--- /dev/null
+warning: the feature `type_alias_impl_trait` is incomplete and may not be safe to use and/or cause compiler crashes
+ --> $DIR/issue-53598.rs:5:32
+ |
+LL | #![cfg_attr(full_tait, feature(type_alias_impl_trait))]
+ | ^^^^^^^^^^^^^^^^^^^^^
+ |
+ = note: `#[warn(incomplete_features)]` on by default
+ = note: see issue #63063 <https://github.com/rust-lang/rust/issues/63063> for more information
+
+error: type parameter `T` is part of concrete type but not used in parameter list for the `impl Trait` type alias
+ --> $DIR/issue-53598.rs:24:42
+ |
+LL | fn foo<T: Debug>(_: T) -> Self::Item {
+ | __________________________________________^
+LL | |
+LL | | S::<T>(Default::default())
+LL | | }
+ | |_____^
+
+error: aborting due to previous error; 1 warning emitted
+