The following code does not compile (tested under GCC 9.1.0)

#include <fmt/format.h>
#include <fmt/color.h>
void test() {
auto x = fmt::format(fmt::fg(fmt::terminal_color::green), "{}", "Test");
}

The template parameter pack Args is not inferred when calling internal::make_args_checked. Passing the pack explicitly helps: {internal::make_args_checked<Args...>(format_str, args...)}