Add regression test for #102467

tests/rustdoc-ui/issue-102467.rs

@@ -0,0 +1,15 @@
+// Regression test for <https://github.com/rust-lang/rust/issues/102467>.
+// It ensures that the expected error is displayed.
+
+#![feature(associated_const_equality)]
+
+trait T {
+    type A: S<C<X = 0i32> = 34>;
+    //~^ ERROR associated type bindings are not allowed here
+}
+
+trait S {
+    const C: i32;
+}
+
+fn main() {}

tests/rustdoc-ui/issue-102467.stderr

@@ -0,0 +1,9 @@
+error[E0229]: associated type bindings are not allowed here
+  --> $DIR/issue-102467.rs:7:17
+   |
+LL |     type A: S<C<X = 0i32> = 34>;
+   |                 ^^^^^^^^ associated type not allowed here
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0229`.