Replace RPITIT current impl with new strategy that lowers as a GAT

52 files changed, 408 insertions, 85 deletions

diff --git a/tests/ui/impl-trait/in-trait/auxiliary/rpitit.rs b/tests/ui/impl-trait/in-trait/auxiliary/rpitit.rs
index 776006124dc..cfc2193f633 100644
--- a/tests/ui/impl-trait/in-trait/auxiliary/rpitit.rs
+++ b/tests/ui/impl-trait/in-trait/auxiliary/rpitit.rs
@@ -1,5 +1,3 @@
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-
 #![feature(return_position_impl_trait_in_trait)]
 
 use std::ops::Deref;
@@ -10,5 +8,7 @@ pub trait Foo {
 
 pub struct Foreign;
 impl Foo for Foreign {
-    fn bar(self) -> &'static () { &() }
+    fn bar(self) -> &'static () {
+        &()
+    }
 }
diff --git a/tests/ui/impl-trait/in-trait/box-coerce-span-in-default.rs b/tests/ui/impl-trait/in-trait/box-coerce-span-in-default.rs
index f5290a5f4af..f5ee4690fa9 100644
--- a/tests/ui/impl-trait/in-trait/box-coerce-span-in-default.rs
+++ b/tests/ui/impl-trait/in-trait/box-coerce-span-in-default.rs
@@ -1,6 +1,4 @@
 // check-pass
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 #![feature(return_position_impl_trait_in_trait)]
 
diff --git a/tests/ui/impl-trait/in-trait/deep-match-works.rs b/tests/ui/impl-trait/in-trait/deep-match-works.rs
index 5c9d2e356fc..78cff97c616 100644
--- a/tests/ui/impl-trait/in-trait/deep-match-works.rs
+++ b/tests/ui/impl-trait/in-trait/deep-match-works.rs
@@ -1,6 +1,4 @@
 // check-pass
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
diff --git a/tests/ui/impl-trait/in-trait/deep-match.rs b/tests/ui/impl-trait/in-trait/deep-match.rs
index 413d054e148..0cae88f349f 100644
--- a/tests/ui/impl-trait/in-trait/deep-match.rs
+++ b/tests/ui/impl-trait/in-trait/deep-match.rs
@@ -1,6 +1,3 @@
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
-
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
 
diff --git a/tests/ui/impl-trait/in-trait/deep-match.stderr b/tests/ui/impl-trait/in-trait/deep-match.stderr
new file mode 100644
index 00000000000..f0ad3c16e9c
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/deep-match.stderr
@@ -0,0 +1,15 @@
+error[E0053]: method `bar` has an incompatible return type for trait
+  --> $DIR/deep-match.rs:11:17
+   |
+LL |     fn bar() -> i32 {
+   |                 ^^^
+   |                 |
+   |                 expected `Wrapper<_>`, found `i32`
+   |                 return type in trait
+   |
+   = note: expected struct `Wrapper<_>`
+                found type `i32`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0053`.
diff --git a/tests/ui/impl-trait/in-trait/default-body-type-err-2.rs b/tests/ui/impl-trait/in-trait/default-body-type-err-2.rs
index 62323776310..45ae2b8ad3a 100644
--- a/tests/ui/impl-trait/in-trait/default-body-type-err-2.rs
+++ b/tests/ui/impl-trait/in-trait/default-body-type-err-2.rs
@@ -1,6 +1,4 @@
 // edition:2021
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 #![allow(incomplete_features)]
 #![feature(async_fn_in_trait)]
diff --git a/tests/ui/impl-trait/in-trait/default-body-type-err-2.stderr b/tests/ui/impl-trait/in-trait/default-body-type-err-2.stderr
new file mode 100644
index 00000000000..cc3bdf0e571
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/default-body-type-err-2.stderr
@@ -0,0 +1,11 @@
+error[E0308]: mismatched types
+  --> $DIR/default-body-type-err-2.rs:8:9
+   |
+LL |         42
+   |         ^^- help: try using a conversion method: `.to_string()`
+   |         |
+   |         expected `String`, found integer
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/impl-trait/in-trait/default-body-type-err.rs b/tests/ui/impl-trait/in-trait/default-body-type-err.rs
index 9bd5b777989..ac9baf91cae 100644
--- a/tests/ui/impl-trait/in-trait/default-body-type-err.rs
+++ b/tests/ui/impl-trait/in-trait/default-body-type-err.rs
@@ -1,6 +1,3 @@
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
-
 #![allow(incomplete_features)]
 #![feature(return_position_impl_trait_in_trait)]
 
