Mark set_size and set_fold as TC opaque

Updated according to suggestions.

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Old title/description:

More TC opaqueness (appropriate???)

Take these as questions, and feel free to edit/close/... . Follow up from !328 (merged).

@Blaisorblade I think adding the TC opaque declarations makes sense. I'm not so sure about the Params instance since it's not clear what's even the canonical Proper that we wish to declare as an instance (and hence, it's not clear what's the desired value for Params should be).

Could you update this MR?

added 1 commit

• e3157145 - Mark set_size and set_fold as TC opaque

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changed title from More TC opaqueness (appropriate???) to Mark set_size and set_fold as TC opaque

changed the description

resolved all threads

Done; can you please merge? (No changelog, since !328 (merged) had none either).

enabled an automatic merge when the pipeline for e3157145 succeeds

Merging. Thanks!

mentioned in commit e9aae334

merged