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we (web engine): Experimental web browser project to understand the limits of Claude
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Rust
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Recursive-descent JavaScript parser with Pratt expression parsing.//!//! Transforms a token stream from the [`crate::lexer::Lexer`] into an//! [`crate::ast::Program`] AST.
use crate::ast::*;use crate::lexer::{LexError, Lexer, SourcePos, Span, Token, TokenKind};use std::fmt;
// ── Error ───────────────────────────────────────────────────
/// An error produced during parsing.#[derive(Debug, Clone, PartialEq)]pub struct ParseError { pub message: String, pub pos: SourcePos,}
impl fmt::Display for ParseError { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { write!( f, "ParseError at {}:{}: {}", self.pos.line, self.pos.col, self.message ) }}
impl From<LexError> for ParseError { fn from(e: LexError) -> Self { ParseError { message: e.message, pos: e.pos, } }}
// ── Parser ──────────────────────────────────────────────────
pub struct Parser { tokens: Vec<Token>, pos: usize, /// When false, `in` is not treated as a binary operator (for-init disambiguation). allow_in: bool,}
impl Parser { /// Parse source as a script. pub fn parse(source: &str) -> Result<Program, ParseError> { let tokens = Lexer::tokenize(source)?; let mut parser = Parser { tokens, pos: 0, allow_in: true, }; parser.parse_program(SourceType::Script) }
/// Parse source as a module. pub fn parse_module(source: &str) -> Result<Program, ParseError> { let tokens = Lexer::tokenize(source)?; let mut parser = Parser { tokens, pos: 0, allow_in: true, }; parser.parse_program(SourceType::Module) }
// ── Token navigation ────────────────────────────────────
fn peek(&self) -> &Token { &self.tokens[self.pos.min(self.tokens.len() - 1)] }
fn peek_kind(&self) -> &TokenKind { &self.peek().kind }
fn peek_ahead(&self, offset: usize) -> &TokenKind { let idx = (self.pos + offset).min(self.tokens.len() - 1); &self.tokens[idx].kind }
fn at(&self, kind: &TokenKind) -> bool { std::mem::discriminant(self.peek_kind()) == std::mem::discriminant(kind) }
fn at_eof(&self) -> bool { matches!(self.peek_kind(), TokenKind::Eof) }
fn advance(&mut self) -> Token { let tok = self.tokens[self.pos.min(self.tokens.len() - 1)].clone(); if self.pos < self.tokens.len() - 1 { self.pos += 1; } tok }
fn eat(&mut self, kind: &TokenKind) -> bool { if self.at(kind) { self.advance(); true } else { false } }
fn expect(&mut self, kind: &TokenKind) -> Result<Token, ParseError> { if self.at(kind) { Ok(self.advance()) } else { Err(self.error(format!("expected {:?}, found {:?}", kind, self.peek_kind()))) } }
fn expect_semicolon(&mut self) -> Result<(), ParseError> { if self.eat(&TokenKind::Semicolon) { return Ok(()); } // ASI: insert semicolon before `}`, at EOF, or after newline if matches!(self.peek_kind(), TokenKind::RBrace | TokenKind::Eof) || self.peek().preceded_by_newline { return Ok(()); } Err(self.error(format!("expected `;`, found {:?}", self.peek_kind()))) }
fn expect_identifier(&mut self) -> Result<String, ParseError> { match self.peek_kind().clone() { TokenKind::Identifier(name) => { self.advance(); Ok(name) } _ => Err(self.error(format!("expected identifier, found {:?}", self.peek_kind()))), } }
fn start_span(&self) -> SourcePos { self.peek().span.start }
fn end_span(&self) -> SourcePos { if self.pos > 0 { self.tokens[self.pos - 1].span.end } else { self.peek().span.start } }
fn span_from(&self, start: SourcePos) -> Span { Span { start, end: self.end_span(), } }
fn error(&self, message: String) -> ParseError { ParseError { message, pos: self.peek().span.start, } }
// ── Program ─────────────────────────────────────────────
fn parse_program(&mut self, source_type: SourceType) -> Result<Program, ParseError> { let start = self.start_span(); let mut body = Vec::new(); while !self.at_eof() { body.push(self.parse_statement_list_item()?); } Ok(Program { body, source_type, span: self.span_from(start), }) }
fn parse_statement_list_item(&mut self) -> Result<Stmt, ParseError> { match self.peek_kind() { TokenKind::Function => self.parse_function_declaration(), TokenKind::Class => self.parse_class_declaration(), TokenKind::Var | TokenKind::Let | TokenKind::Const => { self.parse_variable_declaration_stmt() } TokenKind::Async if matches!(self.peek_ahead(1), TokenKind::Function) && !self.tokens[self.pos + 1].preceded_by_newline => { self.parse_async_function_declaration() } TokenKind::Import if !matches!(self.peek_ahead(1), TokenKind::LParen | TokenKind::Dot) => { self.parse_import_declaration() } TokenKind::Export => self.parse_export_declaration(), _ => self.parse_statement(), } }
// ── Statements ──────────────────────────────────────────
fn parse_statement(&mut self) -> Result<Stmt, ParseError> { match self.peek_kind() { TokenKind::LBrace => self.parse_block_stmt(), TokenKind::Semicolon => { let start = self.start_span(); self.advance(); Ok(Stmt { kind: StmtKind::Empty, span: self.span_from(start), }) } TokenKind::If => self.parse_if(), TokenKind::For => self.parse_for(), TokenKind::While => self.parse_while(), TokenKind::Do => self.parse_do_while(), TokenKind::Switch => self.parse_switch(), TokenKind::Try => self.parse_try(), TokenKind::Return => self.parse_return(), TokenKind::Throw => self.parse_throw(), TokenKind::Break => self.parse_break(), TokenKind::Continue => self.parse_continue(), TokenKind::With => self.parse_with(), TokenKind::Debugger => { let start = self.start_span(); self.advance(); self.expect_semicolon()?; Ok(Stmt { kind: StmtKind::Debugger, span: self.span_from(start), }) } // Labeled statement: `ident: stmt` TokenKind::Identifier(_) if matches!(self.peek_ahead(1), TokenKind::Colon) => { self.parse_labeled() } // Variable declarations can also appear as statements TokenKind::Var | TokenKind::Let | TokenKind::Const => { self.parse_variable_declaration_stmt() } // Function/class declarations in statement position TokenKind::Function => self.parse_function_declaration(), TokenKind::Class => self.parse_class_declaration(), TokenKind::Async if matches!(self.peek_ahead(1), TokenKind::Function) && !self.tokens[self.pos + 1].preceded_by_newline => { self.parse_async_function_declaration() } _ => self.parse_expression_statement(), } }
fn parse_block_stmt(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); let body = self.parse_block_body()?; Ok(Stmt { kind: StmtKind::Block(body), span: self.span_from(start), }) }
fn parse_block_body(&mut self) -> Result<Vec<Stmt>, ParseError> { self.expect(&TokenKind::LBrace)?; let mut body = Vec::new(); while !self.at(&TokenKind::RBrace) && !self.at_eof() { body.push(self.parse_statement_list_item()?); } self.expect(&TokenKind::RBrace)?; Ok(body) }
fn parse_expression_statement(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); let expr = self.parse_expression()?; self.expect_semicolon()?; Ok(Stmt { kind: StmtKind::Expr(expr), span: self.span_from(start), }) }
fn parse_if(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::If)?; self.expect(&TokenKind::LParen)?; let test = self.parse_expression()?; self.expect(&TokenKind::RParen)?; let consequent = Box::new(self.parse_statement()?); let alternate = if self.eat(&TokenKind::Else) { Some(Box::new(self.parse_statement()?)) } else { None }; Ok(Stmt { kind: StmtKind::If { test, consequent, alternate, }, span: self.span_from(start), }) }
fn parse_while(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::While)?; self.expect(&TokenKind::LParen)?; let test = self.parse_expression()?; self.expect(&TokenKind::RParen)?; let body = Box::new(self.parse_statement()?); Ok(Stmt { kind: StmtKind::While { test, body }, span: self.span_from(start), }) }
fn parse_do_while(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Do)?; let body = Box::new(self.parse_statement()?); self.expect(&TokenKind::While)?; self.expect(&TokenKind::LParen)?; let test = self.parse_expression()?; self.expect(&TokenKind::RParen)?; self.expect_semicolon()?; Ok(Stmt { kind: StmtKind::DoWhile { body, test }, span: self.span_from(start), }) }
fn parse_for(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::For)?; self.expect(&TokenKind::LParen)?;
// Check for for-in/for-of with var/let/const if matches!( self.peek_kind(), TokenKind::Var | TokenKind::Let | TokenKind::Const ) { let var_kind = match self.peek_kind() { TokenKind::Var => VarKind::Var, TokenKind::Let => VarKind::Let, TokenKind::Const => VarKind::Const, _ => unreachable!(), }; self.advance(); let pattern = self.parse_binding_pattern()?;
if self.eat(&TokenKind::In) { let right = self.parse_expression()?; self.expect(&TokenKind::RParen)?; let body = Box::new(self.parse_statement()?); return Ok(Stmt { kind: StmtKind::ForIn { left: ForInOfLeft::VarDecl { kind: var_kind, pattern, }, right, body, }, span: self.span_from(start), }); } if self.eat(&TokenKind::Of) { let right = self.parse_assignment_expression()?; self.expect(&TokenKind::RParen)?; let body = Box::new(self.parse_statement()?); return Ok(Stmt { kind: StmtKind::ForOf { left: ForInOfLeft::VarDecl { kind: var_kind, pattern, }, right, body, is_await: false, }, span: self.span_from(start), }); }
// Regular for: parse remaining declarators let mut declarators = vec![VarDeclarator { span: pattern.span, init: if self.eat(&TokenKind::Assign) { Some(self.parse_assignment_expression_no_in()?) } else { None }, pattern, }]; while self.eat(&TokenKind::Comma) { declarators.push(self.parse_var_declarator_no_in()?); } self.expect(&TokenKind::Semicolon)?; let test = if self.at(&TokenKind::Semicolon) { None } else { Some(self.parse_expression()?) }; self.expect(&TokenKind::Semicolon)?; let update = if self.at(&TokenKind::RParen) { None } else { Some(self.parse_expression()?) }; self.expect(&TokenKind::RParen)?; let body = Box::new(self.parse_statement()?); return Ok(Stmt { kind: StmtKind::For { init: Some(ForInit::VarDecl { kind: var_kind, declarators, }), test, update, body, }, span: self.span_from(start), }); }
