I followed the link near the start to the article about std::indirect<T>, which you can use instead of std::unique_ptr<T> for the pImpl idiom: [1]
> Never null: it always holds a value, except in the moved-from state (but features a member function called valueless_after_move() that lets you check the state)
Ugh, what a mess. Surely the whole point of using this rather than unique_ptr is to avoid such a trap! A safe move constructor isn't possible here because you'd either have to re-init your moved-from object, or do element-wise move (with `MyClass(MyClass&& other): impl(std::in_place, *other.impl) {}`) but those would stop your move constructor being noexcept. It would've been much more useful to make the move constructor of indirect be deleted, which is what people typically did with a pImpl-based classes in the past.
> Never null: it always holds a value, except in the moved-from state (but features a member function called valueless_after_move() that lets you check the state)
Ugh, what a mess. Surely the whole point of using this rather than unique_ptr is to avoid such a trap! A safe move constructor isn't possible here because you'd either have to re-init your moved-from object, or do element-wise move (with `MyClass(MyClass&& other): impl(std::in_place, *other.impl) {}`) but those would stop your move constructor being noexcept. It would've been much more useful to make the move constructor of indirect be deleted, which is what people typically did with a pImpl-based classes in the past.
[1] https://mariusbancila.ro/blog/2026/07/23/the-pimpl-idiom-and...