[libcxx-commits] [libcxx] [libcxx] changes `__is_allocator` from a struct to a variable or concept (PR #68629)

[Christopher Di Bella via libcxx-commits]

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@@ -21,13 +21,21 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+#if _LIBCPP_STD_VER >= 20
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cjdb wrote:

Why?

https://github.com/llvm/llvm-project/pull/68629