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Avoid opaque type not constrained errors in the presence of other errors

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This commit is contained in:
Oli Scherer 2024-07-31 12:58:32 +00:00 • committed by Oli Scherer
parent ec3424a905
commit a91c36139a
23 changed files with 56 additions and 135 deletions
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14
compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
View file

@ -226,13 +226,18 @@ impl TaitConstraintLocator<'_> {
constrained = true;
if !opaque_types_defined_by.contains(&self.def_id) {
self.tcx.dcx().emit_err(TaitForwardCompat {
let guar = self.tcx.dcx().emit_err(TaitForwardCompat {
span: hidden_type.span,
item_span: self
.tcx
.def_ident_span(item_def_id)
.unwrap_or_else(|| self.tcx.def_span(item_def_id)),
});
// Avoid "opaque type not constrained" errors on the opaque itself.
self.found = Some(ty::OpaqueHiddenType {
span: DUMMY_SP,
ty: Ty::new_error(self.tcx, guar),
});
}
let concrete_type =
self.tcx.erase_regions(hidden_type.remap_generic_params_to_declaration_params(
@ -248,7 +253,7 @@ impl TaitConstraintLocator<'_> {
if !constrained {
debug!("no constraints in typeck results");
if opaque_types_defined_by.contains(&self.def_id) {
self.tcx.dcx().emit_err(TaitForwardCompat2 {
let guar = self.tcx.dcx().emit_err(TaitForwardCompat2 {
span: self
.tcx
.def_ident_span(item_def_id)
@ -256,6 +261,11 @@ impl TaitConstraintLocator<'_> {
opaque_type_span: self.tcx.def_span(self.def_id),
opaque_type: self.tcx.def_path_str(self.def_id),
});
// Avoid "opaque type not constrained" errors on the opaque itself.
self.found = Some(ty::OpaqueHiddenType {
span: DUMMY_SP,
ty: Ty::new_error(self.tcx, guar),
});
}
return;
};

2
tests/ui/higher-ranked/trait-bounds/normalize-under-binder/norm-before-method-resolution-opaque-type.next.stderr
View file

@ -1,5 +1,5 @@
error[E0284]: type annotations needed: cannot satisfy `Foo == _`
--> $DIR/norm-before-method-resolution-opaque-type.rs:16:19
--> $DIR/norm-before-method-resolution-opaque-type.rs:15:19
|
LL | fn weird_bound<X>(x: &<X as Trait<'static>>::Out<Foo>) -> X
| ^ cannot satisfy `Foo == _`

14
tests/ui/higher-ranked/trait-bounds/normalize-under-binder/norm-before-method-resolution-opaque-type.old.stderr
View file

@ -1,5 +1,5 @@
error: item does not constrain `Foo::{opaque#0}`, but has it in its signature
--> $DIR/norm-before-method-resolution-opaque-type.rs:16:4
--> $DIR/norm-before-method-resolution-opaque-type.rs:15:4
|
LL | fn weird_bound<X>(x: &<X as Trait<'static>>::Out<Foo>) -> X
| ^^^^^^^^^^^
@ -11,16 +11,8 @@ note: this opaque type is in the signature
LL | type Foo = impl Sized;
| ^^^^^^^^^^
error: unconstrained opaque type
--> $DIR/norm-before-method-resolution-opaque-type.rs:13:12
|
LL | type Foo = impl Sized;
| ^^^^^^^^^^
|
= note: `Foo` must be used in combination with a concrete type within the same module
error[E0507]: cannot move out of `*x` which is behind a shared reference
--> $DIR/norm-before-method-resolution-opaque-type.rs:23:13
--> $DIR/norm-before-method-resolution-opaque-type.rs:22:13
|
LL | let x = *x;
| ^^ move occurs because `*x` has type `<X as Trait<'_>>::Out<Foo>`, which does not implement the `Copy` trait
@ -31,6 +23,6 @@ LL - let x = *x;
LL + let x = x;
|
error: aborting due to 3 previous errors
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0507`.

