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Cleanup of eat_while() in lexer #77629

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Oct 10, 2020
Merged

Cleanup of eat_while() in lexer #77629

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34 changes: 14 additions & 20 deletions compiler/rustc_lexer/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -48,6 +48,7 @@ impl Token {
}

/// Enum representing common lexeme types.
// perf note: Changing all `usize` to `u32` doesn't change performance. See #77629
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub enum TokenKind {
// Multi-char tokens:
Expand Down Expand Up @@ -160,6 +161,7 @@ pub enum LiteralKind {
/// - `r##~"abcde"##`: `InvalidStarter`
/// - `r###"abcde"##`: `NoTerminator { expected: 3, found: 2, possible_terminator_offset: Some(11)`
/// - Too many `#`s (>65535): `TooManyDelimiters`
// perf note: It doesn't matter that this makes `Token` 36 bytes bigger. See #77629
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub enum RawStrError {
/// Non `#` characters exist between `r` and `"` eg. `r#~"..`
Expand Down Expand Up @@ -689,7 +691,12 @@ impl Cursor<'_> {
let mut max_hashes = 0;

// Count opening '#' symbols.
let n_start_hashes = self.eat_while(|c| c == '#');
let mut eaten = 0;
while self.first() == '#' {
eaten += 1;
self.bump();
}
let n_start_hashes = eaten;

// Check that string is started.
match self.bump() {
Expand Down Expand Up @@ -724,16 +731,11 @@ impl Cursor<'_> {
// Note that this will not consume extra trailing `#` characters:
// `r###"abcde"####` is lexed as a `RawStr { n_hashes: 3 }`
// followed by a `#` token.
let mut hashes_left = n_start_hashes;
let is_closing_hash = |c| {
if c == '#' && hashes_left != 0 {
hashes_left -= 1;
true
} else {
false
}
};
let n_end_hashes = self.eat_while(is_closing_hash);
let mut n_end_hashes = 0;
while self.first() == '#' && n_end_hashes < n_start_hashes {
n_end_hashes += 1;
self.bump();
}

if n_end_hashes == n_start_hashes {
return (n_start_hashes, None);
Expand Down Expand Up @@ -807,17 +809,9 @@ impl Cursor<'_> {
}

/// Eats symbols while predicate returns true or until the end of file is reached.
/// Returns amount of eaten symbols.
fn eat_while<F>(&mut self, mut predicate: F) -> usize
where
F: FnMut(char) -> bool,
{
let mut eaten: usize = 0;
fn eat_while(&mut self, mut predicate: impl FnMut(char) -> bool) {
while predicate(self.first()) && !self.is_eof() {
eaten += 1;
self.bump();
}

eaten
}
}