clang-16: transcode_iterator.hpp: requires clause differs in template redeclaration

[anarthal]

Looks like clang is complaining about these two declarations:

#if BOOST_PARSER_DETAIL_TEXT_USE_CONCEPTS
        template<
            format FromFormat2,
            format ToFormat2,
            std::input_iterator I2,
            std::sentinel_for<I2> S2,
            transcoding_error_handler ErrorHandler2>
        requires std::convertible_to<std::iter_value_t<I2>, detail::format_to_type_t<FromFormat2>>
#else
        template<
            format FromFormat2,
            format ToFormat2,
            typename I2,
            typename S2,
            typename ErrorHandler2>
#endif
        friend class utf_iterator;

and

#if BOOST_PARSER_DETAIL_TEXT_USE_CONCEPTS
    template<
        format FromFormat,
        format ToFormat,
        std::input_iterator I,
        std::sentinel_for<I> S,
        transcoding_error_handler ErrorHandler>
        requires std::convertible_to<std::iter_value_t<I>, detail::format_to_type_t<FromFormat>>
#else
    template<
        format FromFormat,
        format ToFormat,
        typename I,
        typename S,
        typename ErrorHandler>
#endif
    class utf_iterator

I'd say they are identical except for template names. I don't know whether the standard forces you to use the same names or it's a clang bug.

Failing build: https://drone.cpp.al/boostorg/mysql/542/16/3

Compiler details:

• toolset=clang-16
• cxxstd=20
• variant=debug
• Building with asan and ubsan (although I don't think it makes a difference)
• OS: Ubuntu 22.04