[libcxx-commits] [libcxx] [libc++] Revert undesired `[[nodiscard]]` added to conversion functions (PR #173658)

[A. Jiang via libcxx-commits]

frederick-vs-ja wrote:

CI failure on "windows (mingw-static, true, cc, c++, windows-11-arm)" seems unrelated.

```
  Command Output (stdout):
  --
  # COMPILED WITH
  C:/llvm-mingw/bin/c++.exe C:\a\llvm-project\llvm-project\libcxx\test\std\input.output\stream.buffers\streambuf\streambuf.members\streambuf.pub.pback\sputbackc.pass.cpp  --target=aarch64-w64-windows-gnu -nostdinc++ -I C:/a/llvm-project/llvm-project/build/mingw-static/libcxx/test-suite-install/include/c++/v1 -I C:/a/llvm-project/llvm-project/build/mingw-static/libcxx/test-suite-install/include/c++/v1 -I C:/a/llvm-project/llvm-project/libcxx/test/support -std=c++26 -Werror -Wall -Wctad-maybe-unsupported -Wextra -Wshadow -Wundef -Wunused-template -Wno-unused-command-line-argument -Wno-attributes -Wno-pessimizing-move -Wno-noexcept-type -Wno-atomic-alignment -Wno-reserved-module-identifier -Wdeprecated-copy -Wdeprecated-copy-dtor -Wshift-negative-value -Wno-user-defined-literals -Wno-tautological-compare -Wsign-compare -Wunused-variable -Wunused-parameter -Wunreachable-code -Wno-unused-local-typedef -Wno-local-type-template-args -Wno-c++11-extensions -Wno-unknown-pragmas -Wno-pass-failed -Wno-mismatched-new-delete -Wno-redundant-move -Wno-self-move -Wno-nullability-completeness -flax-vector-conversions=none -D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER -D_LIBCPP_ENABLE_EXPERIMENTAL -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_NONE -Wuser-defined-warnings  -lc++experimental -nostdlib++ -L C:/a/llvm-project/llvm-project/build/mingw-static/libcxx/test-suite-install/lib -lc++ -o C:\a\llvm-project\llvm-project\build\mingw-static\libcxx\test\std\input.output\stream.buffers\streambuf\streambuf.members\streambuf.pub.pback\Output\sputbackc.pass.cpp.dir\t.tmp.exe
  # executed command: C:/llvm-mingw/bin/c++.exe 'C:\a\llvm-project\llvm-project\libcxx\test\std\input.output\stream.buffers\streambuf\streambuf.members\streambuf.pub.pback\sputbackc.pass.cpp' --target=aarch64-w64-windows-gnu -nostdinc++ -I C:/a/llvm-project/llvm-project/build/mingw-static/libcxx/test-suite-install/include/c++/v1 -I C:/a/llvm-project/llvm-project/build/mingw-static/libcxx/test-suite-install/include/c++/v1 -I C:/a/llvm-project/llvm-project/libcxx/test/support -std=c++26 -Werror -Wall -Wctad-maybe-unsupported -Wextra -Wshadow -Wundef -Wunused-template -Wno-unused-command-line-argument -Wno-attributes -Wno-pessimizing-move -Wno-noexcept-type -Wno-atomic-alignment -Wno-reserved-module-identifier -Wdeprecated-copy -Wdeprecated-copy-dtor -Wshift-negative-value -Wno-user-defined-literals -Wno-tautological-compare -Wsign-compare -Wunused-variable -Wunused-parameter -Wunreachable-code -Wno-unused-local-typedef -Wno-local-type-template-args -Wno-c++11-extensions -Wno-unknown-pragmas -Wno-pass-failed -Wno-mismatched-new-delete -Wno-redundant-move -Wno-self-move -Wno-nullability-completeness -flax-vector-conversions=none -D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER -D_LIBCPP_ENABLE_EXPERIMENTAL -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_NONE -Wuser-defined-warnings -lc++experimental -nostdlib++ -L C:/a/llvm-project/llvm-project/build/mingw-static/libcxx/test-suite-install/lib -lc++ -o 'C:\a\llvm-project\llvm-project\build\mingw-static\libcxx\test\std\input.output\stream.buffers\streambuf\streambuf.members\streambuf.pub.pback\Output\sputbackc.pass.cpp.dir\t.tmp.exe'
  # note: command had no output on stdout or stderr
  # EXECUTED AS
  'C:\hostedtoolcache\windows\Python\3.12.10\arm64\python3.exe' 'C:\a\llvm-project\llvm-project\libcxx\utils\run.py' --execdir C:\a\llvm-project\llvm-project\build\mingw-static\libcxx\test\std\input.output\stream.buffers\streambuf\streambuf.members\streambuf.pub.pback\Output\sputbackc.pass.cpp.dir --prepend_env PATH=C:/a/llvm-project/llvm-project/build/mingw-static/libcxx/test-suite-install/bin --  C:\a\llvm-project\llvm-project\build\mingw-static\libcxx\test\std\input.output\stream.buffers\streambuf\streambuf.members\streambuf.pub.pback\Output\sputbackc.pass.cpp.dir\t.tmp.exe
  # executed command: 'C:\hostedtoolcache\windows\Python\3.12.10\arm64\python3.exe' 'C:\a\llvm-project\llvm-project\libcxx\utils\run.py' --execdir 'C:\a\llvm-project\llvm-project\build\mingw-static\libcxx\test\std\input.output\stream.buffers\streambuf\streambuf.members\streambuf.pub.pback\Output\sputbackc.pass.cpp.dir' --prepend_env PATH=C:/a/llvm-project/llvm-project/build/mingw-static/libcxx/test-suite-install/bin -- 'C:\a\llvm-project\llvm-project\build\mingw-static\libcxx\test\std\input.output\stream.buffers\streambuf\streambuf.members\streambuf.pub.pback\Output\sputbackc.pass.cpp.dir\t.tmp.exe'
  # note: command had no output on stdout or stderr
  # error: command failed with exit status: 0xc000070a
```

https://github.com/llvm/llvm-project/pull/173658