fix #28008, fix #28009 implement FutureOr<T>

pkg/analyzer/lib/src/generated/testing/element_factory.dart

 // Copyright (c) 2014, 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.
 
 library analyzer.src.generated.testing.element_factory;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 212 matching lines @@
    * order to ensure that state is not shared between multiple tests.
    */
   static void flushStaticState() {
     _objectElement = null;
   }
 
   static FunctionElementImpl functionElement(String functionName) =>
       functionElement4(functionName, null, null, null, null);
 
   static FunctionElementImpl functionElement2(
-          String functionName, TypeDefiningElement returnElement) =>
-      functionElement3(functionName, returnElement, null, null);
+          String functionName, DartType returnType) =>
+      functionElement3(functionName, returnType, null, null);
 
   static FunctionElementImpl functionElement3(
       String functionName,
-      TypeDefiningElement returnElement,
+      DartType returnType,
       List<TypeDefiningElement> normalParameters,
       List<TypeDefiningElement> optionalParameters) {
     // We don't create parameter elements because we don't have parameter names
     FunctionElementImpl functionElement =
         new FunctionElementImpl(functionName, 0);
     FunctionTypeImpl functionType = new FunctionTypeImpl(functionElement);
     functionElement.type = functionType;
-    // return type
-    if (returnElement == null) {
-      functionElement.returnType = VoidTypeImpl.instance;
-    } else {
-      functionElement.returnType = returnElement.type;
-    }
+    functionElement.returnType = returnType ?? VoidTypeImpl.instance;
     // parameters
     int normalCount = normalParameters == null ? 0 : normalParameters.length;
     int optionalCount =
         optionalParameters == null ? 0 : optionalParameters.length;
     int totalCount = normalCount + optionalCount;
     List<ParameterElement> parameters = new List<ParameterElement>(totalCount);
     for (int i = 0; i < totalCount; i++) {
       ParameterElementImpl parameter = new ParameterElementImpl("a$i", i);
       if (i < normalCount) {
         parameter.type = normalParameters[i].type;
@@ skipping 345 matching lines @@
   }
 
   static TypeParameterElementImpl typeParameterWithType(String name,
       [DartType bound]) {
     TypeParameterElementImpl typeParameter = typeParameterElement(name);
     typeParameter.type = new TypeParameterTypeImpl(typeParameter);
     typeParameter.bound = bound;
     return typeParameter;
   }
 }