Begin parser

dust-lang/src/bytecode.rs

@@ -22,11 +22,14 @@ impl Vm {
 
     pub fn interpret(&mut self) -> Result<Option<Value>, VmError> {
         loop {
-            let instruction = self.read_instruction();
+            let (byte, position) = self.read();
+            let instruction = Instruction::from_byte(byte)
+                .ok_or_else(|| VmError::InvalidInstruction(byte, position))?;
 
             match instruction {
-                Instruction::Constant(index) => {
-                    let value = self.read_constant(*index);
+                Instruction::Constant => {
+                    let (index, _) = self.read();
+                    let value = self.read_constant(index as usize);
 
                     self.stack.push(value.clone());
                 }
@@ -77,8 +80,6 @@ impl Vm {
                     self.stack.push(quotient);
                 }
             }
-
-            self.ip += 1;
         }
     }
 
@@ -100,10 +101,10 @@ impl Vm {
         }
     }
 
-    pub fn read_instruction(&self) -> &Instruction {
-        let (instruction, _) = &self.chunk.code[self.ip];
+    pub fn read(&mut self) -> (u8, Span) {
+        self.ip += 1;
 
-        instruction
+        self.chunk.code[self.ip - 1]
     }
 
     pub fn read_constant(&self, index: usize) -> Value {
@@ -113,6 +114,8 @@ impl Vm {
 
 #[derive(Debug, Clone, PartialEq)]
 pub enum VmError {
+    ChunkOverflow,
+    InvalidInstruction(u8, Span),
     StackUnderflow,
     StackOverflow,
     Value(ValueError),
@@ -126,24 +129,43 @@ impl From<ValueError> for VmError {
 
 #[derive(Debug, Clone, Copy, Eq, PartialEq, Serialize, Deserialize)]
 pub enum Instruction {
-    Constant(usize),
-    Return,
+    Constant = 0,
+    Return = 1,
 
     // Unary
-    Negate,
+    Negate = 2,
 
     // Binary
-    Add,
-    Subtract,
-    Multiply,
-    Divide,
+    Add = 3,
+    Subtract = 4,
+    Multiply = 5,
+    Divide = 6,
 }
 
 impl Instruction {
+    pub fn from_byte(byte: u8) -> Option<Self> {
+        match byte {
+            0 => Some(Self::Constant),
+            1 => Some(Self::Return),
+
+            // Unary
+            2 => Some(Self::Negate),
+
+            // Binary
+            3 => Some(Self::Add),
+            4 => Some(Self::Subtract),
+            5 => Some(Self::Multiply),
+            6 => Some(Self::Divide),
+
+            _ => None,
+        }
+    }
+
     pub fn disassemble(&self, chunk: &Chunk, offset: usize) -> String {
         match self {
-            Instruction::Constant(index) => {
-                let value = &chunk.constants[*index];
+            Instruction::Constant => {
+                let index = chunk.code[offset + 1].0 as usize;
+                let value = &chunk.constants[index];
 
                 format!("{:04} CONSTANT {} {}", offset, index, value)
             }
@@ -163,7 +185,7 @@ impl Instruction {
 
 #[derive(Debug, Clone, Eq, PartialEq, Serialize, Deserialize)]
 pub struct Chunk {
-    code: Vec<(Instruction, Span)>,
+    code: Vec<(u8, Span)>,
     constants: Vec<Value>,
 }
 
@@ -187,14 +209,20 @@ impl Chunk {
         self.code.capacity()
     }
 
-    pub fn write(&mut self, instruction: Instruction, position: Span) {
+    pub fn write(&mut self, instruction: u8, position: Span) {
         self.code.push((instruction, position));
     }
 
-    pub fn push_constant(&mut self, value: Value) -> usize {
-        self.constants.push(value);
+    pub fn push_constant(&mut self, value: Value) -> Result<u8, ChunkError> {
+        let starting_length = self.constants.len();
 
-        self.constants.len() - 1
+        if starting_length + 1 > (u8::MAX as usize) {
+            Err(ChunkError::Overflow)
+        } else {
+            self.constants.push(value);
+
+            Ok(starting_length as u8)
+        }
     }
 
     pub fn clear(&mut self) {
@@ -205,7 +233,9 @@ impl Chunk {
     pub fn disassemble(&self, name: &str) {
         println!("== {} ==", name);
 
-        for (offset, (instruction, position)) in self.code.iter().enumerate() {
+        for (offset, (byte, position)) in self.code.iter().enumerate() {
+            let instruction = Instruction::from_byte(*byte).unwrap();
+
             println!("{} {}", position, instruction.disassemble(self, offset));
         }
     }
@@ -217,6 +247,11 @@ impl Default for Chunk {
     }
 }
 
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum ChunkError {
+    Overflow,
+}
+
 #[cfg(test)]
 pub mod tests {
     use super::*;
@@ -224,11 +259,12 @@ pub mod tests {
     #[test]
     fn negation() {
         let mut chunk = Chunk::new();
-        let constant = chunk.push_constant(Value::integer(42));
+        let constant = chunk.push_constant(Value::integer(42)).unwrap();
 