diff --git a/tests/ui/impl-trait/in-trait/default-body-type-err.stderr b/tests/ui/impl-trait/in-trait/default-body-type-err.stderr
new file mode 100644
index 00000000000..4742eb37d3e
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/default-body-type-err.stderr
@@ -0,0 +1,12 @@
+error[E0271]: type mismatch resolving `<&i32 as Deref>::Target == String`
+  --> $DIR/default-body-type-err.rs:7:22
+   |
+LL |     fn lol(&self) -> impl Deref<Target = String> {
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `i32`, found `String`
+LL |
+LL |         &1i32
+   |         ----- return type was inferred to be `&i32` here
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0271`.
diff --git a/tests/ui/impl-trait/in-trait/default-body-with-rpit.rs b/tests/ui/impl-trait/in-trait/default-body-with-rpit.rs
index 6bcc7b9ef95..0558d95128f 100644
--- a/tests/ui/impl-trait/in-trait/default-body-with-rpit.rs
+++ b/tests/ui/impl-trait/in-trait/default-body-with-rpit.rs
@@ -1,7 +1,5 @@
 // edition:2021
 // known-bug: #108304
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 #![feature(async_fn_in_trait, return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
diff --git a/tests/ui/impl-trait/in-trait/default-body-with-rpit.stderr b/tests/ui/impl-trait/in-trait/default-body-with-rpit.stderr
new file mode 100644
index 00000000000..b5fc9d44d36
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/default-body-with-rpit.stderr
@@ -0,0 +1,24 @@
+error: concrete type differs from previous defining opaque type use
+  --> $DIR/default-body-with-rpit.rs:11:9
+   |
+LL |         ""
+   |         ^^ expected `impl Debug`, got `&'static str`
+   |
+note: previous use here
+  --> $DIR/default-body-with-rpit.rs:10:39
+   |
+LL |       async fn baz(&self) -> impl Debug {
+   |  _______________________________________^
+LL | |         ""
+LL | |     }
+   | |_____^
+
+error[E0720]: cannot resolve opaque type
+  --> $DIR/default-body-with-rpit.rs:10:28
+   |
+LL |     async fn baz(&self) -> impl Debug {
+   |                            ^^^^^^^^^^ cannot resolve opaque type
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0720`.
diff --git a/tests/ui/impl-trait/in-trait/default-body.rs b/tests/ui/impl-trait/in-trait/default-body.rs
index ab6a51c6bcb..b0baf5bb10d 100644
--- a/tests/ui/impl-trait/in-trait/default-body.rs
+++ b/tests/ui/impl-trait/in-trait/default-body.rs
@@ -1,7 +1,5 @@
 // check-pass
 // edition:2021
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 #![feature(async_fn_in_trait, return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
diff --git a/tests/ui/impl-trait/in-trait/default-method-binder-shifting.rs b/tests/ui/impl-trait/in-trait/default-method-binder-shifting.rs
index 187039f449c..817a4d7dbbe 100644
--- a/tests/ui/impl-trait/in-trait/default-method-binder-shifting.rs
+++ b/tests/ui/impl-trait/in-trait/default-method-binder-shifting.rs
@@ -1,6 +1,4 @@
 // check-pass
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 #![feature(return_position_impl_trait_in_trait)]
 
diff --git a/tests/ui/impl-trait/in-trait/default-method-constraint.rs b/tests/ui/impl-trait/in-trait/default-method-constraint.rs
index 4f0bf2e7dfe..28d76241f27 100644
--- a/tests/ui/impl-trait/in-trait/default-method-constraint.rs
+++ b/tests/ui/impl-trait/in-trait/default-method-constraint.rs
@@ -1,6 +1,4 @@
 // check-pass
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 // This didn't work in the previous default RPITIT method hack attempt
 
diff --git a/tests/ui/impl-trait/in-trait/doesnt-satisfy.rs b/tests/ui/impl-trait/in-trait/doesnt-satisfy.rs
index fcd0b51eea4..bb4e0d44f3e 100644
--- a/tests/ui/impl-trait/in-trait/doesnt-satisfy.rs
+++ b/tests/ui/impl-trait/in-trait/doesnt-satisfy.rs
@@ -1,6 +1,3 @@
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
-
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
 
