Add test for disallowed attribute

Author: tiif

tests/ui/internal/unstable_inherent_method.rs

@@ -3,20 +3,21 @@
 #![feature(impl_stability)]
 #![stable(feature = "a", since = "1.1.1" )]
 
-
-/// FIXME(tiif): we haven't allowed marking impl method as 
+/// FIXME(tiif): we haven't allowed marking trait and impl method as
 /// unstable yet, but it should be possible.
 
 #[stable(feature = "a", since = "1.1.1" )]
 pub trait Trait {
     #[unstable(feature = "feat", issue = "none" )]
     #[unstable_feature_bound(foo)]
+    //~^ ERROR: attribute should be applied to `impl` or free function outside of any `impl` or trait
     fn foo();
 }
 
 #[stable(feature = "a", since = "1.1.1" )]
 impl Trait for u8 {
     #[unstable_feature_bound(foo)]
+    //~^ ERROR: attribute should be applied to `impl` or free function outside of any `impl` or trait
     fn foo() {}
 }
 

tests/ui/internal/unstable_inherent_method.stderr

@@ -0,0 +1,20 @@
+error: attribute should be applied to `impl` or free function outside of any `impl` or trait
+  --> $DIR/unstable_inherent_method.rs:12:5
+   |
+LL |     #[unstable_feature_bound(foo)]
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |
+LL |     fn foo();
+   |     --------- not an `impl` or free function
+
+error: attribute should be applied to `impl` or free function outside of any `impl` or trait
+  --> $DIR/unstable_inherent_method.rs:19:5
+   |
+LL |     #[unstable_feature_bound(foo)]
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |
+LL |     fn foo() {}
+   |     ----------- not an `impl` or free function
+
+error: aborting due to 2 previous errors
+