-        chunk.write(Instruction::Constant(constant), Span(0, 1));
-        chunk.write(Instruction::Negate, Span(4, 5));
-        chunk.write(Instruction::Return, Span(2, 3));
+        chunk.write(Instruction::Constant as u8, Span(0, 1));
+        chunk.write(constant, Span(2, 3));
+        chunk.write(Instruction::Negate as u8, Span(4, 5));
+        chunk.write(Instruction::Return as u8, Span(2, 3));
 
         let mut vm = Vm::new(chunk);
         let result = vm.interpret();
@@ -239,13 +275,15 @@ pub mod tests {
     #[test]
     fn addition() {
         let mut chunk = Chunk::new();
-        let left = chunk.push_constant(Value::integer(42));
-        let right = chunk.push_constant(Value::integer(23));
+        let left = chunk.push_constant(Value::integer(42)).unwrap();
+        let right = chunk.push_constant(Value::integer(23)).unwrap();
 
-        chunk.write(Instruction::Constant(left), Span(0, 1));
-        chunk.write(Instruction::Constant(right), Span(2, 3));
-        chunk.write(Instruction::Add, Span(4, 5));
-        chunk.write(Instruction::Return, Span(6, 7));
+        chunk.write(Instruction::Constant as u8, Span(0, 1));
+        chunk.write(left, Span(2, 3));
+        chunk.write(Instruction::Constant as u8, Span(4, 5));
+        chunk.write(right, Span(6, 7));
+        chunk.write(Instruction::Add as u8, Span(8, 9));
+        chunk.write(Instruction::Return as u8, Span(10, 11));
 
         let mut vm = Vm::new(chunk);
         let result = vm.interpret();
@@ -256,13 +294,15 @@ pub mod tests {
     #[test]
     fn subtraction() {
         let mut chunk = Chunk::new();
-        let left = chunk.push_constant(Value::integer(42));
-        let right = chunk.push_constant(Value::integer(23));
+        let left = chunk.push_constant(Value::integer(42)).unwrap();
+        let right = chunk.push_constant(Value::integer(23)).unwrap();
 
-        chunk.write(Instruction::Constant(left), Span(0, 1));
-        chunk.write(Instruction::Constant(right), Span(2, 3));
-        chunk.write(Instruction::Subtract, Span(4, 5));
-        chunk.write(Instruction::Return, Span(6, 7));
+        chunk.write(Instruction::Constant as u8, Span(0, 1));
+        chunk.write(left, Span(2, 3));
+        chunk.write(Instruction::Constant as u8, Span(4, 5));
+        chunk.write(right, Span(6, 7));
+        chunk.write(Instruction::Subtract as u8, Span(8, 9));
+        chunk.write(Instruction::Return as u8, Span(10, 11));
 
         let mut vm = Vm::new(chunk);
         let result = vm.interpret();
@@ -273,13 +313,15 @@ pub mod tests {
     #[test]
     fn multiplication() {
         let mut chunk = Chunk::new();
-        let left = chunk.push_constant(Value::integer(42));
-        let right = chunk.push_constant(Value::integer(23));
+        let left = chunk.push_constant(Value::integer(42)).unwrap();
+        let right = chunk.push_constant(Value::integer(23)).unwrap();
 
-        chunk.write(Instruction::Constant(left), Span(0, 1));
-        chunk.write(Instruction::Constant(right), Span(2, 3));
-        chunk.write(Instruction::Multiply, Span(4, 5));
-        chunk.write(Instruction::Return, Span(6, 7));
+        chunk.write(Instruction::Constant as u8, Span(0, 1));
+        chunk.write(left, Span(2, 3));
+        chunk.write(Instruction::Constant as u8, Span(4, 5));
+        chunk.write(right, Span(6, 7));
+        chunk.write(Instruction::Multiply as u8, Span(8, 9));
+        chunk.write(Instruction::Return as u8, Span(10, 11));
 
         let mut vm = Vm::new(chunk);
         let result = vm.interpret();
@@ -291,13 +333,15 @@ pub mod tests {
 
     fn division() {
         let mut chunk = Chunk::new();
-        let left = chunk.push_constant(Value::integer(42));
-        let right = chunk.push_constant(Value::integer(23));
+        let left = chunk.push_constant(Value::integer(42)).unwrap();
+        let right = chunk.push_constant(Value::integer(23)).unwrap();
 
-        chunk.write(Instruction::Constant(left), Span(0, 1));
-        chunk.write(Instruction::Constant(right), Span(2, 3));
-        chunk.write(Instruction::Divide, Span(4, 5));
-        chunk.write(Instruction::Return, Span(6, 7));
+        chunk.write(Instruction::Constant as u8, Span(0, 1));
+        chunk.write(left, Span(2, 3));
+        chunk.write(Instruction::Constant as u8, Span(4, 5));
+        chunk.write(right, Span(6, 7));
+        chunk.write(Instruction::Divide as u8, Span(8, 9));
+        chunk.write(Instruction::Return as u8, Span(10, 11));
 
         let mut vm = Vm::new(chunk);
         let result = vm.interpret();

dust-lang/src/lib.rs

@@ -18,14 +18,20 @@
 pub mod bytecode;
 pub mod constructor;
 pub mod identifier;
+pub mod lexer;
+pub mod parser;
+pub mod token;
 pub mod r#type;
 pub mod value;
 
