Add UI regression test when querying visibility of generic parameter

Author: GuillaumeGomez

src/test/ui/query-visibility.rs

@@ -0,0 +1,9 @@
+// check-pass
+// Check that it doesn't panic when `Input` gets its visibility checked.
+
+#![crate_type = "lib"]
+
+pub trait Layer<
+    /// Hello.
+    Input,
+> {}