bjoernager/rust
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Avoid unnecessary rust_2018 calls.

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The commit combines two calls into one by saving the result in a local
variable. The commit also moves the check for `async` later, so that
when a different keyword is present the `rust_2018` call will be avoided
completely.
This commit is contained in:
Nicholas Nethercote 2019-06-03 15:34:54 +10:00
parent 425736dc97
commit ab9bbf48db
1 changed files with 11 additions and 8 deletions
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19
src/libsyntax/parse/parser.rs
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@ -2083,13 +2083,6 @@ impl<'a> Parser<'a> {
hi = path.span;
return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs));
}
if self.span.rust_2018() && self.check_keyword(kw::Async) {
return if self.is_async_block() { // check for `async {` and `async move {`
self.parse_async_block(attrs)
} else {
self.parse_lambda_expr(attrs)
};
}
if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
return self.parse_lambda_expr(attrs);
}
@ -2161,6 +2154,16 @@ impl<'a> Parser<'a> {
assert!(self.eat_keyword(kw::Try));
return self.parse_try_block(lo, attrs);
}
// Span::rust_2018() is somewhat expensive; don't get it repeatedly.
let is_span_rust_2018 = self.span.rust_2018();
if is_span_rust_2018 && self.check_keyword(kw::Async) {
return if self.is_async_block() { // check for `async {` and `async move {`
self.parse_async_block(attrs)
} else {
self.parse_lambda_expr(attrs)
};
}
if self.eat_keyword(kw::Return) {
if self.token.can_begin_expr() {
let e = self.parse_expr()?;
@ -2196,7 +2199,7 @@ impl<'a> Parser<'a> {
db.span_label(self.span, "expected expression");
db.note("variable declaration using `let` is a statement");
return Err(db);
} else if self.span.rust_2018() && self.eat_keyword(kw::Await) {
} else if is_span_rust_2018 && self.eat_keyword(kw::Await) {
let (await_hi, e_kind) = self.parse_await_macro_or_alt(lo, self.prev_span)?;
hi = await_hi;
ex = e_kind;