We have two struct ExtensionValue

[doug-q]

one in hugr::ops::constant, one in hugr::extension.

hugr::extension::ExtensionValue describes a static value provided by and Extension;

hugr::ops::constant::ExtensionValue is an opaque Box<dyn CustomConst> used in the Value::Extension variant.

I propose we rename one, although I don't have a good idea for how.

[cqc-alec]

I suggest renaming hugr::ops::constant::ExtensionValue ... maybe to something like ExtensionConst?

[doug-q]

what about CustomValue or OpaqueValue? Probably we would name trait CustomConst as trait CustomValue today right?

[cqc-alec]

Yeah either of those sounds OK to me.