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Rollup merge of #96516 - oli-obk:impl_trait_inference_accidental_permitted, r=jackh726
Revert diagnostic duplication and accidental stabilization fixes #96460 this is an accidental stabilization that we should put into the beta. I believe it is low-risk, because it was literally what we had before #94081 The effect on tests is massive, but mostly deduplication of diagnostics and some minor span changes.
2 parents cd5dc49 + d22c439 commit 109008a

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‎compiler/rustc_typeck/src/check/check.rs

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -102,6 +102,12 @@ pub(super) fn check_fn<'a, 'tcx>(
102102
DUMMY_SP,
103103
param_env,
104104
));
105+
// HACK(oli-obk): we rewrite the declared return type, too, so that we don't end up inferring all
106+
// unconstrained RPIT to have `()` as their hidden type. This would happen because further down we
107+
// compare the ret_coercion with declared_ret_ty, and anything uninferred would be inferred to the
108+
// opaque type itself. That again would cause writeback to assume we have a recursive call site
109+
// and do the sadly stabilized fallback to `()`.
110+
let declared_ret_ty = ret_ty;
105111
fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(ret_ty)));
106112
fcx.ret_type_span = Some(decl.output.span());
107113

‎src/test/ui/associated-types/impl-trait-return-missing-constraint.rs

Lines changed: 0 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -24,7 +24,6 @@ fn bar() -> impl Bar {
2424

2525
fn baz() -> impl Bar<Item = i32> {
2626
//~^ ERROR type mismatch resolving `<impl Bar as Foo>::Item == i32`
27-
//~| ERROR type mismatch resolving `<impl Bar as Foo>::Item == i32`
2827
bar()
2928
}
3029

‎src/test/ui/associated-types/impl-trait-return-missing-constraint.stderr

Lines changed: 1 addition & 24 deletions
Original file line numberDiff line numberDiff line change
@@ -16,29 +16,6 @@ help: consider constraining the associated type `<impl Bar as Foo>::Item` to `i3
1616
LL | fn bar() -> impl Bar<Item = i32> {
1717
| ++++++++++++
1818

19-
error[E0271]: type mismatch resolving `<impl Bar as Foo>::Item == i32`
20-
--> $DIR/impl-trait-return-missing-constraint.rs:25:34
21-
|
22-
LL | fn bar() -> impl Bar {
23-
| -------- the expected opaque type
24-
...
25-
LL | fn baz() -> impl Bar<Item = i32> {
26-
| __________________________________^
27-
LL | |
28-
LL | |
29-
LL | | bar()
30-
LL | | }
31-
| |_^ expected associated type, found `i32`
32-
|
33-
= note: expected associated type `<impl Bar as Foo>::Item`
34-
found type `i32`
35-
= help: consider constraining the associated type `<impl Bar as Foo>::Item` to `i32` or calling a method that returns `<impl Bar as Foo>::Item`
36-
= note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
37-
help: consider constraining the associated type `<impl Bar as Foo>::Item` to `i32`
38-
|
39-
LL | fn bar() -> impl Bar<Item = i32> {
40-
| ++++++++++++
41-
42-
error: aborting due to 2 previous errors
19+
error: aborting due to previous error
4320

4421
For more information about this error, try `rustc --explain E0271`.

‎src/test/ui/conservative_impl_trait.rs

Lines changed: 0 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,6 @@
22

33
fn will_ice(something: &u32) -> impl Iterator<Item = &u32> {
44
//~^ ERROR `()` is not an iterator
5-
//~| ERROR `()` is not an iterator
65
}
76

87
fn main() {}

‎src/test/ui/conservative_impl_trait.stderr

Lines changed: 1 addition & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -6,18 +6,6 @@ LL | fn will_ice(something: &u32) -> impl Iterator<Item = &u32> {
66
|
77
= help: the trait `Iterator` is not implemented for `()`
88