// No var/let/const if self.eat(&TokenKind::Semicolon) { // for(; ...) let test = if self.at(&TokenKind::Semicolon) { None } else { Some(self.parse_expression()?) }; self.expect(&TokenKind::Semicolon)?; let update = if self.at(&TokenKind::RParen) { None } else { Some(self.parse_expression()?) }; self.expect(&TokenKind::RParen)?; let body = Box::new(self.parse_statement()?); return Ok(Stmt { kind: StmtKind::For { init: None, test, update, body, }, span: self.span_from(start), }); }
// Expression init — might be for-in/for-of let old_allow_in = self.allow_in; self.allow_in = false; let init_expr = self.parse_expression()?; self.allow_in = old_allow_in;
if self.eat(&TokenKind::In) { let pattern = self.expr_to_pattern(&init_expr)?; let right = self.parse_expression()?; self.expect(&TokenKind::RParen)?; let body = Box::new(self.parse_statement()?); return Ok(Stmt { kind: StmtKind::ForIn { left: ForInOfLeft::Pattern(pattern), right, body, }, span: self.span_from(start), }); } if self.eat(&TokenKind::Of) { let pattern = self.expr_to_pattern(&init_expr)?; let right = self.parse_assignment_expression()?; self.expect(&TokenKind::RParen)?; let body = Box::new(self.parse_statement()?); return Ok(Stmt { kind: StmtKind::ForOf { left: ForInOfLeft::Pattern(pattern), right, body, is_await: false, }, span: self.span_from(start), }); }
self.expect(&TokenKind::Semicolon)?; let test = if self.at(&TokenKind::Semicolon) { None } else { Some(self.parse_expression()?) }; self.expect(&TokenKind::Semicolon)?; let update = if self.at(&TokenKind::RParen) { None } else { Some(self.parse_expression()?) }; self.expect(&TokenKind::RParen)?; let body = Box::new(self.parse_statement()?); Ok(Stmt { kind: StmtKind::For { init: Some(ForInit::Expr(init_expr)), test, update, body, }, span: self.span_from(start), }) }
fn parse_switch(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Switch)?; self.expect(&TokenKind::LParen)?; let discriminant = self.parse_expression()?; self.expect(&TokenKind::RParen)?; self.expect(&TokenKind::LBrace)?; let mut cases = Vec::new(); while !self.at(&TokenKind::RBrace) && !self.at_eof() { let case_start = self.start_span(); let test = if self.eat(&TokenKind::Case) { Some(self.parse_expression()?) } else { self.expect(&TokenKind::Default)?; None }; self.expect(&TokenKind::Colon)?; let mut consequent = Vec::new(); while !matches!( self.peek_kind(), TokenKind::Case | TokenKind::Default | TokenKind::RBrace ) && !self.at_eof() { consequent.push(self.parse_statement_list_item()?); } cases.push(SwitchCase { test, consequent, span: self.span_from(case_start), }); } self.expect(&TokenKind::RBrace)?; Ok(Stmt { kind: StmtKind::Switch { discriminant, cases, }, span: self.span_from(start), }) }
fn parse_try(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Try)?; let block = self.parse_block_body()?;
let handler = if self.eat(&TokenKind::Catch) { let catch_start = self.start_span(); let param = if self.eat(&TokenKind::LParen) { let pat = self.parse_binding_pattern()?; self.expect(&TokenKind::RParen)?; Some(pat) } else { None }; let body = self.parse_block_body()?; Some(CatchClause { param, body, span: self.span_from(catch_start), }) } else { None };
let finalizer = if self.eat(&TokenKind::Finally) { Some(self.parse_block_body()?) } else { None };
if handler.is_none() && finalizer.is_none() { return Err(self.error("try requires catch or finally".into())); }
Ok(Stmt { kind: StmtKind::Try { block, handler, finalizer, }, span: self.span_from(start), }) }
fn parse_return(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Return)?; // Restricted production: newline after return inserts semicolon let argument = if matches!( self.peek_kind(), TokenKind::Semicolon | TokenKind::RBrace | TokenKind::Eof ) || self.peek().preceded_by_newline { None } else { Some(self.parse_expression()?) }; self.expect_semicolon()?; Ok(Stmt { kind: StmtKind::Return(argument), span: self.span_from(start), }) }
fn parse_throw(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Throw)?; if self.peek().preceded_by_newline { return Err(ParseError { message: "newline not allowed after throw".into(), pos: self.peek().span.start, }); } let argument = self.parse_expression()?; self.expect_semicolon()?; Ok(Stmt { kind: StmtKind::Throw(argument), span: self.span_from(start), }) }
fn parse_break(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Break)?; let label = if !self.peek().preceded_by_newline { if let TokenKind::Identifier(name) = self.peek_kind().clone() { self.advance(); Some(name) } else { None } } else { None }; self.expect_semicolon()?; Ok(Stmt { kind: StmtKind::Break(label), span: self.span_from(start), }) }
fn parse_continue(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Continue)?; let label = if !self.peek().preceded_by_newline { if let TokenKind::Identifier(name) = self.peek_kind().clone() { self.advance(); Some(name) } else { None } } else { None }; self.expect_semicolon()?; Ok(Stmt { kind: StmtKind::Continue(label), span: self.span_from(start), }) }
fn parse_labeled(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); let label = self.expect_identifier()?; self.expect(&TokenKind::Colon)?; let body = Box::new(self.parse_statement()?); Ok(Stmt { kind: StmtKind::Labeled { label, body }, span: self.span_from(start), }) }
fn parse_with(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::With)?; self.expect(&TokenKind::LParen)?; let object = self.parse_expression()?; self.expect(&TokenKind::RParen)?; let body = Box::new(self.parse_statement()?); Ok(Stmt { kind: StmtKind::With { object, body }, span: self.span_from(start), }) }
// ── Variable declarations ───────────────────────────────
fn parse_variable_declaration_stmt(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); let kind = match self.peek_kind() { TokenKind::Var => VarKind::Var, TokenKind::Let => VarKind::Let, TokenKind::Const => VarKind::Const, _ => return Err(self.error("expected var, let, or const".into())), }; self.advance(); let mut declarators = vec![self.parse_var_declarator()?]; while self.eat(&TokenKind::Comma) { declarators.push(self.parse_var_declarator()?); } self.expect_semicolon()?; Ok(Stmt { kind: StmtKind::VarDecl { kind, declarators }, span: self.span_from(start), }) }
fn parse_var_declarator(&mut self) -> Result<VarDeclarator, ParseError> { let start = self.start_span(); let pattern = self.parse_binding_pattern()?; let init = if self.eat(&TokenKind::Assign) { Some(self.parse_assignment_expression()?) } else { None }; Ok(VarDeclarator { pattern, init, span: self.span_from(start), }) }
fn parse_var_declarator_no_in(&mut self) -> Result<VarDeclarator, ParseError> { let start = self.start_span(); let pattern = self.parse_binding_pattern()?; let init = if self.eat(&TokenKind::Assign) { Some(self.parse_assignment_expression_no_in()?) } else { None }; Ok(VarDeclarator { pattern, init, span: self.span_from(start), }) }
// ── Binding patterns (destructuring) ────────────────────
fn parse_binding_pattern(&mut self) -> Result<Pattern, ParseError> { match self.peek_kind() { TokenKind::LBracket => self.parse_array_pattern(), TokenKind::LBrace => self.parse_object_pattern(), _ => { let start = self.start_span(); let name = self.expect_identifier()?; Ok(Pattern { kind: PatternKind::Identifier(name), span: self.span_from(start), }) } } }
fn parse_array_pattern(&mut self) -> Result<Pattern, ParseError> { let start = self.start_span(); self.expect(&TokenKind::LBracket)?; let mut elements = Vec::new(); let mut rest = None; while !self.at(&TokenKind::RBracket) && !self.at_eof() { if self.eat(&TokenKind::Comma) { elements.push(None); continue; } if self.at(&TokenKind::Ellipsis) { self.advance(); rest = Some(Box::new(self.parse_binding_pattern()?)); self.eat(&TokenKind::Comma); // trailing comma after rest break; } let mut pat = self.parse_binding_pattern()?; if self.eat(&TokenKind::Assign) { let right = self.parse_assignment_expression()?; let span = Span { start: pat.span.start, end: right.span.end, }; pat = Pattern { kind: PatternKind::Assign { left: Box::new(pat), right: Box::new(right), }, span, }; } elements.push(Some(pat)); if !self.eat(&TokenKind::Comma) { break; } } self.expect(&TokenKind::RBracket)?; Ok(Pattern { kind: PatternKind::Array { elements, rest }, span: self.span_from(start), }) }
fn parse_object_pattern(&mut self) -> Result<Pattern, ParseError> { let start = self.start_span(); self.expect(&TokenKind::LBrace)?; let mut properties = Vec::new(); let mut rest = None; while !self.at(&TokenKind::RBrace) && !self.at_eof() { if self.at(&TokenKind::Ellipsis) { self.advance(); rest = Some(Box::new(self.parse_binding_pattern()?)); self.eat(&TokenKind::Comma); break; } let prop_start = self.start_span(); let (key, computed) = self.parse_property_name()?; if self.eat(&TokenKind::Colon) { // { key: pattern } let mut value = self.parse_binding_pattern()?; if self.eat(&TokenKind::Assign) { let right = self.parse_assignment_expression()?; let span = Span { start: value.span.start, end: right.span.end, }; value = Pattern { kind: PatternKind::Assign { left: Box::new(value), right: Box::new(right), }, span, }; } properties.push(ObjectPatternProp { key, value, computed, shorthand: false, span: self.span_from(prop_start), }); } else { // Shorthand: { name } or { name = default } let name = match &key { PropertyKey::Identifier(n) => n.clone(), _ => return Err(self.error("shorthand properties require identifier".into())), }; let ident_span = self.span_from(prop_start); let mut value = Pattern { kind: PatternKind::Identifier(name.clone()), span: ident_span, }; if self.eat(&TokenKind::Assign) { let right = self.parse_assignment_expression()?; let span = Span { start: value.span.start, end: right.span.end, }; value = Pattern { kind: PatternKind::Assign { left: Box::new(value), right: Box::new(right), }, span, }; } properties.push(ObjectPatternProp { key, value, computed, shorthand: true, span: self.span_from(prop_start), }); } if !self.eat(&TokenKind::Comma) { break; } } self.expect(&TokenKind::RBrace)?; Ok(Pattern { kind: PatternKind::Object { properties, rest }, span: self.span_from(start), }) }
