closing out Library*NegativeTest issue and adding comments

tests/language/src/Library6NegativeTest.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
-//
+
+// This tests that it is a compile-time error to both import a library
+// that defines a function type alias and to have a local definition for
+// another function type alias with the same name.
+// This name conflict is considered an error even if Fun is never referred to.
 
 #library("Library6NegativeTest.dart");
-#import("Library5a.dart");
+#import("Library5a.dart");  // Defines function type alias Fun
 
-typedef int Fun();  // Expect this to conflict during parsing
+typedef int Fun();  // Conflicts with definition of Fun from library5a
 
 main() {
 }