9-
error[E0277]: `()` is not an iterator
10-
--> $DIR/conservative_impl_trait.rs:3:60
11-
|
12-
LL | fn will_ice(something: &u32) -> impl Iterator<Item = &u32> {
13-
| ____________________________________________________________^
14-
LL | |
15-
LL | |
16-
LL | | }
17-
| |_^ `()` is not an iterator
18-
|
19-
= help: the trait `Iterator` is not implemented for `()`
20-
21-
error: aborting due to 2 previous errors
9+
error: aborting due to previous error
2210

2311
For more information about this error, try `rustc --explain E0277`.

‎src/test/ui/const-generics/defaults/rp_impl_trait_fail.rs

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Original file line numberDiff line numberDiff line change
@@ -5,7 +5,6 @@ impl<const N: u32> Trait for Uwu<N> {}
55

66
fn rawr() -> impl Trait {
77
//~^ error: the trait bound `Uwu<10_u32, 12_u32>: Trait` is not satisfied
8-
//~| error: the trait bound `Uwu<10_u32, 12_u32>: Trait` is not satisfied
98
Uwu::<10, 12>
109
}
1110

@@ -17,13 +16,11 @@ impl Traitor<1, 2> for u64 {}
1716

1817
fn uwu<const N: u8>() -> impl Traitor<N> {
1918
//~^ error: the trait bound `u32: Traitor<N, N>` is not satisfied
20-
//~| error: the trait bound `u32: Traitor<N, N>` is not satisfied
2119
1_u32
2220
}
2321

2422
fn owo() -> impl Traitor {
2523
//~^ error: the trait bound `u64: Traitor<1_u8, 1_u8>` is not satisfied
26-
//~| error: the trait bound `u64: Traitor<1_u8, 1_u8>` is not satisfied
2724
1_u64
2825
}
2926

‎src/test/ui/const-generics/defaults/rp_impl_trait_fail.stderr

Lines changed: 3 additions & 46 deletions
Original file line numberDiff line numberDiff line change
@@ -6,21 +6,8 @@ LL | fn rawr() -> impl Trait {
66
|
77
= help: the trait `Trait` is implemented for `Uwu<N>`
88

9-
error[E0277]: the trait bound `Uwu<10_u32, 12_u32>: Trait` is not satisfied
10-
--> $DIR/rp_impl_trait_fail.rs:6:25
11-
|
12-
LL | fn rawr() -> impl Trait {
13-
| _________________________^
14-
LL | |
15-
LL | |
16-
LL | | Uwu::<10, 12>
17-
LL | | }
18-
| |_^ the trait `Trait` is not implemented for `Uwu<10_u32, 12_u32>`
19-
|
20-
= help: the trait `Trait` is implemented for `Uwu<N>`
21-
229
error[E0277]: the trait bound `u32: Traitor<N, N>` is not satisfied
23-
--> $DIR/rp_impl_trait_fail.rs:18:26
10+
--> $DIR/rp_impl_trait_fail.rs:17:26
2411
|
2512
LL | fn uwu<const N: u8>() -> impl Traitor<N> {
2613
| ^^^^^^^^^^^^^^^ the trait `Traitor<N, N>` is not implemented for `u32`
@@ -29,23 +16,8 @@ LL | fn uwu<const N: u8>() -> impl Traitor<N> {
2916
<u32 as Traitor<N, 2_u8>>
3017
<u64 as Traitor<1_u8, 2_u8>>
3118

32-
error[E0277]: the trait bound `u32: Traitor<N, N>` is not satisfied
33-
--> $DIR/rp_impl_trait_fail.rs:18:42
34-
|
35-
LL | fn uwu<const N: u8>() -> impl Traitor<N> {
36-
| __________________________________________^
37-
LL | |
38-
LL | |
39-
LL | | 1_u32
40-
LL | | }
41-
| |_^ the trait `Traitor<N, N>` is not implemented for `u32`
42-
|
43-
= help: the following other types implement trait `Traitor<N, M>`:
44-
<u32 as Traitor<N, 2_u8>>
45-
<u64 as Traitor<1_u8, 2_u8>>
46-
4719
error[E0277]: the trait bound `u64: Traitor<1_u8, 1_u8>` is not satisfied
48-
--> $DIR/rp_impl_trait_fail.rs:24:13
20+
--> $DIR/rp_impl_trait_fail.rs:22:13
4921
|
5022
LL | fn owo() -> impl Traitor {
5123
| ^^^^^^^^^^^^ the trait `Traitor<1_u8, 1_u8>` is not implemented for `u64`
@@ -54,21 +26,6 @@ LL | fn owo() -> impl Traitor {
5426
<u32 as Traitor<N, 2_u8>>
5527
<u64 as Traitor<1_u8, 2_u8>>
5628

