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.
Compiler output at least up to serialization should be deterministic at this point,
at least when not taking SIL into account. This /should/ mean that changing a
function body should not affect the final built swiftmodule, which means downstream
targets don't need to be rebuilt. Leaving the previous swiftmodule output in place
signals that.
A while back I put in a push to get all the non-determinism out of type checking,
importing, and serialization itself; it looks like we've finally made it. Let's keep
it that way!
rdar://problem/20539158 and others
Swift SVN r29923
Mixed-source targets generally include the generated <Product>-Swift.h
header in many Objective-C (.m) source files. Any change to a Swift file
results in the header being touched, which means all the .m files get
recompiled.
This change makes Swift write the generated header to a temporary file
first, then use the previous commit's moveFileIfDifferent to put it in
its final destination.
rdar://problem/20553459
Swift SVN r28042
