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Auto merge of #98863 - compiler-errors:projection-msg, r=estebank

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Implement special-cased projection error message for some common traits

Not sure what the best phrasing is, but I feel like these are more clear than the plain `<Type as Iterator>::Output == Type` messages.

If this is actually a good idea, are there any other traits this could benefit?
This commit is contained in:
bors 2022-08-08 10:16:20 +00:00
commit f03ce30962
25 changed files with 124 additions and 78 deletions
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62
compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
View File

@ -1315,6 +1315,13 @@ trait InferCtxtPrivExt<'hir, 'tcx> {
error: &MismatchedProjectionTypes<'tcx>,
);
fn maybe_detailed_projection_msg(
&self,
pred: ty::ProjectionPredicate<'tcx>,
normalized_ty: ty::Term<'tcx>,
expected_ty: ty::Term<'tcx>,
) -> Option<String>;
fn fuzzy_match_tys(
&self,
a: Ty<'tcx>,
@ -1542,23 +1549,19 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
normalized_ty,
data.term,
) {
values = Some(infer::ValuePairs::Terms(ExpectedFound::new(
is_normalized_ty_expected,
normalized_ty,
data.term,
)));
values = Some((data, is_normalized_ty_expected, normalized_ty, data.term));
err_buf = error;
err = &err_buf;
}
}
let mut diag = struct_span_err!(
self.tcx.sess,
obligation.cause.span,
E0271,
"type mismatch resolving `{}`",
predicate
);
let msg = values
.and_then(|(predicate, _, normalized_ty, expected_ty)| {
self.maybe_detailed_projection_msg(predicate, normalized_ty, expected_ty)
})
.unwrap_or_else(|| format!("type mismatch resolving `{}`", predicate));
let mut diag = struct_span_err!(self.tcx.sess, obligation.cause.span, E0271, "{msg}");
let secondary_span = match predicate.kind().skip_binder() {
ty::PredicateKind::Projection(proj) => self
.tcx
@ -1596,7 +1599,13 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
&mut diag,
&obligation.cause,
secondary_span,
values,
values.map(|(_, is_normalized_ty_expected, normalized_ty, term)| {
infer::ValuePairs::Terms(ExpectedFound::new(
is_normalized_ty_expected,
normalized_ty,
term,
))
}),
err,
true,
false,
@ -1606,6 +1615,33 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> {
});
}
fn maybe_detailed_projection_msg(
&self,
pred: ty::ProjectionPredicate<'tcx>,
normalized_ty: ty::Term<'tcx>,
expected_ty: ty::Term<'tcx>,
) -> Option<String> {
let trait_def_id = pred.projection_ty.trait_def_id(self.tcx);
let self_ty = pred.projection_ty.self_ty();
if Some(pred.projection_ty.item_def_id) == self.tcx.lang_items().fn_once_output() {
Some(format!(
"expected `{self_ty}` to be a {fn_kind} that returns `{expected_ty}`, but it returns `{normalized_ty}`",
fn_kind = self_ty.prefix_string(self.tcx)
))
} else if Some(trait_def_id) == self.tcx.lang_items().future_trait() {
Some(format!(
"expected `{self_ty}` to be a future that resolves to `{expected_ty}`, but it resolves to `{normalized_ty}`"
))
} else if Some(trait_def_id) == self.tcx.get_diagnostic_item(sym::Iterator) {
Some(format!(
"expected `{self_ty}` to be an iterator that yields `{expected_ty}`, but it yields `{normalized_ty}`"
))
} else {
None
}
}
fn fuzzy_match_tys(
&self,
mut a: Ty<'tcx>,

2
src/test/ui/associated-types/associated-types-overridden-binding-2.rs
View File

@ -4,5 +4,5 @@ trait I32Iterator = Iterator<Item = i32>;
fn main() {
let _: &dyn I32Iterator<Item = u32> = &vec![42].into_iter();
//~^ ERROR type mismatch
//~^ ERROR expected `std::vec::IntoIter<u32>` to be an iterator that yields `i32`, but it yields `u32`
}

2
src/test/ui/associated-types/associated-types-overridden-binding-2.stderr
View File