57-
error[E0277]: the trait bound `u64: Traitor<1_u8, 1_u8>` is not satisfied
58-
--> $DIR/rp_impl_trait_fail.rs:24:26
59-
|
60-
LL | fn owo() -> impl Traitor {
61-
| __________________________^
62-
LL | |
63-
LL | |
64-
LL | | 1_u64
65-
LL | | }
66-
| |_^ the trait `Traitor<1_u8, 1_u8>` is not implemented for `u64`
67-
|
68-
= help: the following other types implement trait `Traitor<N, M>`:
69-
<u32 as Traitor<N, 2_u8>>
70-
<u64 as Traitor<1_u8, 2_u8>>
71-
72-
error: aborting due to 6 previous errors
29+
error: aborting due to 3 previous errors
7330

7431
For more information about this error, try `rustc --explain E0277`.

‎src/test/ui/generator/issue-88653.rs

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Original file line numberDiff line numberDiff line change
@@ -7,13 +7,10 @@ use std::ops::Generator;
77

88
fn foo(bar: bool) -> impl Generator<(bool,)> {
99
//~^ ERROR: type mismatch in generator arguments [E0631]
10-
//~| ERROR: type mismatch in generator arguments [E0631]
11-
//~| NOTE: expected signature of `fn((bool,)) -> _`
1210
//~| NOTE: expected signature of `fn((bool,)) -> _`
1311
//~| NOTE: in this expansion of desugaring of `impl Trait`
1412
|bar| {
1513
//~^ NOTE: found signature of `fn(bool) -> _`
16-
//~| NOTE: found signature of `fn(bool) -> _`
1714
if bar {
1815
yield bar;
1916
}

‎src/test/ui/generator/issue-88653.stderr

Lines changed: 1 addition & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -7,22 +7,6 @@ LL | fn foo(bar: bool) -> impl Generator<(bool,)> {
77
LL | |bar| {
88
| ----- found signature of `fn(bool) -> _`
99

10-
error[E0631]: type mismatch in generator arguments
11-
--> $DIR/issue-88653.rs:8:46
12-
|
13-
LL | fn foo(bar: bool) -> impl Generator<(bool,)> {
14-
| ______________________________________________^
15-
LL | |
16-
LL | |
17-
LL | |
18-
... |
19-
LL | | |bar| {
20-
| | ----- found signature of `fn(bool) -> _`
21-
... |
22-
LL | | }
23-
LL | | }
24-
| |_^ expected signature of `fn((bool,)) -> _`
25-
26-
error: aborting due to 2 previous errors
10+
error: aborting due to previous error
2711

2812
For more information about this error, try `rustc --explain E0631`.

‎src/test/ui/generator/type-mismatch-signature-deduction.rs

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Original file line numberDiff line numberDiff line change
@@ -4,7 +4,6 @@ use std::ops::Generator;
44

55
fn foo() -> impl Generator<Return = i32> {
66
//~^ ERROR type mismatch
7-
//~| ERROR type mismatch
87
|| {
98
if false {
109
return Ok(6);

‎src/test/ui/generator/type-mismatch-signature-deduction.stderr

Lines changed: 4 additions & 20 deletions
Original file line numberDiff line numberDiff line change
@@ -1,18 +1,18 @@
11
error[E0308]: mismatched types
2-
--> $DIR/type-mismatch-signature-deduction.rs:15:9
2+
--> $DIR/type-mismatch-signature-deduction.rs:14:9
33
|
44
LL | 5
55
| ^ expected enum `Result`, found integer
66
|
77
= note: expected type `Result<{integer}, _>`
88
found type `{integer}`
99
note: return type inferred to be `Result<{integer}, _>` here
10-
--> $DIR/type-mismatch-signature-deduction.rs:10:20
10+
--> $DIR/type-mismatch-signature-deduction.rs:9:20
1111
|
1212
LL | return Ok(6);
1313
| ^^^^^
1414

