When checking whether an impl applies, constrain hidden types of opaque types.

We already handle this case this way on the coherence side, and it matches the new solver's behaviour. While there is some breakage around type-alias-impl-trait (see new "type annotations needed" in tests/ui/type-alias-impl-trait/issue-84660-unsoundness.rs), no stable code breaks, and no new stable code is accepted.

23 files changed, 127 insertions, 116 deletions

diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 4a94643d908..86a5d464b7b 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -2539,7 +2539,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         let InferOk { obligations, .. } = self
             .infcx
             .at(&cause, obligation.param_env)
-            .eq(DefineOpaqueTypes::No, placeholder_obligation_trait_ref, impl_trait_ref)
+            .eq(DefineOpaqueTypes::Yes, placeholder_obligation_trait_ref, impl_trait_ref)
             .map_err(|e| {
                 debug!("match_impl: failed eq_trait_refs due to `{}`", e.to_string(self.tcx()))
             })?;
diff --git a/tests/ui/impl-trait/equality.rs b/tests/ui/impl-trait/equality.rs
index 828b5aac896..952f81f1978 100644
--- a/tests/ui/impl-trait/equality.rs
+++ b/tests/ui/impl-trait/equality.rs
@@ -22,7 +22,7 @@ fn sum_to(n: u32) -> impl Foo {
         0
     } else {
         n + sum_to(n - 1)
-        //~^ ERROR cannot add `impl Foo` to `u32`
+        //~^ ERROR cannot satisfy `<u32 as Add<impl Foo>>::Output == i32`
     }
 }
 
@@ -32,12 +32,15 @@ trait Leak: Sized {
 }
 impl<T> Leak for T {
     default type T = ();
-    default fn leak(self) -> Self::T { panic!() }
+    default fn leak(self) -> Self::T {
+        panic!()
+    }
 }
 impl Leak for i32 {
     type T = i32;
-    fn leak(self) -> i32 { self }
+    fn leak(self) -> i32 {
+        self
+    }
 }
 
-fn main() {
-}
+fn main() {}
diff --git a/tests/ui/impl-trait/equality.stderr b/tests/ui/impl-trait/equality.stderr
index 69f4cbbbf42..c9ba1a5ba32 100644
--- a/tests/ui/impl-trait/equality.stderr
+++ b/tests/ui/impl-trait/equality.stderr
@@ -22,20 +22,13 @@ help: change the type of the numeric literal from `u32` to `i32`
 LL |     0_i32
    |       ~~~
 
-error[E0277]: cannot add `impl Foo` to `u32`
+error[E0284]: type annotations needed: cannot satisfy `<u32 as Add<impl Foo>>::Output == i32`
   --> $DIR/equality.rs:24:11
    |
 LL |         n + sum_to(n - 1)
-   |           ^ no implementation for `u32 + impl Foo`
-   |
-   = help: the trait `Add<impl Foo>` is not implemented for `u32`
-   = help: the following other types implement trait `Add<Rhs>`:
-             <&'a u32 as Add<u32>>
-             <&u32 as Add<&u32>>
-             <u32 as Add<&u32>>
-             <u32 as Add>
+   |           ^ cannot satisfy `<u32 as Add<impl Foo>>::Output == i32`
 
 error: aborting due to 2 previous errors; 1 warning emitted
 
-Some errors have detailed explanations: E0277, E0308.
-For more information about an error, try `rustc --explain E0277`.
+Some errors have detailed explanations: E0284, E0308.
+For more information about an error, try `rustc --explain E0284`.
diff --git a/tests/ui/impl-trait/nested_impl_trait.stderr b/tests/ui/impl-trait/nested_impl_trait.stderr
index 1f9a2a5e9d6..f7c708a1dfa 100644
--- a/tests/ui/impl-trait/nested_impl_trait.stderr
+++ b/tests/ui/impl-trait/nested_impl_trait.stderr
@@ -46,19 +46,23 @@ error[E0277]: the trait bound `impl Into<u32>: Into<impl Debug>` is not satisfie
   --> $DIR/nested_impl_trait.rs:6:46
    |
 LL | fn bad_in_ret_position(x: impl Into<u32>) -> impl Into<impl Debug> { x }
-   |                                              ^^^^^^^^^^^^^^^^^^^^^ the trait `From<impl Into<u32>>` is not implemented for `impl Into<u32>`, which is required by `impl Into<u32>: Into<impl Debug>`
+   |                                              ^^^^^^^^^^^^^^^^^^^^^ the trait `Debug` is not implemented for `impl Into<u32>`
    |
-   = help: the trait `Into<U>` is implemented for `T`
-   = note: required for `impl Into<u32>` to implement `Into<impl Debug>`
+help: consider further restricting this bound
+   |
+LL | fn bad_in_ret_position(x: impl Into<u32> + std::fmt::Debug) -> impl Into<impl Debug> { x }
+   |                                          +++++++++++++++++
 