@ -1,4 +1,4 @@
error[E0271]: type mismatch resolving `<std::vec::IntoIter<u32> as Iterator>::Item == i32`
error[E0271]: expected `std::vec::IntoIter<u32>` to be an iterator that yields `i32`, but it yields `u32`
--> $DIR/associated-types-overridden-binding-2.rs:6:43
|
LL | let _: &dyn I32Iterator<Item = u32> = &vec![42].into_iter();

8
src/test/ui/async-await/async-block-control-flow-static-semantics.rs
View File

@ -15,7 +15,7 @@ fn return_targets_async_block_not_fn() -> u8 {
return 0u8;
};
let _: &dyn Future<Output = ()> = &block;
//~^ ERROR type mismatch
//~^ ERROR expected `impl Future<Output = u8>` to be a future that resolves to `()`, but it resolves to `u8`
}
async fn return_targets_async_block_not_async_fn() -> u8 {
@ -24,7 +24,7 @@ async fn return_targets_async_block_not_async_fn() -> u8 {
return 0u8;
};
let _: &dyn Future<Output = ()> = &block;
//~^ ERROR type mismatch resolving `<impl Future<Output = u8> as Future>::Output == ()`
//~^ ERROR expected `impl Future<Output = u8>` to be a future that resolves to `()`, but it resolves to `u8`
}
fn no_break_in_async_block() {
@ -42,7 +42,9 @@ fn no_break_in_async_block_even_with_outer_loop() {
}
struct MyErr;
fn err() -> Result<u8, MyErr> { Err(MyErr) }
fn err() -> Result<u8, MyErr> {
Err(MyErr)
}
fn rethrow_targets_async_block_not_fn() -> Result<u8, MyErr> {
//~^ ERROR mismatched types

8
src/test/ui/async-await/async-block-control-flow-static-semantics.stderr
View File

@ -31,7 +31,7 @@ LL | |
LL | | }
| |_^ expected `u8`, found `()`
error[E0271]: type mismatch resolving `<impl Future<Output = u8> as Future>::Output == ()`
error[E0271]: expected `impl Future<Output = u8>` to be a future that resolves to `()`, but it resolves to `u8`
--> $DIR/async-block-control-flow-static-semantics.rs:26:39
|
LL | let _: &dyn Future<Output = ()> = &block;
@ -47,7 +47,7 @@ LL | fn return_targets_async_block_not_fn() -> u8 {
| |
| implicitly returns `()` as its body has no tail or `return` expression
error[E0271]: type mismatch resolving `<impl Future<Output = u8> as Future>::Output == ()`
error[E0271]: expected `impl Future<Output = u8>` to be a future that resolves to `()`, but it resolves to `u8`
--> $DIR/async-block-control-flow-static-semantics.rs:17:39
|
LL | let _: &dyn Future<Output = ()> = &block;
@ -56,7 +56,7 @@ LL | let _: &dyn Future<Output = ()> = &block;
= note: required for the cast from `impl Future<Output = u8>` to the object type `dyn Future<Output = ()>`
error[E0308]: mismatched types
--> $DIR/async-block-control-flow-static-semantics.rs:47:44
--> $DIR/async-block-control-flow-static-semantics.rs:49:44
|
LL | fn rethrow_targets_async_block_not_fn() -> Result<u8, MyErr> {
| ---------------------------------- ^^^^^^^^^^^^^^^^^ expected enum `Result`, found `()`
@ -67,7 +67,7 @@ LL | fn rethrow_targets_async_block_not_fn() -> Result<u8, MyErr> {
found unit type `()`
error[E0308]: mismatched types
--> $DIR/async-block-control-flow-static-semantics.rs:56:50
--> $DIR/async-block-control-flow-static-semantics.rs:58:50
|
LL | fn rethrow_targets_async_block_not_async_fn() -> Result<u8, MyErr> {
| ---------------------------------------- ^^^^^^^^^^^^^^^^^ expected enum `Result`, found `()`

10
src/test/ui/hrtb/issue-62203-hrtb-ice.rs
View File

@ -38,9 +38,13 @@ fn main() {
let v = Unit2.m(
//~^ ERROR type mismatch
L {
//~^ ERROR type mismatch
f : |x| { drop(x); Unit4 }
});
//~^ ERROR to be a closure that returns `Unit3`, but it returns `Unit4`
f: |x| {
drop(x);
Unit4
},
},
);
}
impl<'a> Ty<'a> for Unit2 {

