Continue implemnting functions; Begin adding types

dust-lang/src/chunk.rs

@@ -3,7 +3,10 @@ use std::fmt::{self, Debug, Display, Formatter};
 use colored::Colorize;
 use serde::{Deserialize, Serialize};
 
-use crate::{AnnotatedError, Identifier, Instruction, Operation, Span, Value};
+use crate::{
+    value::ValueKind, AnnotatedError, Function, Identifier, Instruction, Operation, Span, Type,
+    Value,
+};
 
 #[derive(Clone, PartialOrd, Ord, Serialize, Deserialize)]
 pub struct Chunk {
@@ -214,18 +217,20 @@ impl Chunk {
     pub fn declare_local(
         &mut self,
         identifier: Identifier,
-        mutable: bool,
+        r#type: Option<Type>,
+        is_mutable: bool,
         register_index: u8,
         position: Span,
     ) -> Result<u8, ChunkError> {
         let starting_length = self.locals.len();
 
         if starting_length + 1 > (u8::MAX as usize) {
-            Err(ChunkError::IdentifierOverflow { position })
+            Err(ChunkError::LocalOverflow { position })
         } else {
             self.locals.push(Local::new(
                 identifier,
-                mutable,
+                r#type,
+                is_mutable,
                 self.scope_depth,
                 Some(register_index),
             ));
@@ -308,6 +313,7 @@ impl PartialEq for Chunk {
 #[derive(Debug, Clone, Eq, PartialEq, PartialOrd, Ord, Serialize, Deserialize)]
 pub struct Local {
     pub identifier: Identifier,
+    pub r#type: Option<Type>,
     pub is_mutable: bool,
     pub depth: usize,
     pub register_index: Option<u8>,
@@ -316,12 +322,14 @@ pub struct Local {
 impl Local {
     pub fn new(
         identifier: Identifier,
+        r#type: Option<Type>,
         mutable: bool,
         depth: usize,
         register_index: Option<u8>,
     ) -> Self {
         Self {
             identifier,
+            r#type,
             is_mutable: mutable,
             depth,
             register_index,
@@ -334,6 +342,7 @@ pub struct ChunkDisassembler<'a> {
     chunk: &'a Chunk,
     width: Option<usize>,
     styled: bool,
+    indent: usize,
 }
 
 impl<'a> ChunkDisassembler<'a> {
@@ -357,8 +366,8 @@ impl<'a> ChunkDisassembler<'a> {
         "",
         "Locals",
         "------",
-        "INDEX IDENTIFIER MUTABLE DEPTH REGISTER",
+        "INDEX IDENTIFIER TYPE     MUTABLE DEPTH REGISTER",
-        "----- ---------- ------- ----- --------",
+        "----- ---------- -------- ------- ----- --------",
     ];
 
     /// The default width of the disassembly output. To correctly align the output, this should
@@ -375,6 +384,7 @@ impl<'a> ChunkDisassembler<'a> {
             chunk,
             width: None,
             styled: false,
+            indent: 0,
         }
     }
 
@@ -390,6 +400,12 @@ impl<'a> ChunkDisassembler<'a> {
         self
     }
 
+    pub fn indent(&mut self, indent: usize) -> &mut Self {
+        self.indent = indent;
+
+        self
+    }
+
     pub fn disassemble(&self) -> String {
         let width = self.width.unwrap_or_else(Self::default_width);
         let center = |line: &str| format!("{line:^width$}\n");
@@ -402,9 +418,16 @@ impl<'a> ChunkDisassembler<'a> {
         };
 
         let mut disassembly = String::with_capacity(self.predict_length());
+        let mut push_line = |line: &str| {
+            for _ in 0..self.indent {
+                disassembly.push_str("    ");
+            }
+
+            disassembly.push_str(line);
+        };
         let name_line = style(center(self.name));
 
-        disassembly.push_str(&name_line);
+        push_line(&name_line);
 
         let info_line = center(&format!(
             "{} instructions, {} constants, {} locals",
@@ -420,10 +443,10 @@ impl<'a> ChunkDisassembler<'a> {
             }
         };
 
-        disassembly.push_str(&styled_info_line);
+        push_line(&styled_info_line);
 
         for line in Self::INSTRUCTION_HEADER {
-            disassembly.push_str(&style(center(line)));
+            push_line(&style(center(line)));
         }
 
         for (index, (instruction, position)) in self.chunk.instructions.iter().enumerate() {
@@ -454,11 +477,11 @@ impl<'a> ChunkDisassembler<'a> {
                 "{index:<5} {bytecode:<08X} {operation:15} {info:25} {jump_offset:8} {position:8}"
             );
 
