Parser - Refactored error handling
This commit is contained in:
parent
acb29e7123
commit
0443754007
1 changed files with 63 additions and 74 deletions
131
src/parser.rs
131
src/parser.rs
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@ -2,7 +2,7 @@ use std::collections::HashSet;
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use crate::{
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ast,
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errors::{ErrorHandler, ParserError},
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errors::{ErrorHandler, ErrorKind, SloxError, SloxResult},
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tokens::{Token, TokenType},
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};
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@ -62,9 +62,6 @@ impl FunctionKind {
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}
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}
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/// The result of one of the parser's functions.
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type ParserResult<T> = Result<T, ParserError>;
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impl Parser {
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/// Initialize the parser.
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pub fn new(tokens: Vec<Token>) -> Self {
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@ -120,7 +117,7 @@ impl Parser {
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match self.parse_statement() {
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Ok(node) => stmts.push(node),
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Err(err) => {
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err.report(err_hdl);
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err_hdl.report(err);
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self.synchronize()
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}
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}
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@ -146,7 +143,7 @@ impl Parser {
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/// statement := loop_control_statement
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/// statement := return_statement
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/// ```
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fn parse_statement(&mut self) -> ParserResult<ast::StmtNode> {
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fn parse_statement(&mut self) -> SloxResult<ast::StmtNode> {
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if self.expect(&[TokenType::Var]).is_some() {
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self.parse_var_declaration()
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} else if self.expect(&[TokenType::Fun]).is_some() {
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@ -184,7 +181,7 @@ impl Parser {
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/// ```
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/// expression_stmt := expression ";"
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/// ```
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fn parse_expression_stmt(&mut self) -> ParserResult<ast::StmtNode> {
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fn parse_expression_stmt(&mut self) -> SloxResult<ast::StmtNode> {
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let expression = self.parse_expression()?;
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self.consume(&TokenType::Semicolon, "expected ';' after expression")?;
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Ok(ast::StmtNode::Expression(expression))
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@ -195,10 +192,10 @@ impl Parser {
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/// var_declaration := "var" IDENTIFIER ";"
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/// var_declaration := "var" IDENTIFIER "=" expression ";"
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/// ```
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fn parse_var_declaration(&mut self) -> ParserResult<ast::StmtNode> {
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fn parse_var_declaration(&mut self) -> SloxResult<ast::StmtNode> {
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let name = match self.peek().token_type {
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TokenType::Identifier(_) => self.advance().clone(),
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_ => return Err(ParserError::new(self.peek(), "expected variable name")),
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_ => return self.error("expected variable name"),
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};
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let initializer: Option<ast::ExprNode> = match self.expect(&[TokenType::Equal]) {
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Some(_) => Some(self.parse_expression()?),
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@ -217,16 +214,11 @@ impl Parser {
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/// function := IDENTIFIER function_info
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/// ```
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/// The `kind` parameter is used to generate error messages.
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fn parse_fun_declaration(&mut self, kind: FunctionKind) -> ParserResult<ast::StmtNode> {
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fn parse_fun_declaration(&mut self, kind: FunctionKind) -> SloxResult<ast::StmtNode> {
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// Read the name
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let name = match self.peek().token_type {
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TokenType::Identifier(_) => self.advance().clone(),
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_ => {
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return Err(ParserError::new(
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self.peek(),
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&format!("expected {} name", kind.name()),
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))
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}
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_ => return self.error_mv(format!("expected {} name", kind.name())),
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};
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let (params, block) = self.parse_function_info(kind)?;
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Ok(ast::StmtNode::FunDecl {
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@ -244,7 +236,7 @@ impl Parser {
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fn parse_function_info(
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&mut self,
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kind: FunctionKind,
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) -> ParserResult<(Vec<Token>, Vec<ast::StmtNode>)> {
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) -> SloxResult<(Vec<Token>, Vec<ast::StmtNode>)> {
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// Read the list of parameter names
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self.consume(
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&TokenType::LeftParen,
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@ -256,26 +248,20 @@ impl Parser {
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let mut names: HashSet<String> = HashSet::new();
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loop {
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if params.len() >= kind.max_params() {
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return Err(ParserError::new(
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self.peek(),
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&format!(
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return self.error_mv(format!(
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"{} can't have more than {} parameters",
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kind.name(),
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kind.max_params()
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),
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));