-pub use bytecode::*;
-pub use constructor::*;
-pub use identifier::*;
-pub use r#type::*;
-pub use value::*;
+pub use bytecode::{Chunk, ChunkError, Instruction, Vm};
+pub use constructor::{ConstructError, Constructor};
+pub use identifier::Identifier;
+pub use lexer::{LexError, Lexer};
+pub use parser::{ParseError, Parser};
+pub use r#type::{EnumType, FunctionType, RangeableType, StructType, Type, TypeConflict};
+pub use token::{Token, TokenKind, TokenOwned};
+pub use value::{Struct, Value, ValueError};
 
 use std::fmt::{self, Display, Formatter};
 

dust-lang/src/parser.rs

@@ -0,0 +1,122 @@
+use std::num::ParseIntError;
+
+use crate::{
+    Chunk, ChunkError, Instruction, LexError, Lexer, Span, Token, TokenKind, TokenOwned, Value,
+};
+
+#[derive(Debug)]
+pub struct Parser<'src> {
+    lexer: Lexer<'src>,
+    current_token: Token<'src>,
+    current_position: Span,
+}
+
+impl<'src> Parser<'src> {
+    pub fn new(mut lexer: Lexer<'src>) -> Self {
+        let (current_token, current_position) =
+            lexer.next_token().unwrap_or((Token::Eof, Span(0, 0)));
+
+        Parser {
+            lexer,
+            current_token,
+            current_position,
+        }
+    }
+
+    fn is_eof(&self) -> bool {
+        matches!(self.current_token, Token::Eof)
+    }
+
+    fn advance(&mut self) -> Result<(), ParseError> {
+        let (token, position) = self.lexer.next_token()?;
+
+        self.current_token = token;
+        self.current_position = position;
+
+        Ok(())
+    }
+
+    fn consume(&mut self, expected: TokenKind) -> Result<(), ParseError> {
+        if self.current_token.kind() == expected {
+            self.advance()
+        } else {
+            Err(ParseError::ExpectedToken {
+                expected,
+                found: self.current_token.to_owned(),
+                position: self.current_position,
+            })
+        }
+    }
+
+    fn emit_instruction(&mut self, instruction: Instruction, chunk: &mut Chunk) {
+        chunk.write(instruction as u8, self.current_position);
+    }
+
+    fn parse_prefix(&mut self, chunk: &mut Chunk) -> Result<(), ParseError> {
+        Ok(())
+    }
+
+    fn parse_primary(&mut self, chunk: &mut Chunk) -> Result<(), ParseError> {
+        match self.current_token {
+            Token::Integer(text) => {
+                let integer = text.parse::<i64>()?;
+                let value = Value::integer(integer);
+                let constant_index = chunk.push_constant(value)?;
+
+                chunk.write(Instruction::Constant as u8, self.current_position);
+                chunk.write(constant_index, self.current_position);
+            }
+            Token::LeftParenthesis => {}
+            _ => {
+                return Err(ParseError::ExpectedTokenMultiple {
+                    expected: vec![TokenKind::Integer],
+                    found: self.current_token.to_owned(),
+                    position: self.current_position,
+                })
+            }
+        }
+
+        Ok(())
+    }
+
+    pub fn parse_postfix(&mut self, left: Value, chunk: &mut Chunk) -> Result<(), ParseError> {
+        Ok(())
+    }
+}
+
+#[derive(Debug, PartialEq)]
+pub enum ParseError {
+    ExpectedToken {
+        expected: TokenKind,
+        found: TokenOwned,
+        position: Span,
+    },
+    ExpectedTokenMultiple {
+        expected: Vec<TokenKind>,
+        found: TokenOwned,
+        position: Span,
+    },
+
+    // Wrappers around foreign errors
+    Chunk(ChunkError),
+    Lex(LexError),
+    ParseIntError(ParseIntError),
+}
+
+impl From<ParseIntError> for ParseError {
+    fn from(error: ParseIntError) -> Self {
+        Self::ParseIntError(error)
+    }
+}
+
+impl From<LexError> for ParseError {
+    fn from(error: LexError) -> Self {
+        Self::Lex(error)
+    }
+}
+
+impl From<ChunkError> for ParseError {
+    fn from(error: ChunkError) -> Self {
+        Self::Chunk(error)
+    }
+}

