use super::chunk::Chunk; use super::errors::{Error, ErrorKind, LoxResult}; use super::interner::{InternedStr, Interner}; use super::opcode::{CodeIdx, CodeOffset, ConstantIdx, OpCode, StackIdx}; use super::value::Value; use crate::scanner::{self, Token, TokenKind}; #[cfg(feature = "disassemble")] use super::chunk; #[derive(Debug)] enum Depth { Unitialised, At(usize), } impl Depth { fn above(&self, theirs: usize) -> bool { match self { Depth::Unitialised => false, Depth::At(ours) => *ours > theirs, } } fn below(&self, theirs: usize) -> bool { match self { Depth::Unitialised => false, Depth::At(ours) => *ours < theirs, } } } #[derive(Debug)] struct Local { name: Token, depth: Depth, } #[derive(Debug, Default)] struct Locals { locals: Vec, scope_depth: usize, } struct Compiler> { tokens: T, chunk: Chunk, panic: bool, errors: Vec, strings: Interner, locals: Locals, current: Option, previous: Option, } #[derive(Debug, PartialEq, PartialOrd)] enum Precedence { None, Assignment, // = Or, // or And, // and Equality, // == != Comparison, // < > <= >= Term, // + - Factor, // // // * / Unary, // ! - Call, // . () Primary, } type ParseFn = fn(&mut Compiler) -> LoxResult<()>; struct ParseRule> { prefix: Option>, infix: Option>, precedence: Precedence, } impl> ParseRule { fn new(prefix: Option>, infix: Option>, precedence: Precedence) -> Self { ParseRule { prefix, infix, precedence, } } } impl Precedence { // Return the next highest precedence, if there is one. fn next(&self) -> Self { match self { Precedence::None => Precedence::Assignment, Precedence::Assignment => Precedence::Or, Precedence::Or => Precedence::And, Precedence::And => Precedence::Equality, Precedence::Equality => Precedence::Comparison, Precedence::Comparison => Precedence::Term, Precedence::Term => Precedence::Factor, Precedence::Factor => Precedence::Unary, Precedence::Unary => Precedence::Call, Precedence::Call => Precedence::Primary, Precedence::Primary => { panic!("invalid parser state: no higher precedence than Primary") } } } } fn rule_for>(token: &TokenKind) -> ParseRule { match token { TokenKind::LeftParen => ParseRule::new(Some(Compiler::grouping), None, Precedence::None), TokenKind::Minus => ParseRule::new( Some(Compiler::unary), Some(Compiler::binary), Precedence::Term, ), TokenKind::Plus => ParseRule::new(None, Some(Compiler::binary), Precedence::Term), TokenKind::Slash => ParseRule::new(None, Some(Compiler::binary), Precedence::Factor), TokenKind::Star => ParseRule::new(None, Some(Compiler::binary), Precedence::Factor), TokenKind::Number(_) => ParseRule::new(Some(Compiler::number), None, Precedence::None), TokenKind::True => ParseRule::new(Some(Compiler::literal), None, Precedence::None), TokenKind::False => ParseRule::new(Some(Compiler::literal), None, Precedence::None), TokenKind::Nil => ParseRule::new(Some(Compiler::literal), None, Precedence::None), TokenKind::Bang => ParseRule::new(Some(Compiler::unary), None, Precedence::None), TokenKind::BangEqual => ParseRule::new(None, Some(Compiler::binary), Precedence::Equality), TokenKind::EqualEqual => ParseRule::new(None, Some(Compiler::binary), Precedence::Equality), TokenKind::Greater => ParseRule::new(None, Some(Compiler::binary), Precedence::Comparison), TokenKind::GreaterEqual => { ParseRule::new(None, Some(Compiler::binary), Precedence::Comparison) } TokenKind::Less => ParseRule::new(None, Some(Compiler::binary), Precedence::Comparison), TokenKind::LessEqual => { ParseRule::new(None, Some(Compiler::binary), Precedence::Comparison) } TokenKind::Identifier(_) => { ParseRule::new(Some(Compiler::variable), None, Precedence::None) } TokenKind::String(_) => ParseRule::new(Some(Compiler::string), None, Precedence::None), _ => ParseRule::new(None, None, Precedence::None), } } macro_rules! consume { ( $self:ident, $expected:pat, $err:expr ) => { match $self.current().kind { $expected => $self.advance(), _ => $self.error_at($self.current().line, $err), } }; } impl> Compiler { fn compile(&mut self) -> LoxResult<()> { self.advance(); while !self.match_token(&TokenKind::Eof) { self.declaration()?; } self.end_compiler() } fn advance(&mut self) { self.previous = self.current.take(); self.current = self.tokens.next(); } fn expression(&mut self) -> LoxResult<()> { self.parse_precedence(Precedence::Assignment) } fn var_declaration(&mut self) -> LoxResult<()> { let idx = self.parse_variable()?; if self.match_token(&TokenKind::Equal) { self.expression()?; } else { self.emit_op(OpCode::OpNil); } self.expect_semicolon("expect ';' after variable declaration")?; self.define_variable(idx) } fn define_variable(&mut self, var: Option) -> LoxResult<()> { if self.locals.scope_depth == 0 { self.emit_op(OpCode::OpDefineGlobal(var.expect("should be global"))); } else { self.locals .locals .last_mut() .expect("fatal: variable not yet added at definition") .depth = Depth::At(self.locals.scope_depth); } Ok(()) } fn declaration(&mut self) -> LoxResult<()> { if self.match_token(&TokenKind::Var) { self.var_declaration()?; } else { self.statement()?; } if self.panic { self.synchronise(); } Ok(()) } fn statement(&mut self) -> LoxResult<()> { if self.match_token(&TokenKind::Print) { self.print_statement() } else if self.match_token(&TokenKind::If) { self.if_statement() } else if self.match_token(&TokenKind::LeftBrace) { self.begin_scope(); self.block()?; self.end_scope(); Ok(()) } else { self.expression_statement() } } fn print_statement(&mut self) -> LoxResult<()> { self.expression()?; self.expect_semicolon("expect ';' after print statement")?; self.emit_op(OpCode::OpPrint); Ok(()) } fn begin_scope(&mut self) { self.locals.scope_depth += 1; } fn end_scope(&mut self) { debug_assert!(self.locals.scope_depth > 0, "tried to end global scope"); self.locals.scope_depth -= 1; while self.locals.locals.len() > 0 && self.locals.locals[self.locals.locals.len() - 1] .depth .above(self.locals.scope_depth) { self.emit_op(OpCode::OpPop); self.locals.locals.remove(self.locals.locals.len() - 1); } } fn block(&mut self) -> LoxResult<()> { while !self.check(&TokenKind::RightBrace) && !self.check(&TokenKind::Eof) { self.declaration()?; } consume!( self, TokenKind::RightBrace, ErrorKind::ExpectedToken("Expected '}' after block.") ); Ok(()) } fn expression_statement(&mut self) -> LoxResult<()> { self.expression()?; self.expect_semicolon("expect ';' after expression")?; // TODO(tazjin): Why did I add this originally? // self.emit_op(OpCode::OpPop); Ok(()) } fn if_statement(&mut self) -> LoxResult<()> { consume!( self, TokenKind::LeftParen, ErrorKind::ExpectedToken("Expected '(' after 'if'") ); self.expression()?; consume!( self, TokenKind::RightParen, ErrorKind::ExpectedToken("Expected ')' after condition") ); let then_jump = self.emit_op(OpCode::OpJumpPlaceholder(false)); self.emit_op(OpCode::OpPop); self.statement()?; let else_jump = self.emit_op(OpCode::OpJumpPlaceholder(true)); self.patch_jump(then_jump); self.emit_op(OpCode::OpPop); if self.match_token(&TokenKind::Else) { self.statement()?; } self.patch_jump(else_jump); Ok(()) } fn number(&mut self) -> LoxResult<()> { if let TokenKind::Number(num) = self.previous().kind { self.emit_constant(Value::Number(num), true); return Ok(()); } unreachable!("internal parser error: entered number() incorrectly") } fn grouping(&mut self) -> LoxResult<()> { self.expression()?; consume!