swift

8dfc25ed - [GSB] Filter out conformance constraints derived from concrete conformance.

[GSB] Filter out conformance constraints derived from concrete conformance. When an otherwise abstract conformance constraint is derived from a concrete conformance, retain the abstract conformance by removing the requirement source that involves the concrete conformance. This eliminates our reliance on the concrete conformance, which is not retained as part of the generic signature. Fixes rdar://problem/31163470 and rdar://problem/31520386.