// ── Function declarations ───────────────────────────────
fn parse_function_declaration(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Function)?; let is_generator = self.eat(&TokenKind::Star); let id = Some(self.expect_identifier()?); let (params, body) = self.parse_function_params_and_body()?; Ok(Stmt { kind: StmtKind::FunctionDecl(FunctionDef { id, params, body, is_async: false, is_generator, }), span: self.span_from(start), }) }
fn parse_async_function_declaration(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Async)?; self.expect(&TokenKind::Function)?; let is_generator = self.eat(&TokenKind::Star); let id = Some(self.expect_identifier()?); let (params, body) = self.parse_function_params_and_body()?; Ok(Stmt { kind: StmtKind::FunctionDecl(FunctionDef { id, params, body, is_async: true, is_generator, }), span: self.span_from(start), }) }
fn parse_function_params_and_body(&mut self) -> Result<(Vec<Pattern>, Vec<Stmt>), ParseError> { self.expect(&TokenKind::LParen)?; let params = self.parse_formal_parameters()?; self.expect(&TokenKind::RParen)?; let body = self.parse_block_body()?; Ok((params, body)) }
fn parse_formal_parameters(&mut self) -> Result<Vec<Pattern>, ParseError> { let mut params = Vec::new(); while !self.at(&TokenKind::RParen) && !self.at_eof() { if self.at(&TokenKind::Ellipsis) { self.advance(); params.push(self.parse_binding_pattern()?); self.eat(&TokenKind::Comma); break; } let mut pat = self.parse_binding_pattern()?; if self.eat(&TokenKind::Assign) { let right = self.parse_assignment_expression()?; let span = Span { start: pat.span.start, end: right.span.end, }; pat = Pattern { kind: PatternKind::Assign { left: Box::new(pat), right: Box::new(right), }, span, }; } params.push(pat); if !self.eat(&TokenKind::Comma) { break; } } Ok(params) }
// ── Class declarations ──────────────────────────────────
fn parse_class_declaration(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); let class_def = self.parse_class(true)?; Ok(Stmt { kind: StmtKind::ClassDecl(class_def), span: self.span_from(start), }) }
fn parse_class(&mut self, require_name: bool) -> Result<ClassDef, ParseError> { self.expect(&TokenKind::Class)?; let id = if require_name { Some(self.expect_identifier()?) } else if let TokenKind::Identifier(_) = self.peek_kind() { Some(self.expect_identifier()?) } else { None }; let super_class = if self.eat(&TokenKind::Extends) { Some(Box::new(self.parse_left_hand_side_expression()?)) } else { None }; let body = self.parse_class_body()?; Ok(ClassDef { id, super_class, body, }) }
fn parse_class_body(&mut self) -> Result<Vec<ClassMember>, ParseError> { self.expect(&TokenKind::LBrace)?; let mut members = Vec::new(); while !self.at(&TokenKind::RBrace) && !self.at_eof() { if self.eat(&TokenKind::Semicolon) { continue; } members.push(self.parse_class_member()?); } self.expect(&TokenKind::RBrace)?; Ok(members) }
fn parse_class_member(&mut self) -> Result<ClassMember, ParseError> { let start = self.start_span(); let is_static = self.eat(&TokenKind::Static);
// Check for getter/setter if let TokenKind::Identifier(ref name) = self.peek_kind().clone() { if (name == "get" || name == "set") && !matches!( self.peek_ahead(1), TokenKind::LParen | TokenKind::Assign | TokenKind::Semicolon ) { let kind = if name == "get" { MethodKind::Get } else { MethodKind::Set }; self.advance(); let (key, computed) = self.parse_property_name()?; let (params, body) = self.parse_function_params_and_body()?; return Ok(ClassMember { kind: ClassMemberKind::Method { key, value: FunctionDef { id: None, params, body, is_async: false, is_generator: false, }, kind, is_static, computed, }, span: self.span_from(start), }); } }
// Generator method let is_generator = self.eat(&TokenKind::Star);
// Async method let is_async = if !is_generator && matches!(self.peek_kind(), TokenKind::Async) && !matches!( self.peek_ahead(1), TokenKind::LParen | TokenKind::Assign | TokenKind::Semicolon ) { self.advance(); true } else { false };
let is_generator = is_generator || (is_async && self.eat(&TokenKind::Star));
let (key, computed) = self.parse_property_name()?;
// Check for constructor let method_kind = if !is_static && !computed && key == PropertyKey::Identifier("constructor".into()) { MethodKind::Constructor } else { MethodKind::Method };
if self.at(&TokenKind::LParen) { let (params, body) = self.parse_function_params_and_body()?; Ok(ClassMember { kind: ClassMemberKind::Method { key, value: FunctionDef { id: None, params, body, is_async, is_generator, }, kind: method_kind, is_static, computed, }, span: self.span_from(start), }) } else { // Class field let value = if self.eat(&TokenKind::Assign) { Some(self.parse_assignment_expression()?) } else { None }; self.expect_semicolon()?; Ok(ClassMember { kind: ClassMemberKind::Property { key, value, is_static, computed, }, span: self.span_from(start), }) } }
// ── Import / Export ─────────────────────────────────────
fn parse_import_declaration(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Import)?;
// `import "source"` — side-effect import if let TokenKind::String(source) = self.peek_kind().clone() { self.advance(); self.expect_semicolon()?; return Ok(Stmt { kind: StmtKind::Import { specifiers: vec![], source, }, span: self.span_from(start), }); }
let mut specifiers = Vec::new();
// `import * as ns from "source"` if self.eat(&TokenKind::Star) { self.expect_identifier_matching("as")?; let local = self.expect_identifier()?; specifiers.push(ImportSpecifier::Namespace(local)); } // `import { a, b as c } from "source"` else if self.at(&TokenKind::LBrace) { self.advance(); while !self.at(&TokenKind::RBrace) && !self.at_eof() { let imported = self.expect_identifier()?; let local = if self.eat_identifier_matching("as") { self.expect_identifier()? } else { imported.clone() }; specifiers.push(ImportSpecifier::Named { imported, local }); if !self.eat(&TokenKind::Comma) { break; } } self.expect(&TokenKind::RBrace)?; } // `import defaultExport from "source"` or `import defaultExport, { ... } from "source"` else { let default_name = self.expect_identifier()?; specifiers.push(ImportSpecifier::Default(default_name));
if self.eat(&TokenKind::Comma) { if self.eat(&TokenKind::Star) { self.expect_identifier_matching("as")?; let local = self.expect_identifier()?; specifiers.push(ImportSpecifier::Namespace(local)); } else { self.expect(&TokenKind::LBrace)?; while !self.at(&TokenKind::RBrace) && !self.at_eof() { let imported = self.expect_identifier()?; let local = if self.eat_identifier_matching("as") { self.expect_identifier()? } else { imported.clone() }; specifiers.push(ImportSpecifier::Named { imported, local }); if !self.eat(&TokenKind::Comma) { break; } } self.expect(&TokenKind::RBrace)?; } } }
self.expect_identifier_matching("from")?; let source = match self.peek_kind().clone() { TokenKind::String(s) => { self.advance(); s } _ => return Err(self.error("expected module source string".into())), }; self.expect_semicolon()?; Ok(Stmt { kind: StmtKind::Import { specifiers, source }, span: self.span_from(start), }) }
fn parse_export_declaration(&mut self) -> Result<Stmt, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Export)?;
// `export default ...` if self.eat(&TokenKind::Default) { if matches!(self.peek_kind(), TokenKind::Function) { // Named function → declaration, anonymous → default expression let has_name = matches!(self.peek_ahead(1), TokenKind::Identifier(_)) || (matches!(self.peek_ahead(1), TokenKind::Star) && matches!(self.peek_ahead(2), TokenKind::Identifier(_))); if has_name { let decl = self.parse_function_declaration()?; return Ok(Stmt { kind: StmtKind::Export(ExportDecl::Declaration(Box::new(decl))), span: self.span_from(start), }); } let expr = self.parse_function_expression()?; return Ok(Stmt { kind: StmtKind::Export(ExportDecl::Default(expr)), span: self.span_from(start), }); } if matches!(self.peek_kind(), TokenKind::Class) { // Named class → declaration, anonymous → default expression if matches!(self.peek_ahead(1), TokenKind::Identifier(_)) { let decl = self.parse_class_declaration()?; return Ok(Stmt { kind: StmtKind::Export(ExportDecl::Declaration(Box::new(decl))), span: self.span_from(start), }); } let expr = self.parse_class_expression()?; return Ok(Stmt { kind: StmtKind::Export(ExportDecl::Default(expr)), span: self.span_from(start), }); } let expr = self.parse_assignment_expression()?; self.expect_semicolon()?; return Ok(Stmt { kind: StmtKind::Export(ExportDecl::Default(expr)), span: self.span_from(start), }); }
// `export * from "source"` if self.eat(&TokenKind::Star) { self.expect_identifier_matching("from")?; let source = match self.peek_kind().clone() { TokenKind::String(s) => { self.advance(); s } _ => return Err(self.error("expected module source string".into())), }; self.expect_semicolon()?; return Ok(Stmt { kind: StmtKind::Export(ExportDecl::AllFrom(source)), span: self.span_from(start), }); }
// `export { a, b as c } [from "source"]` if self.at(&TokenKind::LBrace) { self.advance(); let mut specifiers = Vec::new(); while !self.at(&TokenKind::RBrace) && !self.at_eof() { let local = self.expect_identifier()?; let exported = if self.eat_identifier_matching("as") { self.expect_identifier()? } else { local.clone() }; specifiers.push(ExportSpecifier { local, exported }); if !self.eat(&TokenKind::Comma) { break; } } self.expect(&TokenKind::RBrace)?; let source = if self.eat_identifier_matching("from") { match self.peek_kind().clone() { TokenKind::String(s) => { self.advance(); Some(s) } _ => return Err(self.error("expected module source string".into())), } } else { None }; self.expect_semicolon()?; return Ok(Stmt { kind: StmtKind::Export(ExportDecl::Named { specifiers, source }), span: self.span_from(start), }); }