-            disassembly.push_str(&center(&instruction_display));
+            push_line(&center(&instruction_display));
         }
 
         for line in Self::CONSTANT_HEADER {
-            disassembly.push_str(&style(center(line)));
+            push_line(&style(center(line)));
         }
 
         for (index, value_option) in self.chunk.constants.iter().enumerate() {
@@ -474,17 +497,34 @@ impl<'a> ChunkDisassembler<'a> {
                 format!("{index:<5} {value_display:<trucated_length$}")
             };
 
-            disassembly.push_str(&center(&constant_display));
+            push_line(&center(&constant_display));
+
+            if let Some(chunk) = value_option.as_ref().and_then(|value| match value {
+                Value::Raw(value_data) => value_data.as_function().map(|function| function.body()),
+                Value::Reference(arc) => arc.as_function().map(|function| function.body()),
+                Value::Mutable(arc) => todo!(),
+            }) {
+                let mut function_disassembler = chunk.disassembler("function");
+
+                function_disassembler
+                    .styled(self.styled)
+                    .indent(self.indent + 1);
+
+                let function_disassembly = function_disassembler.disassemble();
+
+                push_line(&function_disassembly);
+            }
         }
 
         for line in Self::LOCAL_HEADER {
-            disassembly.push_str(&style(center(line)));
+            push_line(&style(center(line)));
         }
 
         for (
             index,
             Local {
                 identifier,
+                r#type,
                 depth,
                 register_index,
                 is_mutable: mutable,
@@ -496,11 +536,15 @@ impl<'a> ChunkDisassembler<'a> {
                 .map(|value| value.to_string())
                 .unwrap_or_else(|| "empty".to_string());
             let identifier_display = identifier.as_str();
+            let type_display = r#type
+                .as_ref()
+                .map(|r#type| r#type.to_string())
+                .unwrap_or("unknown".to_string());
             let local_display = format!(
-                "{index:<5} {identifier_display:10} {mutable:7} {depth:<5} {register_display:8}"
+                "{index:<5} {identifier_display:10} {type_display:8} {mutable:7} {depth:<5} {register_display:8}"
             );
 
-            disassembly.push_str(&center(&local_display));
+            push_line(&center(&local_display));
         }
 
         let expected_length = self.predict_length();
@@ -573,7 +617,7 @@ pub enum ChunkError {
         index: usize,
         position: Span,
     },
-    IdentifierOverflow {
+    LocalOverflow {
         position: Span,
     },
     IdentifierNotFound {
@@ -594,8 +638,8 @@ impl AnnotatedError for ChunkError {
             ChunkError::ConstantOverflow { .. } => "Constant overflow",
             ChunkError::ConstantIndexOutOfBounds { .. } => "Constant index out of bounds",
             ChunkError::InstructionUnderflow { .. } => "Instruction underflow",
-            ChunkError::LocalIndexOutOfBounds { .. } => "Identifier index out of bounds",
+            ChunkError::LocalIndexOutOfBounds { .. } => "Local index out of bounds",
-            ChunkError::IdentifierOverflow { .. } => "Identifier overflow",
+            ChunkError::LocalOverflow { .. } => "Local overflow",
             ChunkError::IdentifierNotFound { .. } => "Identifier not found",
         }
     }
@@ -611,13 +655,13 @@ impl AnnotatedError for ChunkError {
             }
             ChunkError::InstructionUnderflow { .. } => None,
             ChunkError::LocalIndexOutOfBounds { index, .. } => {
-                Some(format!("Identifier index: {}", index))
+                Some(format!("Local index: {}", index))
             }
             ChunkError::IdentifierNotFound { identifier, .. } => {
                 Some(format!("Identifier: {}", identifier))
             }
-            ChunkError::IdentifierOverflow { .. } => Some("Identifier overflow".to_string()),
+            ChunkError::LocalOverflow { .. } => None,
-            ChunkError::ConstantOverflow { .. } => Some("Constant overflow".to_string()),
+            ChunkError::ConstantOverflow { .. } => None,
         }
     }
 