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}
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if let TokenType::Identifier(name) = &self.peek().token_type {
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if names.contains(name) {
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return Err(ParserError::new(
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self.peek(),
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&format!("duplicate {} parameter", kind.name()),
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));
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return self.error_mv(format!("duplicate {} parameter", kind.name()));
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}
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names.insert(name.to_owned());
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params.push(self.advance().clone());
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} else {
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return Err(ParserError::new(self.peek(), "parameter name expected"));
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return self.error("parameter name expected");
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}
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if self.expect(&[TokenType::Comma]).is_none() {
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break;
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@ -302,7 +288,7 @@ impl Parser {
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/// ```
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/// block := "{" statement* "}"
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/// ```
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fn parse_block(&mut self) -> ParserResult<ast::StmtNode> {
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fn parse_block(&mut self) -> SloxResult<ast::StmtNode> {
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let mut stmts: Vec<ast::StmtNode> = Vec::new();
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while !(self.check(&TokenType::RightBrace) || self.is_at_end()) {
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stmts.push(self.parse_statement()?);
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@ -316,7 +302,7 @@ impl Parser {
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/// if_statement := "if" "(" expression ")" statement
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/// if_statement := "if" "(" expression ")" statement "else" statement
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/// ```
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fn parse_if_statement(&mut self) -> ParserResult<ast::StmtNode> {
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fn parse_if_statement(&mut self) -> SloxResult<ast::StmtNode> {
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self.consume(&TokenType::LeftParen, "expected '(' after 'if'")?;
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let expression = self.parse_expression()?;
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self.consume(
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@ -340,15 +326,10 @@ impl Parser {
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/// labelled_loop := "@" IDENTIFIER while_statement
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/// labelled_loop := "@" IDENTIFIER for_statement
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/// ```
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fn parse_labelled_loop(&mut self) -> ParserResult<ast::StmtNode> {
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fn parse_labelled_loop(&mut self) -> SloxResult<ast::StmtNode> {
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let name_token = match self.peek().token_type {
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TokenType::Identifier(_) => self.advance().clone(),
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_ => {
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return Err(ParserError::new(
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self.peek(),
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"identifier expected after '@'",
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))
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}
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_ => return self.error("identifier expected after '@'"),
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};
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if self.expect(&[TokenType::While]).is_some() {
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@ -356,10 +337,7 @@ impl Parser {
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} else if self.expect(&[TokenType::For]).is_some() {
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self.parse_for_statement(Some(name_token))
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} else {
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Err(ParserError::new(
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self.peek(),
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"'while' or 'for' expected after loop label",
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))
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self.error("'while' or 'for' expected after loop label")
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}
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}
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@ -367,7 +345,7 @@ impl Parser {
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/// ```
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/// while_statement := "while" "(" expression ")" statement
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/// ```
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fn parse_while_statement(&mut self, label: Option<Token>) -> ParserResult<ast::StmtNode> {
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fn parse_while_statement(&mut self, label: Option<Token>) -> SloxResult<ast::StmtNode> {
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self.consume(&TokenType::LeftParen, "expected '(' after 'while'")?;
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let condition = self.parse_expression()?;
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self.consume(
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@ -395,7 +373,7 @@ impl Parser {
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/// for_initializer := expression
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/// for_initializer :=
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/// ```
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fn parse_for_statement(&mut self, label: Option<Token>) -> ParserResult<ast::StmtNode> {
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fn parse_for_statement(&mut self, label: Option<Token>) -> SloxResult<ast::StmtNode> {
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self.consume(&TokenType::LeftParen, "expected '(' after 'for'")?;
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let initializer = if self.expect(&[TokenType::Semicolon]).is_some() {
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@ -458,11 +436,12 @@ impl Parser {
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/// loop_control_statement := "break" ( IDENTIFIER )? ";"
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/// loop_control_statement := "continue" ( IDENTIFIER )? ";"
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/// ```
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fn parse_loop_control_statement(&mut self, stmt_token: &Token) -> ParserResult<ast::StmtNode> {
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fn parse_loop_control_statement(&mut self, stmt_token: &Token) -> SloxResult<ast::StmtNode> {
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if self.loop_state() == &LoopParsingState::None {
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return Err(ParserError::new(
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return Err(SloxError::with_token(
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ErrorKind::Parse,
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stmt_token,
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&format!(
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format!(
