),
                 (Instruction::r#return(true), Span(5, 5))
             ],
-            vec![ValueOwned::integer(1), ValueOwned::integer(2)],
+            vec![Value::integer(1), Value::integer(2)],
             vec![]
         ))
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(3))));
+    assert_eq!(run(source), Ok(Some(Value::integer(3))));
 }
 
 #[test]
@@ -40,16 +40,12 @@ fn add_assign() {
                 (Instruction::get_local(1, 0), Span(23, 24)),
                 (Instruction::r#return(true), Span(24, 24))
             ],
-            vec![
+            vec![Value::integer(1), Value::string("a"), Value::integer(2)],
-                ValueOwned::integer(1),
+            vec![Local::new(1, None, true, Scope::default(), 0)]
-                ValueOwned::string("a"),
-                ValueOwned::integer(2)
-            ],
-            vec![Local::new(1, Type::Integer, true, Scope::default())]
         ))
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(3))));
+    assert_eq!(run(source), Ok(Some(Value::integer(3))));
 }
 
 #[test]
@@ -101,12 +97,12 @@ fn divide() {
                 ),
                 (Instruction::r#return(true), Span(5, 5))
             ],
-            vec![ValueOwned::integer(2)],
+            vec![Value::integer(2)],
             vec![]
         ))
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(1))));
+    assert_eq!(run(source), Ok(Some(Value::integer(1))));
 }
 
 #[test]
@@ -127,12 +123,12 @@ fn divide_assign() {
                 (Instruction::get_local(1, 0), Span(23, 24)),
                 (Instruction::r#return(true), Span(24, 24))
             ],
-            vec![ValueOwned::integer(2), ValueOwned::string("a")],
+            vec![Value::integer(2), Value::string("a")],
-            vec![Local::new(1, Type::Integer, true, Scope::default())]
+            vec![Local::new(1, None, true, Scope::default(), 0)]
         ))
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(1))));
+    assert_eq!(run(source), Ok(Some(Value::integer(1))));
 }
 
 #[test]
@@ -180,17 +176,17 @@ fn math_operator_precedence() {
                 (Instruction::r#return(true), Span(17, 17)),
             ],
             vec![
-                ValueOwned::integer(1),
+                Value::integer(1),
-                ValueOwned::integer(2),
+                Value::integer(2),
-                ValueOwned::integer(3),
+                Value::integer(3),
-                ValueOwned::integer(4),
+                Value::integer(4),
-                ValueOwned::integer(5),
+                Value::integer(5),
             ],
             vec![]
         ))
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(1))));
+    assert_eq!(run(source), Ok(Some(Value::integer(1))));
 }
 
 #[test]
@@ -210,12 +206,12 @@ fn multiply() {
                 ),
                 (Instruction::r#return(true), Span(5, 5)),
             ],
-            vec![ValueOwned::integer(1), ValueOwned::integer(2)],
+            vec![Value::integer(1), Value::integer(2)],
             vec![]
         ))
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(2))));
+    assert_eq!(run(source), Ok(Some(Value::integer(2))));
 }
 
 #[test]
@@ -236,16 +232,12 @@ fn multiply_assign() {
                 (Instruction::get_local(1, 0), Span(22, 23)),
                 (Instruction::r#return(true), Span(23, 23))
             ],
-            vec![
+            vec![Value::integer(2), Value::string("a"), Value::integer(3)],
-                ValueOwned::integer(2),
+            vec![Local::new(1, None, true, Scope::default(), 0),]
-                ValueOwned::string("a"),
-                ValueOwned::integer(3)
-            ],
-            vec![Local::new(1, Type::Integer, true, Scope::default())]
         ))
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(6))));
+    assert_eq!(run(source), Ok(Some(Value::integer(6))));
 }
 
 #[test]
@@ -281,12 +273,12 @@ fn subtract() {
                 ),
                 (Instruction::r#return(true), Span(5, 5)),
             ],
-            vec![ValueOwned::integer(1), ValueOwned::integer(2)],
+            vec![Value::integer(1), Value::integer(2)],
             vec![]
         ))
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(-1))));
+    assert_eq!(run(source), Ok(Some(Value::integer(-1))));
 }
 
 #[test]
@@ -307,16 +299,12 @@ fn subtract_assign() {
                 (Instruction::get_local(1, 0), Span(24, 25)),
                 (Instruction::r#return(true), Span(25, 25)),
             ],
-            vec![
+            vec![Value::integer(42), Value::string("x"), Value::integer(2)],
-                ValueOwned::integer(42),
+            vec![Local::new(1, None, true, Scope::default(), 0)]
-                ValueOwned::string("x"),
-                ValueOwned::integer(2)
-            ],
-            vec![Local::new(1, Type::Integer, true, Scope::default())]
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(40))));
+    assert_eq!(run(source), Ok(Some(Value::integer(40))));
 }
 
