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Add expectation for { when parsing lone coroutine qualifiers #142362

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Merged
merged 1 commit into from
Jun 12, 2025
Merged

Add expectation for { when parsing lone coroutine qualifiers #142362

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32 changes: 19 additions & 13 deletions compiler/rustc_parse/src/parser/expr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1520,22 +1520,20 @@ impl<'a> Parser<'a> {
Ok(this.mk_expr(this.prev_token.span, ExprKind::Underscore))
} else if this.token_uninterpolated_span().at_least_rust_2018() {
// `Span::at_least_rust_2018()` is somewhat expensive; don't get it repeatedly.
let at_async = this.check_keyword(exp!(Async));
// check for `gen {}` and `gen move {}`
// or `async gen {}` and `async gen move {}`
// FIXME: (async) gen closures aren't yet parsed.
// FIXME(gen_blocks): Parse `gen async` and suggest swap
if this.token_uninterpolated_span().at_least_rust_2024()
// check for `gen {}` and `gen move {}`
// or `async gen {}` and `async gen move {}`
&& (this.is_gen_block(kw::Gen, 0)
|| (this.check_keyword(exp!(Async)) && this.is_gen_block(kw::Gen, 1)))
&& this.is_gen_block(kw::Gen, at_async as usize)
{
// FIXME: (async) gen closures aren't yet parsed.
this.parse_gen_block()
} else if this.check_keyword(exp!(Async)) {
// FIXME(gen_blocks): Parse `gen async` and suggest swap
if this.is_gen_block(kw::Async, 0) {
// Check for `async {` and `async move {`,
this.parse_gen_block()
} else {
this.parse_expr_closure()
}
Comment on lines 1522 to -1538
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Shuffled this around while looking through the call path as I found the {async} gen condition a bit heavy on the eyes. Happy to undo this

// Check for `async {` and `async move {`,
} else if this.is_gen_block(kw::Async, 0) {
this.parse_gen_block()
} else if at_async {
this.parse_expr_closure()
} else if this.eat_keyword_noexpect(kw::Await) {
this.recover_incorrect_await_syntax(lo)
} else {
Expand Down Expand Up @@ -2407,6 +2405,14 @@ impl<'a> Parser<'a> {
None
};

if let ClosureBinder::NotPresent = binder
&& coroutine_kind.is_some()
{
// coroutine closures and generators can have the same qualifiers, so we might end up
// in here if there is a missing `|` but also no `{`. Adjust the expectations in that case.
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Hmm... this feels like sth that we'd regularly hit elsewhere, too, because is_gen_block and similar functions won't put their things in the expectation list. Unsure how to resolve that, so what you wrote is ok, but it does feel a bit like papering over a more common issue

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@Veykril Veykril Jun 11, 2025 •
edited
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I was feeling the same about this actually, but I couldn't figure out a solution for this either for the time being. We would need to start consuming the qualifier list before dispatching into the actual coroutine / generator parsing routines I think given we can't build expectations for lookaheads.

self.expected_token_types.insert(TokenType::OpenBrace);
}

let capture_clause = self.parse_capture_clause()?;
let (fn_decl, fn_arg_span) = self.parse_fn_block_decl()?;
let decl_hi = self.prev_token.span;
Expand Down
8 changes: 4 additions & 4 deletions tests/ui/editions/edition-keywords-2018-2015-parsing.stderr
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Expand Up @@ -44,22 +44,22 @@ note: while trying to match `r#async`
LL | (r#async) => (1)
| ^^^^^^^

error: macro expansion ends with an incomplete expression: expected one of `move`, `use`, `|`, or `||`
error: macro expansion ends with an incomplete expression: expected one of `move`, `use`, `{`, `|`, or `||`
--> $DIR/auxiliary/edition-kw-macro-2015.rs:27:23
|
LL | ($i: ident) => ($i)
| ^ expected one of `move`, `use`, `|`, or `||`
| ^ expected one of `move`, `use`, `{`, `|`, or `||`
|
::: $DIR/edition-keywords-2018-2015-parsing.rs:22:8
|
LL | if passes_ident!(async) == 1 {} // FIXME: Edition hygiene bug, async here is 2018 and reserved
| -------------------- in this macro invocation

error: macro expansion ends with an incomplete expression: expected one of `move`, `use`, `|`, or `||`
error: macro expansion ends with an incomplete expression: expected one of `move`, `use`, `{`, `|`, or `||`
--> $DIR/edition-keywords-2018-2015-parsing.rs:24:24
|
LL | if passes_tt!(async) == 1 {}
| ^ expected one of `move`, `use`, `|`, or `||`
| ^ expected one of `move`, `use`, `{`, `|`, or `||`

