[libc++] Fix recursive instantiation in std::array.
The use of the `&& ...` fold expression in std::array's deduction guides
recursively builds a set of binary operator expressions of depth N where
`N` is the number of elements in the initializer.
This is problematic because arrays may be large, and instantiation
depth is limited.
This patch addresses the issue by flattening the SFINAE using
the existing `__all` type trait.
(cherry picked from commit c6eb584c64872fbb779df14acd31c1f3947f6e52)
diff --git a/libcxx/include/array b/libcxx/include/array
index 88e9d57..ddebf91 100644
--- a/libcxx/include/array
+++ b/libcxx/include/array
@@ -359,7 +359,7 @@
#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
template<class _Tp, class... _Args,
- class = typename enable_if<(is_same_v<_Tp, _Args> && ...), void>::type
+ class = _EnableIf<__all<_IsSame<_Tp, _Args>::value...>::value>
>
array(_Tp, _Args...)
-> array<_Tp, 1 + sizeof...(_Args)>;
