module main

type OneD = []Thing

struct Thing {
    item int
}

fn good() [][]Thing {
    println('start good()')
    mut two_d := [][]Thing{}
    mut one_d := []Thing{}
    one_d << Thing{1}
    one_d << Thing{2}
    two_d << one_d
    assert two_d.len == 1, 'two_d length not 1'
    for i, one in two_d {
        for j, item in one {
            println('two_d[${i}][${j}]=${item}')
            assert item == Thing{j + 1}
        }
    }
    println('end good()')
    return two_d
}

fn bad() []OneD {
    println('start bad()')
    mut two_d := []OneD{}
    mut one_d := OneD{}
    one_d << Thing{1}
    one_d << Thing{2}
    assert one_d.len == 2, 'one_d length not 2'
    assert one_d[0] == Thing{1}, 'one_d[0] not 1'
    assert one_d[1] == Thing{2}, 'one_d[1] not 2'
    two_d << one_d
    assert two_d.len == 1, 'two_d length not 1'
    for i, one in two_d {
        for j, item in one {
            println('two_d[${i}][${j}]=${item}')
            assert item == Thing{j + 1}
        }
    }
    println('end bad()')
    return two_d
}

fn test_main() {
    good_two_d := good()
    assert good_two_d.len == 1, 'good_two_d length not 1'
    for i, one_d in good_two_d {
        for j, item in one_d {
            println('good_two_d[${i}][${j}]=${item}')
            assert item == Thing{j + 1}
        }
    }
    bad_two_d := bad()
    assert bad_two_d.len == 1, 'bad_two_d length not 1'
    for i, one_d in bad_two_d {
        for j, item in one_d {
            println('bad_two_d[${i}][${j}]=${item}')
            assert item == Thing{j + 1}
        }
    }
}