When the first branch of a function returns a single-element array, later branches will return weird values

[anonnice1999]

I have a simple function as following:

pragma circom 2.1.7;

function get_gkr__ext__evaluations(i) {
    if (i == 1) {
        return [1]; // one-element array
    }

    if (i == 2) {
        return [1, 2, 3, 4];
    }

    return [0];
}

template X() {
    signal input x;

    var a[4] = get_gkr__ext__evaluations(2);
    for (var i = 0; i < 4; i++) {
        log("a[", i, "]", a[i]);
    }
}

component main {public [x]} = X();

When I try to get the values in the branch i==2, it will returns an array with weird values.

a[ 0 ] 1
a[ 1 ] 1701549928
a[ 2 ] 2108807937
a[ 3 ] 0

But when I change the value in the first branch i==1 to a two-element array, the error will not happen anymore.

pragma circom 2.1.7;

function get_gkr__ext__evaluations(i) {
    if (i == 1) {
        return [1, 1];  // change to two-element array
    }

    if (i == 2) {
        return [1, 2, 3, 4];
    }

    return [0];
}

template X() {
    signal input x;

    var a[4] = get_gkr__ext__evaluations(2);
    for (var i = 0; i < 4; i++) {
        log("a[", i, "]", a[i]);
    }
}

component main {public [x]} = X();

a[ 0 ] 1
a[ 1 ] 2
a[ 2 ] 3
a[ 3 ] 4