swift234

SIL verifier: Check that a class_method's type matches its override abstraction level.

Factor the code to compute an override's vtable type out of SILGen's emitVTableMethod into a method on TypeLowering, and use it to verify the type of class_method instructions. This catches rdar://problem/20874966 at SILGen time instead of letting the devirtualizer barf on it.

Swift SVN r29158