attempt to do the minimum NonZero

src/slice.rs

@@ -9,6 +9,7 @@ use crate::error::{ErrorKind, ShapeError};
 use crate::{ArrayView, ArrayViewMut, Dimension, RawArrayViewMut};
 use std::fmt;
 use std::marker::PhantomData;
+use std::num::NonZeroIsize;
 use std::ops::{Deref, Range, RangeFrom, RangeFull, RangeInclusive, RangeTo, RangeToInclusive};
 
 /// A slice (range with step size).
@@ -48,6 +49,7 @@ impl Slice {
     /// (This method checks with a debug assertion that `step` is not zero.)
     pub fn new(start: isize, end: Option<isize>, step: isize) -> Slice {
         debug_assert_ne!(step, 0, "Slice::new: step must be nonzero");
+        // let step = NonZeroIsize::new(step).unwrap();
         Slice { start, end, step }
     }
 
@@ -129,8 +131,7 @@ impl SliceOrIndex {
     /// `step` must be nonzero.
     /// (This method checks with a debug assertion that `step` is not zero.)
     #[inline]
-    pub fn step_by(self, step: isize) -> Self {
-        debug_assert_ne!(step, 0, "SliceOrIndex::step_by: step must be nonzero");
+    pub fn step_by(self, step: NonZeroIsize) -> Self {
         match self {
             SliceOrIndex::Slice {
                 start,
@@ -139,7 +140,7 @@ impl SliceOrIndex {
             } => SliceOrIndex::Slice {
                 start,
                 end,
-                step: orig_step * step,
+                step: orig_step * step.get(),
             },
             SliceOrIndex::Index(s) => SliceOrIndex::Index(s),
         }
@@ -610,7 +611,7 @@ macro_rules! s(
     };
     // convert range/index and step into SliceOrIndex
     (@convert $r:expr, $s:expr) => {
-        <$crate::SliceOrIndex as ::std::convert::From<_>>::from($r).step_by($s as isize)
+        <$crate::SliceOrIndex as ::std::convert::From<_>>::from($r).step_by(std::num::NonZeroIsize::new($s).unwrap())
     };
     ($($t:tt)*) => {
         // The extra `*&` is a workaround for this compiler bug:

tests/array.rs

@@ -257,7 +257,7 @@ fn test_slice_dyninput_vec_dyn() {
     let info = &SliceInfo::<_, IxDyn>::new(vec![
         SliceOrIndex::from(1..),
         SliceOrIndex::from(1),
-        SliceOrIndex::from(..).step_by(2),
+        SliceOrIndex::from(..).step_by(2isize),
     ])
     .unwrap();
     arr.slice(info.as_ref());