dust-lang/src/token.rs

@@ -0,0 +1,651 @@
+//! Token and TokenOwned types.
+use std::fmt::{self, Display, Formatter};
+
+use serde::{Deserialize, Serialize};
+
+/// Source code token.
+#[derive(Debug, Serialize, Deserialize, PartialEq)]
+pub enum Token<'src> {
+    // End of file
+    Eof,
+
+    // Hard-coded values
+    Boolean(&'src str),
+    Character(char),
+    Float(&'src str),
+    Identifier(&'src str),
+    Integer(&'src str),
+    String(&'src str),
+
+    // Keywords
+    Async,
+    Bool,
+    Break,
+    Else,
+    FloatKeyword,
+    If,
+    Int,
+    Let,
+    Loop,
+    Map,
+    Mut,
+    Str,
+    Struct,
+    While,
+
+    // Symbols
+    BangEqual,
+    Bang,
+    Colon,
+    Comma,
+    Dot,
+    DoubleAmpersand,
+    DoubleDot,
+    DoubleEqual,
+    DoublePipe,
+    Equal,
+    Greater,
+    GreaterEqual,
+    LeftCurlyBrace,
+    LeftParenthesis,
+    LeftSquareBrace,
+    Less,
+    LessEqual,
+    Minus,
+    MinusEqual,
+    Percent,
+    Plus,
+    PlusEqual,
+    RightCurlyBrace,
+    RightParenthesis,
+    RightSquareBrace,
+    Semicolon,
+    Slash,
+    Star,
+}
+
+impl<'src> Token<'src> {
+    #[allow(clippy::len_without_is_empty)]
+    pub fn len(&self) -> usize {
+        match self {
+            Token::Eof => 0,
+            Token::Boolean(text) => text.len(),
+            Token::Character(_) => 3,
+            Token::Float(text) => text.len(),
+            Token::Identifier(text) => text.len(),
+            Token::Integer(text) => text.len(),
+            Token::String(text) => text.len() + 2,
+            Token::Async => 5,
+            Token::Bool => 4,
+            Token::Break => 5,
+            Token::Else => 4,
+            Token::FloatKeyword => 5,
+            Token::If => 2,
+            Token::Int => 3,
+            Token::Let => 3,
+            Token::Loop => 4,
+            Token::Map => 3,
+            Token::Mut => 3,
+            Token::Str => 3,
+            Token::Struct => 6,
+            Token::While => 5,
+            Token::BangEqual => 2,
+            Token::Bang => 1,
+            Token::Colon => 1,
+            Token::Comma => 1,
+            Token::Dot => 1,
+            Token::DoubleAmpersand => 2,
+            Token::DoubleDot => 2,
+            Token::DoubleEqual => 2,
+            Token::DoublePipe => 2,
+            Token::Equal => 1,
+            Token::Greater => 1,
+            Token::GreaterEqual => 2,
+            Token::LeftCurlyBrace => 1,
+            Token::LeftParenthesis => 1,
+            Token::LeftSquareBrace => 1,
+            Token::Less => 1,
+            Token::LessEqual => 2,
+            Token::Minus => 1,
+            Token::MinusEqual => 2,
+            Token::Percent => 1,
+            Token::Plus => 1,
+            Token::PlusEqual => 2,
+            Token::RightCurlyBrace => 1,
+            Token::RightParenthesis => 1,
+            Token::RightSquareBrace => 1,
+            Token::Semicolon => 1,
+            Token::Slash => 1,
+            Token::Star => 1,
+        }
+    }
+
+    pub fn to_owned(&self) -> TokenOwned {
+        match self {
+            Token::Async => TokenOwned::Async,
+            Token::BangEqual => TokenOwned::BangEqual,
+            Token::Bang => TokenOwned::Bang,
+            Token::Bool => TokenOwned::Bool,
+            Token::Boolean(boolean) => TokenOwned::Boolean(boolean.to_string()),
+            Token::Break => TokenOwned::Break,
+            Token::Character(character) => TokenOwned::Character(*character),
+            Token::Colon => TokenOwned::Colon,
+            Token::Comma => TokenOwned::Comma,
+            Token::Dot => TokenOwned::Dot,
+            Token::DoubleAmpersand => TokenOwned::DoubleAmpersand,
+            Token::DoubleDot => TokenOwned::DoubleDot,
+            Token::DoubleEqual => TokenOwned::DoubleEqual,
+            Token::DoublePipe => TokenOwned::DoublePipe,
+            Token::Else => TokenOwned::Else,
+            Token::Eof => TokenOwned::Eof,
+            Token::Equal => TokenOwned::Equal,
+            Token::Float(float) => TokenOwned::Float(float.to_string()),
+            Token::FloatKeyword => TokenOwned::FloatKeyword,
+            Token::Greater => TokenOwned::Greater,
+            Token::GreaterEqual => TokenOwned::GreaterOrEqual,
+            Token::Identifier(text) => TokenOwned::Identifier(text.to_string()),
+            Token::If => TokenOwned::If,
+            Token::Int => TokenOwned::Int,
+            Token::Integer(integer) => TokenOwned::Integer(integer.to_string()),
+            Token::LeftCurlyBrace => TokenOwned::LeftCurlyBrace,
