Fix bug in collecting trait and impl items with derives.

src/test/compile-fail/issue-43023.rs

@@ -0,0 +1,28 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+struct S;
+
+impl S {
+    #[derive(Debug)] //~ ERROR `derive` may only be applied to structs, enums and unions
+    fn f() {
+        file!();
+    }
+}
+
+trait Tr1 {
+    #[derive(Debug)] //~ ERROR `derive` may only be applied to structs, enums and unions
+    fn f();
+}
+
+trait Tr2 {
+    #[derive(Debug)] //~ ERROR `derive` may only be applied to structs, enums and unions
+    type F;
+}