Issue 7469. Report error if type appears in for extends and implements clauses

http://code.google.com/p/dart/issues/detail?id=7469

R=brianwilkerson@google.com
BUG=

Review URL: https://codereview.chromium.org//11612027

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@16282 260f80e4-7a28-3924-810f-c04153c831b5

compiler/java/com/google/dart/compiler/resolver/ResolverErrorCode.java

@@ -197,6 +197,7 @@ public enum ResolverErrorCode implements ErrorCode {
   RETHROW_NOT_IN_CATCH("Re-throw not in a catch block"),
   STATIC_FINAL_REQUIRES_VALUE("Static final fields must have an initial value"),
   STATIC_METHOD_MUST_HAVE_BODY("Static method must have a body"),
+  SUPER_CLASS_IN_IMPLEMENTS("Superclass in implements clause"),
   SUPER_IN_FACTORY_CONSTRUCTOR("Cannot use 'super' in a factory constructor"),
   SUPER_IN_STATIC_METHOD("Cannot use 'super' in a static method"),
   SUPER_OUTSIDE_OF_METHOD("Cannot use 'super' outside of a method"),

compiler/java/com/google/dart/compiler/resolver/SupertypeResolver.java

@@ -4,6 +4,7 @@
 
 package com.google.dart.compiler.resolver;
 
+import com.google.common.base.Objects;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Sets;
 import com.google.dart.compiler.DartCompilerContext;
@@ -111,6 +112,10 @@ public class SupertypeResolver {
               topLevelContext.onError(intNode, ResolverErrorCode.DUPLICATE_IMPLEMENTS_TYPE);
               continue;
             }
+            if (Objects.equal(intType, supertype)) {
+              topLevelContext.onError(intNode, ResolverErrorCode.SUPER_CLASS_IN_IMPLEMENTS);
+              continue;
+            }
             seenImplement.add(intType);
           }
           // OK, add