The inference of _Nullable for weak Objective-C properties was broken
in several ways:
* It was back-patching the type information very late in the process
of checking the attributes for an Objective-C property, which is
just wrong.
* It was using ad hoc checks to try to suppress the warning about
missing nullability specifiers (-Wnullability-completeness), which
didn't actual work in all cases (rdar://problem/22985457)
* It was inferring _Nullable even outside of assumes-nonnull regions,
which is wrong.
Putting the inference of _Nullable for weak Objective-C properties in
the same place as all of the other inference logic fixes all of these
ills.
llvm-svn: 249896
d4f2afa23c