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Rollup merge of #61321 - Centril:is_keyword_ahead, r=petrochenkov
libsyntax: introduce 'fn is_keyword_ahead(dist, keywords)'. Introduces: ```rust /// Returns whether any of the given keywords are `dist` tokens ahead of the current one. fn is_keyword_ahead(&self, dist: usize, kws: &[Symbol]) -> bool { self.look_ahead(dist, |t| kws.iter().any(|&kw| t.is_keyword(kw))) } ``` r? @oli-obk
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‎src/libsyntax/parse/parser.rs

+38-35
Original file line numberDiff line numberDiff line change
@@ -1087,6 +1087,11 @@ impl<'a> Parser<'a> {
10871087
}
10881088
}
10891089

1090+
/// Returns whether any of the given keywords are `dist` tokens ahead of the current one.
1091+
fn is_keyword_ahead(&self, dist: usize, kws: &[Symbol]) -> bool {
1092+
self.look_ahead(dist, |t| kws.iter().any(|&kw| t.is_keyword(kw)))
1093+
}
1094+
10901095
/// Is the current token one of the keywords that signals a bare function type?
10911096
fn token_is_bare_fn_keyword(&mut self) -> bool {
10921097
self.check_keyword(kw::Fn) ||
@@ -4270,7 +4275,7 @@ impl<'a> Parser<'a> {
42704275
self.token.is_keyword(kw::Async) &&
42714276
(
42724277
( // `async move {`
4273-
self.look_ahead(1, |t| t.is_keyword(kw::Move)) &&
4278+
self.is_keyword_ahead(1, &[kw::Move]) &&
42744279
self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
42754280
) || ( // `async {`
42764281
self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
@@ -4280,12 +4285,12 @@ impl<'a> Parser<'a> {
42804285

42814286
fn is_async_fn(&self) -> bool {
42824287
self.token.is_keyword(kw::Async) &&
4283-
self.look_ahead(1, |t| t.is_keyword(kw::Fn))
4288+
self.is_keyword_ahead(1, &[kw::Fn])
42844289
}
42854290

42864291
fn is_do_catch_block(&self) -> bool {
42874292
self.token.is_keyword(kw::Do) &&
4288-
self.look_ahead(1, |t| t.is_keyword(kw::Catch)) &&
4293+
self.is_keyword_ahead(1, &[kw::Catch]) &&
42894294
self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace)) &&
42904295
!self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
42914296
}
@@ -4309,17 +4314,17 @@ impl<'a> Parser<'a> {
43094314

43104315
fn is_existential_type_decl(&self) -> bool {
43114316
self.token.is_keyword(kw::Existential) &&
4312-
self.look_ahead(1, |t| t.is_keyword(kw::Type))
4317+
self.is_keyword_ahead(1, &[kw::Type])
43134318
}
43144319

43154320
fn is_auto_trait_item(&self) -> bool {
43164321
// auto trait
4317-
(self.token.is_keyword(kw::Auto)
4318-
&& self.look_ahead(1, |t| t.is_keyword(kw::Trait)))
4322+
(self.token.is_keyword(kw::Auto) &&
4323+
self.is_keyword_ahead(1, &[kw::Trait]))
43194324
|| // unsafe auto trait
43204325
(self.token.is_keyword(kw::Unsafe) &&
4321-
self.look_ahead(1, |t| t.is_keyword(kw::Auto)) &&
4322-
self.look_ahead(2, |t| t.is_keyword(kw::Trait)))
4326+
self.is_keyword_ahead(1, &[kw::Auto]) &&
4327+
self.is_keyword_ahead(2, &[kw::Trait]))
43234328
}
43244329