diff --git a/tests/ui/impl-trait/in-trait/doesnt-satisfy.stderr b/tests/ui/impl-trait/in-trait/doesnt-satisfy.stderr
new file mode 100644
index 00000000000..7c56ffa10e1
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/doesnt-satisfy.stderr
@@ -0,0 +1,17 @@
+error[E0277]: `()` doesn't implement `std::fmt::Display`
+  --> $DIR/doesnt-satisfy.rs:9:17
+   |
+LL |     fn bar() -> () {}
+   |                 ^^ `()` cannot be formatted with the default formatter
+   |
+   = help: the trait `std::fmt::Display` is not implemented for `()`
+   = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
+note: required by a bound in `Foo::{opaque#0}`
+  --> $DIR/doesnt-satisfy.rs:5:22
+   |
+LL |     fn bar() -> impl std::fmt::Display;
+   |                      ^^^^^^^^^^^^^^^^^ required by this bound in `Foo::{opaque#0}`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/impl-trait/in-trait/dont-project-to-rpitit-with-no-value.rs b/tests/ui/impl-trait/in-trait/dont-project-to-rpitit-with-no-value.rs
index 4d50b8c9278..4719d5d3c67 100644
--- a/tests/ui/impl-trait/in-trait/dont-project-to-rpitit-with-no-value.rs
+++ b/tests/ui/impl-trait/in-trait/dont-project-to-rpitit-with-no-value.rs
@@ -1,6 +1,3 @@
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
-
 #![feature(return_position_impl_trait_in_trait)]
 
 trait MyTrait {
diff --git a/tests/ui/impl-trait/in-trait/dont-project-to-rpitit-with-no-value.stderr b/tests/ui/impl-trait/in-trait/dont-project-to-rpitit-with-no-value.stderr
new file mode 100644
index 00000000000..66ee142ccc4
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/dont-project-to-rpitit-with-no-value.stderr
@@ -0,0 +1,12 @@
+error[E0046]: not all trait items implemented, missing: `foo`
+  --> $DIR/dont-project-to-rpitit-with-no-value.rs:8:1
+   |
+LL |     fn foo(&self) -> impl Sized;
+   |     ---------------------------- `foo` from trait
+...
+LL | impl MyTrait for i32 {
+   | ^^^^^^^^^^^^^^^^^^^^ missing `foo` in implementation
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0046`.
diff --git a/tests/ui/impl-trait/in-trait/early.rs b/tests/ui/impl-trait/in-trait/early.rs
index 831033a5880..9c1c2b50339 100644
--- a/tests/ui/impl-trait/in-trait/early.rs
+++ b/tests/ui/impl-trait/in-trait/early.rs
@@ -1,7 +1,5 @@
 // check-pass
 // edition:2021
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 #![feature(async_fn_in_trait, return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
diff --git a/tests/ui/impl-trait/in-trait/encode.rs b/tests/ui/impl-trait/in-trait/encode.rs
index 98aaf4a6553..efb9f6498ba 100644
--- a/tests/ui/impl-trait/in-trait/encode.rs
+++ b/tests/ui/impl-trait/in-trait/encode.rs
@@ -1,7 +1,5 @@
 // build-pass
 // compile-flags: --crate-type=lib
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
diff --git a/tests/ui/impl-trait/in-trait/foreign-dyn-error.stderr b/tests/ui/impl-trait/in-trait/foreign-dyn-error.stderr
index 6eef392c05f..bfb2be8cbc1 100644
--- a/tests/ui/impl-trait/in-trait/foreign-dyn-error.stderr
+++ b/tests/ui/impl-trait/in-trait/foreign-dyn-error.stderr
@@ -5,7 +5,7 @@ LL |     let _: &dyn rpitit::Foo = todo!();
    |            ^^^^^^^^^^^^^^^^ `Foo` cannot be made into an object
    |
 note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
-  --> $DIR/auxiliary/rpitit.rs:8:21
+  --> $DIR/auxiliary/rpitit.rs:6:21
    |
 LL |     fn bar(self) -> impl Deref<Target = impl Sized>;
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait cannot be made into an object because method `bar` references an `impl Trait` type in its return type
diff --git a/tests/ui/impl-trait/in-trait/foreign.rs b/tests/ui/impl-trait/in-trait/foreign.rs
index b0fbe3a3d4a..b0c93a02935 100644
--- a/tests/ui/impl-trait/in-trait/foreign.rs
+++ b/tests/ui/impl-trait/in-trait/foreign.rs
@@ -1,7 +1,5 @@
 // check-pass
 // aux-build: rpitit.rs
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 extern crate rpitit;
 
@@ -11,7 +9,9 @@ use std::sync::Arc;
 // Implement an RPITIT from another crate.
 struct Local;
 impl Foo for Local {
-    fn bar(self) -> Arc<String> { Arc::new(String::new()) }
+    fn bar(self) -> Arc<String> {
+        Arc::new(String::new())
+    }
 }
 
 fn generic(f: impl Foo) {
diff --git a/tests/ui/impl-trait/in-trait/generics-mismatch.rs b/tests/ui/impl-trait/in-trait/generics-mismatch.rs
index 9259ca193d1..cc0fc720ebb 100644
--- a/tests/ui/impl-trait/in-trait/generics-mismatch.rs
+++ b/tests/ui/impl-trait/in-trait/generics-mismatch.rs
@@ -1,6 +1,3 @@
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
-
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
 
