[libcxx-commits] [libcxx] [libc++][unique_ptr] Implement LWG 4144: Disallow unique_ptr<T&, D> (PR #209018)

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@@ -111,6 +118,8 @@ class _LIBCPP_UNIQUE_PTR_TRIVIAL_ABI unique_ptr {
 public:
   typedef _Tp element_type;
   typedef _Dp deleter_type;
+
+  static_assert(__is_pointable<_Tp>, "unique_ptr<T, D> requires T* to be a valid type");
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emmett2020 wrote:

Thx. I think moving the assertion below the existing `static_assert` would generate additional error message. Since that places it after the pointer alias, `__pointer<_Tp, deleter_type>` attempts to form `_Tp*` first, causing `__pointer` to produce additional errors. Such as:

```bash
  allocator_traits.h:46:1: error:
  '__pointer' declared as a pointer to a reference of type 'int &'
  
```
Therefor, I think the pointability assertion should remain before the pointer alias.

https://github.com/llvm/llvm-project/pull/209018