anchor.diff:      return null;
     }
     @override
  +  ResolverVisitorFactory get resolverVisitorFactory {
  +    fail("Unexpected invocation of getResolverVisitorFactory");
  +    return null;
  +  }
  +  @override
     SourceFactory get sourceFactory {
       fail("Unexpected invocation of getSourceFactory");
       return null;
     }
  +
     @override
     void set sourceFactory(SourceFactory factory) {
       fail("Unexpected invocation of setSourceFactory");
     }
  +
     @override
     AnalysisContextStatistics get statistics {
       fail("Unexpected invocation of getStatistics");
       return null;
     }
  +
     @override
     TypeProvider get typeProvider {
       fail("Unexpected invocation of getTypeProvider");
       return null;
     }
  -
     @override
     TypeResolverVisitorFactory get typeResolverVisitorFactory {
       fail("Unexpected invocation of getTypeResolverVisitorFactory");
       return null;
     }
  -
  -  @override
  -  ResolverVisitorFactory get resolverVisitorFactory {
  -    fail("Unexpected invocation of getResolverVisitorFactory");
  -    return null;
  -  }
  -
     @override
     void addListener(AnalysisListener listener) {
       fail("Unexpected invocation of addListener");
  
positive.code:     return null;
    }
    @override
    Stream<SourcesChangedEvent> get onSourcesChanged {
      fail("Unexpected invocation of onSourcesChanged");
      return null;
  
negative.code:   void setContents(Source source, String contents) {
      fail("Unexpected invocation of setContents");
    }
    @override
    void visitCacheItems(void callback(Source source, SourceEntry dartEntry,
        DataDescriptor rowDesc, CacheState state)) {
  