MSVC always compiles in C++11 mode

[Ahajha]

MSVC's implementation of __cplusplus was broken (always being 199711L) until 2018. Thus, the following code does not set TL_EXPECTED_CXX14:

#if __cplusplus > 201103L
#define TL_EXPECTED_CXX14
#endif

A workaround for the end user is to add /Zc:__cplusplus at the command line, which is available in VS 15.7 onwards.

As far as I can tell, MSVC always compiles in C++14 mode, so the check could just be:

#if __cplusplus > 201103L || defined _MSC_VER
#define TL_EXPECTED_CXX14
#endif

In case you want to be extra sure, according to this documentation, the _MSVC_LANG macro does give the intended language version. So this could be updated to something like:

#ifdef _MSVC_LANG // Or equivalently, _MSC_VER
#if _MSVC_LANG > 201103L
#define TL_EXPECTED_CXX14
#endif // _MSVC_LANG > 201103L
#else // _MSVC_LANG
#if __cplusplus > 201103L
#define TL_EXPECTED_CXX14
#endif // __cplusplus > 201103L
#endif // _MSVC_LANG