diff --git a/tests/ui/impl-trait/in-trait/generics-mismatch.stderr b/tests/ui/impl-trait/in-trait/generics-mismatch.stderr
new file mode 100644
index 00000000000..cd42683e022
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/generics-mismatch.stderr
@@ -0,0 +1,12 @@
+error[E0049]: method `bar` has 1 type parameter but its trait declaration has 0 type parameters
+  --> $DIR/generics-mismatch.rs:11:12
+   |
+LL |     fn bar(&self) -> impl Sized;
+   |           - expected 0 type parameters
+...
+LL |     fn bar<T>(&self) {}
+   |            ^ found 1 type parameter
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0049`.
diff --git a/tests/ui/impl-trait/in-trait/issue-102140.rs b/tests/ui/impl-trait/in-trait/issue-102140.rs
index 4dcac4f5b0e..be1e012acb1 100644
--- a/tests/ui/impl-trait/in-trait/issue-102140.rs
+++ b/tests/ui/impl-trait/in-trait/issue-102140.rs
@@ -1,6 +1,3 @@
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
-
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
 
diff --git a/tests/ui/impl-trait/in-trait/issue-102140.stderr b/tests/ui/impl-trait/in-trait/issue-102140.stderr
new file mode 100644
index 00000000000..5d55b9fa4f9
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/issue-102140.stderr
@@ -0,0 +1,29 @@
+error[E0277]: the trait bound `&dyn MyTrait: MyTrait` is not satisfied
+  --> $DIR/issue-102140.rs:23:22
+   |
+LL |         MyTrait::foo(&self)
+   |         ------------ ^^^^^ the trait `MyTrait` is not implemented for `&dyn MyTrait`
+   |         |
+   |         required by a bound introduced by this call
+   |
+   = help: the trait `MyTrait` is implemented for `Outer`
+
+error[E0277]: the trait bound `&dyn MyTrait: MyTrait` is not satisfied
+  --> $DIR/issue-102140.rs:23:9
+   |
+LL |         MyTrait::foo(&self)
+   |         ^^^^^^^^^^^^^^^^^^^ the trait `MyTrait` is not implemented for `&dyn MyTrait`
+   |
+   = help: the trait `MyTrait` is implemented for `Outer`
+
+error[E0277]: the trait bound `&dyn MyTrait: MyTrait` is not satisfied
+  --> $DIR/issue-102140.rs:23:9
+   |
+LL |         MyTrait::foo(&self)
+   |         ^^^^^^^^^^^^ the trait `MyTrait` is not implemented for `&dyn MyTrait`
+   |
+   = help: the trait `MyTrait` is implemented for `Outer`
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/impl-trait/in-trait/issue-102301.rs b/tests/ui/impl-trait/in-trait/issue-102301.rs
index 1329ca29d06..a93714a658e 100644
--- a/tests/ui/impl-trait/in-trait/issue-102301.rs
+++ b/tests/ui/impl-trait/in-trait/issue-102301.rs
@@ -1,6 +1,4 @@
 // check-pass
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
diff --git a/tests/ui/impl-trait/in-trait/issue-102571.rs b/tests/ui/impl-trait/in-trait/issue-102571.rs
index f0ddab5e7f2..61c91e64417 100644
--- a/tests/ui/impl-trait/in-trait/issue-102571.rs
+++ b/tests/ui/impl-trait/in-trait/issue-102571.rs
@@ -1,6 +1,3 @@
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
-
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
 
diff --git a/tests/ui/impl-trait/in-trait/issue-102571.stderr b/tests/ui/impl-trait/in-trait/issue-102571.stderr
new file mode 100644
index 00000000000..87219941d91
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/issue-102571.stderr
@@ -0,0 +1,14 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-102571.rs:20:9
+   |
+LL |     let () = t.bar();
+   |         ^^   ------- this expression has type `impl Deref<Target = impl std::fmt::Display + ?Sized>`
+   |         |
+   |         expected associated type, found `()`
+   |
+   = note: expected associated type `impl Deref<Target = impl std::fmt::Display + ?Sized>`
+                    found unit type `()`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/impl-trait/in-trait/nested-rpitit.rs b/tests/ui/impl-trait/in-trait/nested-rpitit.rs
index 36020753726..65285e3a3cc 100644
--- a/tests/ui/impl-trait/in-trait/nested-rpitit.rs
+++ b/tests/ui/impl-trait/in-trait/nested-rpitit.rs
@@ -1,6 +1,4 @@
 // check-pass
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
diff --git a/tests/ui/impl-trait/in-trait/object-safety.rs b/tests/ui/impl-trait/in-trait/object-safety.rs
index 016a0aaae4b..dd35b9a2d8a 100644
--- a/tests/ui/impl-trait/in-trait/object-safety.rs
+++ b/tests/ui/impl-trait/in-trait/object-safety.rs
@@ -1,6 +1,3 @@
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
-
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
 
