tbkka f989aa2b22 SR-12486: T.self is Any.Protocol is broken (#31662) ...

* SR-12486: `T.self is Any.Protocol` is broken

This turned out to be fallout from https://github.com/apple/swift/pull/27572
which was in turn motivated by our confusing metatype syntax when generic variables are bound to protocols.

In particular, the earlier PR was an attempt to make the expression
`x is T.Type` (where `T` is a generic type variable bound to a protocol `P`)
behave the same as
`x is P.Type` (where `P` is a protocol).
Unfortunately, the generic `T.Type` actually binds to `P.Protocol` in this case (not `P.Type`), so the original motivation was flawed, and as it happens, `x is T.Type` already behaved the same as `x is P.Protocol` in this situation.

This PR reverts that earlier change and beefs up some of the tests around these behaviors.

Resolves SR-12486

Resolves rdar://62201613

Reverts PR#27572

2020-07-02 13:10:01 -07:00

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