///
/// Convert a number between two bases.
///
/// A number is any slice of digits.
/// A digit is any unsigned integer (e.g. u8, u16, u32, u64, or usize).
/// Bases are specified as unsigned integers.
///
/// Return an `Err(.)` if the conversion is impossible.
/// The tests do not test for specific values inside the `Err(.)`.
///
///
/// You are allowed to change the function signature as long as all test still pass.
///
///
/// Example:
/// Input
///   number: &[4, 2]
///   from_base: 10
///   to_base: 2
/// Result
///   Ok(vec![1, 0, 1, 0, 1, 0])
///
/// The example corresponds to converting the number 42 from decimal
/// which is equivalent to 101010 in binary.
///
///
/// Notes:
///  * The empty slice ( "[]" ) is equal to the number 0.
///  * Never output leading 0 digits. However, your function must be able to
///     process input with leading 0 digits.
///
#[allow(unused_variables)]
pub fn convert(number: &[u32], from_base: u32, to_base: u32) -> Result<Vec<u32>, ()> {
    if number.into_iter().any(|&x| x >= from_base) {
        return Err(());
    }

    if from_base < 2 || to_base < 2 {
        return Err(());
    }

    let mut r = number.into_iter().fold(0, |acc, &x| acc * from_base + x);

    let mut result = (0..)
        .take_while(move |&x| r >= to_base.pow(x as u32))
        .map(|x| {
            let d = r % to_base;
            r /= to_base;
            d
        })
        .collect::<Vec<_>>();

    result.reverse();

    Ok(result)
}

Add rust code for all-your-base
Add rust code for all-your-base

It passed all testcases