 error[E0277]: the trait bound `impl Into<u32>: Into<impl Debug>` is not satisfied
   --> $DIR/nested_impl_trait.rs:19:34
    |
 LL |     fn bad(x: impl Into<u32>) -> impl Into<impl Debug> { x }
-   |                                  ^^^^^^^^^^^^^^^^^^^^^ the trait `From<impl Into<u32>>` is not implemented for `impl Into<u32>`, which is required by `impl Into<u32>: Into<impl Debug>`
+   |                                  ^^^^^^^^^^^^^^^^^^^^^ the trait `Debug` is not implemented for `impl Into<u32>`
+   |
+help: consider further restricting this bound
    |
-   = help: the trait `Into<U>` is implemented for `T`
-   = note: required for `impl Into<u32>` to implement `Into<impl Debug>`
+LL |     fn bad(x: impl Into<u32> + std::fmt::Debug) -> impl Into<impl Debug> { x }
+   |                              +++++++++++++++++
 
 error: aborting due to 7 previous errors
 
diff --git a/tests/ui/impl-trait/recursive-type-alias-impl-trait-declaration.rs b/tests/ui/impl-trait/recursive-type-alias-impl-trait-declaration.rs
index aab10be2de2..7874a21f3ae 100644
--- a/tests/ui/impl-trait/recursive-type-alias-impl-trait-declaration.rs
+++ b/tests/ui/impl-trait/recursive-type-alias-impl-trait-declaration.rs
@@ -11,7 +11,7 @@ impl PartialEq<(Bar, i32)> for Bar {
 }
 
 fn foo() -> Foo {
-    //~^ ERROR can't compare `Bar` with `(Foo, i32)`
+    //~^ ERROR overflow evaluating the requirement `Bar: PartialEq<(Foo, i32)>`
     Bar
 }
 
diff --git a/tests/ui/impl-trait/recursive-type-alias-impl-trait-declaration.stderr b/tests/ui/impl-trait/recursive-type-alias-impl-trait-declaration.stderr
index bc810c0f88f..2d4707f8a27 100644
--- a/tests/ui/impl-trait/recursive-type-alias-impl-trait-declaration.stderr
+++ b/tests/ui/impl-trait/recursive-type-alias-impl-trait-declaration.stderr
@@ -1,15 +1,9 @@
-error[E0277]: can't compare `Bar` with `(Foo, i32)`
+error[E0275]: overflow evaluating the requirement `Bar: PartialEq<(Foo, i32)>`
   --> $DIR/recursive-type-alias-impl-trait-declaration.rs:13:13
    |
 LL | fn foo() -> Foo {
-   |             ^^^ no implementation for `Bar == (Foo, i32)`
-LL |
-LL |     Bar
-   |     --- return type was inferred to be `Bar` here
-   |
-   = help: the trait `PartialEq<(Foo, i32)>` is not implemented for `Bar`
-   = help: the trait `PartialEq<(Bar, i32)>` is implemented for `Bar`
+   |             ^^^
 
 error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0277`.
+For more information about this error, try `rustc --explain E0275`.
diff --git a/tests/ui/type-alias-impl-trait/constrain_in_projection.current.stderr b/tests/ui/type-alias-impl-trait/constrain_in_projection.current.stderr
deleted file mode 100644
index c215d197db4..00000000000
--- a/tests/ui/type-alias-impl-trait/constrain_in_projection.current.stderr
+++ /dev/null
@@ -1,11 +0,0 @@
-error[E0277]: the trait bound `Foo: Trait<Bar>` is not satisfied
-  --> $DIR/constrain_in_projection.rs:24:14
-   |
-LL |     let x = <Foo as Trait<Bar>>::Assoc::default();
-   |              ^^^ the trait `Trait<Bar>` is not implemented for `Foo`
-   |
-   = help: the trait `Trait<()>` is implemented for `Foo`
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/type-alias-impl-trait/constrain_in_projection.rs b/tests/ui/type-alias-impl-trait/constrain_in_projection.rs
index 7d7d16361ae..2a246900106 100644
--- a/tests/ui/type-alias-impl-trait/constrain_in_projection.rs
+++ b/tests/ui/type-alias-impl-trait/constrain_in_projection.rs
@@ -4,7 +4,7 @@
 //@ revisions: current next
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@[next] compile-flags: -Znext-solver
-//@[next]check-pass
+//@check-pass
 
