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andrewpollackandrewpollack
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Revert "Replace usage of ResumeTy in async lowering with Context"
1 parent 7ab8038 commit 8441ca5

14 files changed

+43
-70
lines changed

‎compiler/rustc_ast_lowering/src/expr.rs

+21-36
Original file line numberDiff line numberDiff line change
@@ -16,7 +16,7 @@ use rustc_hir::def::Res;
1616
use rustc_hir::definitions::DefPathData;
1717
use rustc_session::errors::report_lit_error;
1818
use rustc_span::source_map::{respan, DesugaringKind, Span, Spanned};
19-
use rustc_span::symbol::{kw, sym, Ident};
19+
use rustc_span::symbol::{sym, Ident};
2020
use rustc_span::DUMMY_SP;
2121
use thin_vec::thin_vec;
2222

@@ -596,38 +596,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
596596
) -> hir::ExprKind<'hir> {
597597
let output = ret_ty.unwrap_or_else(|| hir::FnRetTy::DefaultReturn(self.lower_span(span)));
598598

599-
// Resume argument type, which should be `&mut Context<'_>`.
600-
// NOTE: Using the `'static` lifetime here is technically cheating.
601-
// The `Future::poll` argument really is `&'a mut Context<'b>`, but we cannot
602-
// express the fact that we are not storing it across yield-points yet,
603-
// and we would thus run into lifetime errors.
604-
// See <https://github.com/rust-lang/rust/issues/68923>.
605-
// Our lowering makes sure we are not mis-using the `_task_context` input type
606-
// in the sense that we are indeed not using it across yield points. We
607-
// get a fresh `&mut Context` for each resume / call of `Future::poll`.
608-
// This "cheating" was previously done with a `ResumeTy` that contained a raw
609-
// pointer, and a `get_context` accessor that pulled the `Context` lifetimes
610-
// out of thin air.
611-
let context_lifetime_ident = Ident::with_dummy_span(kw::StaticLifetime);
612-
let context_lifetime = self.arena.alloc(hir::Lifetime {
613-
hir_id: self.next_id(),
614-
ident: context_lifetime_ident,
615-
res: hir::LifetimeName::Static,
616-
});
617-
let context_path =
618-
hir::QPath::LangItem(hir::LangItem::Context, self.lower_span(span), None);
619-
let context_ty = hir::MutTy {
620-
ty: self.arena.alloc(hir::Ty {
621-
hir_id: self.next_id(),
622-
kind: hir::TyKind::Path(context_path),
623-
span: self.lower_span(span),
624-
}),
625-
mutbl: hir::Mutability::Mut,
626-
};
599+
// Resume argument type: `ResumeTy`
600+
let unstable_span =
601+
self.mark_span_with_reason(DesugaringKind::Async, span, self.allow_gen_future.clone());
602+
let resume_ty = hir::QPath::LangItem(hir::LangItem::ResumeTy, unstable_span, None);
627603
let input_ty = hir::Ty {
628604
hir_id: self.next_id(),
629-
kind: hir::TyKind::Rptr(context_lifetime, context_ty),
630-
span: self.lower_span(span),
605+
kind: hir::TyKind::Path(resume_ty),
606+
span: unstable_span,
631607
};
632608

633609
// The closure/generator `FnDecl` takes a single (resume) argument of type `input_ty`.
@@ -686,9 +662,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
686662
.map_or(false, |attrs| attrs.into_iter().any(|attr| attr.has_name(sym::track_caller)));
687663

688664
let hir_id = self.lower_node_id(closure_node_id);
689-
let unstable_span =
690-
self.mark_span_with_reason(DesugaringKind::Async, span, self.allow_gen_future.clone());
691665
if track_caller {
666+
let unstable_span = self.mark_span_with_reason(
667+
DesugaringKind::Async,
668+
span,
669+
self.allow_gen_future.clone(),
670+
);
692671
self.lower_attrs(
693672
hir_id,
694673
&[Attribute {
@@ -731,7 +710,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
731710
/// mut __awaitee => loop {
732711
/// match unsafe { ::std::future::Future::poll(
733712
/// <::std::pin::Pin>::new_unchecked(&mut __awaitee),
734-
/// task_context,
713+
/// ::std::future::get_context(task_context),
735714
/// ) } {
736715
/// ::std::task::Poll::Ready(result) => break result,
737716
/// ::std::task::Poll::Pending => {}
@@ -772,7 +751,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
772751
// unsafe {
773752
// ::std::future::Future::poll(
774753
// ::std::pin::Pin::new_unchecked(&mut __awaitee),
775-
// task_context,
754+
// ::std::future::get_context(task_context),
776755
// )
777756
// }
778757
let poll_expr = {
@@ -790,10 +769,16 @@ impl<'hir> LoweringContext<'_, 'hir> {
790769
arena_vec![self; ref_mut_awaitee],
791770
Some(expr_hir_id),
792771
);
772+
let get_context = self.expr_call_lang_item_fn_mut(
773+
gen_future_span,
774+
hir::LangItem::GetContext,
775+
arena_vec![self; task_context],
776+
Some(expr_hir_id),
777+
);
793778
let call = self.expr_call_lang_item_fn(
794779
span,
795780
hir::LangItem::FuturePoll,
796-
arena_vec![self; new_unchecked, task_context],
781+
arena_vec![self; new_unchecked, get_context],
797782
Some(expr_hir_id),
798783
);
799784
self.arena.alloc(self.expr_unsafe(call))

