C++: base class and default argument for template class

Fix code completion in case:
struct Foo
{
  int bar;
};

template <typename T1 = Foo>
struct Derived : T1 { };

int main()
{
  Derived<> foo;
  foo. // members from Foo are not proposed
  return 0;
}

Task-number: QTCREATORBUG-12605
Change-Id: Ibe35c7b9a161e789057a4518c72390ac52489a3e
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>

src/plugins/cpptools/cppcompletion_test.cpp

@@ -2268,6 +2268,19 @@ void CppToolsPlugin::test_completion_data()
             "auto func = [](int arg1) { return @; };\n"
         ) << _("ar") << (QStringList()
             << QLatin1String("arg1"));
+
+    QTest::newRow("default_arguments_for_class_templates_and_base_class_QTCREATORBUG-12605") << _(
+            "struct Foo { int foo; };\n"
+            "template <typename T = Foo>\n"
+            "struct Derived : T {};\n"
+            "void fun() {\n"
+            "   Derived<> derived;\n"
+            "   @\n"
+            "}\n"
+        ) << _("derived.") << (QStringList()
+            << QLatin1String("Derived")
+            << QLatin1String("foo")
+            << QLatin1String("Foo"));
 }
 
 void CppToolsPlugin::test_completion_member_access_operator()