+            Token::LeftParenthesis => TokenOwned::LeftParenthesis,
+            Token::LeftSquareBrace => TokenOwned::LeftSquareBrace,
+            Token::Let => TokenOwned::Let,
+            Token::Less => TokenOwned::Less,
+            Token::LessEqual => TokenOwned::LessOrEqual,
+            Token::Loop => TokenOwned::Loop,
+            Token::Map => TokenOwned::Map,
+            Token::Minus => TokenOwned::Minus,
+            Token::MinusEqual => TokenOwned::MinusEqual,
+            Token::Mut => TokenOwned::Mut,
+            Token::Percent => TokenOwned::Percent,
+            Token::Plus => TokenOwned::Plus,
+            Token::PlusEqual => TokenOwned::PlusEqual,
+            Token::RightCurlyBrace => TokenOwned::RightCurlyBrace,
+            Token::RightParenthesis => TokenOwned::RightParenthesis,
+            Token::RightSquareBrace => TokenOwned::RightSquareBrace,
+            Token::Semicolon => TokenOwned::Semicolon,
+            Token::Star => TokenOwned::Star,
+            Token::Slash => TokenOwned::Slash,
+            Token::String(text) => TokenOwned::String(text.to_string()),
+            Token::Str => TokenOwned::Str,
+            Token::Struct => TokenOwned::Struct,
+            Token::While => TokenOwned::While,
+        }
+    }
+
+    pub fn kind(&self) -> TokenKind {
+        match self {
+            Token::Async => TokenKind::Async,
+            Token::BangEqual => TokenKind::BangEqual,
+            Token::Bang => TokenKind::Bang,
+            Token::Bool => TokenKind::Bool,
+            Token::Boolean(_) => TokenKind::Boolean,
+            Token::Break => TokenKind::Break,
+            Token::Character(_) => TokenKind::Character,
+            Token::Colon => TokenKind::Colon,
+            Token::Comma => TokenKind::Comma,
+            Token::Dot => TokenKind::Dot,
+            Token::DoubleAmpersand => TokenKind::DoubleAmpersand,
+            Token::DoubleDot => TokenKind::DoubleDot,
+            Token::DoubleEqual => TokenKind::DoubleEqual,
+            Token::DoublePipe => TokenKind::DoublePipe,
+            Token::Else => TokenKind::Else,
+            Token::Eof => TokenKind::Eof,
+            Token::Equal => TokenKind::Equal,
+            Token::Float(_) => TokenKind::Float,
+            Token::FloatKeyword => TokenKind::FloatKeyword,
+            Token::Greater => TokenKind::Greater,
+            Token::GreaterEqual => TokenKind::GreaterOrEqual,
+            Token::Identifier(_) => TokenKind::Identifier,
+            Token::If => TokenKind::If,
+            Token::Int => TokenKind::Int,
+            Token::Integer(_) => TokenKind::Integer,
+            Token::LeftCurlyBrace => TokenKind::LeftCurlyBrace,
+            Token::LeftParenthesis => TokenKind::LeftParenthesis,
+            Token::LeftSquareBrace => TokenKind::LeftSquareBrace,
+            Token::Let => TokenKind::Let,
+            Token::Less => TokenKind::Less,
+            Token::LessEqual => TokenKind::LessOrEqual,
+            Token::Loop => TokenKind::Loop,
+            Token::Map => TokenKind::Map,
+            Token::Minus => TokenKind::Minus,
+            Token::MinusEqual => TokenKind::MinusEqual,
+            Token::Mut => TokenKind::Mut,
+            Token::Percent => TokenKind::Percent,
+            Token::Plus => TokenKind::Plus,
+            Token::PlusEqual => TokenKind::PlusEqual,
+            Token::RightCurlyBrace => TokenKind::RightCurlyBrace,
+            Token::RightParenthesis => TokenKind::RightParenthesis,
+            Token::RightSquareBrace => TokenKind::RightSquareBrace,
+            Token::Semicolon => TokenKind::Semicolon,
+            Token::Star => TokenKind::Star,
+            Token::Slash => TokenKind::Slash,
+            Token::Str => TokenKind::Str,
+            Token::String(_) => TokenKind::String,
+            Token::Struct => TokenKind::Struct,
+            Token::While => TokenKind::While,
+        }
+    }
+
+    pub fn is_eof(&self) -> bool {
+        matches!(self, Token::Eof)
+    }
+
+    pub fn precedence(&self) -> u8 {
+        match self {
+            Token::Dot => 9,
+            Token::LeftParenthesis | Token::LeftSquareBrace => 8,
+            Token::Star | Token::Slash | Token::Percent => 7,
+            Token::Minus | Token::Plus => 6,
+            Token::DoubleEqual
+            | Token::Less
+            | Token::LessEqual
+            | Token::Greater
+            | Token::GreaterEqual => 5,
+            Token::DoubleAmpersand => 4,
+            Token::DoublePipe => 3,
+            Token::DoubleDot => 2,
