tseeker-pub/rust-crafting-interpreters-part-1
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Parser - Some refactoring of code that handles identifiers

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This commit is contained in:
Emmanuel BENOîT 2023-01-08 11:31:02 +01:00
parent e006a12c80
commit 334dc99752
1 changed files with 21 additions and 29 deletions
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46
src/parser.rs
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@ -200,10 +200,7 @@ impl Parser {
/// var_declaration := "var" IDENTIFIER "=" expression ";"
/// ```
fn parse_var_declaration(&mut self) -> SloxResult<StmtNode> {
let name = match self.peek().token_type {
TokenType::Identifier(_) => self.advance().clone(),
_ => return self.error("expected variable name"),
};
let name = self.consume_identifier("expected variable name")?;
let initializer: Option<ExprNode> = match self.expect(&[TokenType::Equal]) {
Some(_) => Some(self.parse_expression()?),
None => None,
@ -220,12 +217,7 @@ impl Parser {
/// class := IDENTIFIER "{" function* "}"
/// ```
fn parse_class(&mut self) -> SloxResult<StmtNode> {
// Read the name
let name = match self.peek().token_type {
TokenType::Identifier(_) => self.advance().clone(),
_ => return self.error("class name expected"),
};
// Read the body
let name = self.consume_identifier("expected class name")?;
self.consume(&TokenType::LeftBrace, "'{' expected")?;
let mut methods = Vec::new();
while !self.check(&TokenType::RightBrace) && !self.is_at_end() {
@ -245,11 +237,7 @@ impl Parser {
/// ```
/// The `kind` parameter is used to generate error messages.
fn parse_function(&mut self, kind: FunctionKind) -> SloxResult<StmtNode> {
// Read the name
let name = match self.peek().token_type {
TokenType::Identifier(_) => self.advance().clone(),
_ => return self.error_mv(format!("expected {} name", kind.name())),
};
let name = self.consume_identifier(&format!("expected {} name", kind.name()))?;
let (params, block) = self.parse_function_info(kind)?;
Ok(StmtNode::FunDecl(FunDecl {
name,
@ -284,15 +272,12 @@ impl Parser {
kind.max_params()
));
}
if let TokenType::Identifier(name) = &self.peek().token_type {
if names.contains(name) {
let name = self.consume_identifier("parameter name expected")?;
if names.contains(&name.lexeme) {
return self.error_mv(format!("duplicate {} parameter", kind.name()));
}
names.insert(name.to_owned());
names.insert(name.lexeme);
params.push(self.advance().clone());
} else {
return self.error("parameter name expected");
}
if self.expect(&[TokenType::Comma]).is_none() {
break;
}
@ -357,11 +342,7 @@ impl Parser {
/// labelled_loop := "@" IDENTIFIER for_statement
/// ```
fn parse_labelled_loop(&mut self) -> SloxResult<StmtNode> {
let name_token = match self.peek().token_type {
TokenType::Identifier(_) => self.advance().clone(),
_ => return self.error("identifier expected after '@'"),
};
let name_token = self.consume_identifier("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() {
@ -478,7 +459,7 @@ impl Parser {
));
}
let loop_name = if let TokenType::Identifier(_) = self.peek().token_type {
let loop_name = if self.peek().is_identifier() {
let name_token = self.advance().clone();
if !self.find_named_loop(&name_token.lexeme) {
self.expect(&[TokenType::Semicolon]);
@ -817,6 +798,17 @@ impl Parser {
self.previous()
}
/// Advance if the current token is an identifier, returning a clone of
/// the token. If it isn't, an error with the specified message is
/// returned instead.
fn consume_identifier(&mut self, message: &str) -> SloxResult<Token> {
if self.peek().is_identifier() {
Ok(self.advance().clone())
} else {
self.error(message)
}
}
/// Check whether the end of token stream has been reached by checking
/// for the `EOF` token.
fn is_at_end(&self) -> bool {