// `export var/let/const/function/class ...` let decl = self.parse_statement_list_item()?; Ok(Stmt { kind: StmtKind::Export(ExportDecl::Declaration(Box::new(decl))), span: self.span_from(start), }) }
// ── Helper for contextual keywords ──────────────────────
fn expect_identifier_matching(&mut self, expected: &str) -> Result<(), ParseError> { match self.peek_kind().clone() { TokenKind::Identifier(ref name) if name == expected => { self.advance(); Ok(()) } _ => Err(self.error(format!("expected '{}'", expected))), } }
fn eat_identifier_matching(&mut self, expected: &str) -> bool { if let TokenKind::Identifier(ref name) = self.peek_kind() { if name == expected { self.advance(); return true; } } false }
// ── Expressions ─────────────────────────────────────────
fn parse_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); let expr = self.parse_assignment_expression()?; if !self.at(&TokenKind::Comma) { return Ok(expr); } let mut exprs = vec![expr]; while self.eat(&TokenKind::Comma) { exprs.push(self.parse_assignment_expression()?); } Ok(Expr { kind: ExprKind::Sequence(exprs), span: self.span_from(start), }) }
fn parse_assignment_expression(&mut self) -> Result<Expr, ParseError> { // Check for arrow function: `x => ...` or `async x => ...` if let TokenKind::Identifier(ref name) = self.peek_kind().clone() { if matches!(self.peek_ahead(1), TokenKind::Arrow) && !self.peek().preceded_by_newline { let param_start = self.start_span(); let name = name.clone(); self.advance(); // identifier self.advance(); // => let params = vec![Pattern { kind: PatternKind::Identifier(name), span: self.span_from(param_start), }]; return self.parse_arrow_body(param_start, params, false); } }
// Check for `async x => ...` or `async (...)` arrow if matches!(self.peek_kind(), TokenKind::Async) && !self.peek().preceded_by_newline { if let TokenKind::Identifier(_) = self.peek_ahead(1) { if matches!(self.peek_ahead(2), TokenKind::Arrow) { let start = self.start_span(); self.advance(); // async let param_start = self.start_span(); let name = self.expect_identifier()?; self.advance(); // => let params = vec![Pattern { kind: PatternKind::Identifier(name), span: self.span_from(param_start), }]; return self.parse_arrow_body(start, params, true); } } }
let start = self.start_span(); let left = self.parse_conditional_expression()?;
// Check for arrow function after parenthesized expr: `(a, b) => ...` if matches!(self.peek_kind(), TokenKind::Arrow) && !self.peek().preceded_by_newline { self.advance(); // => let params = self.expr_to_params(&left)?; return self.parse_arrow_body(start, params, false); }
// Assignment if let Some(op) = self.peek_assign_op() { self.advance(); let right = self.parse_assignment_expression()?; return Ok(Expr { span: self.span_from(start), kind: ExprKind::Assignment { op, left: Box::new(left), right: Box::new(right), }, }); }
Ok(left) }
fn parse_assignment_expression_no_in(&mut self) -> Result<Expr, ParseError> { let old = self.allow_in; self.allow_in = false; let result = self.parse_assignment_expression(); self.allow_in = old; result }
fn parse_arrow_body( &mut self, start: SourcePos, params: Vec<Pattern>, is_async: bool, ) -> Result<Expr, ParseError> { let body = if self.at(&TokenKind::LBrace) { ArrowBody::Block(self.parse_block_body()?) } else { ArrowBody::Expr(Box::new(self.parse_assignment_expression()?)) }; Ok(Expr { kind: ExprKind::Arrow { params, body, is_async, }, span: self.span_from(start), }) }
fn parse_conditional_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); let expr = self.parse_binary_expression(0)?; if !self.eat(&TokenKind::Question) { return Ok(expr); } let consequent = self.parse_assignment_expression()?; self.expect(&TokenKind::Colon)?; let alternate = self.parse_assignment_expression()?; Ok(Expr { kind: ExprKind::Conditional { test: Box::new(expr), consequent: Box::new(consequent), alternate: Box::new(alternate), }, span: self.span_from(start), }) }
// ── Pratt expression parsing ────────────────────────────
fn parse_binary_expression(&mut self, min_bp: u8) -> Result<Expr, ParseError> { let start = self.start_span(); let mut left = self.parse_unary_expression()?;
loop { let Some((op, left_bp, right_bp)) = self.peek_binary_op() else { break; }; if left_bp < min_bp { break; } self.advance();
let right = self.parse_binary_expression(right_bp)?; let span = self.span_from(start);
left = match op { BinOrLogical::Binary(op) => Expr { kind: ExprKind::Binary { op, left: Box::new(left), right: Box::new(right), }, span, }, BinOrLogical::Logical(op) => Expr { kind: ExprKind::Logical { op, left: Box::new(left), right: Box::new(right), }, span, }, }; }
Ok(left) }
fn parse_unary_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); match self.peek_kind() { TokenKind::Minus => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Unary { op: UnaryOp::Minus, argument: Box::new(arg), }, span: self.span_from(start), }) } TokenKind::Plus => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Unary { op: UnaryOp::Plus, argument: Box::new(arg), }, span: self.span_from(start), }) } TokenKind::Not => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Unary { op: UnaryOp::Not, argument: Box::new(arg), }, span: self.span_from(start), }) } TokenKind::Tilde => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Unary { op: UnaryOp::BitwiseNot, argument: Box::new(arg), }, span: self.span_from(start), }) } TokenKind::Typeof => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Unary { op: UnaryOp::Typeof, argument: Box::new(arg), }, span: self.span_from(start), }) } TokenKind::Void => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Unary { op: UnaryOp::Void, argument: Box::new(arg), }, span: self.span_from(start), }) } TokenKind::Delete => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Unary { op: UnaryOp::Delete, argument: Box::new(arg), }, span: self.span_from(start), }) } TokenKind::PlusPlus => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Update { op: UpdateOp::Increment, argument: Box::new(arg), prefix: true, }, span: self.span_from(start), }) } TokenKind::MinusMinus => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Update { op: UpdateOp::Decrement, argument: Box::new(arg), prefix: true, }, span: self.span_from(start), }) } TokenKind::Await => { self.advance(); let arg = self.parse_unary_expression()?; Ok(Expr { kind: ExprKind::Await(Box::new(arg)), span: self.span_from(start), }) } _ => self.parse_postfix_expression(), } }
fn parse_postfix_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); let mut expr = self.parse_call_expression()?;
if !self.peek().preceded_by_newline { if matches!(self.peek_kind(), TokenKind::PlusPlus) { self.advance(); expr = Expr { kind: ExprKind::Update { op: UpdateOp::Increment, argument: Box::new(expr), prefix: false, }, span: self.span_from(start), }; } else if matches!(self.peek_kind(), TokenKind::MinusMinus) { self.advance(); expr = Expr { kind: ExprKind::Update { op: UpdateOp::Decrement, argument: Box::new(expr), prefix: false, }, span: self.span_from(start), }; } }
Ok(expr) }
fn parse_call_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span();
if matches!(self.peek_kind(), TokenKind::New) { return self.parse_new_expression(); }
let mut expr = self.parse_primary_expression()?;
loop { match self.peek_kind() { TokenKind::Dot => { self.advance(); let prop_start = self.start_span(); let name = self.expect_identifier()?; expr = Expr { kind: ExprKind::Member { object: Box::new(expr), property: Box::new(Expr { kind: ExprKind::Identifier(name), span: self.span_from(prop_start), }), computed: false, }, span: self.span_from(start), }; } TokenKind::LBracket => { self.advance(); let prop = self.parse_expression()?; self.expect(&TokenKind::RBracket)?; expr = Expr { kind: ExprKind::Member { object: Box::new(expr), property: Box::new(prop), computed: true, }, span: self.span_from(start), }; } TokenKind::LParen => { let arguments = self.parse_arguments()?; expr = Expr { kind: ExprKind::Call { callee: Box::new(expr), arguments, }, span: self.span_from(start), }; } TokenKind::QuestionDot => { self.advance(); // ?. can be followed by identifier, [expr], or (args) match self.peek_kind() { TokenKind::LBracket => { self.advance(); let prop = self.parse_expression()?; self.expect(&TokenKind::RBracket)?; expr = Expr { kind: ExprKind::Member { object: Box::new(Expr { kind: ExprKind::OptionalChain { base: Box::new(expr.clone()), }, span: self.span_from(start), }), property: Box::new(prop), computed: true, }, span: self.span_from(start), }; } TokenKind::LParen => { let arguments = self.parse_arguments()?; expr = Expr { kind: ExprKind::Call { callee: Box::new(Expr { kind: ExprKind::OptionalChain { base: Box::new(expr.clone()), }, span: self.span_from(start), }), arguments, }, span: self.span_from(start), }; } _ => { let prop_start = self.start_span(); let name = self.expect_identifier()?; expr = Expr { kind: ExprKind::Member { object: Box::new(Expr { kind: ExprKind::OptionalChain { base: Box::new(expr.clone()), }, span: self.span_from(start), }), property: Box::new(Expr { kind: ExprKind::Identifier(name), span: self.span_from(prop_start), }), computed: false, }, span: self.span_from(start), }; } } } TokenKind::TemplateFull(_) | TokenKind::TemplateHead(_) => { let quasi = self.parse_template_literal()?; expr = Expr { kind: ExprKind::TaggedTemplate { tag: Box::new(expr), quasi: Box::new(quasi), }, span: self.span_from(start), }; } _ => break, } }
Ok(expr) }
fn parse_new_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); self.expect(&TokenKind::New)?;
