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Rework try_overloaded_call_traits to not prefer taking async closure by move
1 parent 20c24c3 commit e988944

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7 files changed

+56
-24
lines changed

7 files changed

+56
-24
lines changed

‎compiler/rustc_hir_typeck/src/callee.rs

+11-7
Original file line numberDiff line numberDiff line change
@@ -183,16 +183,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
183183
kind: TypeVariableOriginKind::TypeInference,
184184
span: callee_expr.span,
185185
});
186+
// We may actually receive a coroutine back whose kind is different
187+
// from the closure that this dispatched from. This is because when
188+
// we have no captures, we automatically implement `FnOnce`. This
189+
// impl forces the closure kind to `FnOnce` i.e. `u8`.
190+
let kind_ty = self.next_ty_var(TypeVariableOrigin {
191+
kind: TypeVariableOriginKind::TypeInference,
192+
span: callee_expr.span,
193+
});
186194
let call_sig = self.tcx.mk_fn_sig(
187195
[coroutine_closure_sig.tupled_inputs_ty],
188196
coroutine_closure_sig.to_coroutine(
189197
self.tcx,
190198
closure_args.parent_args(),
191-
// Inherit the kind ty of the closure, since we're calling this
192-
// coroutine with the most relaxed `AsyncFn*` trait that we can.
193-
// We don't necessarily need to do this here, but it saves us
194-
// computing one more infer var that will get constrained later.
195-
closure_args.kind_ty(),
199+
kind_ty,
196200
self.tcx.coroutine_for_closure(def_id),
197201
tupled_upvars_ty,
198202
),
@@ -263,14 +267,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
263267
// Try the options that are least restrictive on the caller first.
264268
for (opt_trait_def_id, method_name, borrow) in [
265269
(self.tcx.lang_items().fn_trait(), Ident::with_dummy_span(sym::call), true),
266-
(self.tcx.lang_items().fn_mut_trait(), Ident::with_dummy_span(sym::call_mut), true),
267-
(self.tcx.lang_items().fn_once_trait(), Ident::with_dummy_span(sym::call_once), false),
268270
(self.tcx.lang_items().async_fn_trait(), Ident::with_dummy_span(sym::async_call), true),
271+
(self.tcx.lang_items().fn_mut_trait(), Ident::with_dummy_span(sym::call_mut), true),
269272
(
270273
self.tcx.lang_items().async_fn_mut_trait(),
271274
Ident::with_dummy_span(sym::async_call_mut),
272275
true,
273276
),
277+
(self.tcx.lang_items().fn_once_trait(), Ident::with_dummy_span(sym::call_once), false),
274278
(
275279
self.tcx.lang_items().async_fn_once_trait(),
276280
Ident::with_dummy_span(sym::async_call_once),

‎compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

+7-3
Original file line numberDiff line numberDiff line change
@@ -336,11 +336,15 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
336336
let is_const = self.tcx().is_const_fn_raw(def_id);
337337
match self.infcx.closure_kind(self_ty) {
338338
Some(closure_kind) => {
339-
let no_borrows = self
339+
let no_borrows = match self
340340
.infcx
341341
.shallow_resolve(args.as_coroutine_closure().tupled_upvars_ty())
342-
.tuple_fields()
343-
.is_empty();
342+
.kind()
343+
{
344+
ty::Tuple(tys) => tys.is_empty(),
345+
ty::Error(_) => false,
346+
_ => bug!("tuple_fields called on non-tuple"),
347+
};
344348
if no_borrows && closure_kind.extends(kind) {
345349
candidates.vec.push(ClosureCandidate { is_const });
346350
} else if kind == ty::ClosureKind::FnOnce {

