[libcxx-commits] [libcxx] [libc++] Add the __is_replaceable type trait (PR #132408)

[Louis Dionne via libcxx-commits]

================
@@ -120,6 +121,10 @@ class _LIBCPP_TEMPLATE_VIS vector {
       __libcpp_is_trivially_relocatable<pointer>::value && __libcpp_is_trivially_relocatable<allocator_type>::value,
       vector,
       void>;
+  using __replaceable _LIBCPP_NODEBUG =
+      __conditional_t<__is_replaceable<pointer>::value && __container_allocator_is_replaceable<__alloc_traits>::value,
+                      vector,
+                      void>;
----------------
ldionne wrote:

@mordante Can you please explain the issue you see with the code snippet above? I've been staring at it and I'm not sure what you have in mind. Is there something wrong with that code?

https://github.com/llvm/llvm-project/pull/132408