// new new Foo() → new (new Foo()) if matches!(self.peek_kind(), TokenKind::New) { let callee = self.parse_new_expression()?; return Ok(Expr { kind: ExprKind::New { callee: Box::new(callee), arguments: vec![], }, span: self.span_from(start), }); }
let callee = self.parse_primary_expression()?; // Allow member access on the callee let callee = self.parse_member_chain(start, callee)?; let arguments = if self.at(&TokenKind::LParen) { self.parse_arguments()? } else { vec![] }; Ok(Expr { kind: ExprKind::New { callee: Box::new(callee), arguments, }, span: self.span_from(start), }) }
fn parse_member_chain(&mut self, start: SourcePos, mut expr: Expr) -> Result<Expr, ParseError> { loop { match self.peek_kind() { TokenKind::Dot => { self.advance(); let prop_start = self.start_span(); let name = self.expect_identifier()?; expr = Expr { kind: ExprKind::Member { object: Box::new(expr), property: Box::new(Expr { kind: ExprKind::Identifier(name), span: self.span_from(prop_start), }), computed: false, }, span: self.span_from(start), }; } TokenKind::LBracket => { self.advance(); let prop = self.parse_expression()?; self.expect(&TokenKind::RBracket)?; expr = Expr { kind: ExprKind::Member { object: Box::new(expr), property: Box::new(prop), computed: true, }, span: self.span_from(start), }; } _ => break, } } Ok(expr) }
fn parse_left_hand_side_expression(&mut self) -> Result<Expr, ParseError> { self.parse_call_expression() }
fn parse_arguments(&mut self) -> Result<Vec<Expr>, ParseError> { self.expect(&TokenKind::LParen)?; let mut args = Vec::new(); while !self.at(&TokenKind::RParen) && !self.at_eof() { if self.at(&TokenKind::Ellipsis) { let start = self.start_span(); self.advance(); let arg = self.parse_assignment_expression()?; args.push(Expr { kind: ExprKind::Spread(Box::new(arg)), span: self.span_from(start), }); } else { args.push(self.parse_assignment_expression()?); } if !self.eat(&TokenKind::Comma) { break; } } self.expect(&TokenKind::RParen)?; Ok(args) }
// ── Primary expressions ─────────────────────────────────
fn parse_primary_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); match self.peek_kind().clone() { TokenKind::Number(n) => { self.advance(); Ok(Expr { kind: ExprKind::Number(n), span: self.span_from(start), }) } TokenKind::String(s) => { self.advance(); Ok(Expr { kind: ExprKind::String(s), span: self.span_from(start), }) } TokenKind::True => { self.advance(); Ok(Expr { kind: ExprKind::Bool(true), span: self.span_from(start), }) } TokenKind::False => { self.advance(); Ok(Expr { kind: ExprKind::Bool(false), span: self.span_from(start), }) } TokenKind::Null => { self.advance(); Ok(Expr { kind: ExprKind::Null, span: self.span_from(start), }) } TokenKind::This => { self.advance(); Ok(Expr { kind: ExprKind::This, span: self.span_from(start), }) } TokenKind::Identifier(name) => { self.advance(); Ok(Expr { kind: ExprKind::Identifier(name), span: self.span_from(start), }) } TokenKind::LParen => self.parse_parenthesized_expression(), TokenKind::LBracket => self.parse_array_expression(), TokenKind::LBrace => self.parse_object_expression(), TokenKind::Function => self.parse_function_expression(), TokenKind::Class => self.parse_class_expression(), TokenKind::Async => { // async function expression if matches!(self.peek_ahead(1), TokenKind::Function) && !self.tokens[self.pos + 1].preceded_by_newline { return self.parse_async_function_expression(); } // Otherwise treat 'async' as an identifier self.advance(); Ok(Expr { kind: ExprKind::Identifier("async".into()), span: self.span_from(start), }) } TokenKind::TemplateFull(_) | TokenKind::TemplateHead(_) => { self.parse_template_literal() } TokenKind::RegExp { pattern, flags } => { self.advance(); Ok(Expr { kind: ExprKind::RegExp { pattern, flags }, span: self.span_from(start), }) } TokenKind::Yield => { self.advance(); let delegate = self.eat(&TokenKind::Star); let argument = if !self.peek().preceded_by_newline && !matches!( self.peek_kind(), TokenKind::Semicolon | TokenKind::RBrace | TokenKind::RParen | TokenKind::RBracket | TokenKind::Colon | TokenKind::Comma | TokenKind::Eof ) { Some(Box::new(self.parse_assignment_expression()?)) } else { None }; Ok(Expr { kind: ExprKind::Yield { argument, delegate }, span: self.span_from(start), }) } TokenKind::Super => { self.advance(); Ok(Expr { kind: ExprKind::Identifier("super".into()), span: self.span_from(start), }) } TokenKind::Import => { // import() call expression self.advance(); Ok(Expr { kind: ExprKind::Identifier("import".into()), span: self.span_from(start), }) } _ => Err(self.error(format!("unexpected token {:?}", self.peek_kind()))), } }
fn parse_parenthesized_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); self.expect(&TokenKind::LParen)?;
// Empty parens: `() => ...` if self.at(&TokenKind::RParen) { self.advance(); // Must be arrow if !matches!(self.peek_kind(), TokenKind::Arrow) { return Err(self.error("unexpected empty parentheses".into())); } // Arrow will be handled by caller return Ok(Expr { kind: ExprKind::Sequence(vec![]), span: self.span_from(start), }); }
// `(...rest) => ...` if self.at(&TokenKind::Ellipsis) { // This must be an arrow parameter list with rest let rest_start = self.start_span(); self.advance(); let rest_pat = self.parse_binding_pattern()?; self.expect(&TokenKind::RParen)?; // Must be followed by => if !matches!(self.peek_kind(), TokenKind::Arrow) { return Err(self.error("expected '=>'".into())); } let _ = rest_pat; // Will be handled as pattern // Return a marker that the arrow handler will convert return Ok(Expr { kind: ExprKind::Spread(Box::new(Expr { kind: match rest_pat.kind { PatternKind::Identifier(name) => ExprKind::Identifier(name), _ => { return Err(ParseError { message: "complex rest pattern in arrow".into(), pos: rest_start, }) } }, span: rest_pat.span, })), span: self.span_from(start), }); }
let expr = self.parse_expression()?; self.expect(&TokenKind::RParen)?; Ok(expr) }
fn parse_array_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); self.expect(&TokenKind::LBracket)?; let mut elements = Vec::new(); while !self.at(&TokenKind::RBracket) && !self.at_eof() { if self.eat(&TokenKind::Comma) { elements.push(None); continue; } if self.at(&TokenKind::Ellipsis) { let spread_start = self.start_span(); self.advance(); let arg = self.parse_assignment_expression()?; elements.push(Some(ArrayElement::Spread(Expr { kind: ExprKind::Spread(Box::new(arg)), span: self.span_from(spread_start), }))); } else { let elem = self.parse_assignment_expression()?; elements.push(Some(ArrayElement::Expr(elem))); } if !self.eat(&TokenKind::Comma) { break; } } self.expect(&TokenKind::RBracket)?; Ok(Expr { kind: ExprKind::Array(elements), span: self.span_from(start), }) }
fn parse_object_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); self.expect(&TokenKind::LBrace)?; let mut properties = Vec::new(); while !self.at(&TokenKind::RBrace) && !self.at_eof() { let prop = self.parse_object_property()?; properties.push(prop); if !self.eat(&TokenKind::Comma) { break; } } self.expect(&TokenKind::RBrace)?; Ok(Expr { kind: ExprKind::Object(properties), span: self.span_from(start), }) }
fn parse_object_property(&mut self) -> Result<Property, ParseError> { let prop_start = self.start_span();
// Spread: `...expr` if self.at(&TokenKind::Ellipsis) { self.advance(); let arg = self.parse_assignment_expression()?; return Ok(Property { key: PropertyKey::Identifier("".into()), value: Some(arg), kind: PropertyKind::Init, computed: false, shorthand: false, method: false, span: self.span_from(prop_start), }); }
// Getter/setter: `get name() {}` or `set name(v) {}` if let TokenKind::Identifier(ref name) = self.peek_kind().clone() { if (name == "get" || name == "set") && !matches!( self.peek_ahead(1), TokenKind::Colon | TokenKind::Comma | TokenKind::RBrace | TokenKind::LParen | TokenKind::Assign ) { let kind = if name == "get" { PropertyKind::Get } else { PropertyKind::Set }; self.advance(); let (key, computed) = self.parse_property_name()?; let (params, body) = self.parse_function_params_and_body()?; return Ok(Property { key, value: Some(Expr { kind: ExprKind::Function(FunctionDef { id: None, params, body, is_async: false, is_generator: false, }), span: self.span_from(prop_start), }), kind, computed, shorthand: false, method: true, span: self.span_from(prop_start), }); } }
// Generator method: `*name() {}` if self.eat(&TokenKind::Star) { let (key, computed) = self.parse_property_name()?; let (params, body) = self.parse_function_params_and_body()?; return Ok(Property { key, value: Some(Expr { kind: ExprKind::Function(FunctionDef { id: None, params, body, is_async: false, is_generator: true, }), span: self.span_from(prop_start), }), kind: PropertyKind::Init, computed, shorthand: false, method: true, span: self.span_from(prop_start), }); }
// Async method: `async name() {}` let is_async = if matches!(self.peek_kind(), TokenKind::Async) && !matches!( self.peek_ahead(1), TokenKind::Colon | TokenKind::Comma | TokenKind::RBrace | TokenKind::Assign ) && !self .tokens .get(self.pos + 1) .is_none_or(|t| t.preceded_by_newline) { self.advance(); true } else { false };
let is_generator = is_async && self.eat(&TokenKind::Star);
let (key, computed) = self.parse_property_name()?;
// Method shorthand: `name() {}` or `name(params) {}` if self.at(&TokenKind::LParen) { let (params, body) = self.parse_function_params_and_body()?; return Ok(Property { key, value: Some(Expr { kind: ExprKind::Function(FunctionDef { id: None, params, body, is_async, is_generator, }), span: self.span_from(prop_start), }), kind: PropertyKind::Init, computed, shorthand: false, method: true, span: self.span_from(prop_start), }); }
