[libcxx-commits] [libcxx] [libc++] Ensure that `std::expected` has no tail padding (PR #69673)

[A. Jiang via libcxx-commits]

frederick-vs-ja wrote:

It seems that when `__libcpp_datasizeof<__union_t<_Tp, _Err>> == sizeof(__union_t<_Tp, _Err>)`, there shouldn't be a padding array, because reconstruction of the union member won't overwrite the `bool` or a user-provided member.

https://github.com/llvm/llvm-project/pull/69673