1
tests/ui/higher-ranked/trait-bounds/normalize-under-binder/norm-before-method-resolution-opaque-type.rs
View file

@ -11,7 +11,6 @@ impl<'a, T> Trait<'a> for T {
}
type Foo = impl Sized;
//[old]~^ ERROR: unconstrained opaque type
fn weird_bound<X>(x: &<X as Trait<'static>>::Out<Foo>) -> X
//[old]~^ ERROR: item does not constrain

1
tests/ui/impl-trait/issues/issue-86800.rs
View file

@ -23,7 +23,6 @@ struct Context {
type TransactionResult<O> = Result<O, ()>;
type TransactionFuture<'__, O> = impl '__ + Future<Output = TransactionResult<O>>;
//~^ ERROR unconstrained opaque type
fn execute_transaction_fut<'f, F, O>(
//~^ ERROR: item does not constrain

20
tests/ui/impl-trait/issues/issue-86800.stderr
View file

@ -1,5 +1,5 @@
error: item does not constrain `TransactionFuture::{opaque#0}`, but has it in its signature
--> $DIR/issue-86800.rs:28:4
--> $DIR/issue-86800.rs:27:4
|
LL | fn execute_transaction_fut<'f, F, O>(
| ^^^^^^^^^^^^^^^^^^^^^^^
@ -12,7 +12,7 @@ LL | type TransactionFuture<'__, O> = impl '__ + Future<Output = TransactionResu
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: item does not constrain `TransactionFuture::{opaque#0}`, but has it in its signature
--> $DIR/issue-86800.rs:40:14
--> $DIR/issue-86800.rs:39:14
|
LL | async fn do_transaction<O>(
| ^^^^^^^^^^^^^^
@ -25,7 +25,7 @@ LL | type TransactionFuture<'__, O> = impl '__ + Future<Output = TransactionResu
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: item does not constrain `TransactionFuture::{opaque#0}`, but has it in its signature
--> $DIR/issue-86800.rs:44:5
--> $DIR/issue-86800.rs:43:5
|
LL | / {
LL | |
@ -43,16 +43,8 @@ note: this opaque type is in the signature
LL | type TransactionFuture<'__, O> = impl '__ + Future<Output = TransactionResult<O>>;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: unconstrained opaque type
--> $DIR/issue-86800.rs:25:34
|
LL | type TransactionFuture<'__, O> = impl '__ + Future<Output = TransactionResult<O>>;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: `TransactionFuture` must be used in combination with a concrete type within the same module
error[E0792]: expected generic lifetime parameter, found `'_`
--> $DIR/issue-86800.rs:35:5
--> $DIR/issue-86800.rs:34:5
|
LL | type TransactionFuture<'__, O> = impl '__ + Future<Output = TransactionResult<O>>;
| --- this generic parameter must be used with a generic lifetime parameter
@ -61,7 +53,7 @@ LL | f
| ^
error[E0792]: expected generic lifetime parameter, found `'_`
--> $DIR/issue-86800.rs:44:5
--> $DIR/issue-86800.rs:43:5
|
LL | type TransactionFuture<'__, O> = impl '__ + Future<Output = TransactionResult<O>>;
| --- this generic parameter must be used with a generic lifetime parameter
@ -75,6 +67,6 @@ LL | | f(&mut transaction).await
LL | | }
| |_____^
error: aborting due to 6 previous errors
error: aborting due to 5 previous errors
For more information about this error, try `rustc --explain E0792`.

1
tests/ui/impl-trait/recursive-type-alias-impl-trait-declaration-too-subtle.rs
View file

@ -2,7 +2,6 @@
mod a {
type Foo = impl PartialEq<(Foo, i32)>;
//~^ ERROR: unconstrained opaque type
struct Bar;

20
tests/ui/impl-trait/recursive-type-alias-impl-trait-declaration-too-subtle.stderr
View file