diff --git a/tests/ui/impl-trait/in-trait/object-safety.stderr b/tests/ui/impl-trait/in-trait/object-safety.stderr
new file mode 100644
index 00000000000..4a3b3b11465
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/object-safety.stderr
@@ -0,0 +1,49 @@
+error[E0038]: the trait `Foo` cannot be made into an object
+  --> $DIR/object-safety.rs:17:33
+   |
+LL |     let i = Box::new(42_u32) as Box<dyn Foo>;
+   |                                 ^^^^^^^^^^^^ `Foo` cannot be made into an object
+   |
+note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+  --> $DIR/object-safety.rs:7:22
+   |
+LL | trait Foo {
+   |       --- this trait cannot be made into an object...
+LL |     fn baz(&self) -> impl Debug;
+   |                      ^^^^^^^^^^ ...because method `baz` references an `impl Trait` type in its return type
+   = help: consider moving `baz` to another trait
+
+error[E0038]: the trait `Foo` cannot be made into an object
+  --> $DIR/object-safety.rs:20:13
+   |
+LL |     let s = i.baz();
+   |             ^^^^^^^ `Foo` cannot be made into an object
+   |
+note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+  --> $DIR/object-safety.rs:7:22
+   |
+LL | trait Foo {
+   |       --- this trait cannot be made into an object...
+LL |     fn baz(&self) -> impl Debug;
+   |                      ^^^^^^^^^^ ...because method `baz` references an `impl Trait` type in its return type
+   = help: consider moving `baz` to another trait
+
+error[E0038]: the trait `Foo` cannot be made into an object
+  --> $DIR/object-safety.rs:17:13
+   |
+LL |     let i = Box::new(42_u32) as Box<dyn Foo>;
+   |             ^^^^^^^^^^^^^^^^ `Foo` cannot be made into an object
+   |
+note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+  --> $DIR/object-safety.rs:7:22
+   |
+LL | trait Foo {
+   |       --- this trait cannot be made into an object...
+LL |     fn baz(&self) -> impl Debug;
+   |                      ^^^^^^^^^^ ...because method `baz` references an `impl Trait` type in its return type
+   = help: consider moving `baz` to another trait
+   = note: required for the cast from `Box<u32>` to `Box<dyn Foo>`
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0038`.
diff --git a/tests/ui/impl-trait/in-trait/opaque-in-impl-is-opaque.rs b/tests/ui/impl-trait/in-trait/opaque-in-impl-is-opaque.rs
index c07ece15a83..3ac264e8eba 100644
--- a/tests/ui/impl-trait/in-trait/opaque-in-impl-is-opaque.rs
+++ b/tests/ui/impl-trait/in-trait/opaque-in-impl-is-opaque.rs
@@ -1,6 +1,3 @@
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
-
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
 
diff --git a/tests/ui/impl-trait/in-trait/opaque-in-impl-is-opaque.stderr b/tests/ui/impl-trait/in-trait/opaque-in-impl-is-opaque.stderr
new file mode 100644
index 00000000000..15edda48340
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/opaque-in-impl-is-opaque.stderr
@@ -0,0 +1,17 @@
+error[E0308]: mismatched types
+  --> $DIR/opaque-in-impl-is-opaque.rs:17:19
+   |
+LL |     fn bar(&self) -> impl Display {
+   |                      ------------ the found opaque type
+...
+LL |     let x: &str = ().bar();
+   |            ----   ^^^^^^^^ expected `&str`, found opaque type
+   |            |
+   |            expected due to this
+   |
+   = note: expected reference `&str`
+            found opaque type `impl std::fmt::Display`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/impl-trait/in-trait/opaque-in-impl.rs b/tests/ui/impl-trait/in-trait/opaque-in-impl.rs
index f48d9fa26c0..2e06629699a 100644
--- a/tests/ui/impl-trait/in-trait/opaque-in-impl.rs
+++ b/tests/ui/impl-trait/in-trait/opaque-in-impl.rs
@@ -1,6 +1,4 @@
 // check-pass
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
diff --git a/tests/ui/impl-trait/in-trait/return-dont-satisfy-bounds.rs b/tests/ui/impl-trait/in-trait/return-dont-satisfy-bounds.rs
index 65528f212e2..5d9a224ccd6 100644
--- a/tests/ui/impl-trait/in-trait/return-dont-satisfy-bounds.rs
+++ b/tests/ui/impl-trait/in-trait/return-dont-satisfy-bounds.rs
@@ -1,6 +1,3 @@
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
-
 #![feature(return_position_impl_trait_in_trait)]
 
