[libcxx-commits] [libcxx] [libc++] Remove `_Tag` template parameter from __capacity_aware_iterator (PR #224983)

[A. Jiang via libcxx-commits]

frederick-vs-ja wrote:

Maybe it would be better to explain the benefits and troubles in the PR description?

E.g., it seems that the following example will become well-formed with `_Tag` removed.

```c++
#include <optional>

void test() {
  std::optional<int> o1;
  std::optional<int&> o2;
  (void)(o1.begin() == o2.end());
}
```

https://github.com/llvm/llvm-project/pull/224983