‎tests/ui/async-await/async-closures/def-path.stderr

+2-2
Original file line numberDiff line numberDiff line change
@@ -5,11 +5,11 @@ LL | let x = async || {};
55
| -- the expected `async` closure body
66
LL |
77
LL | let () = x();
8-
| ^^ --- this expression has type `{static main::{closure#0}::{closure#0}<?7t> upvar_tys=?15t witness=?6t}`
8+
| ^^ --- this expression has type `{static main::{closure#0}::{closure#0}<?16t> upvar_tys=?15t witness=?6t}`
99
| |
1010
| expected `async` closure body, found `()`
1111
|
12-
= note: expected `async` closure body `{static main::{closure#0}::{closure#0}<?7t> upvar_tys=?15t witness=?6t}`
12+
= note: expected `async` closure body `{static main::{closure#0}::{closure#0}<?16t> upvar_tys=?15t witness=?6t}`
1313
found unit type `()`
1414

1515
error: aborting due to 1 previous error

‎tests/ui/async-await/async-closures/is-not-fn.rs

+1-4
Original file line numberDiff line numberDiff line change
@@ -5,8 +5,5 @@
55
fn main() {
66
fn needs_fn(x: impl FnOnce()) {}
77
needs_fn(async || {});
8-
//~^ ERROR expected a `FnOnce()` closure, found `{coroutine-closure@
9-
// FIXME(async_closures): This should explain in more detail how async fns don't
10-
// implement the regular `Fn` traits. Or maybe we should just fix it and make them
11-
// when there are no upvars or whatever.
8+
//~^ ERROR expected `{[email protected]:7:14}` to be a closure that returns `()`
129
}

‎tests/ui/async-await/async-closures/is-not-fn.stderr

+5-5
Original file line numberDiff line numberDiff line change
@@ -1,13 +1,13 @@
1-
error[E0277]: expected a `FnOnce()` closure, found `{coroutine-closure@$DIR/is-not-fn.rs:7:14: 7:22}`
1+
error[E0271]: expected `{[email protected]:7:14}` to be a closure that returns `()`, but it returns `{async closure body@$DIR/is-not-fn.rs:7:23: 7:25}`
22
--> $DIR/is-not-fn.rs:7:14
33
|
44
LL | needs_fn(async || {});
5-
| -------- ^^^^^^^^^^^ expected an `FnOnce()` closure, found `{coroutine-closure@$DIR/is-not-fn.rs:7:14: 7:22}`
5+
| -------- ^^^^^^^^^^^ expected `()`, found `async` closure body
66
| |
77
| required by a bound introduced by this call
88
|
9-
= help: the trait `FnOnce<()>` is not implemented for `{coroutine-closure@$DIR/is-not-fn.rs:7:14: 7:22}`
10-
= note: wrap the `{coroutine-closure@$DIR/is-not-fn.rs:7:14: 7:22}` in a closure with no arguments: `|| { /* code */ }`
9+
= note: expected unit type `()`
10+
found `async` closure body `{async closure body@$DIR/is-not-fn.rs:7:23: 7:25}`
1111
note: required by a bound in `needs_fn`
1212
--> $DIR/is-not-fn.rs:6:25
1313
|
@@ -16,4 +16,4 @@ LL | fn needs_fn(x: impl FnOnce()) {}
1616

1717
error: aborting due to 1 previous error
1818

19-
For more information about this error, try `rustc --explain E0277`.
19+
For more information about this error, try `rustc --explain E0271`.

‎tests/ui/async-await/async-closures/move-consuming-capture.stderr

+6-3
Original file line numberDiff line numberDiff line change
@@ -5,12 +5,15 @@ LL | let x = async move || {
55
| - move occurs because `x` has type `{coroutine-closure@$DIR/move-consuming-capture.rs:13:17: 13:30}`, which does not implement the `Copy` trait
66
...
77
LL | x().await;
8-
| --- `x` moved due to this method call
8+
| --- `x` moved due to this call
99
LL | x().await;
1010
| ^ value used here after move
1111
|
12-
note: `async_call_once` takes ownership of the receiver `self`, which moves `x`
13-
--> $SRC_DIR/core/src/ops/async_function.rs:LL:COL
12+
note: this value implements `FnOnce`, which causes it to be moved when called
13+
--> $DIR/move-consuming-capture.rs:16:9
14+
|
15+
LL | x().await;
16+
| ^
1417

