Document niches

Author: Kestrer

src/lib.rs

@@ -143,6 +143,10 @@ pub mod examples;
 /// upper bound can be inclusive (`x..=y`) or exclusive (`x..y`). The attributes and visibility
 /// (e.g. `pub`) of the type are forwarded directly to the output type.
 ///
+/// If the type is a struct and the bounded integer's range does not include zero,
+/// the struct will have a niche at zero,
+/// allowing for `Option<BoundedInteger>` to be the same size as `BoundedInteger` itself.
+///
 /// See the [`examples`] module for examples of what this macro generates.
 ///
 /// # Examples

src/types/mod.rs

@@ -690,7 +690,7 @@ macro_rules! define_bounded_integers {
         #[cfg_attr(doc_cfg, doc(cfg(feature = "step_trait")))]
         impl<const MIN: Inner, const MAX: Inner> iter::Step for Bounded<MIN, MAX> {
             #[inline]
-            fn steps_between(start: &Self, end: &Self) -> Option<usize> {
+            fn steps_between(start: &Self, end: &Self) -> (usize, Option<usize>) {
                 iter::Step::steps_between(&start.get(), &end.get())
             }
             #[inline]