[Feature] Support covariant Self

[berbs-fetch]

Use Case

Support covariant Self used in methods and members with the @Mocked annotation.
Since our Mocks are final and Self is a key word this should be supportable? We detect the usage of Self and replace with new class name instead of Self

Feature Proposal

I would like @Mocked to support covariant Self out of the box. Currently this isn't allowed.

@Mocked protocol Test {
    func newInstance() -> Self
}

The code generated is:

@MockedMembers
final class TestMock: Test {
    func newInstance() -> Self // compiler error of "Covariant `Self` or `Self?` can only appear at the top level of property type.
}

Instead I would like this code generated:

@MockedMembers
final class TestMock: Test {
    func newInstance() -> TestMock
}

This is actually the code Xcode recommends to get around the issue.

Alternatives Considered

Manually building the Mock class using @MockedMembers. It works but is undesirable.

Additional Context

No response

Code of Conduct

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