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Optimize Parser::is_composite a little

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This commit is contained in:
Laurențiu Nicola 2019-08-04 14:06:07 +03:00
parent 6f5ac06b47
commit b118f7511c
1 changed files with 35 additions and 19 deletions
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54
crates/ra_parser/src/parser.rs
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@ -6,7 +6,7 @@ use crate::{
event::Event,
ParseError,
SyntaxKind::{self, EOF, ERROR, TOMBSTONE},
TokenSet, TokenSource, T,
Token, TokenSet, TokenSource, T,
};
/// `Parser` struct provides the low-level API for
@ -87,8 +87,9 @@ impl<'t> Parser<'t> {
let mut i = 0;
loop {
let mut kind = self.token_source.lookahead_nth(i).kind;
if let Some((composited, step)) = self.is_composite(kind, i) {
let token = self.token_source.lookahead_nth(i);
let mut kind = token.kind;
if let Some((composited, step)) = self.is_composite(token, i) {
kind = composited;
i += step;
} else {
@ -250,32 +251,47 @@ impl<'t> Parser<'t> {
}
/// helper function for check if it is composite.
fn is_composite(&self, kind: SyntaxKind, n: usize) -> Option<(SyntaxKind, usize)> {
fn is_composite(&self, first: Token, n: usize) -> Option<(SyntaxKind, usize)> {
// We assume the dollars will not occuried between
// mult-byte tokens
let first = self.token_source.lookahead_nth(n);
let jn1 = first.is_jointed_to_next;
if !jn1 && first.kind != T![-] {
return None;
}
let second = self.token_source.lookahead_nth(n + 1);
if first.kind == T![-] && second.kind == T![>] {
return Some((T![->], 2));
}
if !jn1 {
return None;
}
match (first.kind, second.kind) {
(T![:], T![:]) => return Some((T![::], 2)),
(T![=], T![=]) => return Some((T![==], 2)),
(T![=], T![>]) => return Some((T![=>], 2)),
(T![!], T![=]) => return Some((T![!=], 2)),
_ => {}
}
if first.kind != T![.] || second.kind != T![.] {
return None;
}
let third = self.token_source.lookahead_nth(n + 2);
let jn1 = first.is_jointed_to_next;
let la2 = second.kind;
let jn2 = second.is_jointed_to_next;
let la3 = third.kind;
match kind {
T![.] if jn1 && la2 == T![.] && jn2 && la3 == T![.] => Some((T![...], 3)),
T![.] if jn1 && la2 == T![.] && la3 == T![=] => Some((T![..=], 3)),
T![.] if jn1 && la2 == T![.] => Some((T![..], 2)),
T![:] if jn1 && la2 == T![:] => Some((T![::], 2)),
T![=] if jn1 && la2 == T![=] => Some((T![==], 2)),
T![=] if jn1 && la2 == T![>] => Some((T![=>], 2)),
T![!] if jn1 && la2 == T![=] => Some((T![!=], 2)),
T![-] if la2 == T![>] => Some((T![->], 2)),
_ => None,
if jn2 && la3 == T![.] {
return Some((T![...], 3));
}
if la3 == T![=] {
return Some((T![..=], 3));
}
return Some((T![..], 2));
}
fn eat_dollars(&mut self) {