The original reason for making UniqueRepresentation parents was for the
coercion framework: If parents are UniqueRepresentation you can use
equality-by-id and hash them super-easy (by id). Hence they can be looked
up quickly and we can key lookup of coercion-maps easily on fast hashes and
ident
The problematic bullet point in that PR is:
* Don't copy everything from the PARI stack. During the 2018 PARI/GP
atelier, I talked to Karim Belabas about a strategy to achieve this. The
basic idea is that we need to have a linked list containing the Gens which
live on the PARI stack. When the t
