Actually, this patch is not merely a Import -> Import_New substitution. As this line shows, the error will be propagated correctly. However, in the old version we return with a nullptr DC which may be referenced later. This is the reason, why https://reviews.llvm.org/D59692 breaks in the unittests and thus depends on this patch.
The looks mostly good to me.
There is the same deletion in D53757.
Wow, we import types instead of just checking them for structural equivalence. That's OK to leave it in the patch as-is but looks pretty strange. Maybe this even deserves a FIXME.
The Import call was already here: "ToContext.hasSameType(Import(From), To))"