+            Token::Equal | Token::MinusEqual | Token::PlusEqual => 1,
+            _ => 0,
+        }
+    }
+
+    pub fn is_left_associative(&self) -> bool {
+        matches!(
+            self,
+            Token::Dot
+                | Token::DoubleAmpersand
+                | Token::DoublePipe
+                | Token::Plus
+                | Token::Minus
+                | Token::Star
+                | Token::Slash
+                | Token::Percent
+        )
+    }
+
+    pub fn is_right_associative(&self) -> bool {
+        matches!(self, Token::Equal | Token::MinusEqual | Token::PlusEqual)
+    }
+
+    pub fn is_prefix(&self) -> bool {
+        matches!(self, Token::Bang | Token::Minus | Token::Star)
+    }
+
+    pub fn is_postfix(&self) -> bool {
+        matches!(
+            self,
+            Token::Dot | Token::LeftCurlyBrace | Token::LeftParenthesis | Token::LeftSquareBrace
+        )
+    }
+}
+
+impl<'src> Display for Token<'src> {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        match self {
+            Token::Async => write!(f, "async"),
+            Token::BangEqual => write!(f, "!="),
+            Token::Bang => write!(f, "!"),
+            Token::Bool => write!(f, "bool"),
+            Token::Boolean(value) => write!(f, "{}", value),
+            Token::Break => write!(f, "break"),
+            Token::Character(value) => write!(f, "'{}'", value),
+            Token::Colon => write!(f, ":"),
+            Token::Comma => write!(f, ","),
+            Token::Dot => write!(f, "."),
+            Token::DoubleAmpersand => write!(f, "&&"),
+            Token::DoubleDot => write!(f, ".."),
+            Token::DoubleEqual => write!(f, "=="),
+            Token::DoublePipe => write!(f, "||"),
+            Token::Else => write!(f, "else"),
+            Token::Eof => write!(f, "EOF"),
+            Token::Equal => write!(f, "="),
+            Token::Float(value) => write!(f, "{}", value),
+            Token::FloatKeyword => write!(f, "float"),
+            Token::Greater => write!(f, ">"),
+            Token::GreaterEqual => write!(f, ">="),
+            Token::Identifier(value) => write!(f, "{}", value),
+            Token::If => write!(f, "if"),
+            Token::Int => write!(f, "int"),
+            Token::Integer(value) => write!(f, "{}", value),
+            Token::LeftCurlyBrace => write!(f, "{{"),
+            Token::LeftParenthesis => write!(f, "("),
+            Token::LeftSquareBrace => write!(f, "["),
+            Token::Let => write!(f, "let"),
+            Token::Less => write!(f, "<"),
+            Token::LessEqual => write!(f, "<="),
+            Token::Loop => write!(f, "loop"),
+            Token::Map => write!(f, "map"),
+            Token::Minus => write!(f, "-"),
+            Token::MinusEqual => write!(f, "-="),
+            Token::Mut => write!(f, "mut"),
+            Token::Percent => write!(f, "%"),
+            Token::Plus => write!(f, "+"),
+            Token::PlusEqual => write!(f, "+="),
+            Token::RightCurlyBrace => write!(f, "}}"),
+            Token::RightParenthesis => write!(f, ")"),
+            Token::RightSquareBrace => write!(f, "]"),
+            Token::Semicolon => write!(f, ";"),
+            Token::Slash => write!(f, "/"),
+            Token::Star => write!(f, "*"),
+            Token::Str => write!(f, "str"),
+            Token::String(value) => write!(f, "\"{}\"", value),
+            Token::Struct => write!(f, "struct"),
+            Token::While => write!(f, "while"),
+        }
+    }
+}
+
+/// Owned version of `Token`, which owns all the strings.
+///
+/// This is used for errors.
+#[derive(Debug, PartialEq, Clone, Serialize, Deserialize)]
+pub enum TokenOwned {
+    Eof,
+
+    Identifier(String),
+
+    // Hard-coded values
+    Boolean(String),
+    Character(char),
+    Float(String),
+    Integer(String),
+    String(String),
+
+    // Keywords
+    Bool,
+    Break,
+    Else,
+    FloatKeyword,
+    If,
+    Int,
+    Let,
+    Loop,
+    Map,
+    Mut,
+    Str,
+    While,
+
+    // Symbols
+    Async,
+    Bang,
+    BangEqual,
+    Colon,
+    Comma,
+    Dot,
+    DoubleAmpersand,
+    DoubleDot,
+    DoubleEqual,
+    DoublePipe,
+    Equal,
+    Greater,
+    GreaterOrEqual,
+    LeftCurlyBrace,
+    LeftParenthesis,
+    LeftSquareBrace,
+    Less,
+    LessOrEqual,
+    Minus,
+    MinusEqual,
+    Percent,
+    Plus,
+    PlusEqual,
+    RightCurlyBrace,
+    RightParenthesis,
+    RightSquareBrace,
+    Semicolon,
+    Star,
+    Struct,
+    Slash,
+}
+
+impl Display for TokenOwned {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        match self {