‎compiler/rustc_hir/src/lang_items.rs

+2-1
Original file line numberDiff line numberDiff line change
@@ -286,9 +286,10 @@ language_item_table! {
286286

287287
// FIXME(swatinem): the following lang items are used for async lowering and
288288
// should become obsolete eventually.
289+
ResumeTy, sym::ResumeTy, resume_ty, Target::Struct, GenericRequirement::None;
289290
IdentityFuture, sym::identity_future, identity_future_fn, Target::Fn, GenericRequirement::None;
291+
GetContext, sym::get_context, get_context_fn, Target::Fn, GenericRequirement::None;
290292

291-
Context, sym::Context, context, Target::Struct, GenericRequirement::None;
292293
FuturePoll, sym::poll, future_poll_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;
293294

294295
FromFrom, sym::from, from_fn, Target::Method(MethodKind::Trait { body: false }), GenericRequirement::None;

‎compiler/rustc_span/src/symbol.rs

+2-1
Original file line numberDiff line numberDiff line change
@@ -164,7 +164,6 @@ symbols! {
164164
Capture,
165165
Center,
166166
Clone,
167-
Context,
168167
Continue,
169168
Copy,
170169
Count,
@@ -264,6 +263,7 @@ symbols! {
264263
Relaxed,
265264
Release,
266265
Result,
266+
ResumeTy,
267267
Return,
268268
Right,
269269
Rust,
@@ -753,6 +753,7 @@ symbols! {
753753
generic_associated_types_extended,
754754
generic_const_exprs,
755755
generic_param_attrs,
756+
get_context,
756757
global_allocator,
757758
global_asm,
758759
globs,

‎library/core/src/future/mod.rs

+2-8
Original file line numberDiff line numberDiff line change
@@ -44,7 +44,7 @@ pub use poll_fn::{poll_fn, PollFn};
4444
/// non-Send/Sync as well, and we don't want that.
4545
///
4646
/// It also simplifies the HIR lowering of `.await`.
47-
// FIXME(swatinem): This type can be removed when bumping the bootstrap compiler
47+
#[cfg_attr(not(bootstrap), lang = "ResumeTy")]
4848
#[doc(hidden)]
4949
#[unstable(feature = "gen_future", issue = "50547")]
5050
#[derive(Debug, Copy, Clone)]
@@ -61,7 +61,6 @@ unsafe impl Sync for ResumeTy {}
6161
/// This function returns a `GenFuture` underneath, but hides it in `impl Trait` to give
6262
/// better error messages (`impl Future` rather than `GenFuture<[closure.....]>`).
6363
// This is `const` to avoid extra errors after we recover from `const async fn`
64-
// FIXME(swatinem): This fn can be removed when bumping the bootstrap compiler
6564
#[cfg_attr(bootstrap, lang = "from_generator")]
6665
#[doc(hidden)]
6766
#[unstable(feature = "gen_future", issue = "50547")]
@@ -103,8 +102,7 @@ where
103102
GenFuture(gen)
104103
}
105104

106-
// FIXME(swatinem): This fn can be removed when bumping the bootstrap compiler
107-
#[cfg_attr(bootstrap, lang = "get_context")]
105+
#[lang = "get_context"]
108106
#[doc(hidden)]
109107
#[unstable(feature = "gen_future", issue = "50547")]
110108
#[must_use]
@@ -115,10 +113,6 @@ pub unsafe fn get_context<'a, 'b>(cx: ResumeTy) -> &'a mut Context<'b> {
115113
unsafe { &mut *cx.0.as_ptr().cast() }
116114
}
117115

