When an imported Objective-C property has nullability, force that
nullability onto the result of its getter and the parameter of its
setter, so that we have consisteny nullability among the three. SILGen
assumes that this is the case, so this fixes the null_resettable-based
crash in <rdar://problem/20145910>.
Swift SVN r26198
We were losing the nullability of factory methods that turned into
initializers (which should have been mapped to failability), and more
generally, methods with nullability for related result types
(instancetype in Clang, dynamic Self in Swift).
Note that this commit also contains tests for a similar Clang-side fix
where Clang itself wasn't correctly recording that an Objective-C
method with a nullability-qualified instancetype result type in fact
had a related result type.
Found by browsing through the most excellent Swift SDK Analyzer.
Swift SVN r23834
Non-null attributes can indicate non-optionality of pointers. While
these non-null attributes are generally less useful than the
nullability type specifiers, they are occasionally used in the
wild. Addresses rdar://problem/18428099.
Swift SVN r23733
