This is not mandated by the standard, so it goes in libcxx/test/libcxx/.
It's certainly arguable that the algorithms changed here
(`is_heap`, `is_sorted`, `min`, `max`) are harmless and we should
just let them copy their comparators once. But at the same time,
it's nice to have all our algorithms be 100% consistent and never
copy a comparator, not even once.
Differential Revision: https://reviews.llvm.org/D114136
Also, mark these tests as compile-only. They actually are safe to run — notice that
the code "runs" at constexpr-time in C++20, without error — because both of the
input ranges are entirely filled with nullptr, so no matter how you shuffle the
elements, they remain sorted and partitioned and heapified and everything.
But there's no real reason to run them at runtime, so let's just avoid the distraction.
Test cases that fail in trunk right now are commented out with `TODO FIXME`.
Differential Revision: https://reviews.llvm.org/D113906
Nikolas Klauser