swift

e77902e2 - Detect/prevent type variables from leaking across constraint systems.

Detect/prevent type variables from leaking across constraint systems. It's possible some of the asserts will eventually migrate to something like test-and-return, but at least for now let's ensure that we know when this is happening. This is not comprehensive. There are other places we are creating fresh constraint systems and then creating constraints using type variables from a pre-existing constraint systems.