Sha512 cannot hash slices

[dndll]

Aim

Hashing a slice with sha512 in 0.19.2 causes unconstrained comptime issues on noir 0.19.2+47f0130c0d154f1b70eb23f376783beb3f23ad72

Expected Behavior

Hashing slices should be fine, or a code path for hashing unbounded items should be unconstrained.

Bug

Hashing a slice in a test causes:
[simple4x] Testing test_sha512_broken_slices... error: Could not determine loop bound at compile-time

To Reproduce

#[test]
fn test_sha512() {
    let s = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32];
    dep::std::sha512::digest(s);
}

#[test]
fn test_sha512_broken_slices() {
    let s = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32];
    dep::std::sha512::digest(s.as_slice());
}

Installation Method

Compiled from source

Nargo Version

0.19.2+47f0130c0d154f1b70eb23f376783beb3f23ad72

Additional Context

No response

Would you like to submit a PR for this Issue?

No

Support Needs

No response

[vezenovm]

Hashing slices should be fine, or a code path for hashing unbounded items should be unconstrained.

What use case do you see for using an unconstrained hash result?

It is expected for this to fail as .len() on a slice is going to use the dynamic array length value which is not a compile-time constant, even when it is obvious for the user as in this case. This error could definitely be more explicit though with suggestions on how to resolve the error for when someone attempts to do slice.len().