118-
// FIXME(swatinem): This fn is currently needed to work around shortcomings
119-
// in type and lifetime inference.
120-
// See the comment at the bottom of `LoweringContext::make_async_expr` and
121-
// <https://github.com/rust-lang/rust/issues/104826>.
122116
#[cfg_attr(not(bootstrap), lang = "identity_future")]
123117
#[doc(hidden)]
124118
#[unstable(feature = "gen_future", issue = "50547")]

‎library/core/src/task/wake.rs

-1
Original file line numberDiff line numberDiff line change
@@ -174,7 +174,6 @@ impl RawWakerVTable {
174174
/// Currently, `Context` only serves to provide access to a [`&Waker`](Waker)
175175
/// which can be used to wake the current task.
176176
#[stable(feature = "futures_api", since = "1.36.0")]
177-
#[cfg_attr(not(bootstrap), lang = "Context")]
178177
pub struct Context<'a> {
179178
waker: &'a Waker,
180179
// Ensure we future-proof against variance changes by forcing

‎src/test/ui/async-await/async-await-let-else.drop-tracking.stderr

+1-1
Original file line numberDiff line numberDiff line change
@@ -40,7 +40,7 @@ LL | async fn bar2<T>(_: T) -> ! {
4040
LL | | panic!()
4141
LL | | }
4242
| |_^
43-
= note: required because it captures the following types: `&mut Context<'_>`, `Option<bool>`, `impl Future<Output = !>`, `()`
43+
= note: required because it captures the following types: `ResumeTy`, `Option<bool>`, `impl Future<Output = !>`, `()`
4444
note: required because it's used within this `async fn` body
4545
--> $DIR/async-await-let-else.rs:21:32
4646
|

‎src/test/ui/async-await/issue-68112.drop_tracking.stderr

+1-1
Original file line numberDiff line numberDiff line change
@@ -57,7 +57,7 @@ note: required because it appears within the type `impl Future<Output = Arc<RefC
5757
|
5858
LL | fn make_non_send_future2() -> impl Future<Output = Arc<RefCell<i32>>> {
5959
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
60-
= note: required because it captures the following types: `&mut Context<'_>`, `impl Future<Output = Arc<RefCell<i32>>>`, `()`, `Ready<i32>`
60+
= note: required because it captures the following types: `ResumeTy`, `impl Future<Output = Arc<RefCell<i32>>>`, `()`, `Ready<i32>`
6161
note: required because it's used within this `async` block
6262
--> $DIR/issue-68112.rs:60:20
6363
|

‎src/test/ui/async-await/issue-68112.no_drop_tracking.stderr

+1-1
Original file line numberDiff line numberDiff line change
@@ -57,7 +57,7 @@ note: required because it appears within the type `impl Future<Output = Arc<RefC
5757
|
5858
LL | fn make_non_send_future2() -> impl Future<Output = Arc<RefCell<i32>>> {
5959
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
60-
= note: required because it captures the following types: `&mut Context<'_>`, `impl Future<Output = Arc<RefCell<i32>>>`, `()`, `i32`, `Ready<i32>`
60+
= note: required because it captures the following types: `ResumeTy`, `impl Future<Output = Arc<RefCell<i32>>>`, `()`, `i32`, `Ready<i32>`
6161
note: required because it's used within this `async` block
6262
--> $DIR/issue-68112.rs:60:20
6363
|

‎src/test/ui/async-await/issue-69446-fnmut-capture.stderr

-3
Original file line numberDiff line numberDiff line change
@@ -14,9 +14,6 @@ LL | | });
1414
|
1515
= note: `FnMut` closures only have access to their captured variables while they are executing...
1616
= note: ...therefore, they cannot allow references to captured variables to escape
17-
= note: requirement occurs because of a mutable reference to `Context<'_>`
18-
= note: mutable references are invariant over their type parameter
19-
= help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
2017

2118
error: aborting due to previous error
2219

‎src/test/ui/async-await/issue-70935-complex-spans.drop_tracking.stderr

+1-1
Original file line numberDiff line numberDiff line change
@@ -18,7 +18,7 @@ LL | async fn baz<T>(_c: impl FnMut() -> T) where T: Future<Output=()> {
1818
| ___________________________________________________________________^
1919
LL | | }
2020
| |_^
21-
= note: required because it captures the following types: `&mut Context<'_>`, `impl Future<Output = ()>`, `()`
21+
= note: required because it captures the following types: `ResumeTy`, `impl Future<Output = ()>`, `()`
2222
note: required because it's used within this `async` block
2323
--> $DIR/issue-70935-complex-spans.rs:16:5
2424
|

