fmt::basic_appender<char> does not match libstdc++ std::output_iterator concept, because std::iterator_traits<fmt::appender> does not match incrementable iterator concept.
Either removing the std::iterator_traits specialisation, or adding difference_type to it fixes the problem.
The specialisation was added in version 11.0.2
fmt::basic_appender<char>does not match libstdc++std::output_iteratorconcept, becausestd::iterator_traits<fmt::appender>does not match incrementable iterator concept.Either removing the
std::iterator_traitsspecialisation, or addingdifference_typeto it fixes the problem.The specialisation was added in version 11.0.2