Duplicate typedef action

[georgefst]

Description

This is a feature request.

We have a "duplicate this definition" action available on all term definitions. We ought to have the same for type definitions.

Spec

When performed on a type T with constructors A and B, this action would create a new type TCopy with constructors ACopy and BCopy. All parameters and fields would be as in T.

Implementation details

Note that DuplicateDef's implementation (in toProgActionNoInput) relies on CopyPasteSig and CopyPasteBody. We don't yet have equivalents CopyPasteConField and CopyPasteParamKind. The bulk of the work in implementing this whole spec would be adding these low-level copy actions. Note that copying of kinds is something which we'll also need for implementing "raise kind".

[georgefst]

When performed on a type T with constructors A and B, this action would create a new type TCopy with constructors ACopy and BCopy. All parameters and fields would be as in T.

I'm using the same naming system here that we currently have for terms. I actually think T (copy) etc. would be more pleasant. Of course, if we do choose a different naming system we should modify DuplicateDef to use the same one.