[libcxx-commits] [libcxx] [libc++][test] Fix construction and comparison for testing allocators (PR #212702)

[A. Jiang via libcxx-commits]

================
@@ -195,8 +195,14 @@ class test_allocator {
       ++stats_->destroy_count;
     p->~T();
   }
-  TEST_CONSTEXPR friend bool operator==(const test_allocator& x, const test_allocator& y) { return x.data_ == y.data_; }
-  TEST_CONSTEXPR friend bool operator!=(const test_allocator& x, const test_allocator& y) { return !(x == y); }
+  template <class U>
+  TEST_CONSTEXPR friend bool operator==(const test_allocator& x, const test_allocator<U>& y) {
+    return x.data_ == static_cast<const test_allocator&>(y).data_;
----------------
frederick-vs-ja wrote:

> I suppose we won't be supporting GCC15 for much longer. Maybe add a TODO to remove the workaround?

I'm not sure whether the we want to remove the workaround. The original strategy I used was
```C++
    const test_allocator& y2 = y;
    return x.data_ == y2.data_;
```
which was arguably more verbose.

If we cast to `test_allocator` or directly compare `data_` via `get_data()`, then `stats_->construct_count` or `stats_->converted` would have different values.

https://github.com/llvm/llvm-project/pull/212702