Movable for amortized structures

In some cases, a pure amortized data structure may only be efficient when used in a single threaded fashion. This suggests a linear interface

-- Pairing heaps
data PQ a = ...

insert :: Ord a => a -> PQ a %1-> PQ a
merge :: Ord a => PQ a %1-> PQ a %1-> PQ a
extractMin :: Ord a => PQ a %1-> Maybe (Ur a, PQ a)

Would it be appropriate for something like PQ a to be an instance of Moveable? If so, move would be a no-op (move = Unsafe.coerce Ur), and the user would be fully responsible for making sure performance was okay in context. Or would it be better to only have a perflyRiskyMove in the module to make it clear that there's a performance risk?

The Dupable instance is much more obviously reasonable: it would fully reassociate the queue into a "safe" configuration that has no credit. Do we want to provide a module giving an example of a structure like this?

Review the existing Moveable and Dupable interfaces alongside the proposed Pairing heap API. Determine whether a no-op Moveable instance, a clearly risky move operation, or only a Dupable example is appropriate; done means the project has a settled design and documented example or rationale.