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.
Technically, these operations belong in the ObjectiveC module, where NSObject
is defined. Keep them there. However, we need to build the mock ObjectiveC
overlay with `-disable-objc-attr-requires-foundation-module` now.
Previously (a03c40cb2c) we assumed all Swift enums were non-frozen in
ObjC, a weird choice in retrospect. Now that we actually distinguish
frozen and non-frozen enums in Swift, we can use the
'enum_extensibility' attribute to mark them as open or closed in ObjC.
Note that this only matters for Swift libraries compiled with
-enable-resilience, i.e. those that might get a new implementation at
runtime. Everyone else is now declaring a "closed" enum, matching the
behavior in Swift.
(and enums)
Previously this part of the compiler assumed that any imported
struct or enum would have the same name as it does in C, which is
no longer true.
Part of rdar://problem/26372925