@ -1,5 +1,5 @@
error[E0053]: method `eq` has an incompatible type for trait
--> $DIR/recursive-type-alias-impl-trait-declaration-too-subtle.rs:10:30
--> $DIR/recursive-type-alias-impl-trait-declaration-too-subtle.rs:9:30
|
LL | type Foo = impl PartialEq<(Foo, i32)>;
| -------------------------- the found opaque type
@ -15,7 +15,7 @@ LL | fn eq(&self, _other: &(a::Bar, i32)) -> bool {
| ~~~~~~~~~~~~~~
error: item does not constrain `a::Foo::{opaque#0}`, but has it in its signature
--> $DIR/recursive-type-alias-impl-trait-declaration-too-subtle.rs:10:12
--> $DIR/recursive-type-alias-impl-trait-declaration-too-subtle.rs:9:12
|
LL | fn eq(&self, _other: &(Foo, i32)) -> bool {
| ^^
@ -27,16 +27,8 @@ note: this opaque type is in the signature
LL | type Foo = impl PartialEq<(Foo, i32)>;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
error: unconstrained opaque type
--> $DIR/recursive-type-alias-impl-trait-declaration-too-subtle.rs:4:16
|
LL | type Foo = impl PartialEq<(Foo, i32)>;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: `Foo` must be used in combination with a concrete type within the same module
error[E0053]: method `eq` has an incompatible type for trait
--> $DIR/recursive-type-alias-impl-trait-declaration-too-subtle.rs:25:30
--> $DIR/recursive-type-alias-impl-trait-declaration-too-subtle.rs:24:30
|
LL | type Foo = impl PartialEq<(Foo, i32)>;
| -------------------------- the expected opaque type
@ -47,7 +39,7 @@ LL | fn eq(&self, _other: &(Bar, i32)) -> bool {
= note: expected signature `fn(&b::Bar, &(b::Foo, _)) -> _`
found signature `fn(&b::Bar, &(b::Bar, _)) -> _`
note: this item must have the opaque type in its signature in order to be able to register hidden types
--> $DIR/recursive-type-alias-impl-trait-declaration-too-subtle.rs:25:12
--> $DIR/recursive-type-alias-impl-trait-declaration-too-subtle.rs:24:12
|
LL | fn eq(&self, _other: &(Bar, i32)) -> bool {
| ^^
@ -57,13 +49,13 @@ LL | fn eq(&self, _other: &(b::Foo, i32)) -> bool {
| ~~~~~~~~~~~~~~
error: unconstrained opaque type
--> $DIR/recursive-type-alias-impl-trait-declaration-too-subtle.rs:19:16
--> $DIR/recursive-type-alias-impl-trait-declaration-too-subtle.rs:18:16
|
LL | type Foo = impl PartialEq<(Foo, i32)>;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: `Foo` must be used in combination with a concrete type within the same module
error: aborting due to 5 previous errors
error: aborting due to 4 previous errors
For more information about this error, try `rustc --explain E0053`.

10
tests/ui/impl-trait/two_tait_defining_each_other2.current.stderr
View file

@ -11,14 +11,6 @@ note: this opaque type is in the signature
LL | type A = impl Foo;
| ^^^^^^^^
error: unconstrained opaque type
--> $DIR/two_tait_defining_each_other2.rs:6:10
|
LL | type A = impl Foo;
| ^^^^^^^^
|
= note: `A` must be used in combination with a concrete type within the same module
error: opaque type's hidden type cannot be another opaque type from the same scope
--> $DIR/two_tait_defining_each_other2.rs:14:5
|
@ -36,5 +28,5 @@ note: opaque type being used as hidden type
LL | type A = impl Foo;
| ^^^^^^^^
error: aborting due to 3 previous errors
error: aborting due to 2 previous errors

2
tests/ui/impl-trait/two_tait_defining_each_other2.rs
View file

@ -3,7 +3,7 @@
//@[next] compile-flags: -Znext-solver
#![feature(type_alias_impl_trait)]
type A = impl Foo; //[current]~ ERROR unconstrained opaque type
type A = impl Foo;
type B = impl Foo;
trait Foo {}

1
tests/ui/self/arbitrary-self-opaque.rs
View file

@ -2,7 +2,6 @@
struct Foo;
type Bar = impl Sized;
//~^ ERROR unconstrained opaque type
impl Foo {
fn foo(self: Bar) {}