43254330
fn eat_macro_def(&mut self, attrs: &[Attribute], vis: &Visibility, lo: Span)
@@ -5486,7 +5491,7 @@ impl<'a> Parser<'a> {
54865491
(if isolated_self(self, 1) {
54875492
self.bump();
54885493
SelfKind::Region(None, Mutability::Immutable)
5489-
} else if self.look_ahead(1, |t| t.is_keyword(kw::Mut)) &&
5494+
} else if self.is_keyword_ahead(1, &[kw::Mut]) &&
54905495
isolated_self(self, 2) {
54915496
self.bump();
54925497
self.bump();
@@ -5497,7 +5502,7 @@ impl<'a> Parser<'a> {
54975502
let lt = self.expect_lifetime();
54985503
SelfKind::Region(Some(lt), Mutability::Immutable)
54995504
} else if self.look_ahead(1, |t| t.is_lifetime()) &&
5500-
self.look_ahead(2, |t| t.is_keyword(kw::Mut)) &&
5505+
self.is_keyword_ahead(2, &[kw::Mut]) &&
55015506
isolated_self(self, 3) {
55025507
self.bump();
55035508
let lt = self.expect_lifetime();
@@ -5676,8 +5681,7 @@ impl<'a> Parser<'a> {
56765681
/// (returns `false` for things like `const fn`, etc.).
56775682
fn is_const_item(&self) -> bool {
56785683
self.token.is_keyword(kw::Const) &&
5679-
!self.look_ahead(1, |t| t.is_keyword(kw::Fn)) &&
5680-
!self.look_ahead(1, |t| t.is_keyword(kw::Unsafe))
5684+
!self.is_keyword_ahead(1, &[kw::Fn, kw::Unsafe])
56815685
}
56825686

56835687
/// Parses all the "front matter" for a `fn` declaration, up to
@@ -5955,7 +5959,7 @@ impl<'a> Parser<'a> {
59555959
self.look_ahead(1, |t| t.is_lifetime() || t.is_ident()) &&
59565960
self.look_ahead(2, |t| t == &token::Gt || t == &token::Comma ||
59575961
t == &token::Colon || t == &token::Eq) ||
5958-
self.look_ahead(1, |t| t.is_keyword(kw::Const)))
5962+
self.is_keyword_ahead(1, &[kw::Const]))
59595963
}
59605964