1518
error: aborting due to 1 previous error
1619

‎tests/ui/async-await/async-fn/dyn-pos.stderr

+24
Original file line numberDiff line numberDiff line change
@@ -8,6 +8,9 @@ note: for a trait to be "object safe" it needs to allow building a vtable to all
88
--> $SRC_DIR/core/src/ops/async_function.rs:LL:COL
99
|
1010
= note: the trait cannot be made into an object because it contains the generic associated type `CallFuture`
11+
= help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `AsyncFn` for this new enum and using it instead:
12+
&F
13+
std::boxed::Box<F, A>
1114

1215
error[E0038]: the trait `AsyncFnMut` cannot be made into an object
1316
--> $DIR/dyn-pos.rs:5:16
@@ -19,6 +22,10 @@ note: for a trait to be "object safe" it needs to allow building a vtable to all
1922
--> $SRC_DIR/core/src/ops/async_function.rs:LL:COL
2023
|
2124
= note: the trait cannot be made into an object because it contains the generic associated type `CallMutFuture`
25+
= help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `AsyncFnMut` for this new enum and using it instead:
26+
&F
27+
&mut F
28+
std::boxed::Box<F, A>
2229

2330
error[E0038]: the trait `AsyncFn` cannot be made into an object
2431
--> $DIR/dyn-pos.rs:5:16
@@ -30,6 +37,9 @@ note: for a trait to be "object safe" it needs to allow building a vtable to all
3037
--> $SRC_DIR/core/src/ops/async_function.rs:LL:COL
3138
|
3239
= note: the trait cannot be made into an object because it contains the generic associated type `CallFuture`
40+
= help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `AsyncFn` for this new enum and using it instead:
41+
&F
42+
std::boxed::Box<F, A>
3343
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
3444

3545
error[E0038]: the trait `AsyncFnMut` cannot be made into an object
@@ -42,6 +52,10 @@ note: for a trait to be "object safe" it needs to allow building a vtable to all
4252
--> $SRC_DIR/core/src/ops/async_function.rs:LL:COL
4353
|
4454
= note: the trait cannot be made into an object because it contains the generic associated type `CallMutFuture`
55+
= help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `AsyncFnMut` for this new enum and using it instead:
56+
&F
57+
&mut F
58+
std::boxed::Box<F, A>
4559
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
4660

4761
error[E0038]: the trait `AsyncFn` cannot be made into an object
@@ -54,6 +68,9 @@ note: for a trait to be "object safe" it needs to allow building a vtable to all
5468
--> $SRC_DIR/core/src/ops/async_function.rs:LL:COL
5569
|
5670
= note: the trait cannot be made into an object because it contains the generic associated type `CallFuture`
71+
= help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `AsyncFn` for this new enum and using it instead:
72+
&F
73+
std::boxed::Box<F, A>
5774
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
5875

5976
error[E0038]: the trait `AsyncFnMut` cannot be made into an object
@@ -66,6 +83,10 @@ note: for a trait to be "object safe" it needs to allow building a vtable to all
6683
--> $SRC_DIR/core/src/ops/async_function.rs:LL:COL
6784
|
6885
= note: the trait cannot be made into an object because it contains the generic associated type `CallMutFuture`
86+
= help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `AsyncFnMut` for this new enum and using it instead:
87+
&F
88+
&mut F
89+
std::boxed::Box<F, A>
6990
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
7091

7192
error[E0038]: the trait `AsyncFn` cannot be made into an object
@@ -81,6 +102,9 @@ note: for a trait to be "object safe" it needs to allow building a vtable to all
81102
::: $SRC_DIR/core/src/ops/async_function.rs:LL:COL
82103
|
83104
= note: the trait cannot be made into an object because it contains the generic associated type `CallMutFuture`
105+
= help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `AsyncFn` for this new enum and using it instead:
106+
&F
107+
std::boxed::Box<F, A>
84108

85109
error: aborting due to 7 previous errors
86110

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