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"'{}' statement found outside of loop body",
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stmt_token.lexeme
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),
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@ -473,9 +452,10 @@ impl Parser {
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let name_token = self.advance().clone();
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if !self.find_named_loop(&name_token.lexeme) {
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self.expect(&[TokenType::Semicolon]);
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return Err(ParserError::new(
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return Err(SloxError::with_token(
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ErrorKind::Parse,
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&name_token,
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&format!("no reachable loop named '{}'", name_token.lexeme),
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format!("no reachable loop named '{}'", name_token.lexeme),
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));
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}
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Some(name_token)
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@ -497,7 +477,7 @@ impl Parser {
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/// ```
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/// return_statement := "return" expression? ";"
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/// ```
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fn parse_return_statement(&mut self, ret_token: &Token) -> ParserResult<ast::StmtNode> {
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fn parse_return_statement(&mut self, ret_token: &Token) -> SloxResult<ast::StmtNode> {
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if self.can_use_return() {
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let value = if self.check(&TokenType::Semicolon) {
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None
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@ -510,9 +490,10 @@ impl Parser {
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value,
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})
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} else {
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Err(ParserError::new(
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Err(SloxError::with_token(
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ErrorKind::Parse,
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ret_token,
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"'return' found outside of function",
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"'return' found outside of function".to_owned(),
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))
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}
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}
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@ -521,7 +502,7 @@ impl Parser {
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/// ```
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/// expression := assignment
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/// ```
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fn parse_expression(&mut self) -> ParserResult<ast::ExprNode> {
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fn parse_expression(&mut self) -> SloxResult<ast::ExprNode> {
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self.parse_assignment()
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}
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@ -530,7 +511,7 @@ impl Parser {
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/// assignment := IDENTIFIER "=" equality
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/// assignment := equality
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/// ```
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fn parse_assignment(&mut self) -> ParserResult<ast::ExprNode> {
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fn parse_assignment(&mut self) -> SloxResult<ast::ExprNode> {
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let expr = self.parse_logic_or()?;
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if let Some(equals) = self.expect(&[TokenType::Equal]) {
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let value = self.parse_assignment()?;
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@ -540,7 +521,7 @@ impl Parser {
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value: Box::new(value),
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})
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} else {
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Err(ParserError::new(&equals, "invalid assignment target"))
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self.error("invalid assignment target")
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}
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} else {
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Ok(expr)
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@ -551,7 +532,7 @@ impl Parser {
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/// ```
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/// logic_or := logic_and ( "or" logic_and )*
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/// ```
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fn parse_logic_or(&mut self) -> ParserResult<ast::ExprNode> {
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fn parse_logic_or(&mut self) -> SloxResult<ast::ExprNode> {
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let mut expr = self.parse_logic_and()?;
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while let Some(operator) = self.expect(&[TokenType::Or]) {
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let right = self.parse_logic_and()?;
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@ -568,7 +549,7 @@ impl Parser {
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/// ```
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/// logic_and := equality ( "and" equality )*
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/// ```
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fn parse_logic_and(&mut self) -> ParserResult<ast::ExprNode> {
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fn parse_logic_and(&mut self) -> SloxResult<ast::ExprNode> {
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let mut expr = self.parse_equality()?;
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while let Some(operator) = self.expect(&[TokenType::And]) {
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let right = self.parse_equality()?;
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@ -586,7 +567,7 @@ impl Parser {
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/// equality := comparison "==" comparison
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/// equality := comparison "!=" comparison
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/// ```
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fn parse_equality(&mut self) -> ParserResult<ast::ExprNode> {
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fn parse_equality(&mut self) -> SloxResult<ast::ExprNode> {
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let mut expr = self.parse_comparison()?;
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while let Some(operator) = self.expect(&[TokenType::BangEqual, TokenType::EqualEqual]) {
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let right = self.parse_comparison()?;
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@ -604,7 +585,7 @@ impl Parser {
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/// comparison := term comparison_operator term
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/// comparison_operator := "<" | "<=" | ">" | ">="
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/// ```
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fn parse_comparison(&mut self) -> ParserResult<ast::ExprNode> {
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fn parse_comparison(&mut self) -> SloxResult<ast::ExprNode> {
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let mut expr = self.parse_term()?;