error[E0308]: mismatched types
--> $DIR/edition-keywords-2018-2015-parsing.rs:29:33
Expand Down
16 changes: 8 additions & 8 deletions tests/ui/editions/edition-keywords-2018-2018-parsing.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -44,34 +44,34 @@ note: while trying to match `r#async`
LL | (r#async) => (1)
| ^^^^^^^

error: macro expansion ends with an incomplete expression: expected one of `move`, `use`, `|`, or `||`
error: macro expansion ends with an incomplete expression: expected one of `move`, `use`, `{`, `|`, or `||`
--> $DIR/auxiliary/edition-kw-macro-2018.rs:27:23
|
LL | ($i: ident) => ($i)
| ^ expected one of `move`, `use`, `|`, or `||`
| ^ expected one of `move`, `use`, `{`, `|`, or `||`
|
::: $DIR/edition-keywords-2018-2018-parsing.rs:29:8
|
LL | if passes_ident!(async) == 1 {} // FIXME: Edition hygiene bug, async here is 2018 and reserved
| -------------------- in this macro invocation

error: macro expansion ends with an incomplete expression: expected one of `move`, `use`, `|`, or `||`
error: macro expansion ends with an incomplete expression: expected one of `move`, `use`, `{`, `|`, or `||`
--> $DIR/edition-keywords-2018-2018-parsing.rs:31:24
|
LL | if passes_tt!(async) == 1 {}
| ^ expected one of `move`, `use`, `|`, or `||`
| ^ expected one of `move`, `use`, `{`, `|`, or `||`

error: macro expansion ends with an incomplete expression: expected one of `move`, `use`, `|`, or `||`
error: macro expansion ends with an incomplete expression: expected one of `move`, `use`, `{`, `|`, or `||`
--> $DIR/edition-keywords-2018-2018-parsing.rs:14:23
|
LL | ($i: ident) => ($i)
| ^ expected one of `move`, `use`, `|`, or `||`
| ^ expected one of `move`, `use`, `{`, `|`, or `||`

error: macro expansion ends with an incomplete expression: expected one of `move`, `use`, `|`, or `||`
error: macro expansion ends with an incomplete expression: expected one of `move`, `use`, `{`, `|`, or `||`
--> $DIR/edition-keywords-2018-2018-parsing.rs:35:30
|
LL | if local_passes_tt!(async) == 1 {}
| ^ expected one of `move`, `use`, `|`, or `||`
| ^ expected one of `move`, `use`, `{`, `|`, or `||`

error[E0308]: mismatched types
--> $DIR/edition-keywords-2018-2018-parsing.rs:40:33
Expand Down
4 changes: 2 additions & 2 deletions tests/ui/parser/block-no-opening-brace.rs
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Expand Up @@ -27,10 +27,10 @@ fn in_try() {
let x = 0;
}

// FIXME(#80931)
fn in_async() {
async
let x = 0; //~ ERROR expected one of `move`, `use`, `|`, or `||`, found keyword `let`
let x = 0;
//~^ ERROR expected one of `move`, `use`, `{`, `|`, or `||`, found keyword `let`
}

// FIXME(#78168)
Expand Down
6 changes: 3 additions & 3 deletions tests/ui/parser/block-no-opening-brace.stderr
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Expand Up @@ -43,11 +43,11 @@ error: expected expression, found reserved keyword `try`
LL | try
| ^^^ expected expression

error: expected one of `move`, `use`, `|`, or `||`, found keyword `let`
--> $DIR/block-no-opening-brace.rs:33:9
error: expected one of `move`, `use`, `{`, `|`, or `||`, found keyword `let`
--> $DIR/block-no-opening-brace.rs:32:9
|
LL | async
| - expected one of `move`, `use`, `|`, or `||`
| - expected one of `move`, `use`, `{`, `|`, or `||`
LL | let x = 0;
| ^^^ unexpected token

Expand Down
4 changes: 2 additions & 2 deletions tests/ui/parser/misspelled-keywords/async-move.stderr
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@@ -1,8 +1,8 @@
error: expected one of `move`, `use`, `|`, or `||`, found `Move`
error: expected one of `move`, `use`, `{`, `|`, or `||`, found `Move`
--> $DIR/async-move.rs:4:11
|
LL | async Move {}
| ^^^^ expected one of `move`, `use`, `|`, or `||`
| ^^^^ expected one of `move`, `use`, `{`, `|`, or `||`
|
help: write keyword `move` in lowercase
|
Expand Down
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