fs::path::operator+=

path&
operator+=(__string_view __x);

path&
operator+=(value_type __x);

path&
operator+=(path const& __x);

path&
operator+=(string_type const& __x);

path&
operator+=(value_type const* __x);

template<class _Source>
path&
operator+=(_Source const& __x);

template<
    class _ECharT,
    int = 0>
requires __can_convert_char<_ECharT>::value
path&
operator+=(_ECharT __x);