[libcxx-commits] [libcxx] [libc++] Tweak how we check constraints on shared_ptr(nullptr_t) (PR #94996)

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alexfh wrote:

Apparently, people rely on `std::shared_ptr<std::nullptr_t>`, which stops working after this patch: https://gcc.godbolt.org/z/7zrqKT74v

```
#include <functional>
#include <memory>

void f(const std::function<void()>& deleter) {
    auto d = std::shared_ptr<std::nullptr_t>(
          nullptr, [deleter](std::nullptr_t) { deleter(); });
}
```

Do you know if `std::shared_ptr<std::nullptr_t>` should work by the standard?

https://github.com/llvm/llvm-project/pull/94996