59615965
fn parse_impl_body(&mut self) -> PResult<'a, (Vec<ImplItem>, Vec<Attribute>)> {
@@ -6316,7 +6320,7 @@ impl<'a> Parser<'a> {
63166320
// `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`.
63176321
// Because of this, we only `bump` the `(` if we're assured it is appropriate to do so
63186322
// by the following tokens.
6319-
if self.look_ahead(1, |t| t.is_keyword(kw::Crate)) &&
6323+
if self.is_keyword_ahead(1, &[kw::Crate]) &&
63206324
self.look_ahead(2, |t| t != &token::ModSep) // account for `pub(crate::foo)`
63216325
{
63226326
// `pub(crate)`
@@ -6328,7 +6332,7 @@ impl<'a> Parser<'a> {
63286332
VisibilityKind::Crate(CrateSugar::PubCrate),
63296333
);
63306334
return Ok(vis)
6331-
} else if self.look_ahead(1, |t| t.is_keyword(kw::In)) {
6335+
} else if self.is_keyword_ahead(1, &[kw::In]) {
63326336
// `pub(in path)`
63336337
self.bump(); // `(`
63346338
self.bump(); // `in`
@@ -6340,8 +6344,7 @@ impl<'a> Parser<'a> {
63406344
});
63416345
return Ok(vis)
63426346
} else if self.look_ahead(2, |t| t == &token::CloseDelim(token::Paren)) &&
6343-
self.look_ahead(1, |t| t.is_keyword(kw::Super) ||
6344-
t.is_keyword(kw::SelfLower))
6347+
self.is_keyword_ahead(1, &[kw::Super, kw::SelfLower])
63456348
{
63466349
// `pub(self)` or `pub(super)`
63476350
self.bump(); // `(`
@@ -6380,13 +6383,16 @@ impl<'a> Parser<'a> {
63806383
fn parse_defaultness(&mut self) -> Defaultness {
63816384
// `pub` is included for better error messages
63826385
if self.check_keyword(kw::Default) &&
6383-
self.look_ahead(1, |t| t.is_keyword(kw::Impl) ||
6384-
t.is_keyword(kw::Const) ||
6385-
t.is_keyword(kw::Fn) ||
6386-
t.is_keyword(kw::Unsafe) ||
6387-
t.is_keyword(kw::Extern) ||
6388-
t.is_keyword(kw::Type) ||
6389-
t.is_keyword(kw::Pub)) {
6386+
self.is_keyword_ahead(1, &[
6387+
kw::Impl,
6388+
kw::Const,
6389+
kw::Fn,
6390+
kw::Unsafe,
6391+
kw::Extern,
6392+
kw::Type,
6393+
kw::Pub,
6394+
])
6395+
{
63906396
self.bump(); // `default`
63916397
Defaultness::Default
63926398
} else {
@@ -6880,7 +6886,7 @@ impl<'a> Parser<'a> {
68806886
// Ident ["<"...">"] ["where" ...] ("=" | ":") Ty ";"
68816887
if self.check_keyword(kw::Type) ||
68826888
self.check_keyword(kw::Existential) &&
6883-
self.look_ahead(1, |t| t.is_keyword(kw::Type)) {
6889+
self.is_keyword_ahead(1, &[kw::Type]) {
68846890
let existential = self.eat_keyword(kw::Existential);
68856891
assert!(self.eat_keyword(kw::Type));
68866892
Some(self.parse_existential_or_alias(existential))
@@ -7157,7 +7163,7 @@ impl<'a> Parser<'a> {
71577163
let const_span = self.prev_span;
71587164
if self.check_keyword(kw::Fn)
71597165
|| (self.check_keyword(kw::Unsafe)
7160-
&& self.look_ahead(1, |t| t.is_keyword(kw::Fn))) {
7166+
&& self.is_keyword_ahead(1, &[kw::Fn])) {
71617167
// CONST FUNCTION ITEM
71627168
let unsafety = self.parse_unsafety();
71637169
self.bump();
@@ -7202,10 +7208,10 @@ impl<'a> Parser<'a> {
72027208
// `unsafe async fn` or `async fn`
72037209
if (
72047210
self.check_keyword(kw::Unsafe) &&
7205-
self.look_ahead(1, |t| t.is_keyword(kw::Async))
7211+
self.is_keyword_ahead(1, &[kw::Async])
72067212
) || (
72077213
self.check_keyword(kw::Async) &&
7208-
self.look_ahead(1, |t| t.is_keyword(kw::Fn))
7214+
self.is_keyword_ahead(1, &[kw::Fn])
72097215
)
72107216
{
72117217
// ASYNC FUNCTION ITEM
@@ -7239,8 +7245,7 @@ impl<'a> Parser<'a> {
72397245
return Ok(Some(item));
72407246
}
72417247
if self.check_keyword(kw::Unsafe) &&
7242-
(self.look_ahead(1, |t| t.is_keyword(kw::Trait)) ||
7243-
self.look_ahead(1, |t| t.is_keyword(kw::Auto)))
7248+
self.is_keyword_ahead(1, &[kw::Trait, kw::Auto])
72447249
{
72457250
// UNSAFE TRAIT ITEM
72467251
self.bump(); // `unsafe`
@@ -7263,11 +7268,9 @@ impl<'a> Parser<'a> {
72637268
}
72647269
if self.check_keyword(kw::Impl) ||
72657270
self.check_keyword(kw::Unsafe) &&
7266-
self.look_ahead(1, |t| t.is_keyword(kw::Impl)) ||
7267-
self.check_keyword(kw::Default) &&
7268-
self.look_ahead(1, |t| t.is_keyword(kw::Impl)) ||
7271+
self.is_keyword_ahead(1, &[kw::Impl]) ||
72697272
self.check_keyword(kw::Default) &&
7270-
self.look_ahead(1, |t| t.is_keyword(kw::Unsafe)) {
7273+
self.is_keyword_ahead(1, &[kw::Impl, kw::Unsafe]) {
72717274
// IMPL ITEM
72727275
let defaultness = self.parse_defaultness();
72737276
let unsafety = self.parse_unsafety();
@@ -7360,7 +7363,7 @@ impl<'a> Parser<'a> {
73607363
}
73617364
if self.check_keyword(kw::Trait)
73627365
|| (self.check_keyword(kw::Auto)
7363-
&& self.look_ahead(1, |t| t.is_keyword(kw::Trait)))
7366+
&& self.is_keyword_ahead(1, &[kw::Trait]))
73647367
{
73657368
let is_auto = if self.eat_keyword(kw::Trait) {
73667369
IsAuto::No

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