 #![feature(type_alias_impl_trait)]
 
@@ -22,7 +22,6 @@ impl Trait<()> for Foo {
 
 fn bop(_: Bar) {
     let x = <Foo as Trait<Bar>>::Assoc::default();
-    //[current]~^ `Foo: Trait<Bar>` is not satisfied
 }
 
 fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/constrain_in_projection2.current.stderr b/tests/ui/type-alias-impl-trait/constrain_in_projection2.current.stderr
index 69df5c77f9d..0d6eac4216b 100644
--- a/tests/ui/type-alias-impl-trait/constrain_in_projection2.current.stderr
+++ b/tests/ui/type-alias-impl-trait/constrain_in_projection2.current.stderr
@@ -1,13 +1,19 @@
-error[E0277]: the trait bound `Foo: Trait<Bar>` is not satisfied
+error[E0283]: type annotations needed: cannot satisfy `Foo: Trait<Bar>`
   --> $DIR/constrain_in_projection2.rs:27:14
    |
 LL |     let x = <Foo as Trait<Bar>>::Assoc::default();
-   |              ^^^ the trait `Trait<Bar>` is not implemented for `Foo`
+   |              ^^^ help: use the fully qualified path to an implementation: `<Type as Trait>::Assoc`
    |
-   = help: the following other types implement trait `Trait<T>`:
-             <Foo as Trait<()>>
-             <Foo as Trait<u32>>
+note: multiple `impl`s satisfying `Foo: Trait<Bar>` found
+  --> $DIR/constrain_in_projection2.rs:18:1
+   |
+LL | impl Trait<()> for Foo {
+   | ^^^^^^^^^^^^^^^^^^^^^^
+...
+LL | impl Trait<u32> for Foo {
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+   = note: associated types cannot be accessed directly on a `trait`, they can only be accessed through a specific `impl`
 
 error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0277`.
+For more information about this error, try `rustc --explain E0283`.
diff --git a/tests/ui/type-alias-impl-trait/constrain_in_projection2.rs b/tests/ui/type-alias-impl-trait/constrain_in_projection2.rs
index af222f6c153..0066131f015 100644
--- a/tests/ui/type-alias-impl-trait/constrain_in_projection2.rs
+++ b/tests/ui/type-alias-impl-trait/constrain_in_projection2.rs
@@ -25,8 +25,7 @@ impl Trait<u32> for Foo {
 
 fn bop(_: Bar) {
     let x = <Foo as Trait<Bar>>::Assoc::default();
-    //[next]~^ ERROR: cannot satisfy `Foo: Trait<Bar>`
-    //[current]~^^ ERROR: `Foo: Trait<Bar>` is not satisfied
+    //~^ ERROR: cannot satisfy `Foo: Trait<Bar>`
 }
 
 fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/issue-84660-unsoundness.stderr b/tests/ui/type-alias-impl-trait/issue-84660-unsoundness.current.stderr
index 461da20f37b..a7ff097e8bf 100644
--- a/tests/ui/type-alias-impl-trait/issue-84660-unsoundness.stderr
+++ b/tests/ui/type-alias-impl-trait/issue-84660-unsoundness.current.stderr
@@ -1,5 +1,5 @@
 error[E0119]: conflicting implementations of trait `Trait<Bar, _>`
-  --> $DIR/issue-84660-unsoundness.rs:23:1
+  --> $DIR/issue-84660-unsoundness.rs:28:1
    |
 LL | impl<In, Out> Trait<Bar, In> for Out {
    | ------------------------------------ first implementation here
diff --git a/tests/ui/type-alias-impl-trait/issue-84660-unsoundness.next.stderr b/tests/ui/type-alias-impl-trait/issue-84660-unsoundness.next.stderr
new file mode 100644
index 00000000000..607f0b062ab
--- /dev/null
+++ b/tests/ui/type-alias-impl-trait/issue-84660-unsoundness.next.stderr
@@ -0,0 +1,23 @@
+error[E0284]: type annotations needed: cannot satisfy `<Out as Trait<Bar, In>>::Out == ()`
+  --> $DIR/issue-84660-unsoundness.rs:22:37
+   |
+LL |       fn convert(_i: In) -> Self::Out {
+   |  _____________________________________^
+LL | |
+LL | |         unreachable!();
+LL | |     }
+   | |_____^ cannot satisfy `<Out as Trait<Bar, In>>::Out == ()`
+
+error[E0119]: conflicting implementations of trait `Trait<Bar, _>`
+  --> $DIR/issue-84660-unsoundness.rs:28:1
+   |
+LL | impl<In, Out> Trait<Bar, In> for Out {
+   | ------------------------------------ first implementation here
+...
+LL | impl<In, Out> Trait<(), In> for Out {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0119, E0284.
+For more information about an error, try `rustc --explain E0119`.
diff --git a/tests/ui/type-alias-impl-trait/issue-84660-unsoundness.rs b/tests/ui/type-alias-impl-trait/issue-84660-unsoundness.rs
index 48d4b0c96ff..99a5d36066b 100644
--- a/tests/ui/type-alias-impl-trait/issue-84660-unsoundness.rs
+++ b/tests/ui/type-alias-impl-trait/issue-84660-unsoundness.rs
@@ -1,6 +1,10 @@
 // Another example from issue #84660, this time weaponized as a safe transmute: an opaque type in an
 // impl header being accepted was used to create unsoundness.
 
+//@ revisions: current next
+//@ ignore-compare-mode-next-solver (explicit revisions)
+//@[next] compile-flags: -Znext-solver
+
 #![feature(type_alias_impl_trait)]
 
 trait Foo {}
@@ -16,11 +20,13 @@ trait Trait<T, In> {
 impl<In, Out> Trait<Bar, In> for Out {
     type Out = Out;
     fn convert(_i: In) -> Self::Out {
+        //[next]~^ ERROR: type annotations needed
         unreachable!();
     }
 }
 
-impl<In, Out> Trait<(), In> for Out { //~ ERROR conflicting implementations of trait `Trait<Bar, _>`
+impl<In, Out> Trait<(), In> for Out {
+    //~^ ERROR conflicting implementations of trait `Trait<Bar, _>`
     type Out = In;
     fn convert(i: In) -> Self::Out {
         i
diff --git a/tests/ui/type-alias-impl-trait/nested-tait-inference.rs b/tests/ui/type-alias-impl-trait/nested-tait-inference.rs
index 82248971692..70495c44706 100644
--- a/tests/ui/type-alias-impl-trait/nested-tait-inference.rs
+++ b/tests/ui/type-alias-impl-trait/nested-tait-inference.rs
@@ -1,18 +1,21 @@
 #![feature(type_alias_impl_trait)]
 #![allow(dead_code)]
 
+//@ revisions: current next
+//@ ignore-compare-mode-next-solver (explicit revisions)
+//@[next] compile-flags: -Znext-solver
+//@check-pass
+
 use std::fmt::Debug;
 
 type FooX = impl Debug;
 
-trait Foo<A> { }
+trait Foo<A> {}
 
-impl Foo<()> for () { }
+impl Foo<()> for () {}
 
 fn foo() -> impl Foo<FooX> {
-    //~^ ERROR: the trait bound `(): Foo<FooX>` is not satisfied
-    // FIXME(type-alias-impl-trait): We could probably make this work.
     ()
 }
 
