Head does not compile in MSVC 16.10.1 with /std:c++latest /Zc:__cplusplus

[Spammed]

MSVC 16.10.1 fails to compile current head with /std:c++latest /Zc:__cplusplus (-> #define __cplusplus 201705L)
but fails not with /std:c++latest /Zc:__cplusplus- (-> #define __cplusplus 199711L).

Code sample see: https://godbolt.org/z/e7zehe6fG

Compilation fails with message

format.h(899,29): error C3615: constexpr function 'fmt::v7::detail::count_digits' cannot result in a constant expression
format.h(904,35): message : failure was caused by variable declaration with non-automatic storage

[vitaut]

The godbolt example compiles successfully. Was it supposed to demonstrate an error?

[DanielaE]

I ran into the same problem.
Fixed with #2352

[vitaut]

Fixed in 3423d75. That piece of code is going away completely soon so we don't need the workaround, esp. broken one =).

[DanielaE]

Oh well, it took me ages to find out why gcc would fail to compile all of the time ...

[Spammed]

Sorry, my code example should show the error, but not on Godbolt.

In addition, I have been fooled by Visual Studio:
In Visual Studio 16.10.1 (or 16.11 Preview 1.0) with /std:c++latest + /Zc:__cplusplus the compiler and Intellisense do not quite agree about __cplusplus:
Intellisense thinks __cpluplus would be '201705', but the compiled program outputs '202004'.
What a mess!