Build failure under Apple clang 14

[anarthal]

Build log is here (edited link): https://github.com/boostorg/mysql/actions/runs/8084450940/job/22089745435

This looks closely related to llvm/llvm-project#54765. This build is in GHA using macos-latest (no container here since OSX doesn't support it).

Compiler details as reported by b2:

• Apple clang version 14.0.0 (clang-1400.0.29.202)
• Target: x86_64-apple-darwin21.6.0
• InstalledDir: /Applications/Xcode_14.2.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
• cxxstd=20
• variant=debug,release (happens in both)

[tzlaine]

Unfortunately, C++20 mode is not going to work for any version of Clang before (LLVM) Clang 15. Their concepts implementation does not play nice with libstdc++'s lib, nor does their own lib have all of implemented properly, even though it defines __cpp_lib_ranges.

There is a workaround, though. You can define BOOST_PARSER_DISABLE_CONCEPTS and that should work even in C++20 builds, since it will use the non-concept C++17 implementations.

[tzlaine]

Ah. I just realized the proper fix for this is for me to disable the use of concept constraints in Clang < 16. I mentioned this in #131.