swift234

Allow ArchetypeTypes to appear in same-type requirements.

This can occur
(1) when parsing SIL
(2) for a method in a protocol extension
(3) of a protocol with a constrained associated type
(4) where the method is also generic
(5) and has a same-type constraint between its generic parameter and the
    associated type.

I'm not sure if it can ever occur elsewhere.

rdar://problem/22126470

Swift SVN r31009