15-
error[E0271]: type mismatch resolving `<[generator@$DIR/type-mismatch-signature-deduction.rs:8:5: 16:6] as Generator>::Return == i32`
15+
error[E0271]: type mismatch resolving `<[generator@$DIR/type-mismatch-signature-deduction.rs:7:5: 15:6] as Generator>::Return == i32`
1616
--> $DIR/type-mismatch-signature-deduction.rs:5:13
1717
|
1818
LL | fn foo() -> impl Generator<Return = i32> {
@@ -21,23 +21,7 @@ LL | fn foo() -> impl Generator<Return = i32> {
2121
= note: expected enum `Result<{integer}, _>`
2222
found type `i32`
2323

24-
error[E0271]: type mismatch resolving `<[generator@$DIR/type-mismatch-signature-deduction.rs:8:5: 16:6] as Generator>::Return == i32`
25-
--> $DIR/type-mismatch-signature-deduction.rs:5:42
26-
|
27-
LL | fn foo() -> impl Generator<Return = i32> {
28-
| __________________________________________^
29-
LL | |
30-
LL | |
31-
LL | | || {
32-
... |
33-
LL | | }
34-
LL | | }
35-
| |_^ expected enum `Result`, found `i32`
36-
|
37-
= note: expected enum `Result<{integer}, _>`
38-
found type `i32`
39-
40-
error: aborting due to 3 previous errors
24+
error: aborting due to 2 previous errors
4125

4226
Some errors have detailed explanations: E0271, E0308.
4327
For more information about an error, try `rustc --explain E0271`.

‎src/test/ui/impl-trait/bound-normalization-fail.rs

Lines changed: 0 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -24,7 +24,6 @@ mod impl_trait {
2424
/// `T::Assoc` can't be normalized any further here.
2525
fn foo_fail<T: Trait>() -> impl FooLike<Output = T::Assoc> {
2626
//~^ ERROR: type mismatch
27-
//~| ERROR: type mismatch
2827
Foo(())
2928
}
3029
}
@@ -42,7 +41,6 @@ mod lifetimes {
4241
fn foo2_fail<'a, T: Trait<'a>>() -> impl FooLike<Output = T::Assoc> {
4342
//~^ ERROR `impl Trait` return type cannot contain a projection or `Self` that references lifetimes from a parent scope
4443
//~| ERROR: type mismatch
45-
//~| ERROR: type mismatch
4644
Foo(())
4745
}
4846
}

‎src/test/ui/impl-trait/bound-normalization-fail.stderr

Lines changed: 3 additions & 50 deletions
Original file line numberDiff line numberDiff line change
@@ -16,37 +16,14 @@ help: consider constraining the associated type `<T as impl_trait::Trait>::Assoc
1616
LL | fn foo_fail<T: Trait<Assoc = ()>>() -> impl FooLike<Output = T::Assoc> {
1717
| ++++++++++++
1818

19-
error[E0271]: type mismatch resolving `<Foo<()> as FooLike>::Output == <T as impl_trait::Trait>::Assoc`
20-
--> $DIR/bound-normalization-fail.rs:25:64
21-
|
22-
LL | fn foo_fail<T: Trait>() -> impl FooLike<Output = T::Assoc> {
23-
| ________________________________________________________________^
24-
LL | |
25-
LL | |
26-
LL | | Foo(())
27-
LL | | }
28-
| |_____^ type mismatch resolving `<Foo<()> as FooLike>::Output == <T as impl_trait::Trait>::Assoc`
29-
|
30-
note: expected this to be `()`
31-
--> $DIR/bound-normalization-fail.rs:14:19
32-
|
33-
LL | type Output = T;
34-
| ^
35-
= note: expected unit type `()`
36-
found associated type `<T as impl_trait::Trait>::Assoc`
37-
help: consider constraining the associated type `<T as impl_trait::Trait>::Assoc` to `()`
38-
|
39-
LL | fn foo_fail<T: Trait<Assoc = ()>>() -> impl FooLike<Output = T::Assoc> {
40-
| ++++++++++++
41-
4219
error[E0760]: `impl Trait` return type cannot contain a projection or `Self` that references lifetimes from a parent scope
43-
--> $DIR/bound-normalization-fail.rs:42:41
20+
--> $DIR/bound-normalization-fail.rs:41:41
4421
|
4522
LL | fn foo2_fail<'a, T: Trait<'a>>() -> impl FooLike<Output = T::Assoc> {
4623
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
4724