( self, TokenKind::RightParen, ErrorKind::ExpectedToken("Expected ')' after expression") ); Ok(()) } fn unary(&mut self) -> LoxResult<()> { // TODO(tazjin): Avoid clone let kind = self.previous().kind.clone(); // Compile the operand self.parse_precedence(Precedence::Unary)?; // Emit operator instruction match kind { TokenKind::Bang => self.emit_op(OpCode::OpNot), TokenKind::Minus => self.emit_op(OpCode::OpNegate), _ => unreachable!("only called for unary operator tokens"), }; Ok(()) } fn binary(&mut self) -> LoxResult<()> { // Remember the operator let operator = self.previous().kind.clone(); // Compile the right operand let rule: ParseRule = rule_for(&operator); self.parse_precedence(rule.precedence.next())?; // Emit operator instruction match operator { TokenKind::Minus => self.emit_op(OpCode::OpSubtract), TokenKind::Plus => self.emit_op(OpCode::OpAdd), TokenKind::Star => self.emit_op(OpCode::OpMultiply), TokenKind::Slash => self.emit_op(OpCode::OpDivide), TokenKind::BangEqual => { self.emit_op(OpCode::OpEqual); self.emit_op(OpCode::OpNot) } TokenKind::EqualEqual => self.emit_op(OpCode::OpEqual), TokenKind::Greater => self.emit_op(OpCode::OpGreater), TokenKind::GreaterEqual => { self.emit_op(OpCode::OpLess); self.emit_op(OpCode::OpNot) } TokenKind::Less => self.emit_op(OpCode::OpLess), TokenKind::LessEqual => { self.emit_op(OpCode::OpGreater); self.emit_op(OpCode::OpNot) } _ => unreachable!("only called for binary operator tokens"), }; Ok(()) } fn literal(&mut self) -> LoxResult<()> { match self.previous().kind { TokenKind::Nil => self.emit_op(OpCode::OpNil), TokenKind::True => self.emit_op(OpCode::OpTrue), TokenKind::False => self.emit_op(OpCode::OpFalse), _ => unreachable!("only called for literal value tokens"), }; Ok(()) } fn string(&mut self) -> LoxResult<()> { let val = match &self.previous().kind { TokenKind::String(s) => s.clone(), _ => unreachable!("only called for strings"), }; let id = self.strings.intern(val); self.emit_constant(Value::String(id.into()), true); Ok(()) } fn named_variable(&mut self, name: Token) -> LoxResult<()> { let local_idx = self.resolve_local(&name); let ident = if local_idx.is_some() { None } else { Some(self.identifier_constant(&name)?) }; if self.match_token(&TokenKind::Equal) { self.expression()?; match local_idx { Some(idx) => self.emit_op(OpCode::OpSetLocal(idx)), None => self.emit_op(OpCode::OpSetGlobal(ident.unwrap())), }; } else { match local_idx { Some(idx) => self.emit_op(OpCode::OpGetLocal(idx)), None => self.emit_op(OpCode::OpGetGlobal(ident.unwrap())), }; } Ok(()) } fn variable(&mut self) -> LoxResult<()> { let name = self.previous().clone(); self.named_variable(name) } fn parse_precedence(&mut self, precedence: Precedence) -> LoxResult<()> { self.advance(); let rule: ParseRule = rule_for(&self.previous().kind); let prefix_fn = match rule.prefix { None => unimplemented!("expected expression or something, unclear"), Some(func) => func, }; prefix_fn(self)?; while precedence <= rule_for::(&self.current().kind).precedence { self.advance(); match rule_for::(&self.previous().kind).infix { Some(func) => { func(self)?; } None => { unreachable!("invalid compiler state: error in parse rules") } } } Ok(()) } fn identifier_str(&mut self, token: &Token) -> LoxResult { let ident = match &token.kind { TokenKind::Identifier(ident) => ident.to_string(), _ => { return Err(Error { line: self.current().line, kind: ErrorKind::ExpectedToken("Expected identifier"), }) } }; Ok(self.strings.intern(ident)) } fn identifier_constant(&mut self, name: &Token) -> LoxResult { let ident = self.identifier_str(name)?; Ok(self.emit_constant(Value::String(ident.into()), false)) } fn resolve_local(&self, name: &Token) -> Option { for (idx, local) in self.locals.locals.iter().enumerate().rev() { if name.lexeme == local.name.lexeme { if let Depth::Unitialised = local.depth { // TODO(tazjin): *return* err panic!