message: Use positive step values
diff: @@ -46,11 +46,7 @@ fn char_range<'a>(
  step: isize,
  inclusive: bool,
  ) -> Option<Box<Iterator<Item = small::String> + 'a>> {
  - if !start.is_ascii_alphabetic()
  - || !end.is_ascii_alphabetic()
  - || step == 0
  - || step.checked_abs()? > u8::MAX as isize
  - {
  + if !start.is_ascii_alphabetic() || !end.is_ascii_alphabetic() || step == 0 {
  return None;
  }
  @@ -58,11 +54,12 @@ fn char_range<'a>(
  end += 1;
  }
  + let char_step = step.checked_abs()? as usize;
  if start < end {
  - Some(Box::new((start..end).step_by(step as usize).map(|x| (x as char).to_string().into())))
  + Some(Box::new((start..end).step_by(char_step).map(|x| (x as char).to_string().into())))
  } else {
  Some(Box::new(
  - (end..=start).rev().step_by(step as usize).map(|x| (x as char).to_string().into()),
  + (end..=start).rev().step_by(char_step).map(|x| (x as char).to_string().into()),
  ))
  }
  }
  