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while let Some(operator) = self.expect(&[
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TokenType::Greater,
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@ -627,7 +608,7 @@ impl Parser {
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/// term := factor ( "+" factor )*
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/// term := factor ( "-" factor )*
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/// ```
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fn parse_term(&mut self) -> ParserResult<ast::ExprNode> {
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fn parse_term(&mut self) -> SloxResult<ast::ExprNode> {
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let mut expr = self.parse_factor()?;
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while let Some(operator) = self.expect(&[TokenType::Minus, TokenType::Plus]) {
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let right = self.parse_factor()?;
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@ -645,7 +626,7 @@ impl Parser {
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/// factor := unary ( "*" unary )*
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/// factor := unary ( "/" unary )*
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/// ```
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fn parse_factor(&mut self) -> ParserResult<ast::ExprNode> {
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fn parse_factor(&mut self) -> SloxResult<ast::ExprNode> {
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let mut expr = self.parse_unary()?;
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while let Some(operator) = self.expect(&[TokenType::Slash, TokenType::Star]) {
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let right = self.parse_unary()?;
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@ -664,7 +645,7 @@ impl Parser {
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/// unary := "!" unary
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/// unary := primary call_arguments*
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/// ```
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fn parse_unary(&mut self) -> ParserResult<ast::ExprNode> {
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fn parse_unary(&mut self) -> SloxResult<ast::ExprNode> {
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if let Some(operator) = self.expect(&[TokenType::Bang, TokenType::Minus]) {
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Ok(ast::ExprNode::Unary {
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operator,
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@ -686,7 +667,7 @@ impl Parser {
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/// primary := IDENTIFIER
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/// primary := "fun" function_info
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/// ```
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fn parse_primary(&mut self) -> ParserResult<ast::ExprNode> {
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fn parse_primary(&mut self) -> SloxResult<ast::ExprNode> {
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if self.expect(&[TokenType::LeftParen]).is_some() {
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let expr = self.parse_expression()?;
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self.consume(&TokenType::RightParen, "expected ')' after expression")?;
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@ -708,7 +689,7 @@ impl Parser {
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TokenType::Identifier(_) => Ok(ast::ExprNode::Variable {
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name: self.advance().clone(),
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}),
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_ => Err(ParserError::new(self.peek(), "expected expression")),
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_ => self.error("expected expression"),
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}
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}
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}
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@ -718,18 +699,12 @@ impl Parser {
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/// call := expression "(" arguments? ")"
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/// arguments := expression ( "," expression )*
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/// ```
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fn parse_call_arguments(
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&mut self,
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callee: ast::ExprNode,
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) -> Result<ast::ExprNode, ParserError> {
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fn parse_call_arguments(&mut self, callee: ast::ExprNode) -> Result<ast::ExprNode, SloxError> {
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let mut arguments = Vec::new();
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if !self.check(&TokenType::RightParen) {
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loop {
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if arguments.len() == 255 {
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return Err(ParserError::new(
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self.peek(),
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"functions may not have more than 255 arguments",
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));
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return self.error("functions may not have more than 255 arguments");
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}
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arguments.push(self.parse_expression()?);
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if self.expect(&[TokenType::Comma]).is_none() {
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@ -764,11 +739,11 @@ impl Parser {
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/// Consume a token of a given type. If no matching token is found, a
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/// parse error is returned instead. Otherwise the read pointer is moved.
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fn consume(&mut self, token_type: &TokenType, error: &str) -> ParserResult<&Token> {
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fn consume(&mut self, token_type: &TokenType, error: &str) -> SloxResult<&Token> {
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if self.check(token_type) {
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Ok(self.advance())
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} else {
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Err(ParserError::new(self.peek(), error))
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self.error(error)
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}
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}
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@ -841,4 +816,18 @@ impl Parser {
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pos -= 1;
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}
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}
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/// Generate an error at the current token.
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fn error<O>(&self, message: &str) -> SloxResult<O> {
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self.error_mv(message.to_owned())
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}
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/// Generate an error at the current token.
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fn error_mv<O>(&self, message: String) -> SloxResult<O> {
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Err(SloxError::with_token(
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ErrorKind::Parse,
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self.peek(),
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message,
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))
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}
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}
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