https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109162
--- Comment #21 from 康桓瑋 <hewillk at gmail dot com> --- > Furthermore the standard specifies these formatters as delegating to > formatter<ranges::ref_view<const? _Container>, charT>, which in turn > delegates to range_formatter. This patch avoids one level of indirection, > and dependency of ranges::ref_view. This is technically observable if > user specializes formatter<std::ref_view<PD>> where PD is program defined > container, but I do not think this is the case worth extra indirection. That is highly intentional to fix incorrect formatting when the container is a string. See https://cplusplus.github.io/LWG/issue3881
