MSVC compilation fix.

Author: IRainman

tests/basictest.cpp

@@ -21,6 +21,16 @@
 #endif // #ifndef FASTFLOAT_CONSTEXPR_TESTS
 #endif // FASTFLOAT_IS_CONSTEXPR
 
+// MSVC's constexpr evaluation and some constexpr-friendly std library pieces
+// (like i/o and certain std::numeric_limits members) aren't suitable for the
+// compile-time tests in this file on MSVC; disable the constexpr tests when
+// compiling with MSVC (but allow them for clang/clang-cl).
+#if defined(_MSC_VER) && !defined(__clang__)
+#  ifdef FASTFLOAT_CONSTEXPR_TESTS
+#    undef FASTFLOAT_CONSTEXPR_TESTS
+#  endif
+#endif
+
 #if FASTFLOAT_HAS_BIT_CAST
 #include <bit>
 #endif