Add test for issue 30867

Author: clubby789

tests/ui/traits/hrtb-related-type-params-30867.rs

@@ -0,0 +1,14 @@
+//@ check-pass
+//! Tests that HRTB impl selection covers type parameters not directly related
+//! to the trait.
+//! Test for <https://github.com/rust-lang/rust/issues/30867>
+
+#![crate_type = "lib"]
+
+trait Unary<T> {}
+impl<T, U, F: Fn(T) -> U> Unary<T> for F {}
+fn unary<F: for<'a> Unary<&'a T>, T>() {}
+
+pub fn test<F: for<'a> Fn(&'a i32) -> &'a i32>() {
+    unary::<F, i32>()
+}