anchor.diff:      implements FunctionTypeAliasElement {
     MockFunctionTypeAliasElement() : super(ElementKind.FUNCTION_TYPE_ALIAS);
   
  +  @override
     CompilationUnitElement get enclosingElement {
       return internalError("not supported.");
     }
   
  +  @override
     TypeAlias computeNode() => internalError("not supported.");
   }
   
  
positive.code:     implements ParameterElement {
    MockParameterElement() : super(ElementKind.PARAMETER);
  
    String get defaultValueCode => internalError("not supported.");
  
    bool get isCovariant => internalError("not supported.");
  
    bool get isInitializingFormal => internalError("not supported.");
  
    get parameterKind => internalError("not supported.");
  
    List<ParameterElement> get parameters => internalError("not supported.");
  
    get type => null;
  
    get typeParameters => internalError("not supported.");
  
    get constantValue => internalError("not supported.");
  
    computeConstantValue() => internalError("not supported.");
  
    void appendToWithoutDelimiters(StringBuffer buffer) {
      return internalError("not supported.");
    }
  
    FormalParameter computeNode() => internalError("not supported.");
  }
  
negative.code:     implements FunctionElement {
    MockFunctionElement() : super(ElementKind.FUNCTION);
  
    @override
    bool get isEntryPoint => internalError("not supported.");
  
    @override
    get typeParameters => internalError("not supported.");
  
    @override
    FunctionType get type => internalError("not supported.");
  
    @override
    DartType get returnType => internalError("not supported.");
  
    @override
    FunctionDeclaration computeNode() => internalError("not supported.");
  }
  
  