// Shorthand: `{ name }` or `{ name = default }` if !computed && matches!( self.peek_kind(), TokenKind::Comma | TokenKind::RBrace | TokenKind::Assign ) { let name = match &key { PropertyKey::Identifier(n) => n.clone(), _ => return Err(self.error("expected identifier for shorthand property".into())), }; let value = if self.eat(&TokenKind::Assign) { let default = self.parse_assignment_expression()?; Some(Expr { kind: ExprKind::Assignment { op: AssignOp::Assign, left: Box::new(Expr { kind: ExprKind::Identifier(name.clone()), span: self.span_from(prop_start), }), right: Box::new(default), }, span: self.span_from(prop_start), }) } else { Some(Expr { kind: ExprKind::Identifier(name), span: self.span_from(prop_start), }) }; return Ok(Property { key, value, kind: PropertyKind::Init, computed, shorthand: true, method: false, span: self.span_from(prop_start), }); }
// Regular: `key: value` self.expect(&TokenKind::Colon)?; let value = self.parse_assignment_expression()?; Ok(Property { key, value: Some(value), kind: PropertyKind::Init, computed, shorthand: false, method: false, span: self.span_from(prop_start), }) }
fn parse_property_name(&mut self) -> Result<(PropertyKey, bool), ParseError> { match self.peek_kind().clone() { TokenKind::Identifier(name) => { self.advance(); Ok((PropertyKey::Identifier(name), false)) } TokenKind::String(s) => { self.advance(); Ok((PropertyKey::String(s), false)) } TokenKind::Number(n) => { self.advance(); Ok((PropertyKey::Number(n), false)) } TokenKind::LBracket => { self.advance(); let expr = self.parse_assignment_expression()?; self.expect(&TokenKind::RBracket)?; Ok((PropertyKey::Computed(expr), true)) } // Keywords can also be property names _ if is_keyword(self.peek_kind()) => { let name = format!("{}", self.peek_kind()); self.advance(); Ok((PropertyKey::Identifier(name), false)) } _ => Err(self.error(format!( "expected property name, found {:?}", self.peek_kind() ))), } }
fn parse_function_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Function)?; let is_generator = self.eat(&TokenKind::Star); let id = if let TokenKind::Identifier(_) = self.peek_kind() { Some(self.expect_identifier()?) } else { None }; let (params, body) = self.parse_function_params_and_body()?; Ok(Expr { kind: ExprKind::Function(FunctionDef { id, params, body, is_async: false, is_generator, }), span: self.span_from(start), }) }
fn parse_async_function_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); self.expect(&TokenKind::Async)?; self.expect(&TokenKind::Function)?; let is_generator = self.eat(&TokenKind::Star); let id = if let TokenKind::Identifier(_) = self.peek_kind() { Some(self.expect_identifier()?) } else { None }; let (params, body) = self.parse_function_params_and_body()?; Ok(Expr { kind: ExprKind::Function(FunctionDef { id, params, body, is_async: true, is_generator, }), span: self.span_from(start), }) }
fn parse_class_expression(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); let class_def = self.parse_class(false)?; Ok(Expr { kind: ExprKind::Class(class_def), span: self.span_from(start), }) }
fn parse_template_literal(&mut self) -> Result<Expr, ParseError> { let start = self.start_span(); match self.peek_kind().clone() { TokenKind::TemplateFull(s) => { self.advance(); Ok(Expr { kind: ExprKind::TemplateLiteral { quasis: vec![s], expressions: vec![], }, span: self.span_from(start), }) } TokenKind::TemplateHead(s) => { self.advance(); let mut quasis = vec![s]; let mut expressions = Vec::new(); loop { expressions.push(self.parse_expression()?); match self.peek_kind().clone() { TokenKind::TemplateMiddle(s) => { self.advance(); quasis.push(s); } TokenKind::TemplateTail(s) => { self.advance(); quasis.push(s); break; } _ => { return Err(self.error("expected template continuation or tail".into())); } } } Ok(Expr { kind: ExprKind::TemplateLiteral { quasis, expressions, }, span: self.span_from(start), }) } _ => Err(self.error("expected template literal".into())), } }
// ── Operator tables ─────────────────────────────────────
fn peek_binary_op(&self) -> Option<(BinOrLogical, u8, u8)> { let kind = self.peek_kind(); let (op, left_bp, right_bp) = match kind { TokenKind::Or => (BinOrLogical::Logical(LogicalOp::Or), 2, 3), TokenKind::And => (BinOrLogical::Logical(LogicalOp::And), 4, 5), TokenKind::Nullish => (BinOrLogical::Logical(LogicalOp::Nullish), 6, 7), TokenKind::Pipe => (BinOrLogical::Binary(BinaryOp::BitOr), 8, 9), TokenKind::Caret => (BinOrLogical::Binary(BinaryOp::BitXor), 10, 11), TokenKind::Amp => (BinOrLogical::Binary(BinaryOp::BitAnd), 12, 13), TokenKind::Eq => (BinOrLogical::Binary(BinaryOp::Eq), 14, 15), TokenKind::Ne => (BinOrLogical::Binary(BinaryOp::Ne), 14, 15), TokenKind::StrictEq => (BinOrLogical::Binary(BinaryOp::StrictEq), 14, 15), TokenKind::StrictNe => (BinOrLogical::Binary(BinaryOp::StrictNe), 14, 15), TokenKind::Lt => (BinOrLogical::Binary(BinaryOp::Lt), 16, 17), TokenKind::Gt => (BinOrLogical::Binary(BinaryOp::Gt), 16, 17), TokenKind::Le => (BinOrLogical::Binary(BinaryOp::Le), 16, 17), TokenKind::Ge => (BinOrLogical::Binary(BinaryOp::Ge), 16, 17), TokenKind::Instanceof => (BinOrLogical::Binary(BinaryOp::Instanceof), 16, 17), TokenKind::In if self.allow_in => (BinOrLogical::Binary(BinaryOp::In), 16, 17), TokenKind::Shl => (BinOrLogical::Binary(BinaryOp::Shl), 18, 19), TokenKind::Shr => (BinOrLogical::Binary(BinaryOp::Shr), 18, 19), TokenKind::Ushr => (BinOrLogical::Binary(BinaryOp::Ushr), 18, 19), TokenKind::Plus => (BinOrLogical::Binary(BinaryOp::Add), 20, 21), TokenKind::Minus => (BinOrLogical::Binary(BinaryOp::Sub), 20, 21), TokenKind::Star => (BinOrLogical::Binary(BinaryOp::Mul), 22, 23), TokenKind::Slash => (BinOrLogical::Binary(BinaryOp::Div), 22, 23), TokenKind::Percent => (BinOrLogical::Binary(BinaryOp::Rem), 22, 23), TokenKind::Exp => (BinOrLogical::Binary(BinaryOp::Exp), 25, 24), // right-assoc _ => return None, }; Some((op, left_bp, right_bp)) }
fn peek_assign_op(&self) -> Option<AssignOp> { match self.peek_kind() { TokenKind::Assign => Some(AssignOp::Assign), TokenKind::PlusAssign => Some(AssignOp::AddAssign), TokenKind::MinusAssign => Some(AssignOp::SubAssign), TokenKind::StarAssign => Some(AssignOp::MulAssign), TokenKind::SlashAssign => Some(AssignOp::DivAssign), TokenKind::PercentAssign => Some(AssignOp::RemAssign), TokenKind::ExpAssign => Some(AssignOp::ExpAssign), TokenKind::ShlAssign => Some(AssignOp::ShlAssign), TokenKind::ShrAssign => Some(AssignOp::ShrAssign), TokenKind::UshrAssign => Some(AssignOp::UshrAssign), TokenKind::AmpAssign => Some(AssignOp::BitAndAssign), TokenKind::PipeAssign => Some(AssignOp::BitOrAssign), TokenKind::CaretAssign => Some(AssignOp::BitXorAssign), TokenKind::AndAssign => Some(AssignOp::AndAssign), TokenKind::OrAssign => Some(AssignOp::OrAssign), TokenKind::NullishAssign => Some(AssignOp::NullishAssign), _ => None, } }
// ── Expression ↔ Pattern conversion ─────────────────────
fn expr_to_pattern(&self, expr: &Expr) -> Result<Pattern, ParseError> { let span = expr.span; match &expr.kind { ExprKind::Identifier(name) => Ok(Pattern { kind: PatternKind::Identifier(name.clone()), span, }), ExprKind::Array(elements) => { let mut pats = Vec::new(); let mut rest = None; for elem in elements { match elem { None => pats.push(None), Some(ArrayElement::Spread(e)) => { if let ExprKind::Spread(inner) = &e.kind { rest = Some(Box::new(self.expr_to_pattern(inner)?)); } else { rest = Some(Box::new(self.expr_to_pattern(e)?)); } } Some(ArrayElement::Expr(e)) => { pats.push(Some(self.expr_to_pattern(e)?)); } } } Ok(Pattern { kind: PatternKind::Array { elements: pats, rest, }, span, }) } ExprKind::Object(properties) => { let mut pats = Vec::new(); let mut rest = None; for prop in properties { if prop.key == PropertyKey::Identifier("".into()) { if let Some(val) = &prop.value { // Spread property rest = Some(Box::new(self.expr_to_pattern(val)?)); } continue; } let value = if let Some(val) = &prop.value { self.expr_to_pattern(val)? } else { continue; }; pats.push(ObjectPatternProp { key: prop.key.clone(), value, computed: prop.computed, shorthand: prop.shorthand, span: prop.span, }); } Ok(Pattern { kind: PatternKind::Object { properties: pats, rest, }, span, }) } ExprKind::Assignment { op: AssignOp::Assign, left, right, } => { let left_pat = self.expr_to_pattern(left)?; Ok(Pattern { kind: PatternKind::Assign { left: Box::new(left_pat), right: right.clone(), }, span, }) } ExprKind::Spread(inner) => self.expr_to_pattern(inner), _ => Err(ParseError { message: "invalid destructuring pattern".into(), pos: span.start, }), } }
fn expr_to_params(&self, expr: &Expr) -> Result<Vec<Pattern>, ParseError> { match &expr.kind { ExprKind::Sequence(exprs) if exprs.is_empty() => Ok(vec![]), ExprKind::Sequence(exprs) => { let mut params = Vec::new(); for e in exprs { params.push(self.expr_to_pattern(e)?); } Ok(params) } ExprKind::Spread(inner) => { let pat = self.expr_to_pattern(inner)?; Ok(vec![pat]) } _ => { // Single expression as single parameter Ok(vec![self.expr_to_pattern(expr)?]) } } }}
// ── Helpers ─────────────────────────────────────────────────
/// Distinguishes binary operators from logical operators in Pratt parsing.enum BinOrLogical { Binary(BinaryOp), Logical(LogicalOp),}
/// Returns true if the token kind is a keyword (used for property name parsing).fn is_keyword(kind: &TokenKind) -> bool { matches!( kind, TokenKind::Await | TokenKind::Break | TokenKind::Case | TokenKind::Catch | TokenKind::Class | TokenKind::Const | TokenKind::Continue | TokenKind::Debugger | TokenKind::Default | TokenKind::Delete | TokenKind::Do | TokenKind::Else | TokenKind::Export | TokenKind::Extends | TokenKind::Finally | TokenKind::For | TokenKind::Function | TokenKind::If | TokenKind::Import | TokenKind::In | TokenKind::Instanceof | TokenKind::Let | TokenKind::New | TokenKind::Of | TokenKind::Return | TokenKind::Static | TokenKind::Super | TokenKind::Switch | TokenKind::This | TokenKind::Throw | TokenKind::Try | TokenKind::Typeof | TokenKind::Var | TokenKind::Void | TokenKind::While | TokenKind::With | TokenKind::Yield | TokenKind::Async | TokenKind::True | TokenKind::False | TokenKind::Null )}