-fn main() { }
+fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/nested-tait-inference2.current.stderr b/tests/ui/type-alias-impl-trait/nested-tait-inference2.current.stderr
new file mode 100644
index 00000000000..c7b7af152ab
--- /dev/null
+++ b/tests/ui/type-alias-impl-trait/nested-tait-inference2.current.stderr
@@ -0,0 +1,17 @@
+error[E0283]: type annotations needed: cannot satisfy `(): Foo<FooX>`
+  --> $DIR/nested-tait-inference2.rs:17:13
+   |
+LL | fn foo() -> impl Foo<FooX> {
+   |             ^^^^^^^^^^^^^^
+   |
+note: multiple `impl`s satisfying `(): Foo<FooX>` found
+  --> $DIR/nested-tait-inference2.rs:14:1
+   |
+LL | impl Foo<()> for () {}
+   | ^^^^^^^^^^^^^^^^^^^
+LL | impl Foo<u32> for () {}
+   | ^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0283`.
diff --git a/tests/ui/type-alias-impl-trait/nested-tait-inference2.next.stderr b/tests/ui/type-alias-impl-trait/nested-tait-inference2.next.stderr
new file mode 100644
index 00000000000..9647d9e376e
--- /dev/null
+++ b/tests/ui/type-alias-impl-trait/nested-tait-inference2.next.stderr
@@ -0,0 +1,9 @@
+error[E0284]: type annotations needed: cannot satisfy `impl Foo<FooX> == ()`
+  --> $DIR/nested-tait-inference2.rs:19:5
+   |
+LL |     ()
+   |     ^^ cannot satisfy `impl Foo<FooX> == ()`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0284`.
diff --git a/tests/ui/type-alias-impl-trait/nested-tait-inference2.rs b/tests/ui/type-alias-impl-trait/nested-tait-inference2.rs
index 0d7f5bad25f..fe2f76e552a 100644
--- a/tests/ui/type-alias-impl-trait/nested-tait-inference2.rs
+++ b/tests/ui/type-alias-impl-trait/nested-tait-inference2.rs
@@ -1,6 +1,10 @@
 #![feature(type_alias_impl_trait)]
 #![allow(dead_code)]
 
+//@ revisions: current next
+//@ ignore-compare-mode-next-solver (explicit revisions)
+//@[next] compile-flags: -Znext-solver
+
 use std::fmt::Debug;
 
 type FooX = impl Debug;
@@ -11,8 +15,9 @@ impl Foo<()> for () {}
 impl Foo<u32> for () {}
 
 fn foo() -> impl Foo<FooX> {
-    //~^ ERROR: the trait bound `(): Foo<FooX>` is not satisfied
+    //[current]~^ ERROR: cannot satisfy `(): Foo<FooX>`
     ()
+    //[next]~^ ERROR: cannot satisfy `impl Foo<FooX> == ()`
 }
 
 fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/nested-tait-inference2.stderr b/tests/ui/type-alias-impl-trait/nested-tait-inference2.stderr
deleted file mode 100644
index 241342b0509..00000000000
--- a/tests/ui/type-alias-impl-trait/nested-tait-inference2.stderr
+++ /dev/null
@@ -1,16 +0,0 @@
-error[E0277]: the trait bound `(): Foo<FooX>` is not satisfied
-  --> $DIR/nested-tait-inference2.rs:13:13
-   |
-LL | fn foo() -> impl Foo<FooX> {
-   |             ^^^^^^^^^^^^^^ the trait `Foo<FooX>` is not implemented for `()`
-LL |
-LL |     ()
-   |     -- return type was inferred to be `()` here
-   |
-   = help: the following other types implement trait `Foo<A>`:
-             <() as Foo<()>>
-             <() as Foo<u32>>
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/type-alias-impl-trait/normalize-hidden-types.current.stderr b/tests/ui/type-alias-impl-trait/normalize-hidden-types.current.stderr
index a40dac06a01..eff29303bf1 100644
--- a/tests/ui/type-alias-impl-trait/normalize-hidden-types.current.stderr
+++ b/tests/ui/type-alias-impl-trait/normalize-hidden-types.current.stderr
@@ -22,21 +22,17 @@ note: previous use here
 LL |     fn define_1() -> Opaque { dyn_hoops::<_>(0) }
    |                               ^^^^^^^^^^^^^^^^^
 
-error[E0308]: mismatched types
+error: concrete type differs from previous defining opaque type use
   --> $DIR/normalize-hidden-types.rs:43:25
    |
-LL |     type Opaque = impl Sized;
-   |                   ---------- the expected opaque type
-...
 LL |         let _: Opaque = dyn_hoops::<u8>(0);
-   |                ------   ^^^^^^^^^^^^^^^^^^ expected opaque type, found `*const dyn FnOnce(())`
-   |                |
-   |                expected due to this
-   |
-   = note: expected opaque type `typeck::Opaque`
-              found raw pointer `*const (dyn FnOnce(()) + 'static)`
-   = help: consider constraining the associated type `<u8 as Trait>::Gat<'_>` to `()` or calling a method that returns `<u8 as Trait>::Gat<'_>`
-   = note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
+   |                         ^^^^^^^^^^^^^^^^^^ expected `*const (dyn FnOnce(()) + 'static)`, got `*const dyn for<'a> FnOnce(<u8 as Trait>::Gat<'a>)`
+   |
+note: previous use here
+  --> $DIR/normalize-hidden-types.rs:44:9
+   |
+LL |         None
+   |         ^^^^
 