 #[test]

dust-lang/tests/native_functions.rs

@@ -17,10 +17,7 @@ fn panic() {
                 ),
                 (Instruction::r#return(true), Span(27, 27))
             ],
-            vec![
+            vec![Value::string("Goodbye world!"), Value::integer(42)],
-                ValueOwned::string("Goodbye world!"),
-                ValueOwned::integer(42)
-            ],
             vec![]
         )),
     );
@@ -53,10 +50,10 @@ fn to_string() {
                 ),
                 (Instruction::r#return(true), Span(13, 13))
             ],
-            vec![ValueOwned::integer(42)],
+            vec![Value::integer(42)],
             vec![]
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::string("42"))))
+    assert_eq!(run(source), Ok(Some(Value::string("42"))))
 }

dust-lang/tests/scopes.rs

@@ -9,7 +9,7 @@ fn allow_access_to_parent_scope() {
         }
     "#;
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(1))));
+    assert_eq!(run(source), Ok(Some(Value::integer(1))));
 }
 
 #[test]
@@ -44,22 +44,22 @@ fn block_scope() {
                 (Instruction::r#return(false), Span(165, 165))
             ],
             vec![
-                ValueOwned::integer(0),
+                Value::integer(0),
-                ValueOwned::string("a"),
+                Value::string("a"),
-                ValueOwned::integer(42),
+                Value::integer(42),
-                ValueOwned::string("b"),
+                Value::string("b"),
-                ValueOwned::integer(1),
+                Value::integer(1),
-                ValueOwned::string("c"),
+                Value::string("c"),
-                ValueOwned::integer(2),
+                Value::integer(2),
-                ValueOwned::string("d"),
+                Value::string("d"),
-                ValueOwned::string("e"),
+                Value::string("e"),
             ],
             vec![
-                Local::new(1, Type::Integer, false, Scope::new(0, 0)),
+                Local::new(1, None, false, Scope::new(0, 0), 0),
-                Local::new(3, Type::Integer, false, Scope::new(1, 1)),
+                Local::new(3, None, false, Scope::new(1, 1), 1),
-                Local::new(5, Type::Integer, false, Scope::new(2, 2)),
+                Local::new(5, None, false, Scope::new(2, 2), 2),
-                Local::new(7, Type::Integer, false, Scope::new(1, 1)),
+                Local::new(7, None, false, Scope::new(1, 1), 3),
-                Local::new(8, Type::Integer, false, Scope::new(0, 0)),
+                Local::new(8, None, false, Scope::new(0, 0), 4),
             ]
         )),
     );
@@ -115,27 +115,27 @@ fn multiple_block_scopes() {
                 (Instruction::r#return(false), Span(307, 307))
             ],
             vec![
-                ValueOwned::integer(0),
+                Value::integer(0),
-                ValueOwned::string("a"),
+                Value::string("a"),
-                ValueOwned::integer(42),
+                Value::integer(42),
-                ValueOwned::string("b"),
+                Value::string("b"),
-                ValueOwned::integer(1),
+                Value::integer(1),
-                ValueOwned::string("c"),
+                Value::string("c"),
-                ValueOwned::integer(2),
+                Value::integer(2),
-                ValueOwned::string("d"),
+                Value::string("d"),
-                ValueOwned::string("q"),
+                Value::string("q"),
-                ValueOwned::string("e"),
+                Value::string("e"),
             ],
             vec![
-                Local::new(1, Type::Integer, false, Scope::new(0, 0)),
+                Local::new(1, None, false, Scope::new(0, 0), 0),
-                Local::new(3, Type::Integer, false, Scope::new(1, 1)),
+                Local::new(3, None, false, Scope::new(1, 1), 1),
-                Local::new(5, Type::Integer, false, Scope::new(2, 2)),
+                Local::new(5, None, false, Scope::new(2, 2), 2),
-                Local::new(7, Type::Integer, false, Scope::new(1, 1)),
+                Local::new(7, None, false, Scope::new(1, 1), 3),
-                Local::new(8, Type::Integer, false, Scope::new(0, 0)),
+                Local::new(8, None, false, Scope::new(0, 0), 4),
-                Local::new(3, Type::Integer, false, Scope::new(1, 3)),
+                Local::new(3, None, false, Scope::new(1, 3), 5),
-                Local::new(5, Type::Integer, false, Scope::new(2, 4)),
+                Local::new(5, None, false, Scope::new(2, 4), 6),
-                Local::new(7, Type::Integer, false, Scope::new(1, 3)),
+                Local::new(7, None, false, Scope::new(1, 3), 7),
-                Local::new(9, Type::Integer, false, Scope::new(0, 0)),
+                Local::new(9, None, false, Scope::new(0, 0), 8),
             ]
         )),
     );

