warning: identifier '_c' preceded by whitespace in a literal operator declaration is deprecated

[RFoe]

boost-hana 1.88 clang 20.1.0 c++26

// boost/bool.h: 198
    namespace literals {
        template <char ...c>
        constexpr auto operator"" _c() {
            return hana::llong<ic_detail::parse<sizeof...(c)>({c...})>{};
        }
    }

/boost/hana/bool.hpp:198:35: warning: identifier '_c' preceded by whitespace in a literal operator declaration is deprecated