@@ -629,7 +673,7 @@ impl AnnotatedError for ChunkError {
             ChunkError::IdentifierNotFound { position, .. } => *position,
             ChunkError::InstructionUnderflow { position, .. } => *position,
             ChunkError::LocalIndexOutOfBounds { position, .. } => *position,
-            ChunkError::IdentifierOverflow { position, .. } => *position,
+            ChunkError::LocalOverflow { position, .. } => *position,
             ChunkError::ConstantOverflow { position, .. } => *position,
         }
     }

dust-lang/src/lexer.rs

@@ -93,6 +93,10 @@ impl<'src> Lexer<'src> {
         }
     }
 
+    pub fn skip_to(&mut self, position: usize) {
+        self.position = position;
+    }
+
     /// Produce the next token.
     pub fn next_token(&mut self) -> Result<(Token<'src>, Span), LexError> {
         self.skip_whitespace();
@@ -539,6 +543,7 @@ impl<'src> Lexer<'src> {
             "loop" => Token::Loop,
             "map" => Token::Map,
             "mut" => Token::Mut,
+            "str" => Token::Str,
             "struct" => Token::Struct,
             "true" => Token::Boolean("true"),
             "while" => Token::While,

dust-lang/src/parser.rs

@@ -8,7 +8,7 @@ use colored::Colorize;
 
 use crate::{
     AnnotatedError, Chunk, ChunkError, DustError, Identifier, Instruction, LexError, Lexer,
-    Operation, Span, Token, TokenKind, TokenOwned, Value,
+    Operation, Span, Token, TokenKind, TokenOwned, Type, Value,
 };
 
 pub fn parse(source: &str) -> Result<Chunk, DustError> {
@@ -17,7 +17,11 @@ pub fn parse(source: &str) -> Result<Chunk, DustError> {
 
     while !parser.is_eof() {
         parser
-            .parse_statement(true)
+            .parse_statement(Allowed {
+                assignment: true,
+                explicit_return: false,
+                implicit_return: true,
+            })
             .map_err(|error| DustError::Parse { error, source })?;
     }
 
@@ -39,9 +43,8 @@ impl<'src> Parser<'src> {
     pub fn new(mut lexer: Lexer<'src>) -> Result<Self, ParseError> {
         let (current_token, current_position) = lexer.next_token()?;
 
-        log::info!("Begin chunk");
         log::info!(
-            "{} at {}",
+            "Begin chunk with {} at {}",
             current_token.to_string().bold(),
             current_position.to_string()
         );
@@ -81,7 +84,7 @@ impl<'src> Parser<'src> {
         }
     }
 
-    fn decrement_register(&mut self) -> Result<(), ParseError> {
+    fn _decrement_register(&mut self) -> Result<(), ParseError> {
         let current = self.current_register;
 
         if current == 0 {
@@ -140,8 +143,7 @@ impl<'src> Parser<'src> {
         self.chunk.push_instruction(instruction, position);
     }
 
-    fn emit_constant(&mut self, value: Value) -> Result<(), ParseError> {
+    fn emit_constant(&mut self, value: Value, position: Span) -> Result<(), ParseError> {
-        let position = self.previous_position;
         let constant_index = self.chunk.push_constant(value, position)?;
 
         self.emit_instruction(
@@ -152,11 +154,7 @@ impl<'src> Parser<'src> {
         Ok(())
     }
 
-    fn parse_boolean(
+    fn parse_boolean(&mut self, _: Allowed) -> Result<(), ParseError> {
-        &mut self,
-        _allow_assignment: bool,
-        _allow_return: bool,
-    ) -> Result<(), ParseError> {
         let boolean_text = if let Token::Boolean(text) = self.current_token {
             text
         } else {
@@ -171,7 +169,6 @@ impl<'src> Parser<'src> {
         let boolean = boolean_text.parse::<bool>().unwrap();
 
         self.advance()?;
-
         self.emit_instruction(
             Instruction::load_boolean(self.current_register, boolean, false),
             position,
@@ -180,11 +177,9 @@ impl<'src> Parser<'src> {
         Ok(())
     }
 
-    fn parse_byte(
+    fn parse_byte(&mut self, _: Allowed) -> Result<(), ParseError> {
-        &mut self,
+        let position = self.current_position;
-        _allow_assignment: bool,
+
-        _allow_return: bool,
-    ) -> Result<(), ParseError> {
         if let Token::Byte(text) = self.current_token {
             self.advance()?;
 
@@ -195,33 +190,29 @@ impl<'src> Parser<'src> {
                 })?;
             let value = Value::byte(byte);
 
-            self.emit_constant(value)?;
+            self.emit_constant(value, position)?;
         }
 
         Ok(())
     }
 
-    fn parse_character(
+    fn parse_character(&mut self, _: Allowed) -> Result<(), ParseError> {
-        &mut self,
+        let position = self.current_position;
-        _allow_assignment: bool,
+
-        _allow_return: bool,
-    ) -> Result<(), ParseError> {
         if let Token::Character(character) = self.current_token {
             self.advance()?;
 
             let value = Value::character(character);
 
-            self.emit_constant(value)?;
+            self.emit_constant(value, position)?;
         }
 
