Unconstrained print of mutable array panics

[michaeljklein]

Aim

Attempted to debug an unconstrained function by printing an intermediate mutable-array value:

unconstrained fn foo(arr: &mut [Field; 0]) {
    println(arr);
}

unconstrained fn main() {
    let mut arr = [0; 0];
    foo(&mut arr);
}

Note that this may be related to #7274, but will require distinct regression testing because the panic occurs in a different location.

Expected Behavior

Expected the array to be printed successfully or else fail with a user error.

Bug

nargo execute panics:

The application panicked (crashed).
Message:  internal error: entered unreachable code: println and format strings do not support mutable references.
Location: compiler/noirc_frontend/src/monomorphization/mod.rs:1593

This is a bug. We may have already fixed this in newer versions of Nargo so try searching for similar issues at https://github.com/noir-lang/noir/issues/.
If there isn't an open issue for this bug, consider opening one at https://github.com/noir-lang/noir/issues/new?labels=bug&template=bug_report.yml

To Reproduce

Workaround

Yes

Workaround Description

Make a copy of the array before printing:

let arr_copy: [Field; _] = *arr;
println(arr_copy);

Additional Context

No response

Project Impact

Nice-to-have

Blocker Context

No response

Nargo Version

nargo version = 1.0.0-beta.1 noirc version = 1.0.0-beta.1+130d99125a09110a3ee3e877d88d83b5aa37f369 (git version hash: 130d991, is dirty: false)

NoirJS Version

No response

Proving Backend Tooling & Version

No response

Would you like to submit a PR for this Issue?

None

Support Needs

No response