// ── Tests ───────────────────────────────────────────────────
#[cfg(test)]mod tests { use super::*;
fn parse(src: &str) -> Program { Parser::parse(src).unwrap() }
fn parse_expr(src: &str) -> Expr { let prog = parse(src); match &prog.body[0].kind { StmtKind::Expr(e) => e.clone(), _ => panic!("expected expression statement, got {:?}", prog.body[0].kind), } }
fn parse_stmt(src: &str) -> Stmt { let prog = parse(src); prog.body[0].clone() }
// ── Literals ────────────────────────────────────────
#[test] fn test_number_literal() { let expr = parse_expr("42"); assert_eq!(expr.kind, ExprKind::Number(42.0)); }
#[test] fn test_string_literal() { let expr = parse_expr("\"hello\""); assert_eq!(expr.kind, ExprKind::String("hello".into())); }
#[test] fn test_boolean_literals() { assert_eq!(parse_expr("true").kind, ExprKind::Bool(true)); assert_eq!(parse_expr("false").kind, ExprKind::Bool(false)); }
#[test] fn test_null_literal() { assert_eq!(parse_expr("null").kind, ExprKind::Null); }
#[test] fn test_this() { assert_eq!(parse_expr("this").kind, ExprKind::This); }
#[test] fn test_identifier() { assert_eq!(parse_expr("foo").kind, ExprKind::Identifier("foo".into())); }
#[test] fn test_regexp() { let expr = parse_expr("x = /test/gi"); match &expr.kind { ExprKind::Assignment { right, .. } => { assert_eq!( right.kind, ExprKind::RegExp { pattern: "test".into(), flags: "gi".into() } ); } _ => panic!("expected assignment"), } }
// ── Binary expressions ──────────────────────────────
#[test] fn test_addition() { let expr = parse_expr("1 + 2"); match expr.kind { ExprKind::Binary { op, left, right } => { assert_eq!(op, BinaryOp::Add); assert_eq!(left.kind, ExprKind::Number(1.0)); assert_eq!(right.kind, ExprKind::Number(2.0)); } _ => panic!("expected binary"), } }
#[test] fn test_precedence() { // 1 + 2 * 3 should be 1 + (2 * 3) let expr = parse_expr("1 + 2 * 3"); match expr.kind { ExprKind::Binary { op: BinaryOp::Add, left, right, } => { assert_eq!(left.kind, ExprKind::Number(1.0)); match right.kind { ExprKind::Binary { op: BinaryOp::Mul, .. } => {} _ => panic!("expected multiply on right"), } } _ => panic!("expected binary add"), } }
#[test] fn test_exponentiation_right_assoc() { // 2 ** 3 ** 2 should be 2 ** (3 ** 2) let expr = parse_expr("2 ** 3 ** 2"); match expr.kind { ExprKind::Binary { op: BinaryOp::Exp, left, right, } => { assert_eq!(left.kind, ExprKind::Number(2.0)); match right.kind { ExprKind::Binary { op: BinaryOp::Exp, .. } => {} _ => panic!("expected exp on right"), } } _ => panic!("expected binary exp"), } }
#[test] fn test_comparison() { let expr = parse_expr("a === b"); match expr.kind { ExprKind::Binary { op: BinaryOp::StrictEq, .. } => {} _ => panic!("expected strict eq"), } }
#[test] fn test_logical_operators() { let expr = parse_expr("a && b || c"); // Should be (a && b) || c because && has higher precedence match expr.kind { ExprKind::Logical { op: LogicalOp::Or, .. } => {} _ => panic!("expected logical or"), } }
// ── Unary expressions ───────────────────────────────
#[test] fn test_unary_minus() { let expr = parse_expr("-x"); match expr.kind { ExprKind::Unary { op: UnaryOp::Minus, argument, } => { assert_eq!(argument.kind, ExprKind::Identifier("x".into())); } _ => panic!("expected unary minus"), } }
#[test] fn test_typeof() { let expr = parse_expr("typeof x"); match expr.kind { ExprKind::Unary { op: UnaryOp::Typeof, .. } => {} _ => panic!("expected typeof"), } }
#[test] fn test_prefix_increment() { let expr = parse_expr("++x"); match expr.kind { ExprKind::Update { op: UpdateOp::Increment, prefix: true, .. } => {} _ => panic!("expected prefix increment"), } }
#[test] fn test_postfix_decrement() { let expr = parse_expr("x--"); match expr.kind { ExprKind::Update { op: UpdateOp::Decrement, prefix: false, .. } => {} _ => panic!("expected postfix decrement"), } }
// ── Conditional expression ──────────────────────────
#[test] fn test_ternary() { let expr = parse_expr("a ? b : c"); match expr.kind { ExprKind::Conditional { test, consequent, alternate, } => { assert_eq!(test.kind, ExprKind::Identifier("a".into())); assert_eq!(consequent.kind, ExprKind::Identifier("b".into())); assert_eq!(alternate.kind, ExprKind::Identifier("c".into())); } _ => panic!("expected conditional"), } }
// ── Assignment ──────────────────────────────────────
#[test] fn test_assignment() { let expr = parse_expr("x = 42"); match expr.kind { ExprKind::Assignment { op: AssignOp::Assign, left, right, } => { assert_eq!(left.kind, ExprKind::Identifier("x".into())); assert_eq!(right.kind, ExprKind::Number(42.0)); } _ => panic!("expected assignment"), } }
#[test] fn test_compound_assignment() { let expr = parse_expr("x += 1"); match expr.kind { ExprKind::Assignment { op: AssignOp::AddAssign, .. } => {} _ => panic!("expected add-assign"), } }
// ── Member expressions ──────────────────────────────
#[test] fn test_dot_access() { let expr = parse_expr("a.b"); match expr.kind { ExprKind::Member { computed: false, .. } => {} _ => panic!("expected member access"), } }
#[test] fn test_bracket_access() { let expr = parse_expr("a[0]"); match expr.kind { ExprKind::Member { computed: true, .. } => {} _ => panic!("expected computed member"), } }
// ── Call expressions ────────────────────────────────
#[test] fn test_function_call() { let expr = parse_expr("foo(1, 2)"); match expr.kind { ExprKind::Call { callee, arguments, .. } => { assert_eq!(callee.kind, ExprKind::Identifier("foo".into())); assert_eq!(arguments.len(), 2); } _ => panic!("expected call"), } }
#[test] fn test_method_call() { let expr = parse_expr("obj.method()"); match expr.kind { ExprKind::Call { callee, .. } => match callee.kind { ExprKind::Member { .. } => {} _ => panic!("expected member callee"), }, _ => panic!("expected call"), } }
#[test] fn test_new_expression() { let expr = parse_expr("new Foo(1)"); match expr.kind { ExprKind::New { callee, arguments, .. } => { assert_eq!(callee.kind, ExprKind::Identifier("Foo".into())); assert_eq!(arguments.len(), 1); } _ => panic!("expected new"), } }
// ── Array and object literals ───────────────────────
#[test] fn test_array_literal() { let expr = parse_expr("[1, 2, 3]"); match expr.kind { ExprKind::Array(elements) => { assert_eq!(elements.len(), 3); } _ => panic!("expected array"), } }
#[test] fn test_object_literal() { let expr = parse_expr("({a: 1, b: 2})"); match expr.kind { ExprKind::Object(props) => { assert_eq!(props.len(), 2); assert_eq!(props[0].key, PropertyKey::Identifier("a".into())); } _ => panic!("expected object"), } }
#[test] fn test_shorthand_property() { let expr = parse_expr("({x, y})"); match expr.kind { ExprKind::Object(props) => { assert!(props[0].shorthand); assert!(props[1].shorthand); } _ => panic!("expected object"), } }
#[test] fn test_computed_property() { let expr = parse_expr("({[key]: value})"); match expr.kind { ExprKind::Object(props) => { assert!(props[0].computed); } _ => panic!("expected object"), } }
// ── Arrow functions ─────────────────────────────────
#[test] fn test_arrow_single_param() { let expr = parse_expr("x => x + 1"); match expr.kind { ExprKind::Arrow { params, body: ArrowBody::Expr(_), is_async: false, } => { assert_eq!(params.len(), 1); } _ => panic!("expected arrow"), } }
#[test] fn test_arrow_multi_param() { let expr = parse_expr("(a, b) => a + b"); match expr.kind { ExprKind::Arrow { params, .. } => { assert_eq!(params.len(), 2); } _ => panic!("expected arrow"), } }
#[test] fn test_arrow_body_block() { let expr = parse_expr("() => { return 1; }"); match expr.kind { ExprKind::Arrow { body: ArrowBody::Block(stmts), .. } => { assert_eq!(stmts.len(), 1); } _ => panic!("expected arrow with block body"), } }
// ── Template literals ───────────────────────────────
#[test] fn test_template_no_subst() { let expr = parse_expr("`hello`"); match expr.kind { ExprKind::TemplateLiteral { quasis, expressions, } => { assert_eq!(quasis, vec!["hello"]); assert!(expressions.is_empty()); } _ => panic!("expected template literal"), } }
#[test] fn test_template_with_subst() { let expr = parse_expr("`hello ${name}!`"); match expr.kind { ExprKind::TemplateLiteral { quasis, expressions, } => { assert_eq!(quasis, vec!["hello ", "!"]); assert_eq!(expressions.len(), 1); } _ => panic!("expected template literal"), } }
// ── Spread ──────────────────────────────────────────
#[test] fn test_spread_in_call() { let expr = parse_expr("foo(...args)"); match expr.kind { ExprKind::Call { arguments, .. } => { assert_eq!(arguments.len(), 1); assert!(matches!(arguments[0].kind, ExprKind::Spread(_))); } _ => panic!("expected call"), } }
// ── Variable declarations ───────────────────────────
#[test] fn test_var_decl() { let stmt = parse_stmt("var x = 42;"); match stmt.kind { StmtKind::VarDecl { kind, declarators } => { assert_eq!(kind, VarKind::Var); assert_eq!(declarators.len(), 1); assert!(matches!( declarators[0].pattern.kind, PatternKind::Identifier(ref n) if n == "x" )); assert!(declarators[0].init.is_some()); } _ => panic!("expected var decl"), } }
#[test] fn test_const_decl() { let stmt = parse_stmt("const [a, b] = arr;"); match stmt.kind { StmtKind::VarDecl { kind: VarKind::Const, declarators, } => { assert!(matches!( declarators[0].pattern.kind, PatternKind::Array { .. } )); } _ => panic!("expected const decl"), } }
#[test] fn test_destructuring_object() { let stmt = parse_stmt("let { a, b: c } = obj;"); match stmt.kind { StmtKind::VarDecl { declarators, .. } => match &declarators[0].pattern.kind { PatternKind::Object { properties, .. } => { assert_eq!(properties.len(), 2); assert!(properties[0].shorthand); assert!(!properties[1].shorthand); } _ => panic!("expected object pattern"), }, _ => panic!("expected var decl"), } }
// ── Function declaration ────────────────────────────
