swift234

Sema: Diagnose init calls as uses of generic params.

We currently emit the allocating initializer of an @objc initializer of a generic ObjC class as a true generic function rather than pseudogeneric (rdar://problem/27796375). This would be a breaking change and has nonobvious tradeoffs if we "fix" it, so for the time being, just diagnose attempts to invoke an initializer from inside an @objc generic extension method. It's easy to work around by as!-casting the result of constructing the upper bound type. Fixes rdar://problem/26867815.