4825
error[E0271]: type mismatch resolving `<Foo<()> as FooLike>::Output == <T as lifetimes::Trait<'static>>::Assoc`
49-
--> $DIR/bound-normalization-fail.rs:42:41
26+
--> $DIR/bound-normalization-fail.rs:41:41
5027
|
5128
LL | fn foo2_fail<'a, T: Trait<'a>>() -> impl FooLike<Output = T::Assoc> {
5229
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type mismatch resolving `<Foo<()> as FooLike>::Output == <T as lifetimes::Trait<'static>>::Assoc`
@@ -63,31 +40,7 @@ help: consider constraining the associated type `<T as lifetimes::Trait<'static>
6340
LL | fn foo2_fail<'a, T: Trait<'a, Assoc = ()>>() -> impl FooLike<Output = T::Assoc> {
6441
| ++++++++++++
6542

66-
error[E0271]: type mismatch resolving `<Foo<()> as FooLike>::Output == <T as lifetimes::Trait<'static>>::Assoc`
67-
--> $DIR/bound-normalization-fail.rs:42:73
68-
|
69-
LL | fn foo2_fail<'a, T: Trait<'a>>() -> impl FooLike<Output = T::Assoc> {
70-
| _________________________________________________________________________^
71-
LL | |
72-
LL | |
73-
LL | |
74-
LL | | Foo(())
75-
LL | | }
76-
| |_____^ type mismatch resolving `<Foo<()> as FooLike>::Output == <T as lifetimes::Trait<'static>>::Assoc`
77-
|
78-
note: expected this to be `()`
79-
--> $DIR/bound-normalization-fail.rs:14:19
80-
|
81-
LL | type Output = T;
82-
| ^
83-
= note: expected unit type `()`
84-
found associated type `<T as lifetimes::Trait<'static>>::Assoc`
85-
help: consider constraining the associated type `<T as lifetimes::Trait<'static>>::Assoc` to `()`
86-
|
87-
LL | fn foo2_fail<'a, T: Trait<'a, Assoc = ()>>() -> impl FooLike<Output = T::Assoc> {
88-
| ++++++++++++
89-
90-
error: aborting due to 5 previous errors
43+
error: aborting due to 3 previous errors
9144

9245
Some errors have detailed explanations: E0271, E0760.
9346
For more information about an error, try `rustc --explain E0271`.

‎src/test/ui/impl-trait/cross-return-site-inference.rs

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -29,17 +29,17 @@ fn baa(b: bool) -> impl std::fmt::Debug {
2929
}
3030

3131
fn muh() -> Result<(), impl std::fmt::Debug> {
32-
Err("whoops")?; //~ ERROR `?` couldn't convert the error to `impl Debug`
32+
Err("whoops")?; //~^ ERROR type annotations needed
3333
Ok(())
3434
}
3535

3636
fn muh2() -> Result<(), impl std::fmt::Debug> {
37-
return Err(From::from("foo")); //~ ERROR the trait bound `impl Debug: From<&str>` is not satisfied
37+
return Err(From::from("foo")); //~^ ERROR type annotations needed
3838
Ok(())
3939
}
4040

4141
fn muh3() -> Result<(), impl std::fmt::Debug> {
42-
Err(From::from("foo")) //~ ERROR the trait bound `impl Debug: From<&str>` is not satisfied
42+
Err(From::from("foo")) //~^ ERROR type annotations needed
4343
}
4444

4545
fn main() {}

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