+            TokenOwned::Async => Token::Async.fmt(f),
+            TokenOwned::Bang => Token::Bang.fmt(f),
+            TokenOwned::BangEqual => Token::BangEqual.fmt(f),
+            TokenOwned::Bool => Token::Bool.fmt(f),
+            TokenOwned::Boolean(boolean) => Token::Boolean(boolean).fmt(f),
+            TokenOwned::Break => Token::Break.fmt(f),
+            TokenOwned::Character(character) => Token::Character(*character).fmt(f),
+            TokenOwned::Colon => Token::Colon.fmt(f),
+            TokenOwned::Comma => Token::Comma.fmt(f),
+            TokenOwned::Dot => Token::Dot.fmt(f),
+            TokenOwned::DoubleAmpersand => Token::DoubleAmpersand.fmt(f),
+            TokenOwned::DoubleDot => Token::DoubleDot.fmt(f),
+            TokenOwned::DoubleEqual => Token::DoubleEqual.fmt(f),
+            TokenOwned::DoublePipe => Token::DoublePipe.fmt(f),
+            TokenOwned::Else => Token::Else.fmt(f),
+            TokenOwned::Eof => Token::Eof.fmt(f),
+            TokenOwned::Equal => Token::Equal.fmt(f),
+            TokenOwned::Float(float) => Token::Float(float).fmt(f),
+            TokenOwned::FloatKeyword => Token::FloatKeyword.fmt(f),
+            TokenOwned::Greater => Token::Greater.fmt(f),
+            TokenOwned::GreaterOrEqual => Token::GreaterEqual.fmt(f),
+            TokenOwned::Identifier(text) => Token::Identifier(text).fmt(f),
+            TokenOwned::If => Token::If.fmt(f),
+            TokenOwned::Int => Token::Int.fmt(f),
+            TokenOwned::Integer(integer) => Token::Integer(integer).fmt(f),
+            TokenOwned::LeftCurlyBrace => Token::LeftCurlyBrace.fmt(f),
+            TokenOwned::LeftParenthesis => Token::LeftParenthesis.fmt(f),
+            TokenOwned::LeftSquareBrace => Token::LeftSquareBrace.fmt(f),
+            TokenOwned::Let => Token::Let.fmt(f),
+            TokenOwned::Less => Token::Less.fmt(f),
+            TokenOwned::LessOrEqual => Token::LessEqual.fmt(f),
+            TokenOwned::Loop => Token::Loop.fmt(f),
+            TokenOwned::Map => Token::Map.fmt(f),
+            TokenOwned::Minus => Token::Minus.fmt(f),
+            TokenOwned::MinusEqual => Token::MinusEqual.fmt(f),
+            TokenOwned::Mut => Token::Mut.fmt(f),
+            TokenOwned::Percent => Token::Percent.fmt(f),
+            TokenOwned::Plus => Token::Plus.fmt(f),
+            TokenOwned::PlusEqual => Token::PlusEqual.fmt(f),
+            TokenOwned::RightCurlyBrace => Token::RightCurlyBrace.fmt(f),
+            TokenOwned::RightParenthesis => Token::RightParenthesis.fmt(f),
+            TokenOwned::RightSquareBrace => Token::RightSquareBrace.fmt(f),
+            TokenOwned::Semicolon => Token::Semicolon.fmt(f),
+            TokenOwned::Star => Token::Star.fmt(f),
+            TokenOwned::Slash => Token::Slash.fmt(f),
+            TokenOwned::Str => Token::Str.fmt(f),
+            TokenOwned::String(string) => Token::String(string).fmt(f),
+            TokenOwned::Struct => Token::Struct.fmt(f),
+            TokenOwned::While => Token::While.fmt(f),
+        }
+    }
+}
+
+/// Token representation that holds no data.
+#[derive(Debug, PartialEq, Clone, Serialize, Deserialize)]
+pub enum TokenKind {
+    Eof,
+
+    Identifier,
+
+    // Hard-coded values
+    Boolean,
+    Character,
+    Float,
+    Integer,
+    String,
+
+    // Keywords
+    Async,
+    Bool,
+    Break,
+    Else,
+    FloatKeyword,
+    If,
+    Int,
+    Let,
+    Loop,
+    Map,
+    Str,
+    While,
+
+    // Symbols
+    BangEqual,
+    Bang,
+    Colon,
+    Comma,
+    Dot,
+    DoubleAmpersand,
+    DoubleDot,
+    DoubleEqual,
+    DoublePipe,
+    Equal,
+    Greater,
+    GreaterOrEqual,
+    LeftCurlyBrace,
+    LeftParenthesis,
+    LeftSquareBrace,
+    Less,
+    LessOrEqual,
+    Minus,
+    MinusEqual,
+    Mut,
+    Percent,
+    Plus,
+    PlusEqual,
+    RightCurlyBrace,
+    RightParenthesis,
+    RightSquareBrace,
+    Semicolon,
+    Star,
+    Struct,
+    Slash,
+}
+
+impl Display for TokenKind {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        match self {
+            TokenKind::Async => Token::Async.fmt(f),
+            TokenKind::Bang => Token::Bang.fmt(f),
+            TokenKind::BangEqual => Token::BangEqual.fmt(f),
+            TokenKind::Bool => Token::Bool.fmt(f),
+            TokenKind::Boolean => write!(f, "boolean value"),
+            TokenKind::Break => Token::Break.fmt(f),
+            TokenKind::Character => write!(f, "character value"),
+            TokenKind::Colon => Token::Colon.fmt(f),
