Declared in <mp-units/utility/format.h>
template<
std::forward_iterator It,
typename Char = std::iter_value_t<It>>
[[nodiscard]]
constexpr
It
parse_dynamic_spec(
It begin,
It end,
int& value,
fmt_arg_ref<Char>& ref,
std::basic_format_parse_context<Char>& ctx);
The return value should not be discarded.