Nargo debugger fails when zero opcodes

[michaeljklein]

Aim

Nargo debugger should return the expected error without panicing when running on code with zero ACIR opcodes.

It currently panics here:

noir/acvm-repo/acvm/src/pwg/mod.rs

Line 350 in 96a74bb

let Opcode::Brillig(brillig) = &self.opcodes[self.instruction_pointer] else {

Expected Behavior

nargo debug fails without a panic

Bug

nargo debug fails with a panic when you call continue.

To Reproduce

Running on the following main.nr file:

fn main() {
    let x1 = &mut 42;
    let set_x1 = |y| { *x1 = y; };

    assert(*x1 == 42);
    set_x1(44);
    assert(*x1 == 44);
    set_x1(*x1);
    assert(*x1 == 44);
}

#[test]
fn test_main() {
    main();
}

cargo run execute succeeds, cargo run debug fails, but only after continue:

❯ cargo run execute
    Finished dev [optimized + debuginfo] target(s) in 0.31s
     Running `/Users/michaelklein/Coding/rust/noir/target/debug/nargo execute`
[missing_closure_env] Circuit witness successfully solved

❯ cargo run debug
    Finished dev [optimized + debuginfo] target(s) in 0.23s
     Running `/Users/michaelklein/Coding/rust/noir/target/debug/nargo debug`
[missing_closure_env] Starting debugger
Finished execution
> continue
(Continuing execution...)
The application panicked (crashed).
Message:  index out of bounds: the len is 0 but the index is 0
Location: /Users/michaelklein/Coding/rust/noir/acvm-repo/acvm/src/pwg/mod.rs:350

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
❯ cargo run info --json
    Finished dev [optimized + debuginfo] target(s) in 0.21s
     Running `/Users/michaelklein/Coding/rust/noir/target/debug/nargo info --json`
{"programs":[{"name":"missing_closure_env","acir_opcodes":0,"circuit_size":5}],"contracts":[]}

Installation Method

None

Nargo Version

No response

Additional Context

No response

Would you like to submit a PR for this Issue?

No

Support Needs

No response