swift

449aa2f6 - Mark conformances as "used" when the GenericSignatureBuilder needs them.

Mark conformances as "used" when the GenericSignatureBuilder needs them. When the type checker forms a GenericSignatureBuilder to process requirements, the GSB may look up concrete conformances. Route such requests through TypeChecker::conformsToProtocol() so they can be marked as used. This fixes multi-file scenarios where conformances from another file might be used only in a generic signature in the primary file, e.g., rdar://problem/31759258.