Add test to confirm usage of unstable foreign type error

Signed-off-by: Emmanuel Ugwu <emmanuelugwu121@gmail.com>

Author: kantnero

tests/ui/lint/auxiliary/lint_stability.rs

@@ -1,5 +1,6 @@
 #![crate_name="lint_stability"]
 #![crate_type = "lib"]
+#![feature(extern_types)]
 #![feature(staged_api)]
 #![feature(associated_type_defaults)]
 #![stable(feature = "lint_stability", since = "1.0.0")]
@@ -186,3 +187,8 @@ macro_rules! macro_test_arg {
 macro_rules! macro_test_arg_nested {
     ($func:ident) => (macro_test_arg!($func()));
 }
+
+extern "C" {
+    #[unstable(feature = "unstable_test_feature", issue = "none")]
+    pub type UnstableForeignType;
+}

tests/ui/lint/lint-stability.rs

@@ -9,10 +9,6 @@
 #![feature(extern_types)]
 #![stable(feature = "rust1", since = "1.0.0")]
 
-extern "C" {
-    #[unstable(feature = "fn_static", issue = "none")]
-    type Ty;
-}
 #[macro_use]
 extern crate lint_stability;
 
@@ -22,6 +18,9 @@ mod cross_crate {
 
     use lint_stability::*;
 
+    fn test_foreign_type(_: &mut UnstableForeignType) { //~ ERROR use of unstable library feature
+    }
+
     fn test() {
         type Foo = MethodTester;
         let foo = MethodTester;