QMetaEnum doesn't support negative enumerator values

In tst_QMetaObject::checkScope():

MyAnotherEnum3 is an enumerator with value "-1"; this test:
QCOMPARE(me2.keyToValue("MyAnotherEnum3", &ok), -1);

only passes due to integer overflow. The enumerators are stored as uint
in the generated code:
uint(MyNamespace::MyClass2::MyAnotherEnum3)

uint(-1) is 4294967295; keyToValue() returns int(4294967295) which overflows and becomes -1 letting the test pass.

I am not sure how this should be fixed; at least it should be documented in QMetaEnum API docs.