         Ok(())
     }
 
-    fn parse_float(
+    fn parse_float(&mut self, _: Allowed) -> Result<(), ParseError> {
-        &mut self,
+        let position = self.current_position;
-        _allow_assignment: bool,
+
-        _allow_return: bool,
-    ) -> Result<(), ParseError> {
         if let Token::Float(text) = self.current_token {
             self.advance()?;
 
@@ -233,17 +224,15 @@ impl<'src> Parser<'src> {
                 })?;
             let value = Value::float(float);
 
-            self.emit_constant(value)?;
+            self.emit_constant(value, position)?;
         }
 
         Ok(())
     }
 
-    fn parse_integer(
+    fn parse_integer(&mut self, _: Allowed) -> Result<(), ParseError> {
-        &mut self,
+        let position = self.current_position;
-        _allow_assignment: bool,
+
-        _allow_return: bool,
-    ) -> Result<(), ParseError> {
         if let Token::Integer(text) = self.current_token {
             self.advance()?;
 
@@ -255,43 +244,33 @@ impl<'src> Parser<'src> {
                 })?;
             let value = Value::integer(integer);
 
-            self.emit_constant(value)?;
+            self.emit_constant(value, position)?;
         }
 
         Ok(())
     }
 
-    fn parse_string(
+    fn parse_string(&mut self, _: Allowed) -> Result<(), ParseError> {
-        &mut self,
+        let position = self.current_position;
-        _allow_assignment: bool,
+
-        _allow_return: bool,
-    ) -> Result<(), ParseError> {
         if let Token::String(text) = self.current_token {
             self.advance()?;
 
             let value = Value::string(text);
 
-            self.emit_constant(value)?;
+            self.emit_constant(value, position)?;
         }
 
         Ok(())
     }
 
-    fn parse_grouped(
+    fn parse_grouped(&mut self, _: Allowed) -> Result<(), ParseError> {
-        &mut self,
-        _allow_assignment: bool,
-        _allow_return: bool,
-    ) -> Result<(), ParseError> {
         self.allow(TokenKind::LeftParenthesis)?;
         self.parse(Precedence::Assignment)?; // Do not allow assignment
         self.expect(TokenKind::RightParenthesis)
     }
 
-    fn parse_unary(
+    fn parse_unary(&mut self, _: Allowed) -> Result<(), ParseError> {
-        &mut self,
-        _allow_assignment: bool,
-        _allow_return: bool,
-    ) -> Result<(), ParseError> {
         let operator = self.current_token;
         let operator_position = self.current_position;
 
@@ -428,6 +407,7 @@ impl<'src> Parser<'src> {
 
             current
         };
+
         let mut new_instruction = match operator.kind() {
             TokenKind::Plus => Instruction::add(register, left, right),
             TokenKind::PlusEqual => Instruction::add(register, left, right),
@@ -605,11 +585,7 @@ impl<'src> Parser<'src> {
         Ok(())
     }
 
-    fn parse_variable(
+    fn parse_variable(&mut self, allowed: Allowed) -> Result<(), ParseError> {
-        &mut self,
-        allow_assignment: bool,
-        _allow_return: bool,
-    ) -> Result<(), ParseError> {
         let token = self.current_token;
         let start_position = self.current_position;
 
@@ -617,7 +593,7 @@ impl<'src> Parser<'src> {
 
         let local_index = self.parse_identifier_from(token, start_position)?;
 
-        if allow_assignment && self.allow(TokenKind::Equal)? {
+        if allowed.assignment && self.allow(TokenKind::Equal)? {
             let is_mutable = self
                 .chunk
                 .get_local(local_index, start_position)?
@@ -687,16 +663,31 @@ impl<'src> Parser<'src> {
         }
     }
 
-    fn parse_block(
+    fn parse_type_from(&mut self, token: Token, position: Span) -> Result<Type, ParseError> {
-        &mut self,
+        match token {
-        _allow_assignment: bool,
+            Token::Bool => Ok(Type::Boolean),
-        _allow_return: bool,
+            Token::FloatKeyword => Ok(Type::Float),
-    ) -> Result<(), ParseError> {
+            Token::Int => Ok(Type::Integer),
-        self.expect(TokenKind::LeftCurlyBrace)?;
+            Token::Str => Ok(Type::String { length: None }),
+            _ => Err(ParseError::ExpectedTokenMultiple {
+                expected: &[
+                    TokenKind::Bool,
+                    TokenKind::FloatKeyword,
+                    TokenKind::Int,
+                    TokenKind::Str,
+                ],
+                found: self.current_token.to_owned(),
+                position,
+            }),
+        }
+    }
+
+    fn parse_block(&mut self, allowed: Allowed) -> Result<(), ParseError> {
+        self.advance()?;
         self.chunk.begin_scope();
 
         while !self.allow(TokenKind::RightCurlyBrace)? && !self.is_eof() {
-            self.parse_statement(_allow_return)?;
+            self.parse_statement(allowed)?;
         }
 
         self.chunk.end_scope();
@@ -704,11 +695,7 @@ impl<'src> Parser<'src> {
         Ok(())
     }
 