 trait Foo<T> {
diff --git a/tests/ui/impl-trait/in-trait/return-dont-satisfy-bounds.stderr b/tests/ui/impl-trait/in-trait/return-dont-satisfy-bounds.stderr
new file mode 100644
index 00000000000..668fc6cbe7f
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/return-dont-satisfy-bounds.stderr
@@ -0,0 +1,16 @@
+error[E0277]: the trait bound `impl Foo<u8>: Foo<char>` is not satisfied
+  --> $DIR/return-dont-satisfy-bounds.rs:10:34
+   |
+LL |     fn foo<F2: Foo<u8>>(self) -> impl Foo<u8> {
+   |                                  ^^^^^^^^^^^^ the trait `Foo<char>` is not implemented for `impl Foo<u8>`
+   |
+   = help: the trait `Foo<char>` is implemented for `Bar`
+note: required by a bound in `Foo::{opaque#0}`
+  --> $DIR/return-dont-satisfy-bounds.rs:4:30
+   |
+LL |     fn foo<F2>(self) -> impl Foo<T>;
+   |                              ^^^^^^ required by this bound in `Foo::{opaque#0}`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/impl-trait/in-trait/reveal.rs b/tests/ui/impl-trait/in-trait/reveal.rs
index 1f42ec744db..d6ede1cc495 100644
--- a/tests/ui/impl-trait/in-trait/reveal.rs
+++ b/tests/ui/impl-trait/in-trait/reveal.rs
@@ -1,6 +1,4 @@
 // check-pass
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
diff --git a/tests/ui/impl-trait/in-trait/signature-mismatch.rs b/tests/ui/impl-trait/in-trait/signature-mismatch.rs
index 23dd71acecb..1d63a6f3ce2 100644
--- a/tests/ui/impl-trait/in-trait/signature-mismatch.rs
+++ b/tests/ui/impl-trait/in-trait/signature-mismatch.rs
@@ -1,6 +1,4 @@
 // edition:2021
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
diff --git a/tests/ui/impl-trait/in-trait/signature-mismatch.stderr b/tests/ui/impl-trait/in-trait/signature-mismatch.stderr
new file mode 100644
index 00000000000..616f1ac35a9
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/signature-mismatch.stderr
@@ -0,0 +1,61 @@
+error: return type captures more lifetimes than trait definition
+  --> $DIR/signature-mismatch.rs:34:47
+   |
+LL |     fn async_fn<'a>(&self, buff: &'a [u8]) -> impl Future<Output = Vec<u8>> + 'a {
+   |                 -- this lifetime was captured ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: hidden type must only reference lifetimes captured by this impl trait
+  --> $DIR/signature-mismatch.rs:15:40
+   |
+LL |     fn async_fn(&self, buff: &[u8]) -> impl Future<Output = Vec<u8>>;
+   |                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: hidden type inferred to be `impl Future<Output = Vec<u8>> + 'a`
+
+error: return type captures more lifetimes than trait definition
+  --> $DIR/signature-mismatch.rs:39:57
+   |
+LL |     fn async_fn_early<'a: 'a>(&self, buff: &'a [u8]) -> impl Future<Output = Vec<u8>> + 'a {
+   |                       -- this lifetime was captured     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: hidden type must only reference lifetimes captured by this impl trait
+  --> $DIR/signature-mismatch.rs:16:57
+   |
+LL |     fn async_fn_early<'a: 'a>(&self, buff: &'a [u8]) -> impl Future<Output = Vec<u8>>;
+   |                                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: hidden type inferred to be `impl Future<Output = Vec<u8>> + 'a`
+
+error: return type captures more lifetimes than trait definition
+  --> $DIR/signature-mismatch.rs:47:10
+   |
+LL |     fn async_fn_multiple<'a, 'b>(
+   |                              -- this lifetime was captured
+...
+LL |     ) -> impl Future<Output = Vec<u8>> + Captures2<'a, 'b> {
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: hidden type must only reference lifetimes captured by this impl trait
+  --> $DIR/signature-mismatch.rs:18:12
+   |
+LL |         -> impl Future<Output = Vec<u8>> + Captures<'a>;
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: hidden type inferred to be `impl Future<Output = Vec<u8>> + Captures2<'a, 'b>`
+
+error[E0309]: the parameter type `T` may not live long enough
+  --> $DIR/signature-mismatch.rs:56:10
+   |
+LL |     ) -> impl Future<Output = Vec<u8>> {
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `impl Future<Output = Vec<u8>>` will meet its required lifetime bounds...
+   |
+note: ...that is required by this bound
+  --> $DIR/signature-mismatch.rs:23:42
+   |
+LL |     ) -> impl Future<Output = Vec<u8>> + 'a;
+   |                                          ^^
+help: consider adding an explicit lifetime bound...
+   |
+LL |     fn async_fn_reduce_outlive<'a, 'b, T: 'a>(
+   |                                         ++++
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0309`.
diff --git a/tests/ui/impl-trait/in-trait/specialization-broken.rs b/tests/ui/impl-trait/in-trait/specialization-broken.rs
index 658d0709717..2fcffdf3f9a 100644
--- a/tests/ui/impl-trait/in-trait/specialization-broken.rs
+++ b/tests/ui/impl-trait/in-trait/specialization-broken.rs
@@ -1,6 +1,3 @@
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
-
 // FIXME(compiler-errors): I'm not exactly sure if this is expected to pass or not.
 // But we fixed an ICE anyways.
 
