anchor.diff:  
     void _validateInterceptorImplementsAllObjectMethods(
         ClassEntity interceptorClass) {
  -    if (interceptorClass == null) return;
       ClassEntity objectClass = commonElements.objectClass;
       elementEnvironment.forEachClassMember(objectClass,
           (_, MemberEntity member) {
         if (!member.isInstanceMember) return;
         MemberEntity interceptorMember = elementEnvironment
  -          .lookupLocalClassMember(interceptorClass, member.memberName);
  +          .lookupLocalClassMember(interceptorClass, member.memberName)!;
         // Interceptors must override all Object methods due to calling convention
         // differences.
         assert(
  
positive.code:     }
    }
  
    void registerModuleData(ModuleData data) {
      if (data == null) {
        _modularStrategy = KernelModularStrategy(_compilerTask, _elementMap);
      } else {
  
negative.code:     _annotationProcessor = KernelAnnotationProcessor(
          elementMap, elementMap.nativeBasicDataBuilder, _irAnnotationData);
      for (Uri uri in libraries) {
        LibraryEntity library = elementEnvironment.lookupLibrary(uri)!;
        if (maybeEnableNative(library.canonicalUri)) {
          _annotationProcessor.extractNativeAnnotations(library);
        }
  