15
src/test/ui/hrtb/issue-62203-hrtb-ice.stderr
View File

@ -1,8 +1,8 @@
error[E0271]: type mismatch resolving `for<'r> <L<[closure@$DIR/issue-62203-hrtb-ice.rs:42:17: 42:20]> as T0<'r, (&'r u8,)>>::O == <_ as Ty<'r>>::V`
error[E0271]: type mismatch resolving `for<'r> <L<[closure@$DIR/issue-62203-hrtb-ice.rs:42:16: 42:19]> as T0<'r, (&'r u8,)>>::O == <_ as Ty<'r>>::V`
--> $DIR/issue-62203-hrtb-ice.rs:38:19
|
LL | let v = Unit2.m(
| ^ type mismatch resolving `for<'r> <L<[closure@$DIR/issue-62203-hrtb-ice.rs:42:17: 42:20]> as T0<'r, (&'r u8,)>>::O == <_ as Ty<'r>>::V`
| ^ type mismatch resolving `for<'r> <L<[closure@$DIR/issue-62203-hrtb-ice.rs:42:16: 42:19]> as T0<'r, (&'r u8,)>>::O == <_ as Ty<'r>>::V`
|
note: expected this to be `<_ as Ty<'_>>::V`
--> $DIR/issue-62203-hrtb-ice.rs:21:14
@ -22,7 +22,7 @@ LL | where
LL | F: for<'r> T0<'r, (<Self as Ty<'r>>::V,), O = <B as Ty<'r>>::V>,
| ^^^^^^^^^^^^^^^^^^^^ required by this bound in `T1::m`
error[E0271]: type mismatch resolving `for<'r> <[closure@$DIR/issue-62203-hrtb-ice.rs:42:17: 42:20] as FnOnce<((&'r u8,),)>>::Output == Unit3`
error[E0271]: expected `[closure@$DIR/issue-62203-hrtb-ice.rs:42:16: 42:19]` to be a closure that returns `Unit3`, but it returns `Unit4`
--> $DIR/issue-62203-hrtb-ice.rs:40:9
|
LL | let v = Unit2.m(
@ -30,11 +30,14 @@ LL | let v = Unit2.m(
LL |
LL | / L {
LL | |
LL | | f : |x| { drop(x); Unit4 }
LL | | });
LL | | f: |x| {
LL | | drop(x);
LL | | Unit4
LL | | },
LL | | },
| |_________^ expected struct `Unit3`, found struct `Unit4`
|
note: required because of the requirements on the impl of `for<'r> T0<'r, (&'r u8,)>` for `L<[closure@$DIR/issue-62203-hrtb-ice.rs:42:17: 42:20]>`
note: required because of the requirements on the impl of `for<'r> T0<'r, (&'r u8,)>` for `L<[closure@$DIR/issue-62203-hrtb-ice.rs:42:16: 42:19]>`
--> $DIR/issue-62203-hrtb-ice.rs:17:16
|
LL | impl<'a, A, T> T0<'a, A> for L<T>

2
src/test/ui/impl-trait/issues/issue-78722.rs
View File

@ -7,7 +7,7 @@ type F = impl core::future::Future<Output = u8>;
struct Bug {
V1: [(); {
fn concrete_use() -> F {
//~^ ERROR type mismatch
//~^ ERROR expected `impl Future<Output = ()>` to be a future that resolves to `u8`, but it resolves to `()`
async {}
}
let f: F = async { 1 };

2
src/test/ui/impl-trait/issues/issue-78722.stderr
View File

@ -16,7 +16,7 @@ LL | let f: F = async { 1 };
LL | }],
| - value is dropped here
error[E0271]: type mismatch resolving `<impl Future<Output = ()> as Future>::Output == u8`
error[E0271]: expected `impl Future<Output = ()>` to be a future that resolves to `u8`, but it resolves to `()`
--> $DIR/issue-78722.rs:9:30
|
LL | fn concrete_use() -> F {

2
src/test/ui/intrinsics/const-eval-select-bad.rs
View File

@ -27,7 +27,7 @@ fn baz(n: bool) -> i32 {
const fn return_ty_mismatch() {
const_eval_select((1,), foo, bar);
//~^ ERROR type mismatch
//~^ ERROR expected `fn(i32) -> bool {bar}` to be a fn item that returns `i32`, but it returns `bool`
}
const fn args_ty_mismatch() {