-    fn parse_list(
+    fn parse_list(&mut self, _: Allowed) -> Result<(), ParseError> {
-        &mut self,
-        _allow_assignment: bool,
-        _allow_return: bool,
-    ) -> Result<(), ParseError> {
         let start = self.current_position.0;
 
         self.advance()?;
@@ -745,7 +732,8 @@ impl<'src> Parser<'src> {
         Ok(())
     }
 
-    fn parse_if(&mut self, allow_assignment: bool, allow_return: bool) -> Result<(), ParseError> {
+    fn parse_if(&mut self, mut allowed: Allowed) -> Result<(), ParseError> {
+        allowed.implicit_return = false;
         let length = self.chunk.len();
 
         self.advance()?;
@@ -762,7 +750,7 @@ impl<'src> Parser<'src> {
         }
 
         if let Token::LeftCurlyBrace = self.current_token {
-            self.parse_block(allow_assignment, allow_return)?;
+            self.parse_block(allowed)?;
         }
 
         let last_operation = self.chunk.get_last_operation()?;
@@ -780,28 +768,25 @@ impl<'src> Parser<'src> {
 
         if self.allow(TokenKind::Else)? {
             if let Token::If = self.current_token {
-                self.parse_if(allow_assignment, allow_return)?;
+                self.parse_if(allowed)?;
             }
 
             if let Token::LeftCurlyBrace = self.current_token {
-                self.parse_block(allow_assignment, allow_return)?;
+                self.parse_block(allowed)?;
             }
         }
 
         Ok(())
     }
 
-    fn parse_while(
+    fn parse_while(&mut self, mut allowed: Allowed) -> Result<(), ParseError> {
-        &mut self,
-        allow_assignment: bool,
-        allow_return: bool,
-    ) -> Result<(), ParseError> {
         self.advance()?;
 
+        allowed.implicit_return = false;
         let jump_start = self.chunk.len();
 
         self.parse(Precedence::Assignment)?; // Do not allow assignment
-        self.parse_block(allow_assignment, allow_return)?;
+        self.parse_block(allowed)?;
 
         let jump_end = self.chunk.len();
         let jump_distance = jump_end.abs_diff(jump_start) as u8;
@@ -847,20 +832,27 @@ impl<'src> Parser<'src> {
         Ok(())
     }
 
-    fn parse_statement(&mut self, allow_return: bool) -> Result<(), ParseError> {
+    fn parse_statement(&mut self, allowed: Allowed) -> Result<(), ParseError> {
         match self.current_token {
             Token::Let => {
-                self.parse_let_statement(true, allow_return)?;
+                self.parse_let_statement(Allowed {
+                    assignment: true,
+                    explicit_return: false,
+                    implicit_return: false,
+                })?;
                 self.allow(TokenKind::Semicolon)?;
             }
             Token::LeftCurlyBrace => {
-                self.parse_block(true, true)?;
+                self.parse_block(allowed)?;
                 self.allow(TokenKind::Semicolon)?;
             }
             _ => {
                 self.parse_expression()?;
 
-                if !self.allow(TokenKind::Semicolon)? && self.is_eof() {
+                if allowed.implicit_return
+                    && !self.allow(TokenKind::Semicolon)?
+                    && (self.is_eof() || matches!(self.current_token, Token::RightCurlyBrace))
+                {
                     self.emit_instruction(Instruction::r#return(), self.current_position);
                 }
             }
@@ -869,19 +861,15 @@ impl<'src> Parser<'src> {
         Ok(())
     }
 
-    fn parse_let_statement(
+    fn parse_let_statement(&mut self, allowed: Allowed) -> Result<(), ParseError> {
-        &mut self,
+        if !allowed.assignment {
-        allow_assignment: bool,
-        _allow_return: bool,
-    ) -> Result<(), ParseError> {
-        if !allow_assignment {
             return Err(ParseError::ExpectedExpression {
                 found: self.current_token.to_owned(),
                 position: self.current_position,
             });
         }
 