dust-lang/tests/unary_operations.rs

@@ -12,12 +12,12 @@ fn negate() {
                 (*Instruction::negate(0, 0).set_b_is_constant(), Span(0, 1)),
                 (Instruction::r#return(true), Span(5, 5)),
             ],
-            vec![ValueOwned::integer(42)],
+            vec![Value::integer(42)],
             vec![]
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(-42))));
+    assert_eq!(run(source), Ok(Some(Value::integer(-42))));
 }
 
 #[test]
@@ -38,5 +38,5 @@ fn not() {
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::boolean(false))));
+    assert_eq!(run(source), Ok(Some(Value::boolean(false))));
 }

dust-lang/tests/variables.rs

@@ -13,8 +13,8 @@ fn define_local() {
                 (Instruction::define_local(0, 0, false), Span(4, 5)),
                 (Instruction::r#return(false), Span(11, 11))
             ],
-            vec![ValueOwned::integer(42), ValueOwned::string("x")],
+            vec![Value::integer(42), Value::string("x")],
-            vec![Local::new(1, Type::Integer, false, Scope::default())]
+            vec![Local::new(1, None, false, Scope::default(), 0)]
         )),
     );
 
@@ -54,14 +54,10 @@ fn set_local() {
                 (Instruction::get_local(2, 0), Span(24, 25)),
                 (Instruction::r#return(true), Span(25, 25)),
             ],
-            vec![
+            vec![Value::integer(41), Value::string("x"), Value::integer(42)],
-                ValueOwned::integer(41),
+            vec![Local::new(1, None, true, Scope::default(), 0)]
-                ValueOwned::string("x"),
-                ValueOwned::integer(42)
-            ],
-            vec![Local::new(1, Type::Integer, true, Scope::default())]
         )),
     );
 
-    assert_eq!(run(source), Ok(Some(ValueOwned::integer(42))));
+    assert_eq!(run(source), Ok(Some(Value::integer(42))));
 }

dust-shell/src/main.rs

@@ -1,11 +1,8 @@
-use std::{
+use std::{fs::read_to_string, io::Write};
-    fs::read_to_string,
-    io::{stdout, Write},
-};
 
 use clap::Parser;
 use colored::Colorize;
-use dust_lang::{compile, format, lex, output_token_list, run};
+use dust_lang::{compile, format, run};
 use log::{Level, LevelFilter};
 
 #[derive(Parser)]
@@ -14,7 +11,7 @@ struct Cli {
     #[arg(short, long)]
     command: Option<String>,
 
-    /// Whether to output formatted source code instead of running the program
+    /// Whether to output formatted source code
     #[arg(short, long)]
     format: bool,
 
@@ -26,7 +23,7 @@ struct Cli {
     #[arg(long)]
     format_colored: Option<bool>,
 
-    /// Whether to output the disassembled chunk instead of running the program
+    /// Whether to output the disassembled chunk
     #[arg(short, long)]
     parse: bool,
 
@@ -34,10 +31,6 @@ struct Cli {
     #[arg(long)]
     style_disassembly: Option<bool>,
 
-    /// Whether to tokenize the source code instead of running the program
-    #[arg(short, long)]
-    tokenize: bool,
-
     /// Log level
     #[arg(short, long)]
     log: Option<LevelFilter>,
@@ -85,11 +78,11 @@ fn main() {
     };
 
     if args.format {
-        log::info!("Formatting source");
-
         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) => {
@@ -98,20 +91,11 @@ fn main() {
         }
     }
 
-    if args.tokenize {
-        log::info!("Tokenizing source");
-
-        match lex(source) {
-            Ok(tokens) => output_token_list(&tokens, &mut stdout()),
-            Err(error) => eprintln!("{}", error.report()),
-        }
-    }
-
     if args.parse {
-        log::info!("Parsing source");
-
         let styled = args.style_disassembly.unwrap_or(true);
 
+        log::info!("Parsing source");
+
         match compile(source) {
             Ok(chunk) => {
                 let disassembly = chunk
@@ -128,7 +112,7 @@ fn main() {
         }
     }
 
-    if args.format || args.tokenize || args.parse {
+    if args.format || args.parse {
         return;
     }