("can't read variable in its own initialiser"); } return Some(StackIdx(idx)); } } None } fn add_local(&mut self, name: Token) { let local = Local { name, depth: Depth::Unitialised, }; self.locals.locals.push(local); } fn declare_variable(&mut self) -> LoxResult<()> { if self.locals.scope_depth == 0 { return Ok(()); } let name = self.previous().clone(); for local in self.locals.locals.iter().rev() { if local.depth.below(self.locals.scope_depth) { break; } if name.lexeme == local.name.lexeme { return Err(Error { kind: ErrorKind::VariableShadowed(name.lexeme.into()), line: name.line, }); } } self.add_local(name); Ok(()) } fn parse_variable(&mut self) -> LoxResult> { consume!( self, TokenKind::Identifier(_), ErrorKind::ExpectedToken("expected identifier") ); self.declare_variable()?; if self.locals.scope_depth > 0 { return Ok(None); } let name = self.previous().clone(); let id = self.identifier_str(&name)?; Ok(Some(self.emit_constant(Value::String(id.into()), false))) } fn current_chunk(&mut self) -> &mut Chunk { &mut self.chunk } fn end_compiler(&mut self) -> LoxResult<()> { self.emit_op(OpCode::OpReturn); #[cfg(feature = "disassemble")] { chunk::disassemble_chunk(&self.chunk); println!("== compilation finished =="); } Ok(()) } fn emit_op(&mut self, op: OpCode) -> CodeIdx { let line = self.previous().line; self.current_chunk().add_op(op, line) } fn emit_constant(&mut self, val: Value, with_op: bool) -> ConstantIdx { let idx = ConstantIdx(self.chunk.add_constant(val)); if with_op { self.emit_op(OpCode::OpConstant(idx)); } idx } fn patch_jump(&mut self, idx: CodeIdx) { let offset = CodeOffset(self.chunk.code.len() - idx.0 - 1); if let OpCode::OpJumpPlaceholder(true) = self.chunk.code[idx.0] { self.chunk.code[idx.0] = OpCode::OpJump(offset); return; } if let OpCode::OpJumpPlaceholder(false) = self.chunk.code[idx.0] { self.chunk.code[idx.0] = OpCode::OpJumpIfFalse(offset); return; } panic!( "attempted to patch unsupported op: {:?}", self.chunk.code[idx.0] ); } fn previous(&self) -> &Token { self.previous .as_ref() .expect("invalid internal compiler state: missing previous token") } fn current(&self) -> &Token { self.current .as_ref() .expect("invalid internal compiler state: missing current token") } fn error_at(&mut self, line: usize, kind: ErrorKind) { if self.panic { return; } self.panic = true; self.errors.push(Error { kind, line }) } fn match_token(&mut self, token: &TokenKind) -> bool { if !self.check(token) { return false; } self.advance(); true } fn check(&self, token: &TokenKind) -> bool { return self.current().kind == *token; } fn synchronise(&mut self) { self.panic = false; while self.current().kind != TokenKind::Eof { if self.previous().kind == TokenKind::Semicolon { return; } match self.current().kind { TokenKind::Class | TokenKind::Fun | TokenKind::Var | TokenKind::For | TokenKind::If | TokenKind::While | TokenKind::Print | TokenKind::Return => return, _ => { self.advance(); } } } } fn expect_semicolon(&mut self, msg: &'static str) -> LoxResult<()> { consume!(self, TokenKind::Semicolon, ErrorKind::ExpectedToken(msg)); Ok(()) } } pub fn compile(code: &str) -> Result<(Interner, Chunk), Vec> { let chars = code.chars().collect::>(); let tokens = scanner::scan(&chars) .map_err(|errors| errors.into_iter().map(Into::into).collect::>())?; let mut compiler = Compiler { tokens: tokens.into_iter().peekable(), chunk: Default::default(), panic: false, errors: vec![], strings: Interner::with_capacity(1024), locals: Default::default(), current: None, previous: None, }; compiler.compile()?; if compiler.errors.is_empty() { Ok((compiler.strings, compiler.chunk)) } else { Err(compiler.errors) } }