14
tests/ui/self/arbitrary-self-opaque.stderr
View file

@ -1,5 +1,5 @@
error[E0307]: invalid `self` parameter type: `Bar`
--> $DIR/arbitrary-self-opaque.rs:8:18
--> $DIR/arbitrary-self-opaque.rs:7:18
|
LL | fn foo(self: Bar) {}
| ^^^
@ -8,7 +8,7 @@ LL | fn foo(self: Bar) {}
= help: consider changing to `self`, `&self`, `&mut self`, `self: Box<Self>`, `self: Rc<Self>`, `self: Arc<Self>`, or `self: Pin<P>` (where P is one of the previous types except `Self`)
error: item does not constrain `Bar::{opaque#0}`, but has it in its signature
--> $DIR/arbitrary-self-opaque.rs:8:8
--> $DIR/arbitrary-self-opaque.rs:7:8
|
LL | fn foo(self: Bar) {}
| ^^^
@ -20,14 +20,6 @@ note: this opaque type is in the signature
LL | type Bar = impl Sized;
| ^^^^^^^^^^
error: unconstrained opaque type
--> $DIR/arbitrary-self-opaque.rs:4:12
|
LL | type Bar = impl Sized;
| ^^^^^^^^^^
|
= note: `Bar` must be used in combination with a concrete type within the same module
error: aborting due to 3 previous errors
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0307`.

1
tests/ui/type-alias-impl-trait/bad-tait-no-substs.rs
View file

@ -3,7 +3,6 @@
#![feature(type_alias_impl_trait)]
trait Trait<T> {}
type Alias<'a, U> = impl Trait<U>;
//~^ ERROR unconstrained opaque type
pub enum UninhabitedVariants {
Tuple(Alias),

22
tests/ui/type-alias-impl-trait/bad-tait-no-substs.stderr
View file

@ -1,5 +1,5 @@
error[E0106]: missing lifetime specifier
--> $DIR/bad-tait-no-substs.rs:9:11
--> $DIR/bad-tait-no-substs.rs:8:11
|
LL | Tuple(Alias),
| ^^^^^ expected named lifetime parameter
@ -11,7 +11,7 @@ LL ~ Tuple(Alias<'a>),
|
error[E0107]: missing generics for type alias `Alias`
--> $DIR/bad-tait-no-substs.rs:9:11
--> $DIR/bad-tait-no-substs.rs:8:11
|
LL | Tuple(Alias),
| ^^^^^ expected 1 generic argument
@ -27,7 +27,7 @@ LL | Tuple(Alias<U>),
| +++
error[E0792]: non-defining opaque type use in defining scope
--> $DIR/bad-tait-no-substs.rs:9:11
--> $DIR/bad-tait-no-substs.rs:8:11
|
LL | Tuple(Alias),
| ^^^^^ argument `'_` is not a generic parameter
@ -39,7 +39,7 @@ LL | type Alias<'a, U> = impl Trait<U>;
| ^^^^^^^^^^^^^
error: item does not constrain `Alias::{opaque#0}`, but has it in its signature
--> $DIR/bad-tait-no-substs.rs:15:4
--> $DIR/bad-tait-no-substs.rs:14:4
|
LL | fn uwu(x: UninhabitedVariants) {
| ^^^
@ -51,22 +51,14 @@ note: this opaque type is in the signature
LL | type Alias<'a, U> = impl Trait<U>;
| ^^^^^^^^^^^^^
error: unconstrained opaque type
--> $DIR/bad-tait-no-substs.rs:5:21
|
LL | type Alias<'a, U> = impl Trait<U>;
| ^^^^^^^^^^^^^
|
= note: `Alias` must be used in combination with a concrete type within the same module
error[E0004]: non-exhaustive patterns: `UninhabitedVariants::Tuple(_)` not covered
--> $DIR/bad-tait-no-substs.rs:17:11
--> $DIR/bad-tait-no-substs.rs:16:11
|
LL | match x {}
| ^ pattern `UninhabitedVariants::Tuple(_)` not covered
|
note: `UninhabitedVariants` defined here
--> $DIR/bad-tait-no-substs.rs:8:10
--> $DIR/bad-tait-no-substs.rs:7:10
|
LL | pub enum UninhabitedVariants {
| ^^^^^^^^^^^^^^^^^^^
@ -80,7 +72,7 @@ LL + UninhabitedVariants::Tuple(_) => todo!(),
LL + }
|
error: aborting due to 6 previous errors
error: aborting due to 5 previous errors
Some errors have detailed explanations: E0004, E0106, E0107, E0792.
For more information about an error, try `rustc --explain E0004`.