-        self.allow(TokenKind::Let)?;
+        self.expect(TokenKind::Let)?;
 
         let is_mutable = self.allow(TokenKind::Mut)?;
         let position = self.current_position;
@@ -896,40 +884,104 @@ impl<'src> Parser<'src> {
                 position: self.current_position,
             });
         };
+        let explicit_type = if self.allow(TokenKind::Colon)? {
+            Some(self.parse_type_from(self.current_token, self.current_position)?)
+        } else {
+            None
+        };
+
+        let register = self.current_register;
 
         self.expect(TokenKind::Equal)?;
         self.parse_expression()?;
-        self.increment_register()?;
+
+        if self.current_register == register {
+            self.increment_register()?;
+        }
 
         let (previous_instruction, previous_position) = self.chunk.get_last_instruction()?;
-        let register = previous_instruction.a();
-        let local_index =
-            self.chunk
-                .declare_local(identifier, is_mutable, register, *previous_position)?;
 
-        self.emit_instruction(
+        if let Operation::LoadConstant | Operation::LoadBoolean | Operation::Add =
-            Instruction::define_local(register, local_index, is_mutable),
+            previous_instruction.operation()
-            position,
+        {
-        );
+            let register = previous_instruction.a();
-        self.allow(TokenKind::Semicolon)?;
+            let local_index = self.chunk.declare_local(
+                identifier,
+                explicit_type,
+                is_mutable,
+                register,
+                *previous_position,
+            )?;
+
+            self.emit_instruction(
+                Instruction::define_local(register, local_index, is_mutable),
+                position,
+            );
+        }
 
         Ok(())
     }
 
-    fn parse_function(
+    fn parse_function(&mut self, _: Allowed) -> Result<(), ParseError> {
-        &mut self,
+        let function_start = self.current_position.0;
-        _allow_assignment: bool,
-        _allow_return: bool,
-    ) -> Result<(), ParseError> {
-        self.advance()?;
-
-        self.expect(TokenKind::LeftParenthesis)?;
-
         let mut function_parser = Parser::new(self.lexer)?;
 
-        self.expect(TokenKind::RightParenthesis)?;
+        function_parser.expect(TokenKind::LeftParenthesis)?;
 
-        function_parser.parse_block(false, true)?;
+        while function_parser.current_token != Token::RightParenthesis {
+            let start = function_parser.current_position.0;
+            let is_mutable = function_parser.allow(TokenKind::Mut)?;
+            let parameter = if let Token::Identifier(text) = function_parser.current_token {
+                function_parser.advance()?;
+
+                Identifier::new(text)
+            } else {
+                return Err(ParseError::ExpectedToken {
+                    expected: TokenKind::Identifier,
+                    found: function_parser.current_token.to_owned(),
+                    position: function_parser.current_position,
+                });
+            };
+
+            function_parser.expect(TokenKind::Colon)?;
+
+            let r#type = function_parser.parse_type_from(
+                function_parser.current_token,
+                function_parser.current_position,
+            )?;
+
+            function_parser.advance()?;
+
+            let end = function_parser.current_position.1;
+            let local_index = function_parser.chunk.declare_local(
+                parameter,
+                Some(r#type),
+                is_mutable,
+                function_parser.current_register,
+                Span(start, end),
+            )?;
+
+            function_parser.chunk.define_local(
+                local_index,
+                function_parser.current_register,
+                Span(start, end),
+            )?;
+            function_parser.increment_register()?;
+            function_parser.allow(TokenKind::Comma)?;
+        }
+
+        function_parser.advance()?;
+        function_parser.expect(TokenKind::LeftCurlyBrace)?;
+
+        while function_parser.current_token != Token::RightCurlyBrace {
+            function_parser.parse_statement(Allowed {
+                assignment: true,
+                explicit_return: true,
+                implicit_return: true,
+            })?;
+        }
+
+        function_parser.advance()?;
 
         self.previous_token = function_parser.previous_token;
         self.previous_position = function_parser.previous_position;
@@ -937,8 +989,10 @@ impl<'src> Parser<'src> {
         self.current_position = function_parser.current_position;
 
         let function = Value::function(function_parser.take_chunk());
+        let function_end = self.current_position.1;
 
-        self.emit_constant(function)?;
+        self.lexer.skip_to(function_end);
+        self.emit_constant(function, Span(function_start, function_end))?;
 
         Ok(())
     }
@@ -954,7 +1008,14 @@ impl<'src> Parser<'src> {
                 self.current_token.to_string().bold(),
             );
 
-            prefix_parser(self, allow_assignment, allow_return)?;
+            prefix_parser(
+                self,
+                Allowed {
+                    assignment: true,
+                    explicit_return: allow_return,
+                    implicit_return: allow_return,
+                },
+            )?;
             parsed = true;
         }
 
