[libcxx-commits] [libcxx] [libc++] Fix UB in <expected> related to "has value" flag (#68552) (PR #68733)

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EricWF wrote:

> The calls to `std::construct_at` might overwrite the previously set `__has_value_` flag, so reverse the order everywhere.

You're saying that constructing the value in the expected might change the value of `__has_value_`? I don't understand.

https://github.com/llvm/llvm-project/pull/68733