2
src/test/ui/intrinsics/const-eval-select-bad.stderr
View File

@ -51,7 +51,7 @@ note: required by a bound in `const_eval_select`
LL | G: FnOnce<ARG, Output = RET> + ~const Destruct,
| ^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `const_eval_select`
error[E0271]: type mismatch resolving `<fn(i32) -> bool {bar} as FnOnce<(i32,)>>::Output == i32`
error[E0271]: expected `fn(i32) -> bool {bar}` to be a fn item that returns `i32`, but it returns `bool`
--> $DIR/const-eval-select-bad.rs:29:5
|
LL | const_eval_select((1,), foo, bar);

11
src/test/ui/issues/issue-31173.rs
View File

@ -3,12 +3,13 @@ use std::vec::IntoIter;
pub fn get_tok(it: &mut IntoIter<u8>) {
let mut found_e = false;
let temp: Vec<u8> = it.take_while(|&x| {
found_e = true;
false
})
let temp: Vec<u8> = it
.take_while(|&x| {
found_e = true;
false
})
.cloned()
//~^ ERROR type mismatch resolving
//~^ ERROR to be an iterator that yields `&_`, but it yields `u8`
.collect(); //~ ERROR the method
}

18
src/test/ui/issues/issue-31173.stderr
View File

@ -1,5 +1,5 @@
error[E0271]: type mismatch resolving `<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:6:39: 6:43]> as Iterator>::Item == &_`
--> $DIR/issue-31173.rs:10:10
error[E0271]: expected `TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:7:21: 7:25]>` to be an iterator that yields `&_`, but it yields `u8`
--> $DIR/issue-31173.rs:11:10
|
LL | .cloned()
| ^^^^^^ expected reference, found `u8`
@ -12,11 +12,11 @@ note: required by a bound in `cloned`
LL | Self: Sized + Iterator<Item = &'a T>,
| ^^^^^^^^^^^^ required by this bound in `cloned`
error[E0599]: the method `collect` exists for struct `Cloned<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:6:39: 6:43]>>`, but its trait bounds were not satisfied
--> $DIR/issue-31173.rs:12:10
error[E0599]: the method `collect` exists for struct `Cloned<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:7:21: 7:25]>>`, but its trait bounds were not satisfied
--> $DIR/issue-31173.rs:13:10
|
LL | .collect();
| ^^^^^^^ method cannot be called on `Cloned<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:6:39: 6:43]>>` due to unsatisfied trait bounds
| ^^^^^^^ method cannot be called on `Cloned<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:7:21: 7:25]>>` due to unsatisfied trait bounds
|
::: $SRC_DIR/core/src/iter/adapters/cloned.rs:LL:COL
|
@ -29,10 +29,10 @@ LL | pub struct TakeWhile<I, P> {
| -------------------------- doesn't satisfy `<_ as Iterator>::Item = &_`
|
= note: the following trait bounds were not satisfied:
`<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:6:39: 6:43]> as Iterator>::Item = &_`
which is required by `Cloned<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:6:39: 6:43]>>: Iterator`
`Cloned<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:6:39: 6:43]>>: Iterator`
which is required by `&mut Cloned<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:6:39: 6:43]>>: Iterator`
`<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:7:21: 7:25]> as Iterator>::Item = &_`
which is required by `Cloned<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:7:21: 7:25]>>: Iterator`
`Cloned<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:7:21: 7:25]>>: Iterator`
which is required by `&mut Cloned<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:7:21: 7:25]>>: Iterator`
error: aborting due to 2 previous errors

6
src/test/ui/issues/issue-33941.rs
View File

@ -3,7 +3,7 @@
use std::collections::HashMap;
fn main() {
for _ in HashMap::new().iter().cloned() {} //~ ERROR type mismatch
//~^ ERROR type mismatch
//~| ERROR type mismatch
for _ in HashMap::new().iter().cloned() {} //~ ERROR expected `std::collections::hash_map::Iter<'_, _, _>` to be an iterator that yields `&_`, but it yields `(&_, &_)`
//~^ ERROR expected `std::collections::hash_map::Iter<'_, _, _>` to be an iterator that yields `&_`, but it yields `(&_, &_)`
//~| ERROR expected `std::collections::hash_map::Iter<'_, _, _>` to be an iterator that yields `&_`, but it yields `(&_, &_)`
}