@@ -1056,7 +1117,14 @@ impl Display for Precedence {
     }
 }
 
-type PrefixFunction<'a> = fn(&mut Parser<'a>, bool, bool) -> Result<(), ParseError>;
+#[derive(Debug, Clone, Copy)]
+struct Allowed {
+    assignment: bool,
+    explicit_return: bool,
+    implicit_return: bool,
+}
+
+type PrefixFunction<'a> = fn(&mut Parser<'a>, Allowed) -> Result<(), ParseError>;
 type InfixFunction<'a> = fn(&mut Parser<'a>) -> Result<(), ParseError>;
 
 #[derive(Debug, Clone, Copy)]
@@ -1374,19 +1442,19 @@ impl AnnotatedError for ParseError {
     fn details(&self) -> Option<String> {
         match self {
             Self::CannotMutateImmutableVariable { identifier, .. } => {
-                Some(format!("Cannot mutate immutable variable \"{identifier}\""))
+                Some(format!("Cannot mutate immutable variable {identifier}"))
             }
-            Self::ExpectedExpression { found, .. } => Some(format!("Found \"{found}\"")),
+            Self::ExpectedExpression { found, .. } => Some(format!("Found {found}")),
             Self::ExpectedToken {
                 expected, found, ..
-            } => Some(format!("Expected \"{expected}\", found \"{found}\"")),
+            } => Some(format!("Expected {expected} but found {found}")),
             Self::ExpectedTokenMultiple {
                 expected, found, ..
             } => {
                 let mut details = String::from("Expected");
 
                 for (index, token) in expected.iter().enumerate() {
-                    details.push_str(&format!(" \"{token}\""));
+                    details.push_str(&format!(" {token}"));
 
                     if index < expected.len() - 2 {
                         details.push_str(", ");
@@ -1397,18 +1465,18 @@ impl AnnotatedError for ParseError {
                     }
                 }
 
-                details.push_str(&format!(" found \"{found}\""));
+                details.push_str(&format!(" but found {found}"));
 
                 Some(details)
             }
             Self::ExpectedMutableVariable { found, .. } => {
-                Some(format!("Expected mutable variable, found \"{found}\""))
+                Some(format!("Expected mutable variable, found {found}"))
             }
             Self::InvalidAssignmentTarget { found, .. } => {
-                Some(format!("Invalid assignment target, found \"{found}\""))
+                Some(format!("Invalid assignment target, found {found}"))
             }
             Self::UndefinedVariable { identifier, .. } => {
-                Some(format!("Undefined variable \"{identifier}\""))
+                Some(format!("Undefined variable {identifier}"))
             }
             Self::RegisterOverflow { .. } => None,
             Self::RegisterUnderflow { .. } => None,
@@ -1430,10 +1498,10 @@ impl AnnotatedError for ParseError {
             Self::UndefinedVariable { position, .. } => *position,
             Self::RegisterOverflow { position } => *position,
             Self::RegisterUnderflow { position } => *position,
-            Self::Chunk(error) => error.position(),
-            Self::Lex(error) => error.position(),
             Self::ParseFloatError { position, .. } => *position,
             Self::ParseIntError { position, .. } => *position,
+            Self::Chunk(error) => error.position(),
+            Self::Lex(error) => error.position(),
         }
     }
 }

dust-lang/src/value.rs

@@ -45,7 +45,7 @@ use serde::{
     Deserialize, Deserializer, Serialize, Serializer,
 };
 
-use crate::{Chunk, EnumType, FunctionType, Identifier, RangeableType, StructType, Type};
+use crate::{Chunk, EnumType, Identifier, RangeableType, StructType, Type};
 
 /// Dust value representation
 ///
@@ -1063,6 +1063,14 @@ impl ValueData {
         }
     }
 
+    pub fn as_function(&self) -> Option<&Function> {
+        if let ValueData::Function(function) = self {
+            Some(function)
+        } else {
+            None
+        }
+    }
+
     pub fn is_rangeable(&self) -> bool {
         matches!(
             self,
@@ -1452,6 +1460,10 @@ pub struct Function {
 }
 
 impl Function {
+    pub fn body(&self) -> &Chunk {
+        &self.body
+    }
+
     pub fn call(
         self,
         _type_arguments: Option<Vec<Type>>,

dust-lang/src/vm.rs

@@ -482,7 +482,7 @@ impl Vm {
         }
     }
 
-    fn pop(&mut self, position: Span) -> Result<Value, VmError> {
+    fn _pop(&mut self, position: Span) -> Result<Value, VmError> {
         if let Some(register) = self.register_stack.pop() {
             let value = register.ok_or(VmError::EmptyRegister {
                 index: self.register_stack.len().saturating_sub(1),

dust-lang/tests/expressions.rs

@@ -39,7 +39,7 @@ fn add_assign() {
                 (Instruction::r#return(), Span(24, 24))
             ],
             vec![Value::integer(1), Value::integer(2)],
-            vec![Local::new(Identifier::new("a"), true, 0, Some(0))]
+            vec![Local::new(Identifier::new("a"), None, true, 0, Some(0))]
         ))
     );
 
