`AliasableBox<T>` does not implement `Into<UniqueBox<T>>`

[yyny]

AliasableBox<T> should

impl<T: ?Sized> From<AliasableBox<T>> for UniqueBox<T> { ... }

to match the other aliasable types.

[robofinch]

Because of the orphan rule, I'm fairly sure that this is impossible.

In particular, I think it would run into error[E0210]: type parameter `T` must be covered by another type when it appears before the first local type.