diff --git a/tests/ui/impl-trait/in-trait/specialization-broken.stderr b/tests/ui/impl-trait/in-trait/specialization-broken.stderr
new file mode 100644
index 00000000000..dc621d6b8a8
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/specialization-broken.stderr
@@ -0,0 +1,31 @@
+error[E0053]: method `bar` has an incompatible type for trait
+  --> $DIR/specialization-broken.rs:16:22
+   |
+LL | default impl<U> Foo for U
+   |              - this type parameter
+...
+LL |     fn bar(&self) -> U {
+   |                      ^
+   |                      |
+   |                      expected associated type, found type parameter `U`
+   |                      help: change the output type to match the trait: `impl Sized`
+   |
+note: type in trait
+  --> $DIR/specialization-broken.rs:9:22
+   |
+LL |     fn bar(&self) -> impl Sized;
+   |                      ^^^^^^^^^^
+   = note: expected signature `fn(&U) -> impl Sized`
+              found signature `fn(&U) -> U`
+
+error: method with return-position `impl Trait` in trait cannot be specialized
+  --> $DIR/specialization-broken.rs:16:5
+   |
+LL |     fn bar(&self) -> U {
+   |     ^^^^^^^^^^^^^^^^^^
+   |
+   = note: specialization behaves in inconsistent and surprising ways with `#![feature(return_position_impl_trait_in_trait)]`, and for now is disallowed
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0053`.
diff --git a/tests/ui/impl-trait/in-trait/specialization-substs-remap.rs b/tests/ui/impl-trait/in-trait/specialization-substs-remap.rs
index dbc5d38f192..c9ee877db8e 100644
--- a/tests/ui/impl-trait/in-trait/specialization-substs-remap.rs
+++ b/tests/ui/impl-trait/in-trait/specialization-substs-remap.rs
@@ -1,6 +1,4 @@
 // check-pass
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 #![feature(specialization)]
 #![feature(return_position_impl_trait_in_trait)]
diff --git a/tests/ui/impl-trait/in-trait/success.rs b/tests/ui/impl-trait/in-trait/success.rs
index 0e69e0490c7..4cbe682b46f 100644
--- a/tests/ui/impl-trait/in-trait/success.rs
+++ b/tests/ui/impl-trait/in-trait/success.rs
@@ -1,6 +1,4 @@
 // check-pass
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
diff --git a/tests/ui/impl-trait/in-trait/trait-more-generics-than-impl.rs b/tests/ui/impl-trait/in-trait/trait-more-generics-than-impl.rs
index c2e394a1f66..0bbe50ea6fd 100644
--- a/tests/ui/impl-trait/in-trait/trait-more-generics-than-impl.rs
+++ b/tests/ui/impl-trait/in-trait/trait-more-generics-than-impl.rs
@@ -1,6 +1,3 @@
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
-
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
 
diff --git a/tests/ui/impl-trait/in-trait/trait-more-generics-than-impl.stderr b/tests/ui/impl-trait/in-trait/trait-more-generics-than-impl.stderr
new file mode 100644
index 00000000000..8ff54cad951
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/trait-more-generics-than-impl.stderr
@@ -0,0 +1,12 @@
+error[E0049]: method `bar` has 0 type parameters but its trait declaration has 1 type parameter
+  --> $DIR/trait-more-generics-than-impl.rs:11:11
+   |
+LL |     fn bar<T>() -> impl Sized;
+   |            - expected 1 type parameter
+...
+LL |     fn bar() -> impl Sized {}
+   |           ^ found 0 type parameters
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0049`.
diff --git a/tests/ui/impl-trait/in-trait/unconstrained-lt.rs b/tests/ui/impl-trait/in-trait/unconstrained-lt.rs
index f966be43a6e..07c8606f9fe 100644
--- a/tests/ui/impl-trait/in-trait/unconstrained-lt.rs
+++ b/tests/ui/impl-trait/in-trait/unconstrained-lt.rs
@@ -1,6 +1,3 @@
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
-
 #![feature(return_position_impl_trait_in_trait)]
 
 trait Foo {
@@ -10,7 +7,9 @@ trait Foo {
 impl<'a, T> Foo for T {
     //~^ ERROR the lifetime parameter `'a` is not constrained by the impl trait, self type, or predicates
 
