tweak FunctionTypeImpl to support generic methods

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

Index: pkg/analyzer/lib/src/generated/testing/test_type_provider.dart
diff --git a/pkg/analyzer/lib/src/generated/testing/test_type_provider.dart b/pkg/analyzer/lib/src/generated/testing/test_type_provider.dart
index 5b5204a3d752f8acde2fc57558a13ab4179b9f3c..3b08997f1c0d60c5f08321f7119d243cb8f22764 100644
--- a/pkg/analyzer/lib/src/generated/testing/test_type_provider.dart
+++ b/pkg/analyzer/lib/src/generated/testing/test_type_provider.dart
@@ -601,16 +601,14 @@ class TestTypeProvider implements TypeProvider {
     List<DartType> typeArguments =
         TypeParameterTypeImpl.getTypes(classElement.typeParameters);
     for (PropertyAccessorElement accessor in classElement.accessors) {
-      FunctionTypeImpl functionType = accessor.type as FunctionTypeImpl;
-      functionType.typeArguments = typeArguments;
+      (accessor as ExecutableElementImpl).type = new FunctionTypeImpl(accessor);
     }
     for (MethodElement method in classElement.methods) {
-      FunctionTypeImpl functionType = method.type as FunctionTypeImpl;
-      functionType.typeArguments = typeArguments;
+      (method as ExecutableElementImpl).type = new FunctionTypeImpl(method);
     }
     for (ConstructorElement constructor in classElement.constructors) {
-      FunctionTypeImpl functionType = constructor.type as FunctionTypeImpl;
-      functionType.typeArguments = typeArguments;
+      (constructor as ExecutableElementImpl).type =
+          new FunctionTypeImpl(constructor);
     }
   }