 error: concrete type differs from previous defining opaque type use
   --> $DIR/normalize-hidden-types.rs:52:25
@@ -52,4 +48,3 @@ LL |         None
 
 error: aborting due to 4 previous errors
 
-For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/type-alias-impl-trait/self-referential-2.current.stderr b/tests/ui/type-alias-impl-trait/self-referential-2.current.stderr
deleted file mode 100644
index 3ae3590ca7f..00000000000
--- a/tests/ui/type-alias-impl-trait/self-referential-2.current.stderr
+++ /dev/null
@@ -1,14 +0,0 @@
-error[E0277]: can't compare `i32` with `Foo`
-  --> $DIR/self-referential-2.rs:10:13
-   |
-LL | fn bar() -> Bar {
-   |             ^^^ no implementation for `i32 == Foo`
-LL |     42_i32
-   |     ------ return type was inferred to be `i32` here
-   |
-   = help: the trait `PartialEq<Foo>` is not implemented for `i32`
-   = help: the trait `PartialEq` is implemented for `i32`
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/type-alias-impl-trait/self-referential-2.rs b/tests/ui/type-alias-impl-trait/self-referential-2.rs
index f96364ccfcd..f4102f2e2cb 100644
--- a/tests/ui/type-alias-impl-trait/self-referential-2.rs
+++ b/tests/ui/type-alias-impl-trait/self-referential-2.rs
@@ -1,14 +1,14 @@
 //@ revisions: current next
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@[next] compile-flags: -Znext-solver
-//@[next] check-pass
+//@ check-pass
 #![feature(type_alias_impl_trait)]
 
 type Foo = impl std::fmt::Debug;
 type Bar = impl PartialEq<Foo>;
 
 fn bar() -> Bar {
-    42_i32 //[current]~^ ERROR can't compare `i32` with `Foo`
+    42_i32
 }
 
 fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/self-referential-3.rs b/tests/ui/type-alias-impl-trait/self-referential-3.rs
index b33051da2d7..3b015ab322a 100644
--- a/tests/ui/type-alias-impl-trait/self-referential-3.rs
+++ b/tests/ui/type-alias-impl-trait/self-referential-3.rs
@@ -5,7 +5,7 @@
 type Bar<'a, 'b> = impl PartialEq<Bar<'a, 'b>> + std::fmt::Debug;
 
 fn bar<'a, 'b>(i: &'a i32) -> Bar<'a, 'b> {
-    //~^ ERROR can't compare `&i32` with `Bar<'a, 'b>`
+    //~^ ERROR overflow normalizing the type alias `Bar<'a, 'b>`
     i
 }
 
diff --git a/tests/ui/type-alias-impl-trait/self-referential-3.stderr b/tests/ui/type-alias-impl-trait/self-referential-3.stderr
index 32eac622e51..caa9f9691dd 100644
--- a/tests/ui/type-alias-impl-trait/self-referential-3.stderr
+++ b/tests/ui/type-alias-impl-trait/self-referential-3.stderr
@@ -1,15 +1,11 @@
-error[E0277]: can't compare `&i32` with `Bar<'a, 'b>`
+error[E0275]: overflow normalizing the type alias `Bar<'a, 'b>`
   --> $DIR/self-referential-3.rs:7:31
    |
 LL | fn bar<'a, 'b>(i: &'a i32) -> Bar<'a, 'b> {
-   |                               ^^^^^^^^^^^ no implementation for `&i32 == Bar<'a, 'b>`
-LL |
-LL |     i
-   |     - return type was inferred to be `&i32` here
+   |                               ^^^^^^^^^^^
    |
-   = help: the trait `PartialEq<Bar<'a, 'b>>` is not implemented for `&i32`
-   = help: the trait `PartialEq` is implemented for `i32`
+   = note: in case this is a recursive type alias, consider using a struct, enum, or union instead
 
 error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0277`.
+For more information about this error, try `rustc --explain E0275`.