#[test] fn test_function_decl() { let stmt = parse_stmt("function add(a, b) { return a + b; }"); match stmt.kind { StmtKind::FunctionDecl(def) => { assert_eq!(def.id, Some("add".into())); assert_eq!(def.params.len(), 2); assert!(!def.is_async); assert!(!def.is_generator); assert_eq!(def.body.len(), 1); } _ => panic!("expected function decl"), } }
#[test] fn test_generator_function() { let stmt = parse_stmt("function* gen() { yield 1; }"); match stmt.kind { StmtKind::FunctionDecl(def) => { assert!(def.is_generator); } _ => panic!("expected function decl"), } }
#[test] fn test_async_function() { let stmt = parse_stmt("async function fetch() { await get(); }"); match stmt.kind { StmtKind::FunctionDecl(def) => { assert!(def.is_async); } _ => panic!("expected function decl"), } }
#[test] fn test_default_params() { let stmt = parse_stmt("function f(a, b = 10) {}"); match stmt.kind { StmtKind::FunctionDecl(def) => { assert_eq!(def.params.len(), 2); assert!(matches!(def.params[1].kind, PatternKind::Assign { .. })); } _ => panic!("expected function decl"), } }
#[test] fn test_rest_params() { let stmt = parse_stmt("function f(...args) {}"); match stmt.kind { StmtKind::FunctionDecl(def) => { assert_eq!(def.params.len(), 1); assert!(matches!( def.params[0].kind, PatternKind::Identifier(ref n) if n == "args" )); } _ => panic!("expected function decl"), } }
// ── Class declaration ───────────────────────────────
#[test] fn test_class_decl() { let stmt = parse_stmt("class Foo { constructor() {} method() {} }"); match stmt.kind { StmtKind::ClassDecl(def) => { assert_eq!(def.id, Some("Foo".into())); assert_eq!(def.body.len(), 2); } _ => panic!("expected class decl"), } }
#[test] fn test_class_extends() { let stmt = parse_stmt("class Bar extends Foo {}"); match stmt.kind { StmtKind::ClassDecl(def) => { assert!(def.super_class.is_some()); } _ => panic!("expected class decl"), } }
#[test] fn test_class_getter_setter() { let stmt = parse_stmt("class C { get x() { return 1; } set x(v) {} }"); match stmt.kind { StmtKind::ClassDecl(def) => { assert_eq!(def.body.len(), 2); match &def.body[0].kind { ClassMemberKind::Method { kind, .. } => { assert_eq!(*kind, MethodKind::Get); } _ => panic!("expected getter"), } } _ => panic!("expected class decl"), } }
// ── Control flow statements ─────────────────────────
#[test] fn test_if_else() { let stmt = parse_stmt("if (x) { a(); } else { b(); }"); match stmt.kind { StmtKind::If { alternate, .. } => { assert!(alternate.is_some()); } _ => panic!("expected if"), } }
#[test] fn test_for_loop() { let stmt = parse_stmt("for (let i = 0; i < 10; i++) {}"); match stmt.kind { StmtKind::For { init, test, update, .. } => { assert!(init.is_some()); assert!(test.is_some()); assert!(update.is_some()); } _ => panic!("expected for"), } }
#[test] fn test_for_in() { let stmt = parse_stmt("for (const key in obj) {}"); assert!(matches!(stmt.kind, StmtKind::ForIn { .. })); }
#[test] fn test_for_of() { let stmt = parse_stmt("for (const item of arr) {}"); assert!(matches!(stmt.kind, StmtKind::ForOf { .. })); }
#[test] fn test_while_loop() { let stmt = parse_stmt("while (true) {}"); assert!(matches!(stmt.kind, StmtKind::While { .. })); }
#[test] fn test_do_while() { let stmt = parse_stmt("do {} while (true);"); assert!(matches!(stmt.kind, StmtKind::DoWhile { .. })); }
#[test] fn test_switch() { let stmt = parse_stmt("switch (x) { case 1: break; default: break; }"); match stmt.kind { StmtKind::Switch { cases, .. } => { assert_eq!(cases.len(), 2); assert!(cases[0].test.is_some()); assert!(cases[1].test.is_none()); // default } _ => panic!("expected switch"), } }
#[test] fn test_try_catch() { let stmt = parse_stmt("try { f(); } catch (e) { g(); }"); match stmt.kind { StmtKind::Try { handler, finalizer, .. } => { assert!(handler.is_some()); assert!(finalizer.is_none()); } _ => panic!("expected try"), } }
#[test] fn test_try_catch_finally() { let stmt = parse_stmt("try {} catch (e) {} finally {}"); match stmt.kind { StmtKind::Try { handler, finalizer, .. } => { assert!(handler.is_some()); assert!(finalizer.is_some()); } _ => panic!("expected try"), } }
#[test] fn test_return() { let stmt = parse_stmt("function f() { return 42; }"); match stmt.kind { StmtKind::FunctionDecl(def) => match &def.body[0].kind { StmtKind::Return(Some(expr)) => { assert_eq!(expr.kind, ExprKind::Number(42.0)); } _ => panic!("expected return"), }, _ => panic!("expected function"), } }
#[test] fn test_throw() { let stmt = parse_stmt("function f() { throw new Error(); }"); match stmt.kind { StmtKind::FunctionDecl(def) => { assert!(matches!(def.body[0].kind, StmtKind::Throw(_))); } _ => panic!("expected function"), } }
#[test] fn test_break_continue() { let prog = parse("while (true) { break; continue; }"); let while_stmt = &prog.body[0]; match &while_stmt.kind { StmtKind::While { body, .. } => match &body.kind { StmtKind::Block(stmts) => { assert!(matches!(stmts[0].kind, StmtKind::Break(None))); assert!(matches!(stmts[1].kind, StmtKind::Continue(None))); } _ => panic!("expected block"), }, _ => panic!("expected while"), } }
#[test] fn test_labeled_statement() { let stmt = parse_stmt("outer: for (;;) {}"); match stmt.kind { StmtKind::Labeled { label, .. } => { assert_eq!(label, "outer"); } _ => panic!("expected labeled"), } }
// ── Import / Export ─────────────────────────────────
#[test] fn test_import_default() { let stmt = parse_stmt("import foo from \"mod\";"); match stmt.kind { StmtKind::Import { specifiers, source } => { assert_eq!(source, "mod"); assert_eq!(specifiers.len(), 1); assert!(matches!(&specifiers[0], ImportSpecifier::Default(n) if n == "foo")); } _ => panic!("expected import"), } }
#[test] fn test_import_named() { let prog = Parser::parse_module("import { a, b as c } from \"mod\";").unwrap(); match &prog.body[0].kind { StmtKind::Import { specifiers, .. } => { assert_eq!(specifiers.len(), 2); } _ => panic!("expected import"), } }
#[test] fn test_import_namespace() { let prog = Parser::parse_module("import * as ns from \"mod\";").unwrap(); match &prog.body[0].kind { StmtKind::Import { specifiers, .. } => { assert!(matches!(&specifiers[0], ImportSpecifier::Namespace(n) if n == "ns")); } _ => panic!("expected import"), } }
#[test] fn test_export_default() { let prog = Parser::parse_module("export default 42;").unwrap(); match &prog.body[0].kind { StmtKind::Export(ExportDecl::Default(expr)) => { assert_eq!(expr.kind, ExprKind::Number(42.0)); } _ => panic!("expected export default"), } }
#[test] fn test_export_named() { let prog = Parser::parse_module("export { a, b as c };").unwrap(); match &prog.body[0].kind { StmtKind::Export(ExportDecl::Named { specifiers, .. }) => { assert_eq!(specifiers.len(), 2); } _ => panic!("expected export named"), } }
#[test] fn test_export_declaration() { let prog = Parser::parse_module("export const x = 1;").unwrap(); match &prog.body[0].kind { StmtKind::Export(ExportDecl::Declaration(_)) => {} _ => panic!("expected export declaration"), } }
#[test] fn test_export_default_anonymous_function() { let prog = Parser::parse_module("export default function() {}").unwrap(); match &prog.body[0].kind { StmtKind::Export(ExportDecl::Default(expr)) => { assert!(matches!(expr.kind, ExprKind::Function(ref def) if def.id.is_none())); } _ => panic!("expected export default anonymous function"), } }
#[test] fn test_export_default_anonymous_class() { let prog = Parser::parse_module("export default class {}").unwrap(); match &prog.body[0].kind { StmtKind::Export(ExportDecl::Default(expr)) => { assert!(matches!(expr.kind, ExprKind::Class(ref def) if def.id.is_none())); } _ => panic!("expected export default anonymous class"), } }
#[test] fn test_export_default_anonymous_generator() { let prog = Parser::parse_module("export default function*() {}").unwrap(); match &prog.body[0].kind { StmtKind::Export(ExportDecl::Default(expr)) => { assert!(matches!( expr.kind, ExprKind::Function(ref def) if def.id.is_none() && def.is_generator )); } _ => panic!("expected export default anonymous generator"), } }
// ── ASI (Automatic Semicolon Insertion) ─────────────
#[test] fn test_asi_newline() { let prog = parse("let x = 1\nlet y = 2"); assert_eq!(prog.body.len(), 2); }
#[test] fn test_asi_before_rbrace() { let stmt = parse_stmt("function f() { return 1 }"); match stmt.kind { StmtKind::FunctionDecl(def) => { assert_eq!(def.body.len(), 1); } _ => panic!("expected function"), } }
// ── Complex programs ────────────────────────────────
#[test] fn test_fibonacci() { let src = r#" function fib(n) { if (n <= 1) return n; return fib(n - 1) + fib(n - 2); } "#; let prog = parse(src); assert_eq!(prog.body.len(), 1); assert!(matches!(prog.body[0].kind, StmtKind::FunctionDecl(_))); }
#[test] fn test_class_with_methods() { let src = r#" class Animal { constructor(name) { this.name = name; } speak() { return this.name; } static create(name) { return new Animal(name); } } "#; let prog = parse(src); assert_eq!(prog.body.len(), 1); match &prog.body[0].kind { StmtKind::ClassDecl(def) => { assert_eq!(def.body.len(), 3); } _ => panic!("expected class"), } }
#[test] fn test_for_of_destructuring() { let stmt = parse_stmt("for (const [k, v] of map) {}"); match stmt.kind { StmtKind::ForOf { left, .. } => match left { ForInOfLeft::VarDecl { pattern, .. } => { assert!(matches!(pattern.kind, PatternKind::Array { .. })); } _ => panic!("expected var decl"), }, _ => panic!("expected for-of"), } }
#[test] fn test_multiple_statements() { let src = "let x = 1; let y = 2; x + y;"; let prog = parse(src); assert_eq!(prog.body.len(), 3); }
// ── Error cases ─────────────────────────────────────
#[test] fn test_error_unexpected_token() { assert!(Parser::parse(")").is_err()); }
#[test] fn test_error_unterminated_block() { assert!(Parser::parse("{ let x = 1;").is_err()); }
#[test] fn test_error_missing_paren() { assert!(Parser::parse("if x {}").is_err()); }}