-    fn test() -> &'a () { &() }
+    fn test() -> &'a () {
+        &()
+    }
 }
 
 fn main() {}
diff --git a/tests/ui/impl-trait/in-trait/unconstrained-lt.stderr b/tests/ui/impl-trait/in-trait/unconstrained-lt.stderr
new file mode 100644
index 00000000000..cfce3556720
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/unconstrained-lt.stderr
@@ -0,0 +1,9 @@
+error[E0207]: the lifetime parameter `'a` is not constrained by the impl trait, self type, or predicates
+  --> $DIR/unconstrained-lt.rs:7:6
+   |
+LL | impl<'a, T> Foo for T {
+   |      ^^ unconstrained lifetime parameter
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0207`.
diff --git a/tests/ui/impl-trait/in-trait/variances-of-gat.rs b/tests/ui/impl-trait/in-trait/variances-of-gat.rs
index 4008ece94da..0d19e1ff416 100644
--- a/tests/ui/impl-trait/in-trait/variances-of-gat.rs
+++ b/tests/ui/impl-trait/in-trait/variances-of-gat.rs
@@ -1,6 +1,4 @@
 // check-pass
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 #![feature(return_position_impl_trait_in_trait)]
 
diff --git a/tests/ui/impl-trait/in-trait/wf-bounds.rs b/tests/ui/impl-trait/in-trait/wf-bounds.rs
index f8c1e561d5c..ee873f94b26 100644
--- a/tests/ui/impl-trait/in-trait/wf-bounds.rs
+++ b/tests/ui/impl-trait/in-trait/wf-bounds.rs
@@ -1,6 +1,4 @@
 // issue #101663
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]
diff --git a/tests/ui/impl-trait/in-trait/wf-bounds.stderr b/tests/ui/impl-trait/in-trait/wf-bounds.stderr
new file mode 100644
index 00000000000..beac6620911
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/wf-bounds.stderr
@@ -0,0 +1,57 @@
+error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
+  --> $DIR/wf-bounds.rs:15:22
+   |
+LL |     fn nya() -> impl Wf<Vec<[u8]>>;
+   |                      ^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[u8]`
+note: required by a bound in `Vec`
+  --> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
+
+error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
+  --> $DIR/wf-bounds.rs:18:23
+   |
+LL |     fn nya2() -> impl Wf<[u8]>;
+   |                       ^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[u8]`
+note: required by a bound in `Wf`
+  --> $DIR/wf-bounds.rs:8:10
+   |
+LL | trait Wf<T> {
+   |          ^ required by this bound in `Wf`
+help: consider relaxing the implicit `Sized` restriction
+   |
+LL | trait Wf<T: ?Sized> {
+   |           ++++++++
+
+error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
+  --> $DIR/wf-bounds.rs:21:44
+   |
+LL |     fn nya3() -> impl Wf<(), Output = impl Wf<Vec<[u8]>>>;
+   |                                            ^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[u8]`
+note: required by a bound in `Vec`
+  --> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
+
+error[E0277]: `T` doesn't implement `std::fmt::Display`
+  --> $DIR/wf-bounds.rs:24:26
+   |
+LL |     fn nya4<T>() -> impl Wf<NeedsDisplay<T>>;
+   |                          ^^^^^^^^^^^^^^^^^^^ `T` cannot be formatted with the default formatter
+   |
+   = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
+note: required by a bound in `NeedsDisplay`
+  --> $DIR/wf-bounds.rs:12:24
+   |
+LL | struct NeedsDisplay<T: Display>(T);
+   |                        ^^^^^^^ required by this bound in `NeedsDisplay`
+help: consider restricting type parameter `T`
+   |
+LL |     fn nya4<T: std::fmt::Display>() -> impl Wf<NeedsDisplay<T>>;
+   |              +++++++++++++++++++
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/impl-trait/in-trait/where-clause.rs b/tests/ui/impl-trait/in-trait/where-clause.rs
index 88d86e2b541..87bac519cf3 100644
--- a/tests/ui/impl-trait/in-trait/where-clause.rs
+++ b/tests/ui/impl-trait/in-trait/where-clause.rs
@@ -1,7 +1,5 @@
 // check-pass
 // edition: 2021
-// [next] compile-flags: -Zlower-impl-trait-in-trait-to-assoc-ty
-// revisions: current next
 
 #![feature(return_position_impl_trait_in_trait)]
 #![allow(incomplete_features)]