2
tests/ui/type-alias-impl-trait/const_generic_type.infer.stderr
View file

@ -1,5 +1,5 @@
error: `Bar` is forbidden as the type of a const generic parameter
--> $DIR/const_generic_type.rs:8:24
--> $DIR/const_generic_type.rs:7:24
|
LL | async fn test<const N: crate::Bar>() {
| ^^^^^^^^^^

16
tests/ui/type-alias-impl-trait/const_generic_type.no_infer.stderr
View file

@ -1,5 +1,5 @@
error: `Bar` is forbidden as the type of a const generic parameter
--> $DIR/const_generic_type.rs:8:24
--> $DIR/const_generic_type.rs:7:24
|
LL | async fn test<const N: crate::Bar>() {
| ^^^^^^^^^^
@ -7,7 +7,7 @@ LL | async fn test<const N: crate::Bar>() {
= note: the only supported types are integers, `bool`, and `char`
error: item does not constrain `Bar::{opaque#0}`, but has it in its signature
--> $DIR/const_generic_type.rs:8:10
--> $DIR/const_generic_type.rs:7:10
|
LL | async fn test<const N: crate::Bar>() {
| ^^^^
@ -20,7 +20,7 @@ LL | type Bar = impl std::fmt::Display;
| ^^^^^^^^^^^^^^^^^^^^^^
error: item does not constrain `Bar::{opaque#0}`, but has it in its signature
--> $DIR/const_generic_type.rs:8:38
--> $DIR/const_generic_type.rs:7:38
|
LL | async fn test<const N: crate::Bar>() {
| ______________________________________^
@ -39,13 +39,5 @@ note: this opaque type is in the signature
LL | type Bar = impl std::fmt::Display;
| ^^^^^^^^^^^^^^^^^^^^^^
error: unconstrained opaque type
--> $DIR/const_generic_type.rs:5:12
|
LL | type Bar = impl std::fmt::Display;
| ^^^^^^^^^^^^^^^^^^^^^^
|
= note: `Bar` must be used in combination with a concrete type within the same module
error: aborting due to 4 previous errors
error: aborting due to 3 previous errors

1
tests/ui/type-alias-impl-trait/const_generic_type.rs
View file

@ -3,7 +3,6 @@
#![feature(type_alias_impl_trait)]
type Bar = impl std::fmt::Display;
//[no_infer]~^ ERROR: unconstrained opaque type
async fn test<const N: crate::Bar>() {
//~^ ERROR: `Bar` is forbidden as the type of a const generic parameter

1
tests/ui/type-alias-impl-trait/hkl_forbidden4.rs
View file

@ -8,7 +8,6 @@
use std::future::Future;
type FutNothing<'a> = impl 'a + Future<Output = ()>;
//~^ ERROR: unconstrained opaque type
async fn operation(_: &mut ()) -> () {
//~^ ERROR: concrete type differs from previous