‎src/test/ui/async-await/partial-drop-partial-reinit.drop_tracking.stderr

+1-1
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,7 @@ LL | async fn foo() {
1111
|
1212
= help: within `impl Future<Output = ()>`, the trait `Send` is not implemented for `NotSend`
1313
= note: required because it appears within the type `(NotSend,)`
14-
= note: required because it captures the following types: `&mut Context<'_>`, `(NotSend,)`, `()`, `impl Future<Output = ()>`
14+
= note: required because it captures the following types: `ResumeTy`, `(NotSend,)`, `()`, `impl Future<Output = ()>`
1515
note: required because it's used within this `async fn` body
1616
--> $DIR/partial-drop-partial-reinit.rs:31:16
1717
|

‎src/test/ui/async-await/partial-drop-partial-reinit.no_drop_tracking.stderr

+1-1
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,7 @@ LL | async fn foo() {
1111
|
1212
= help: within `impl Future<Output = ()>`, the trait `Send` is not implemented for `NotSend`
1313
= note: required because it appears within the type `(NotSend,)`
14-
= note: required because it captures the following types: `&mut Context<'_>`, `(NotSend,)`, `impl Future<Output = ()>`, `()`
14+
= note: required because it captures the following types: `ResumeTy`, `(NotSend,)`, `impl Future<Output = ()>`, `()`
1515
note: required because it's used within this `async fn` body
1616
--> $DIR/partial-drop-partial-reinit.rs:31:16
1717
|

‎src/test/ui/regions/closure-in-projection-issue-97405.rs

+2-2
Original file line numberDiff line numberDiff line change
@@ -22,11 +22,11 @@ fn good_generic_fn<T>() {
2222
// This should fail because `T` ends up in the upvars of the closure.
2323
fn bad_generic_fn<T: Copy>(t: T) {
2424
assert_static(opaque(async move { t; }).next());
25-
//~^ ERROR the parameter type `T` may not live long enough
25+
//~^ ERROR the associated type `<impl Iterator as Iterator>::Item` may not live long enough
2626
assert_static(opaque(move || { t; }).next());
2727
//~^ ERROR the associated type `<impl Iterator as Iterator>::Item` may not live long enough
2828
assert_static(opaque(opaque(async move { t; }).next()).next());
29-
//~^ ERROR the parameter type `T` may not live long enough
29+
//~^ ERROR the associated type `<impl Iterator as Iterator>::Item` may not live long enough
3030
}
3131

3232
fn main() {}

‎src/test/ui/regions/closure-in-projection-issue-97405.stderr

+8-12
Original file line numberDiff line numberDiff line change
@@ -1,13 +1,11 @@
1-
error[E0310]: the parameter type `T` may not live long enough
1+
error[E0310]: the associated type `<impl Iterator as Iterator>::Item` may not live long enough
22
--> $DIR/closure-in-projection-issue-97405.rs:24:5
33
|
44
LL | assert_static(opaque(async move { t; }).next());
5-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds
6-
|
7-
help: consider adding an explicit lifetime bound...
5+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
86
|
9-
LL | fn bad_generic_fn<T: Copy + 'static>(t: T) {
10-
| +++++++++
7+
= help: consider adding an explicit lifetime bound `<impl Iterator as Iterator>::Item: 'static`...
8+
= note: ...so that the type `<impl Iterator as Iterator>::Item` will meet its required lifetime bounds
119

1210
error[E0310]: the associated type `<impl Iterator as Iterator>::Item` may not live long enough
1311
--> $DIR/closure-in-projection-issue-97405.rs:26:5
@@ -18,16 +16,14 @@ LL | assert_static(opaque(move || { t; }).next());
1816
= help: consider adding an explicit lifetime bound `<impl Iterator as Iterator>::Item: 'static`...
1917
= note: ...so that the type `<impl Iterator as Iterator>::Item` will meet its required lifetime bounds
2018

21-
error[E0310]: the parameter type `T` may not live long enough
19+
error[E0310]: the associated type `<impl Iterator as Iterator>::Item` may not live long enough
2220
--> $DIR/closure-in-projection-issue-97405.rs:28:5
2321
|
2422
LL | assert_static(opaque(opaque(async move { t; }).next()).next());
25-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds
26-
|
27-
help: consider adding an explicit lifetime bound...
23+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2824
|
29-
LL | fn bad_generic_fn<T: Copy + 'static>(t: T) {
30-
| +++++++++
25+
= help: consider adding an explicit lifetime bound `<impl Iterator as Iterator>::Item: 'static`...
26+
= note: ...so that the type `<impl Iterator as Iterator>::Item` will meet its required lifetime bounds
3127

3228
error: aborting due to 3 previous errors
3329

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