Incoherence of default type casting in loops

[TAdev0]

Aim

While trying to use the loop index for a comparison, I ran into an error :

    for i in 0..8 {
        for j in 0..8 {                   
             if  (i + j < 8) {...}

This code will not compile either with nargo 0.19.2 or an older version. The error is as follows :

error: Comparisons are invalid on Field types. Try casting the operands to a sized integer type first

Expected Behavior

We expect both loop index and hardcoded values to default to u64 in order to seamlessly use them to do comparisons.

Bug

There are 2 ways to make this code compile with Nargo:

Option 1 : explicitly declare loop indexes i and j as u64, though they are supposed to default to u64 if no other type is specified. In this situation, 8 which is of type TypeVariableKind::IntegerOrField, seems to default to u64 only if we explicitly declare i and j as u64.

    for i in 0..8 {
        for j in 0..8 {                   
             if  (i as u64 + j as u64 < 8) {...}
        }
    )

Option 2 : explicitly declare 8 value to a u64 type, which is supposed to default to a field type if no other type is specified. In this situation, i and j are treated like u64 by default.

    for i in 0..8 {
        for j in 0..8 {                   
             if  (i + j < 8 as u64) {...}
        }
    }

Installation Method

Noirup

Nargo Version

nargo 0.19.2 and older versions

Would you like to submit a PR for this Issue?

Yes