22
tests/ui/type-alias-impl-trait/hkl_forbidden4.stderr
View file

@ -1,5 +1,5 @@
error: item does not constrain `FutNothing::{opaque#0}`, but has it in its signature
--> $DIR/hkl_forbidden4.rs:19:10
--> $DIR/hkl_forbidden4.rs:18:10
|
LL | async fn call<F>(_f: F)
| ^^^^
@ -12,7 +12,7 @@ LL | type FutNothing<'a> = impl 'a + Future<Output = ()>;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: item does not constrain `FutNothing::{opaque#0}`, but has it in its signature
--> $DIR/hkl_forbidden4.rs:23:1
--> $DIR/hkl_forbidden4.rs:22:1
|
LL | / {
LL | |
@ -27,16 +27,8 @@ note: this opaque type is in the signature
LL | type FutNothing<'a> = impl 'a + Future<Output = ()>;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: unconstrained opaque type
--> $DIR/hkl_forbidden4.rs:10:23
|
LL | type FutNothing<'a> = impl 'a + Future<Output = ()>;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: `FutNothing` must be used in combination with a concrete type within the same module
error[E0792]: expected generic lifetime parameter, found `'any`
--> $DIR/hkl_forbidden4.rs:15:5
--> $DIR/hkl_forbidden4.rs:14:5
|
LL | async fn operation(_: &mut ()) -> () {
| - this generic parameter must be used with a generic lifetime parameter
@ -45,19 +37,19 @@ LL | call(operation).await
| ^^^^^^^^^^^^^^^
error: concrete type differs from previous defining opaque type use
--> $DIR/hkl_forbidden4.rs:13:1
--> $DIR/hkl_forbidden4.rs:12:1
|
LL | async fn operation(_: &mut ()) -> () {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `FutNothing<'_>`, got `{async fn body of operation()}`
|
note: previous use here
--> $DIR/hkl_forbidden4.rs:15:5
--> $DIR/hkl_forbidden4.rs:14:5
|
LL | call(operation).await
| ^^^^^^^^^^^^^^^
error[E0792]: expected generic lifetime parameter, found `'any`
--> $DIR/hkl_forbidden4.rs:23:1
--> $DIR/hkl_forbidden4.rs:22:1
|
LL | type FutNothing<'a> = impl 'a + Future<Output = ()>;
| -- this generic parameter must be used with a generic lifetime parameter
@ -68,6 +60,6 @@ LL | |
LL | | }
| |_^
error: aborting due to 6 previous errors
error: aborting due to 5 previous errors
For more information about this error, try `rustc --explain E0792`.

1
tests/ui/type-alias-impl-trait/nested-tait-inference3.rs
View file

@ -4,7 +4,6 @@
use std::fmt::Debug;
type FooX = impl Debug;
//~^ ERROR unconstrained opaque type
trait Foo<A> {}

12
tests/ui/type-alias-impl-trait/nested-tait-inference3.stderr
View file

@ -1,5 +1,5 @@
error: item does not constrain `FooX::{opaque#0}`, but has it in its signature
--> $DIR/nested-tait-inference3.rs:13:4
--> $DIR/nested-tait-inference3.rs:12:4
|
LL | fn foo() -> impl Foo<FooX> {
| ^^^
@ -11,13 +11,5 @@ note: this opaque type is in the signature
LL | type FooX = impl Debug;
| ^^^^^^^^^^
error: unconstrained opaque type
--> $DIR/nested-tait-inference3.rs:6:13
|
LL | type FooX = impl Debug;
| ^^^^^^^^^^
|
= note: `FooX` must be used in combination with a concrete type within the same module
error: aborting due to 2 previous errors
error: aborting due to 1 previous error

1
tests/ui/type-alias-impl-trait/no_inferrable_concrete_type.rs
View file

@ -5,7 +5,6 @@
mod foo {
pub type Foo = impl Copy;
//~^ ERROR unconstrained opaque type
// make compiler happy about using 'Foo'
pub fn bar(x: Foo) -> Foo {

12
tests/ui/type-alias-impl-trait/no_inferrable_concrete_type.stderr
View file

@ -1,5 +1,5 @@
error: item does not constrain `Foo::{opaque#0}`, but has it in its signature
--> $DIR/no_inferrable_concrete_type.rs:11:12
--> $DIR/no_inferrable_concrete_type.rs:10:12
|
LL | pub fn bar(x: Foo) -> Foo {
| ^^^
@ -11,13 +11,5 @@ note: this opaque type is in the signature
LL | pub type Foo = impl Copy;
| ^^^^^^^^^
error: unconstrained opaque type
--> $DIR/no_inferrable_concrete_type.rs:7:20
|
LL | pub type Foo = impl Copy;
| ^^^^^^^^^
|
= note: `Foo` must be used in combination with a concrete type within the same module
error: aborting due to 2 previous errors
error: aborting due to 1 previous error