Warn about overriding operator== but not hashCode.

dart/sdk/lib/_internal/compiler/implementation/compiler.dart

 // 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.
 
 part of dart2js;
 
 /**
  * If true, print a warning for each method that was resolved, but not
  * compiled.
  */
@@ skipping 1137 matching lines @@
                   api.Diagnostic.WARNING);
   }
 
   void reportInfo(Spannable node, MessageKind errorCode,
                   [Map arguments = const {}]) {
     reportMessage(spanFromSpannable(node),
                   errorCode.error(arguments),
                   api.Diagnostic.INFO);
   }
 
+  void reportLint(Spannable node, MessageKind errorCode,
+                  [Map arguments = const {}]) {
+    reportMessage(spanFromSpannable(node),
+                  errorCode.error(arguments),
+                  api.Diagnostic.LINT);
+  }
+
   void reportInternalError(Spannable node, String message) {
     reportMessage(spanFromSpannable(node),
                   MessageKind.GENERIC.error({'text': message}),
                   api.Diagnostic.ERROR);
   }
 
   void reportMessage(SourceSpan span, Diagnostic message, api.Diagnostic kind) {
     // TODO(ahe): The names Diagnostic and api.Diagnostic are in
     // conflict. Fix it.
     reportDiagnostic(span, "$message", kind);
@@ skipping 264 matching lines @@
 
   void close() {}
 
   toString() => name;
 
   /// Convenience method for getting an [api.CompilerOutputProvider].
   static NullSink outputProvider(String name, String extension) {
     return new NullSink('$name.$extension');
   }
 }