Use zcash_script’s new Script trait

[sellout]

Motivation

This is a precursor to testing the Rust implementation of Zcash Script.

Blocked-On: ZcashFoundation/zcash_script#171 and publishing a new version of zcash_script with those changes.

Solution

This uses a trait that wraps the C++ Zcash Script implementation. As we progress toward cutting over to a Rust implementation, this trait will additionally have impls for the Rust version and a variant that runs both C++ & Rust, comparing the results.

Additionally, this eliminates a few cases from zebra_script::Error that can never be produced.

Tests

The tests are the same as the previous zebra_script tests – there should be no change in behavior.

Follow-up Work

This is blocked on a release of zcash_script containing ZcashFoundation/zcash_script#171.

PR Author's Checklist

• The PR name will make sense to users.
• The PR provides a CHANGELOG summary.
• The solution is tested.
• The documentation is up to date.
• The PR has a priority label.

PR Reviewer's Checklist

• The PR Author's checklist is complete.
• The PR resolves the issue.

[sellout]

This depends on ZcashFoundation/zcash_script#171.

[mpguerra]

Thank you for your PR! We're focusing on changes for NU6 testnet activation at the moment so we won't be able to prioritise this review for another week or two.

[sellout]

Re: the unchecked checkboxes

• there are no visible changes to add to the CHANGELOG and
• I don’t have permissions to add labels.

[arya2]

Re: the unchecked checkboxes

• there are no visible changes to add to the CHANGELOG and

We usually check boxes if they don't apply to the PR.

• I don’t have permissions to add labels.

Added a priority label.

Added a do-not-merge label as well, we should wait until the changes in zcash_script have been published before merging this PR.

[mpguerra]

Added a do-not-merge label as well, we should wait until the changes in zcash_script have been published before merging this PR.

What's next here? I see ZcashFoundation/zcash_script#171 has merged

[conradoplg]

What's next here? I see ZcashFoundation/zcash_script#171 has merged

We should double check this PR works with zcash_script main branch, and then I can make a zcash_script release and we point to that instead.

[sellout]

We should double check this PR works with zcash_script main branch, and then I can make a zcash_script release and we point to that instead.

I can do this, but wondering how to show that it’s successful – should I put up a temporary PR that just fetches zcash_script from GH instead of the crate registry and shows that everything still passes? And we’ll just close it afterward?

Also, I’m happy for there to be a zcash_script release now, but I figured it would be fine to leave it until the next PR or two land on zcash_script, which contain the actual Rust implementation.

[sellout]

This didn't turn up in zcash_script tests because there it always passes a regular function and not a closure.

@sellout is this something you can look into, or would you like for us to investigate?

Yeah, I’ll look at this. I’m making other changes in zcash_script now, so I’ll add a test with a closure and make sure that’s working.

[sellout]

@conradoplg I put up ZcashFoundation/zcash_script#216. I tried it against this branch (with some additional changes here) and it worked.

I think that counts as a bugfix release, as it doesn’t affect the cases that already worked. But there are changes in ZcashFoundation/zcash_script#209 (and others coming) that do affect the interface (although in fairly minor ways – like the set of Error variants).

[conradoplg]

This should be good to go. I did the simplest thing and just added a comparison-interpreter feature that enables the comparison interpreter.

I tested by manually pointing to my local copy of zcash_script, and adding a warning there just before the comparison check, regardless of the result, and confirmed the warning appeared if and only if the feature was enabled.

[oxarbitrage]

please fix conflicts.

[conradoplg]

please fix conflicts.

Oops, done

[conradoplg]

I'm admin-merging this, because there is some CI issue making some jobs to be forever pending. We'll investigate the issue later with a external PR of our own. (My guess is some patch job issue)

[str4d]

Post-hoc utACK (working through my review backlog)