swift

b6d48fb8 - [ConstraintSystem] Fix a logic error in computing potential bindings.

[ConstraintSystem] Fix a logic error in computing potential bindings. A change was made to attempt to use constraints that we have between type variables to inform potential bindings, such that if we have: $T1 <: $T2 we would use $T1's bindings to add to the bindings of $T2. This is only valid if we're adding bindings where $T1 is the supertype, though, otherwise we could have the constraints: $T1 <: $T2 $T1 <: X imply that $T2 is a supertype of X, which doesn't make sense. Fixes rdar://problem/40810000 (aka https://bugs.swift.org/browse/SR-7875). (cherry picked from commit 54b2504699267039950673bc3133b93ce83ef179)