+            TokenKind::Comma => Token::Comma.fmt(f),
+            TokenKind::Dot => Token::Dot.fmt(f),
+            TokenKind::DoubleAmpersand => Token::DoubleAmpersand.fmt(f),
+            TokenKind::DoubleDot => Token::DoubleDot.fmt(f),
+            TokenKind::DoubleEqual => Token::DoubleEqual.fmt(f),
+            TokenKind::DoublePipe => Token::DoublePipe.fmt(f),
+            TokenKind::Else => Token::Else.fmt(f),
+            TokenKind::Eof => Token::Eof.fmt(f),
+            TokenKind::Equal => Token::Equal.fmt(f),
+            TokenKind::Float => write!(f, "float value"),
+            TokenKind::FloatKeyword => Token::FloatKeyword.fmt(f),
+            TokenKind::Greater => Token::Greater.fmt(f),
+            TokenKind::GreaterOrEqual => Token::GreaterEqual.fmt(f),
+            TokenKind::Identifier => write!(f, "identifier"),
+            TokenKind::If => Token::If.fmt(f),
+            TokenKind::Int => Token::Int.fmt(f),
+            TokenKind::Integer => write!(f, "integer value"),
+            TokenKind::LeftCurlyBrace => Token::LeftCurlyBrace.fmt(f),
+            TokenKind::LeftParenthesis => Token::LeftParenthesis.fmt(f),
+            TokenKind::LeftSquareBrace => Token::LeftSquareBrace.fmt(f),
+            TokenKind::Let => Token::Let.fmt(f),
+            TokenKind::Less => Token::Less.fmt(f),
+            TokenKind::LessOrEqual => Token::LessEqual.fmt(f),
+            TokenKind::Loop => Token::Loop.fmt(f),
+            TokenKind::Map => Token::Map.fmt(f),
+            TokenKind::Minus => Token::Minus.fmt(f),
+            TokenKind::MinusEqual => Token::MinusEqual.fmt(f),
+            TokenKind::Mut => Token::Mut.fmt(f),
+            TokenKind::Percent => Token::Percent.fmt(f),
+            TokenKind::Plus => Token::Plus.fmt(f),
+            TokenKind::PlusEqual => Token::PlusEqual.fmt(f),
+            TokenKind::RightCurlyBrace => Token::RightCurlyBrace.fmt(f),
+            TokenKind::RightParenthesis => Token::RightParenthesis.fmt(f),
+            TokenKind::RightSquareBrace => Token::RightSquareBrace.fmt(f),
+            TokenKind::Semicolon => Token::Semicolon.fmt(f),
+            TokenKind::Star => Token::Star.fmt(f),
+            TokenKind::Str => Token::Str.fmt(f),
+            TokenKind::Slash => Token::Slash.fmt(f),
+            TokenKind::String => write!(f, "string value"),
+            TokenKind::Struct => Token::Struct.fmt(f),
+            TokenKind::While => Token::While.fmt(f),
+        }
+    }
+}
+
+#[cfg(test)]
+pub(crate) mod tests {
+    use super::*;
+
+    pub fn all_tokens<'src>() -> [Token<'src>; 47] {
+        [
+            Token::Async,
+            Token::Bang,
+            Token::BangEqual,
+            Token::Bool,
+            Token::Break,
+            Token::Colon,
+            Token::Comma,
+            Token::Dot,
+            Token::DoubleAmpersand,
+            Token::DoubleDot,
+            Token::DoubleEqual,
+            Token::DoublePipe,
+            Token::Else,
+            Token::Eof,
+            Token::Equal,
+            Token::FloatKeyword,
+            Token::Greater,
+            Token::GreaterEqual,
+            Token::If,
+            Token::Int,
+            Token::LeftCurlyBrace,
+            Token::LeftParenthesis,
+            Token::LeftSquareBrace,
+            Token::Let,
+            Token::Less,
+            Token::LessEqual,
+            Token::Map,
+            Token::Minus,
+            Token::MinusEqual,
+            Token::Mut,
+            Token::Percent,
+            Token::Plus,
+            Token::PlusEqual,
+            Token::RightCurlyBrace,
+            Token::RightParenthesis,
+            Token::RightSquareBrace,
+            Token::Semicolon,
+            Token::Star,
+            Token::Str,
+            Token::Slash,
+            Token::Boolean("true"),
+            Token::Float("0.0"),
+            Token::Integer("0"),
+            Token::String("string"),
+            Token::Identifier("foobar"),
+            Token::Struct,
+            Token::While,
+        ]
+    }
+
+    #[test]
+    fn token_displays() {
+        for token in all_tokens().iter() {
+            let display = token.to_string();
+
+            assert_eq!(display, token.to_owned().to_string());
+
+            if let Token::Boolean(_)
+            | Token::Float(_)
+            | Token::Identifier(_)
+            | Token::Integer(_)
+            | Token::String(_) = token
+            {
+                continue;
+            } else {
+                assert_eq!(display, token.kind().to_string());
+            }
+        }
+    }
+}