fix(ssa): Handle array arguments to side effectual constrain statements

[vezenovm]

…ffects

Description

Problem*

Resolves the error that occurs in this PR (#3739)

No issue as was discovered and fixed quickly.

Summary*

Using an array as an argument in a side effectual constrain statement will cause this panic:

Message:  internal error: entered unreachable code: Can only cast to a numeric
Location: compiler/noirc_evaluator/src/ssa/acir_gen/mod.rs:1652

Here is an example program which would previously fail that is included as a regression test:

struct Bar {
    inner: [u32; 3],
}

fn main(y: pub u32) {
    let bar = Bar { inner: [100, 101, 102] };

    // The assert inside the if should be hit
    if y < 10 {
        assert(bar.inner ==  [100, 101, 102]);
    }

    // The assert inside the if should not be hit
    if y > 10 {
        assert(bar.inner == [0, 1, 2]);
    }
}

Without this fix it is not possible to constrain arrays inside of if statements based upon witness conditions.

Additional Context

Documentation*

Check one:

• No documentation needed.
• Documentation included in this PR.
• [Exceptional Case] Documentation to be submitted in a separate PR.

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

[jfecher]

Would we still need this fix if assertions just took a boolean in SSA and the equality was a separate instruction?

[vezenovm]

Would we still need this fix if assertions just took a boolean in SSA and the equality was a separate instruction?

I don't think so, as we would only be constraining on the boolean. I went with this solution for now as this seems like an easy bug to run into and making equality a separate instruction is a larger change.

[jfecher]

LGTM