Why is it allowed to shadow the `Self` type?

Evolution Discussion
7

I am surprised by this behavior (I barely use reference types, but when I do, I never referenced Self).

I found a post explaining it (with a lot of discussion): Why Is Covariant Self more flexible on protocols than classes? - #3 by Slava_Pestov . Basically it behaves differently due to interoperability with Objective-C.

Without that understanding this would be very confusing:

func g() -> Self {
    C()  // Error: Cannot convert return expression of type 'C' to return type 'Self'
}
func h() -> C {
    Self()  // Ok
}

Self is a headache in reference types. Duly noted.

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