Fix another unguarded cast to an impl class (issue 26034, case 2)

pkg/analyzer/test/src/dart/element/element_test.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.test.src.dart.element.element_test;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/element/element.dart';
@@ skipping 102 matching lines @@
     // A
     {
       ClassElement elementA = unitElement.getType("A");
       ClassTypeAlias nodeA = elementA.computeNode();
       expect(nodeA, isNotNull);
       expect(nodeA.name.name, "A");
       expect(nodeA.element, same(elementA));
     }
   }
 
+  void test_constructors_mixinApplicationWithHandle() {
+    AnalysisContext context = createAnalysisContext();
+    context.sourceFactory = new SourceFactory([]);
+
+    ElementLocation location = new ElementLocationImpl.con2('');
+    ClassElementImpl classA = ElementFactory.classElement2("A");
+    classA.mixinApplication = true;
+    TestElementResynthesizer resynthesizer =
+        new TestElementResynthesizer(context, {location: classA});
+    ClassElementHandle classAHandle =
+        new ClassElementHandle(resynthesizer, location);
+    ClassElementImpl classB =
+        ElementFactory.classElement("B", new InterfaceTypeImpl(classAHandle));
+    classB.mixinApplication = true;
+
+    expect(classB.constructors, hasLength(1));
+  }
+
   void test_getAllSupertypes_interface() {
     ClassElement classA = ElementFactory.classElement2("A");
     ClassElement classB = ElementFactory.classElement("B", classA.type);
     ClassElementImpl elementC = ElementFactory.classElement2("C");
     InterfaceType typeObject = classA.supertype;
     InterfaceType typeA = classA.type;
     InterfaceType typeB = classB.type;
     InterfaceType typeC = elementC.type;
     elementC.interfaces = <InterfaceType>[typeB];
     List<InterfaceType> supers = elementC.allSupertypes;
@@ skipping 4037 matching lines @@
 }
 
 class _FunctionTypeImplTest_isSubtypeOf_baseCase_classFunction
     extends InterfaceTypeImpl {
   _FunctionTypeImplTest_isSubtypeOf_baseCase_classFunction(ClassElement arg0)
       : super(arg0);
 
   @override
   bool get isDartCoreFunction => true;
 }