Should CustomType bounds be derivable from the type args?

[aborgna-q]

Some Custom types may be able to specify stricter bounds for some type instantiations.
For example, a List[T] may be Bound.Any in general but Bound.Copyable if T: Copyable.

Note that that cannot be assumed in general. We could for example define a custom type resembling a tuple (qubit, T), in which case the type would always be Bound.Any independently of T.

Should we have some mechanism to compute the bounds given on instantiation?

[aborgna-q]

Nvm, this is already implemented for typedefs
https://github.com/CQCL/hugr/blob/abd70c99291f41fce57ed8d8b0692faa63117b74/hugr-core/src/extension/type_def.rs#L14-L23

(it's just missing from the spec)