#[no_predicates] makes compiler panic if used within a brillig function

[sirasistant]

Aim

Using no_predicates in a poseidon function to make it more performant in acir, but also use it in unconstrained functions.

Expected Behavior

It should compile

Bug

The application panicked (crashed).
Message:  not yet implemented: enable_side_effects not supported by brillig
Location: compiler/noirc_evaluator/src/brillig/brillig_gen/brillig_block.rs:701

To Reproduce

use dep::std::hash::{pedersen_hash_with_separator, poseidon2::Poseidon2};

global NUM_HASHES = 2;
global HASH_LENGTH = 10;

#[no_predicates]
pub fn poseidon_hash<N>(inputs: [Field; N]) -> Field {
    Poseidon2::hash(inputs, inputs.len())
}

unconstrained fn main(
    to_hash: [[Field; HASH_LENGTH]; NUM_HASHES],
    enable: [bool; NUM_HASHES]
) -> pub [Field; NUM_HASHES + 1] {
    let mut result = [0; NUM_HASHES + 1];
    for i in 0..NUM_HASHES {
        let enable = enable[i];
        let to_hash = to_hash[i];
        if enable {
            result[i] = poseidon_hash(to_hash);
        }
    }

    // We want to make sure that the function marked with `#[no_predicates]` with a numeric generic
    // is monomorphized correctly.
    let mut double_preimage = [0; 20];
    for i in 0..HASH_LENGTH * 2 {
        double_preimage[i] = to_hash[0][i % HASH_LENGTH];
    }
    result[NUM_HASHES] = poseidon_hash(double_preimage);

    result
}

Project Impact

None

Impact Context

No response

Workaround

None

Workaround Description

No response

Additional Context

No response

Installation Method

None

Nargo Version

No response

NoirJS Version

No response

Would you like to submit a PR for this Issue?

None

Support Needs

No response

[sirasistant]

This is caused because the inliner leaves the poseidon_hash acir function existing since it's no predicates, and then it's flattened. But a flattened function isn't convertible to brillig, so brillig_gen fails trying to generate brillig code for it