@@ -105,11 +105,11 @@ fn block_scope() {
                 Value::integer(1)
             ],
             vec![
-                Local::new(Identifier::new("a"), false, 0, Some(0)),
+                Local::new(Identifier::new("a"), None, false, 0, Some(0)),
-                Local::new(Identifier::new("b"), false, 1, Some(1)),
+                Local::new(Identifier::new("b"), None, false, 1, Some(1)),
-                Local::new(Identifier::new("c"), false, 2, Some(2)),
+                Local::new(Identifier::new("c"), None, false, 2, Some(2)),
-                Local::new(Identifier::new("d"), false, 1, Some(3)),
+                Local::new(Identifier::new("d"), None, false, 1, Some(3)),
-                Local::new(Identifier::new("e"), false, 0, Some(4)),
+                Local::new(Identifier::new("e"), None, false, 0, Some(4)),
             ]
         )),
     );
@@ -148,7 +148,7 @@ fn define_local() {
                 (Instruction::define_local(0, 0, false), Span(4, 5)),
             ],
             vec![Value::integer(42)],
-            vec![Local::new(Identifier::new("x"), false, 0, Some(0))]
+            vec![Local::new(Identifier::new("x"), None, false, 0, Some(0))]
         )),
     );
 
@@ -197,7 +197,7 @@ fn divide_assign() {
                 (Instruction::r#return(), Span(24, 24))
             ],
             vec![Value::integer(2), Value::integer(2)],
-            vec![Local::new(Identifier::new("a"), true, 0, Some(0))]
+            vec![Local::new(Identifier::new("a"), None, true, 0, Some(0))]
         ))
     );
 
@@ -261,7 +261,7 @@ fn equality_assignment_long() {
                 (Instruction::r#return(), Span(44, 44)),
             ],
             vec![Value::integer(4), Value::integer(4)],
-            vec![Local::new(Identifier::new("a"), false, 0, Some(0))]
+            vec![Local::new(Identifier::new("a"), None, false, 0, Some(0))]
         )),
     );
 
@@ -290,7 +290,7 @@ fn equality_assignment_short() {
                 (Instruction::r#return(), Span(17, 17)),
             ],
             vec![Value::integer(4), Value::integer(4)],
-            vec![Local::new(Identifier::new("a"), false, 0, Some(0))]
+            vec![Local::new(Identifier::new("a"), None, false, 0, Some(0))]
         )),
     );
 
@@ -686,7 +686,7 @@ fn multiply_assign() {
                 (Instruction::r#return(), Span(23, 23))
             ],
             vec![Value::integer(2), Value::integer(3)],
-            vec![Local::new(Identifier::new("a"), true, 0, Some(0)),]
+            vec![Local::new(Identifier::new("a"), None, true, 0, Some(0)),]
         ))
     );
 
@@ -825,7 +825,7 @@ fn set_local() {
                 (Instruction::r#return(), Span(25, 25)),
             ],
             vec![Value::integer(41), Value::integer(42)],
-            vec![Local::new(Identifier::new("x"), true, 0, Some(0)),]
+            vec![Local::new(Identifier::new("x"), None, true, 0, Some(0)),]
         )),
     );
 
@@ -874,7 +874,7 @@ fn subtract_assign() {
                 (Instruction::r#return(), Span(25, 25)),
             ],
             vec![Value::integer(42), Value::integer(2)],
-            vec![Local::new(Identifier::new("x"), true, 0, Some(0)),]
+            vec![Local::new(Identifier::new("x"), None, true, 0, Some(0)),]
         )),
     );
 
@@ -901,8 +901,8 @@ fn variable_and() {
             ],
             vec![],
             vec![
-                Local::new(Identifier::new("a"), false, 0, Some(0)),
+                Local::new(Identifier::new("a"), None, false, 0, Some(0)),
-                Local::new(Identifier::new("b"), false, 0, Some(1)),
+                Local::new(Identifier::new("b"), None, false, 0, Some(1)),
             ]
         ))
     );
@@ -931,7 +931,7 @@ fn r#while() {
                 (Instruction::r#return(), Span(42, 42)),
             ],
             vec![Value::integer(0), Value::integer(5), Value::integer(1),],
-            vec![Local::new(Identifier::new("x"), true, 0, Some(0)),]
+            vec![Local::new(Identifier::new("x"), None, true, 0, Some(0)),]
         )),
     );