[bug#12473] Throw on unsigned type in NumericRange#reverse

Author: NthPortal

library/src/scala/collection/immutable/NumericRange.scala

@@ -153,7 +153,13 @@ sealed class NumericRange[T](
  override def splitAt(n: Int): (NumericRange[T], NumericRange[T]) = (take(n), drop(n))
 
  override def reverse: NumericRange[T] =
- if (isEmpty) this else new NumericRange.Inclusive(last, start, -step)
+ if (isEmpty) this
+ else {
+ val newStep = -step
+ if (num.sign(newStep) == num.sign(step)) {
+ throw new ArithmeticException("number type is unsigned, and .reverse requires a negative step")
+ } else new NumericRange.Inclusive(last, start, newStep)
+ }
 
  import NumericRange.defaultOrdering