[libc++][NFCI] Remove uses of _LIBCPP_INLINE_VAR
All supported compilers provide support for inline variables in C++17 now.
Also, as a fly-by fix, replace some uses of _LIBCPP_CONSTEXPR by just
constexpr.
The only exception in this patch is `std::ignore`, which is provided
prior to C++17. Since it is defined in an anonymous namespace, it always
has internal linkage anyway, so using an inline variable there doesn't
provide any benefit. Instead, `inline` was removed entirely on `std::ignore`.
Differential Revision: https://reviews.llvm.org/D110243
NOKEYCHECK=True
GitOrigin-RevId: cb793e1a3655b8a571cb621db9d221c46f32ba9f
diff --git a/include/variant b/include/variant
index b69b697..ea120d4 100644
--- a/include/variant
+++ b/include/variant
@@ -266,7 +266,7 @@
struct _LIBCPP_TEMPLATE_VIS variant_size;
template <class _Tp>
-_LIBCPP_INLINE_VAR constexpr size_t variant_size_v = variant_size<_Tp>::value;
+inline constexpr size_t variant_size_v = variant_size<_Tp>::value;
template <class _Tp>
struct _LIBCPP_TEMPLATE_VIS variant_size<const _Tp> : variant_size<_Tp> {};
@@ -306,7 +306,7 @@
using type = __type_pack_element<_Ip, _Types...>;
};
-_LIBCPP_INLINE_VAR constexpr size_t variant_npos = static_cast<size_t>(-1);
+inline constexpr size_t variant_npos = static_cast<size_t>(-1);
constexpr int __choose_index_type(unsigned int __num_elem) {
if (__num_elem < numeric_limits<unsigned char>::max())