6
src/test/ui/issues/issue-33941.stderr
View File

@ -1,4 +1,4 @@
error[E0271]: type mismatch resolving `<std::collections::hash_map::Iter<'_, _, _> as Iterator>::Item == &_`
error[E0271]: expected `std::collections::hash_map::Iter<'_, _, _>` to be an iterator that yields `&_`, but it yields `(&_, &_)`
--> $DIR/issue-33941.rs:6:36
|
LL | for _ in HashMap::new().iter().cloned() {}
@ -12,7 +12,7 @@ note: required by a bound in `cloned`
LL | Self: Sized + Iterator<Item = &'a T>,
| ^^^^^^^^^^^^ required by this bound in `cloned`
error[E0271]: type mismatch resolving `<std::collections::hash_map::Iter<'_, _, _> as Iterator>::Item == &_`
error[E0271]: expected `std::collections::hash_map::Iter<'_, _, _>` to be an iterator that yields `&_`, but it yields `(&_, &_)`
--> $DIR/issue-33941.rs:6:14
|
LL | for _ in HashMap::new().iter().cloned() {}
@ -23,7 +23,7 @@ LL | for _ in HashMap::new().iter().cloned() {}
= note: required because of the requirements on the impl of `Iterator` for `Cloned<std::collections::hash_map::Iter<'_, _, _>>`
= note: required because of the requirements on the impl of `IntoIterator` for `Cloned<std::collections::hash_map::Iter<'_, _, _>>`
error[E0271]: type mismatch resolving `<std::collections::hash_map::Iter<'_, _, _> as Iterator>::Item == &_`
error[E0271]: expected `std::collections::hash_map::Iter<'_, _, _>` to be an iterator that yields `&_`, but it yields `(&_, &_)`
--> $DIR/issue-33941.rs:6:14
|
LL | for _ in HashMap::new().iter().cloned() {}

2
src/test/ui/never_type/fallback-closure-wrap.fallback.stderr
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@ -1,4 +1,4 @@
error[E0271]: type mismatch resolving `<[closure@$DIR/fallback-closure-wrap.rs:18:40: 18:47] as FnOnce<()>>::Output == ()`
error[E0271]: expected `[closure@$DIR/fallback-closure-wrap.rs:18:40: 18:47]` to be a closure that returns `()`, but it returns `!`
--> $DIR/fallback-closure-wrap.rs:18:31
|
LL | let error = Closure::wrap(Box::new(move || {

2
src/test/ui/never_type/fallback-closure-wrap.rs
View File

@ -16,7 +16,7 @@ use std::marker::PhantomData;
fn main() {
let error = Closure::wrap(Box::new(move || {
//[fallback]~^ ERROR type mismatch resolving
//[fallback]~^ to be a closure that returns `()`, but it returns `!`
panic!("Can't connect to server.");
}) as Box<dyn FnMut()>);
}

8
src/test/ui/traits/assoc-type-in-superbad.rs
View File

@ -4,13 +4,13 @@
use std::vec::IntoIter;
pub trait Foo: Iterator<Item=<Self as Foo>::Key> {
pub trait Foo: Iterator<Item = <Self as Foo>::Key> {
type Key;
}
impl Foo for IntoIter<i32> {
type Key = u32; //~ ERROR type mismatch
type Key = u32;
//~^ ERROR expected `std::vec::IntoIter<i32>` to be an iterator that yields `u32`, but it yields `i32`
}
fn main() {
}
fn main() {}

6
src/test/ui/traits/assoc-type-in-superbad.stderr
View File

@ -1,4 +1,4 @@
error[E0271]: type mismatch resolving `<std::vec::IntoIter<i32> as Iterator>::Item == u32`
error[E0271]: expected `std::vec::IntoIter<i32>` to be an iterator that yields `u32`, but it yields `i32`
--> $DIR/assoc-type-in-superbad.rs:12:16
|
LL | type Key = u32;
@ -7,8 +7,8 @@ LL | type Key = u32;
note: required by a bound in `Foo`
--> $DIR/assoc-type-in-superbad.rs:7:25
|
LL | pub trait Foo: Iterator<Item=<Self as Foo>::Key> {
| ^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `Foo`
LL | pub trait Foo: Iterator<Item = <Self as Foo>::Key> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `Foo`
error: aborting due to previous error

