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refactor: add fallible peek_last_token()

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This commit is contained in:
Aaron Blankstein
2023-01-31 09:37:45 -06:00
parent ee72c0f5b6
commit 63eab619e6
2 changed files with 18 additions and 3 deletions
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4
clarity/src/vm/ast/errors.rs
View File

@@ -88,6 +88,9 @@ pub enum ParseErrors {
ExpectedWhitespace,
// Notes
NoteToMatchThis(Token),
/// Should be an unreachable error
UnexpectedParserFailure,
}
#[derive(Debug, PartialEq)]
@@ -294,6 +297,7 @@ impl DiagnosableError for ParseErrors {
ParseErrors::IllegalUtf8String(s) => format!("illegal UTF8 string \"{}\"", s),
ParseErrors::ExpectedWhitespace => "expected whitespace before expression".to_string(),
ParseErrors::NoteToMatchThis(token) => format!("to match this '{}'", token),
ParseErrors::UnexpectedParserFailure => "unexpected failure while parsing".to_string(),
}
}

17
clarity/src/vm/ast/parser/v2/mod.rs
View File

@@ -153,6 +153,17 @@ impl<'a> Parser<'a> {
}
}
/// Get a reference to the last processed token. If there is no last token,
/// raises an UnexpectedParserFailure.
fn peek_last_token(&self) -> ParseResult<&PlacedToken> {
if self.next_token == 0 {
return Err(ParseError::new(ParseErrors::UnexpectedParserFailure));
}
self.tokens
.get(self.next_token - 1)
.ok_or_else(|| ParseError::new(ParseErrors::UnexpectedParserFailure))
}
fn skip_to_end(&mut self) {
self.next_token = self.tokens.len();
}
@@ -220,7 +231,7 @@ impl<'a> Parser<'a> {
*whitespace = self.ignore_whitespace();
Ok(None)
} else {
let token = self.tokens[self.next_token - 1].clone();
let token = self.peek_last_token()?.clone();
match token.token {
Token::Rparen => {
span.end_line = token.span.end_line;
@@ -279,7 +290,7 @@ impl<'a> Parser<'a> {
// mimic parse_node_or_eof() behavior
// if last token was an EOF, error out the tuple
// if the last token was something else, just yield back to the parse loop
let last_token = self.tokens[self.next_token - 1].clone();
let last_token = self.peek_last_token()?.clone();
match last_token.token {
Token::Eof => {
self.add_diagnostic(
@@ -359,7 +370,7 @@ impl<'a> Parser<'a> {
// mimic parse_node_or_eof() behavior
// if last token was an EOF, error out the tuple
// if the last token was something else, just yield back to the parse loop
let last_token = self.tokens[self.next_token - 1].clone();
let last_token = self.peek_last_token()?.clone();
match last_token.token {
Token::Eof => {
// This indicates we have reached the end of the input.