In the reverse interop header we generated move constructors that call
abort at runtime. This is problematic for several reasons:
* In C++14 and below some of our own generated functions like _make
ended up calling the move constructor. Those are calling abort and
also trigger unreachable code warning in newer versions of Clang.
In C++17 and up it is fine due to the guaranteed copy elision.
* Type traits are fooled and think these types are movable. As a result,
libraries could generate calls to the aborting move ctor.
This PR removes the generation of move operations. As we generate copy
operations, the compiler will not declare or define the move operations
implicitly. Whenever the user goes out of their way and try to move an
object they will get a copy instead.
rdar://150793518
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.
