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Does std::polymorphic require passed types to be copyable?

Looks like it depends on the specific operation(s) you want to perform [0]. For instance, constructing a std::polymorphic<T> from an object of type T or derived from T requires that that object is copy-constructible (among other requirements), but copy-assigning one std::polymorphic<T> to another only requires that T is complete.

[0]: https://eel.is/c++draft/polymorphic

Well, https://eel.is/c++draft/polymorphic#assign-2.2 requires copy-constructibility.

Ah, you're right, that's a bad example. I had assumed that that kind of precondition would be explicitly mentioned so I didn't read the rest of the text as closely as I should have.

Perhaps move-assignment would have been a better example? That one at least mentions construction using an rvalue so I think that specific operation would work for move-only types.

Though now that I think about a bit more I suppose it's a bit of a moot point since the constructors all look like they require a copy-constructible T

Yes, there is currently no move-only std::polymorphic, like there is a move-only std::indirect ...

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