diff --git a/src/parser.rs b/src/parser.rs index 52cb6bb..134f30e 100644 --- a/src/parser.rs +++ b/src/parser.rs @@ -21,6 +21,15 @@ pub enum LoopParsingState { NamedLoop(String), } +impl From<&Option> for LoopParsingState { + fn from(value: &Option) -> Self { + match &value { + None => LoopParsingState::UnnamedLoop, + Some(name) => LoopParsingState::NamedLoop(name.lexeme.clone()), + } + } +} + /// The result of one of the parser's functions. type ParserResult = Result; @@ -97,6 +106,7 @@ impl Parser { /// statement := "print" expression ";" /// statement := declaration ";" /// statement := block + /// statement := labelled_loop /// statement := if_statement /// statement := while_statement /// statement := for_statement @@ -107,15 +117,14 @@ impl Parser { self.parse_declaration() } else if self.expect(&[TokenType::LeftBrace]).is_some() { self.parse_block() + } else if self.expect(&[TokenType::Address]).is_some() { + self.parse_labelled_loop() } else if self.expect(&[TokenType::If]).is_some() { self.parse_if_statement() } else if self.expect(&[TokenType::While]).is_some() { - self.loop_state.push(LoopParsingState::UnnamedLoop); - let result = self.parse_while_statement(); - self.loop_state.pop(); - result + self.parse_while_statement(None) } else if self.expect(&[TokenType::For]).is_some() { - self.parse_for_statement(LoopParsingState::UnnamedLoop) + self.parse_for_statement(None) } else if let Some(lcs) = self.expect(&[TokenType::Break, TokenType::Continue]) { self.parse_loop_control_statement(&lcs) } else if self.expect(&[TokenType::Print]).is_some() { @@ -196,19 +205,56 @@ impl Parser { }) } + /// Parse the following rule: + /// ``` + /// labelled_loop := "@" IDENTIFIER while_statement + /// labelled_loop := "@" IDENTIFIER for_statement + /// ``` + fn parse_labelled_loop(&mut self) -> ParserResult { + let name_token = match self.peek().token_type { + TokenType::Identifier(_) => self.advance().clone(), + _ => { + return Err(ParserError::new( + self.peek(), + "identifier expected after '@'", + )) + } + }; + + if self.expect(&[TokenType::While]).is_some() { + self.parse_while_statement(Some(name_token)) + } else if self.expect(&[TokenType::For]).is_some() { + self.parse_for_statement(Some(name_token)) + } else { + Err(ParserError::new( + self.peek(), + "'while' or 'for' expected after loop label", + )) + } + } + /// Parse the following rule: /// ``` /// while_statement := "while" "(" expression ")" statement /// ``` - fn parse_while_statement(&mut self) -> ParserResult { + fn parse_while_statement(&mut self, label: Option) -> ParserResult { self.consume(&TokenType::LeftParen, "expected '(' after 'while'")?; let condition = self.parse_expression()?; self.consume( &TokenType::RightParen, "expected ')' after condition in 'while' statement", )?; - let body = Box::new(self.parse_statement()?); - Ok(ast::StmtNode::WhileStmt { condition, body }) + let body = Box::new({ + self.loop_state.push(LoopParsingState::from(&label)); + let result = self.parse_statement(); + self.loop_state.pop(); + result? + }); + Ok(ast::StmtNode::WhileStmt { + label, + condition, + body, + }) } /// Parse the following rules: @@ -218,7 +264,7 @@ impl Parser { /// for_initializer := expression /// for_initializer := /// ``` - fn parse_for_statement(&mut self, loop_state: LoopParsingState) -> ParserResult { + fn parse_for_statement(&mut self, label: Option) -> ParserResult { self.consume(&TokenType::LeftParen, "expected '(' after 'for'")?; let initializer = if self.expect(&[TokenType::Semicolon]).is_some() { @@ -258,7 +304,7 @@ impl Parser { // Generate a while loop, with an optional initializer which may be // inside a specific block if the initializer declares a variable. let body_stmt = { - self.loop_state.push(loop_state); + self.loop_state.push(LoopParsingState::from(&label)); let result = self.parse_statement(); self.loop_state.pop(); result? @@ -276,6 +322,7 @@ impl Parser { body_stmt }; let while_stmt = ast::StmtNode::WhileStmt { + label, condition, body: Box::new(body_with_incr), };