2
src/test/ui/type-alias-impl-trait/issue-57961.rs
View File

@ -8,7 +8,7 @@ trait Foo {
impl Foo for () {
type Bar = std::vec::IntoIter<u32>;
//~^ ERROR type mismatch resolving `<std::vec::IntoIter<u32> as Iterator>::Item == X
//~^ ERROR expected `std::vec::IntoIter<u32>` to be an iterator that yields `X`, but it yields `u32`
}
fn incoherent() {

2
src/test/ui/type-alias-impl-trait/issue-57961.stderr
View File

@ -1,4 +1,4 @@
error[E0271]: type mismatch resolving `<std::vec::IntoIter<u32> as Iterator>::Item == X`
error[E0271]: expected `std::vec::IntoIter<u32>` to be an iterator that yields `X`, but it yields `u32`
--> $DIR/issue-57961.rs:10:16
|
LL | type X = impl Sized;

6
src/test/ui/type-alias-impl-trait/issue-98604.rs
View File

@ -1,13 +1,11 @@
// edition:2018
type AsyncFnPtr = Box<
dyn Fn() -> std::pin::Pin<Box<dyn std::future::Future<Output = ()>>>,
>;
type AsyncFnPtr = Box<dyn Fn() -> std::pin::Pin<Box<dyn std::future::Future<Output = ()>>>>;
async fn test() {}
#[allow(unused_must_use)]
fn main() {
Box::new(test) as AsyncFnPtr;
//~^ ERROR type mismatch
//~^ ERROR expected `fn() -> impl Future<Output = ()> {test}` to be a fn item that returns `Pin<Box<(dyn Future<Output = ()> + 'static)>>`, but it returns `impl Future<Output = ()>`
}

6
src/test/ui/type-alias-impl-trait/issue-98604.stderr
View File

@ -1,11 +1,11 @@
error[E0271]: type mismatch resolving `<fn() -> impl Future<Output = ()> {test} as FnOnce<()>>::Output == Pin<Box<(dyn Future<Output = ()> + 'static)>>`
--> $DIR/issue-98604.rs:11:5
error[E0271]: expected `fn() -> impl Future<Output = ()> {test}` to be a fn item that returns `Pin<Box<(dyn Future<Output = ()> + 'static)>>`, but it returns `impl Future<Output = ()>`
--> $DIR/issue-98604.rs:9:5
|
LL | Box::new(test) as AsyncFnPtr;
| ^^^^^^^^^^^^^^ expected struct `Pin`, found opaque type
|
note: while checking the return type of the `async fn`
--> $DIR/issue-98604.rs:7:17
--> $DIR/issue-98604.rs:5:17
|
LL | async fn test() {}
| ^ checked the `Output` of this `async fn`, found opaque type

6
src/test/ui/type-alias-impl-trait/issue-98608.rs
View File

@ -1,8 +1,10 @@
fn hi() -> impl Sized { std::ptr::null::<u8>() }
fn hi() -> impl Sized {
std::ptr::null::<u8>()
}
fn main() {
let b: Box<dyn Fn() -> Box<u8>> = Box::new(hi);
//~^ ERROR type mismatch resolving `<fn() -> impl Sized {hi} as FnOnce<()>>::Output == Box<u8>`
//~^ ERROR expected `fn() -> impl Sized {hi}` to be a fn item that returns `Box<u8>`, but it returns `impl Sized`
let boxed = b();
let null = *boxed;
println!("{null:?}");

6
src/test/ui/type-alias-impl-trait/issue-98608.stderr
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@ -1,7 +1,7 @@
error[E0271]: type mismatch resolving `<fn() -> impl Sized {hi} as FnOnce<()>>::Output == Box<u8>`
--> $DIR/issue-98608.rs:4:39
error[E0271]: expected `fn() -> impl Sized {hi}` to be a fn item that returns `Box<u8>`, but it returns `impl Sized`
--> $DIR/issue-98608.rs:6:39
|
LL | fn hi() -> impl Sized { std::ptr::null::<u8>() }
LL | fn hi() -> impl Sized {
| ---------- the found opaque type
...
LL | let b: Box<dyn Fn() -> Box<u8>> = Box::new(hi);