I tested this with 7.0.1 (but couldn't see a fitting fix in 7.0.2):

The following line will produce the string "1.0-1.000000", but there is no named argument specified:
auto expr = fmt::format("{namedArg}-{:f}", 1.0);

I expected an exception.

It correctly fails to compile when using fmt::format(FMT_STRING("{namedArg}-{:f}", 1.0));