durations of floating point type or smaller than `long long` cause "conditional expression is constant" on MSVC

[lefticus]

/W4 is required. Seems to happen in any version of {fmt}, cannot reproduce in GCC or Clang

They appear to be similar but unrelated warnings.

Here is a minimal repro:

https://compiler-explorer.com/z/Yve79WaTf

#include <fmt/format.h>
#include <fmt/chrono.h>
#include <chrono>

int main()
{
  // this works
  //using milliseconds = std::chrono::duration<long long, std::milli>;

  // but this does not
  //using milliseconds = std::chrono::duration<int, std::milli>;

  // and neither does this
  using milliseconds = std::chrono::duration<double, std::milli>;

  fmt::print("ms {}", milliseconds{});
}

Warning stems from this line:

fmt/include/fmt/chrono.h

Lines 246 to 260 in d141cdb

	if (Factor::num != 1) {
	constexpr auto max1 = detail::max_value<IntermediateRep>() /
	static_cast<IntermediateRep>(Factor::num);
	if (count > max1) {
	ec = 1;
	return {};
	}
	constexpr auto min1 = std::numeric_limits<IntermediateRep>::lowest() /
	static_cast<IntermediateRep>(Factor::num);
	if (count < min1) {
	ec = 1;
	return {};
	}
	count *= static_cast<IntermediateRep>(Factor::num);
	}

and this line:

fmt/include/fmt/chrono.h

Lines 82 to 87 in d141cdb

	if (F::digits > T::digits &&
	from > static_cast<From>(detail::max_value<To>())) {
	ec = 1;
	return {};
	}
	}

[vitaut]

AFAICS this has been fixed in #2518 already.