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optimize keyword parsing

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This commit is contained in:
Folkert 2021-03-08 15:48:22 +01:00
parent c2525d2407
commit 5029469825
1 changed files with 18 additions and 22 deletions
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40
compiler/parse/src/parser.rs
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@ -1128,31 +1128,27 @@ where
ToError: Fn(Row, Col) -> E,
E: 'a,
{
move |arena, state: State<'a>| {
let initial_state = state.clone();
// first parse the keyword characters
let (_, _, after_keyword_state) = ascii_string(keyword)
.parse(arena, state)
.map_err(|(_, _, state)| (NoProgress, if_error(state.line, state.column), state))?;
move |_, mut state: State<'a>| {
let width = keyword.len();
// then we must have at least one space character
// TODO this is potentially wasteful if there are a lot of spaces
match peek_utf8_char(&after_keyword_state) {
Ok((next, _width)) if next == ' ' || next == '#' || next == '\n' => {
// give back the state after parsing the keyword, but before the whitespace
// that way we can attach the whitespace to whatever follows
Ok((MadeProgress, (), after_keyword_state))
if !state.bytes.starts_with(keyword.as_bytes()) {
return Err((NoProgress, if_error(state.line, state.column), state));
}
// the next character should not be an identifier character
// to prevent treating `whence` or `iffy` as keywords
match state.bytes.get(width) {
Some(next) if *next == b' ' || *next == b'#' || *next == b'\n' => {
state.column += width as u16;
state.bytes = &state.bytes[width..];
Ok((MadeProgress, (), state))
}
_ => {
// this is not a keyword, maybe it's `whence` or `iffy`
// anyway, make no progress and return the initial state
// so we can try something else
Err((
NoProgress,
if_error(initial_state.line, initial_state.column),
initial_state,
))
None => {
state.column += width as u16;
state.bytes = &state.bytes[width..];
Ok((MadeProgress, (), state))
}
Some(_) => Err((NoProgress, if_error(state.line, state.column), state)),
}
}
}