Stabilize associated type position impl Trait (ATPIT)

Author: traviscross

tests/ui/impl-trait/issue-55872-1.rs

@@ -1,5 +1,3 @@
-#![feature(impl_trait_in_assoc_type)]
-
 pub trait Bar {
     type E: Copy;
 

tests/ui/impl-trait/issue-55872-1.stderr

@@ -1,5 +1,5 @@
 error[E0276]: impl has stricter requirements than trait
-  --> $DIR/issue-55872-1.rs:12:15
+  --> $DIR/issue-55872-1.rs:10:15
    |
 LL |     fn foo<T>() -> Self::E;
    |     ----------------------- definition of `foo` from trait
@@ -8,7 +8,7 @@ LL |     fn foo<T: Default>() -> Self::E {
    |               ^^^^^^^ impl has extra requirement `T: Default`
 
 error[E0277]: the trait bound `S: Copy` is not satisfied in `(S, T)`
-  --> $DIR/issue-55872-1.rs:12:29
+  --> $DIR/issue-55872-1.rs:10:29
    |
 LL |     fn foo<T: Default>() -> Self::E {
    |                             ^^^^^^^ within `(S, T)`, the trait `Copy` is not implemented for `S`, which is required by `(S, T): Copy`
@@ -20,7 +20,7 @@ LL | impl<S: Default + std::marker::Copy> Bar for S {
    |                 +++++++++++++++++++
 
 error[E0277]: the trait bound `T: Copy` is not satisfied in `(S, T)`
-  --> $DIR/issue-55872-1.rs:12:29
+  --> $DIR/issue-55872-1.rs:10:29
    |
 LL |     fn foo<T: Default>() -> Self::E {
    |                             ^^^^^^^ within `(S, T)`, the trait `Copy` is not implemented for `T`, which is required by `(S, T): Copy`

tests/ui/impl-trait/issue-55872-2.rs

@@ -1,7 +1,5 @@
 // edition:2018
 
-#![feature(impl_trait_in_assoc_type)]
-
 pub trait Bar {
     type E: Send;