swift

37436a4b - [Completion] Better handle merging of lookup base types

[Completion] Better handle merging of lookup base types For unresolved member completion, we were preferring the more general type, when we ought to be preferring the more specific type. Additionally, for both unresolved member and postfix completion we were opening archetypes, which doesn't work as expected since we don't compare requirements. Factor out the logic that deals with merging base types for lookup, and have it prefer either the subtype, or the optional type in the case of optional promotion. rdar://126168123