[libc++] Refactor __debug_three_way_comp

This makes __debug_three_way_comp consistent with __debug_less and
in particular gets rid of a potential use-after-move caused by the
use of std::forward. In the previous version of the code, we would
call `__do_compare_assert` after forwarding the arguments into the
comparator, which could end up using the arguments after they've been
moved from.

This also simplifies how we call `__do_compare_assert` by using
`if constexpr` and adds a missing test for proxy iterators in
lexicographical_compare_three_way, which could have found this
issue.

Differential Revision: https://reviews.llvm.org/D152753
3 files changed
tree: f4011371e9366516776b762c8802fd38f3f27a2b
  1. .github/
  2. bolt/
  3. clang/
  4. clang-tools-extra/
  5. cmake/
  6. compiler-rt/
  7. cross-project-tests/
  8. flang/
  9. libc/
  10. libclc/
  11. libcxx/
  12. libcxxabi/
  13. libunwind/
  14. lld/
  15. lldb/
  16. llvm/
  17. llvm-libgcc/
  18. mlir/
  19. openmp/
  20. polly/
  21. pstl/
  22. runtimes/
  23. third-party/
  24. utils/
  25. .arcconfig
  26. .arclint
  27. .clang-format
  28. .clang-tidy
  29. .git-blame-ignore-revs
  30. .gitignore
  31. .mailmap
  32. CONTRIBUTING.md
  33. LICENSE.TXT
  34. README.md
  35. SECURITY.md
README.md

The LLVM Compiler Infrastructure

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