PrintAsClang is supposed to emit declarations in the same order regardless of the compiler’s internal state, but we have repeatedly found that our current criteria are inadequate, resulting in non-functionality-affecting changes to generated header content. Add a diagnostic that’s emitted when this happens soliciting a bug report.
Since there *should* be no cases where the compiler fails to order declarations, this diagnostic is never actually emitted. Instead, we test this change by enabling `-verify` on nearly all PrintAsClang tests to make sure they are unaffected.
This did demonstrate a missing criterion that only mattered in C++ mode: extensions that varied only in their generic signature were not sorted stably. Add a sort criterion for this.
Generic subclasses of @objc classes are thus no longer @objc, but still
have implicitly @objc members.
Explicit @objc on generic classes or classes that inherit from @objc
classes is now forbidden with a diagnostic. Users need to know that
while they can override Objective-C methods and properties in such
a class, they cannot refer to the class by name from Objective-C code,
since it will not appear in the bridging header.
Fixes <rdar://problem/21342574>.
Swift SVN r30494
