diff options
Diffstat (limited to 'users/tazjin/rlox/src/bytecode/compiler.rs')
| -rw-r--r-- | users/tazjin/rlox/src/bytecode/compiler.rs | 163 |
1 files changed, 157 insertions, 6 deletions
diff --git a/users/tazjin/rlox/src/bytecode/compiler.rs b/users/tazjin/rlox/src/bytecode/compiler.rs index a6675d1c20b6..28b00cbb6ed8 100644 --- a/users/tazjin/rlox/src/bytecode/compiler.rs +++ b/users/tazjin/rlox/src/bytecode/compiler.rs @@ -8,12 +8,47 @@ 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<Local>, + scope_depth: usize, +} + struct Compiler<T: Iterator<Item = Token>> { tokens: T, chunk: Chunk, panic: bool, errors: Vec<Error>, strings: Interner, + locals: Locals, current: Option<Token>, previous: Option<Token>, @@ -200,7 +235,14 @@ impl<T: Iterator<Item = Token>> Compiler<T> { } fn define_variable(&mut self, var: usize) -> LoxResult<()> { - self.emit_op(OpCode::OpDefineGlobal(var)); + if self.locals.scope_depth == 0 { + self.emit_op(OpCode::OpDefineGlobal(var)); + } else { + self.locals.locals.last_mut() + .expect("fatal: variable not yet added at definition") + .depth = Depth::At(self.locals.scope_depth); + } + Ok(()) } @@ -221,6 +263,11 @@ impl<T: Iterator<Item = Token>> Compiler<T> { fn statement(&mut self) -> LoxResult<()> { if self.match_token(&TokenKind::Print) { self.print_statement() + } else if self.match_token(&TokenKind::LeftBrace) { + self.begin_scope(); + self.block()?; + self.end_scope(); + Ok(()) } else { self.expression_statement() } @@ -233,6 +280,37 @@ impl<T: Iterator<Item = Token>> Compiler<T> { 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")?; @@ -341,15 +419,29 @@ impl<T: Iterator<Item = Token>> Compiler<T> { } fn named_variable(&mut self) -> LoxResult<()> { - let ident = self.identifier_str(Self::previous)?; - let constant_id = - self.emit_constant(Value::String(ident.into()), false); + let local_idx = self.resolve_local(); + + let ident = if local_idx.is_some() { + None + } else { + Some(self.identifier_constant()?) + }; if self.match_token(&TokenKind::Equal) { self.expression()?; - self.emit_op(OpCode::OpSetGlobal(constant_id)); + match local_idx { + Some(idx) => self.emit_op(OpCode::OpSetLocal(idx)), + None => { + self.emit_op(OpCode::OpSetGlobal(ident.unwrap())); + } + } } else { - self.emit_op(OpCode::OpGetGlobal(constant_id)); + match local_idx { + Some(idx) => self.emit_op(OpCode::OpGetLocal(idx)), + None => { + self.emit_op(OpCode::OpGetGlobal(ident.unwrap())) + } + } } Ok(()) @@ -401,6 +493,59 @@ impl<T: Iterator<Item = Token>> Compiler<T> { Ok(self.strings.intern(ident)) } + fn identifier_constant(&mut self) -> LoxResult<usize> { + let ident = self.identifier_str(Self::previous)?; + Ok(self.emit_constant(Value::String(ident.into()), false)) + } + + fn resolve_local(&mut self) -> Option<usize> { + dbg!(&self.locals); + for (idx, local) in self.locals.locals.iter().enumerate().rev() { + if self.previous().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(idx); + } + } + + None + } + + fn add_local(&mut self, name: Token) -> LoxResult<()> { + let local = Local { + name, + depth: Depth::Unitialised, + }; + + self.locals.locals.push(local); + Ok(()) // TODO(tazjin): needed? + } + + 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) + } + fn parse_variable(&mut self) -> LoxResult<usize> { consume!( self, @@ -408,6 +553,11 @@ impl<T: Iterator<Item = Token>> Compiler<T> { ErrorKind::ExpectedToken("expected identifier") ); + self.declare_variable()?; + if self.locals.scope_depth > 0 { + return Ok(0); // TODO(tazjin): grr sentinel + } + let id = self.identifier_str(Self::previous)?; Ok(self.emit_constant(Value::String(id.into()), false)) } @@ -520,6 +670,7 @@ pub fn compile(code: &str) -> Result<(Interner, Chunk), Vec<Error>> { panic: false, errors: vec![], strings: Interner::with_capacity(1024), + locals: Default::default(), current: None, previous: None, }; |