Add regression test for #96287

src/test/rustdoc-ui/issue-96287.rs

@@ -0,0 +1,17 @@
+#![feature(type_alias_impl_trait)]
+
+pub trait TraitWithAssoc {
+    type Assoc;
+}
+
+pub type Foo<V> = impl Trait<V::Assoc>;
+//~^ ERROR
+//~^^ ERROR
+
+pub trait Trait<U> {}
+
+impl<W> Trait<W> for () {}
+
+pub fn foo_desugared<T: TraitWithAssoc>(_: T) -> Foo<T> {
+    ()
+}

src/test/rustdoc-ui/issue-96287.stderr

@@ -0,0 +1,15 @@
+error[E0220]: associated type `Assoc` not found for `V`
+  --> $DIR/issue-96287.rs:7:33
+   |
+LL | pub type Foo<V> = impl Trait<V::Assoc>;
+   |                                 ^^^^^ there is a similarly named associated type `Assoc` in the trait `TraitWithAssoc`
+
+error[E0220]: associated type `Assoc` not found for `V`
+  --> $DIR/issue-96287.rs:7:33
+   |
+LL | pub type Foo<V> = impl Trait<V::Assoc>;
+   |                                 ^^^^^ there is a similarly named associated type `Assoc` in the trait `TraitWithAssoc`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0220`.