Remove implementing Deref<Target = [T]> for HistoryBuf

There is already `as_slice()` which gives access to the underlying
backing array where the elements are not in the order of writing.

With automatic dereferencing, functions like `iter()` or `windows()` are
automatically available for `HistoryBuf` and are returning items in an
order which does not reflect the write order and will likely surprise
users which did not carefully read all the documentation on for
`HistoryBuf` like me.

Author: sirhcel

CHANGELOG.md

@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Implement `defmt::Format` for `CapacityError`.
 - Implement `TryFrom` for `Deque` from array.
 - Switch from `serde` to `serde_core` for enabling faster compilations.
+- Removed `impl Deref` for `HistoryBuf` to make accessing the raw backing array explicit (use `as_slice()`).
 
 ## [v0.9.1] - 2025-08-19
 

src/history_buf.rs

@@ -34,7 +34,6 @@
 use core::fmt;
 use core::marker::PhantomData;
 use core::mem::MaybeUninit;
-use core::ops::Deref;
 use core::ptr;
 use core::slice;
 
@@ -572,18 +571,10 @@ impl<T, S: HistoryBufStorage<T> + ?Sized> Drop for HistoryBufInner<T, S> {
     }
 }
 
-impl<T, S: HistoryBufStorage<T> + ?Sized> Deref for HistoryBufInner<T, S> {
-    type Target = [T];
-
-    fn deref(&self) -> &[T] {
-        self.as_slice()
-    }
-}
-
 impl<T, S: HistoryBufStorage<T> + ?Sized> AsRef<[T]> for HistoryBufInner<T, S> {
     #[inline]
     fn as_ref(&self) -> &[T] {
-        self
+        self.as_slice()
     }
 }
 
@@ -592,7 +583,7 @@ where
     T: fmt::Debug,
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        <[T] as fmt::Debug>::fmt(self, f)
+        <[T] as fmt::Debug>::fmt(self.as_slice(), f)
     }
 }
 
@@ -660,7 +651,6 @@ mod tests {
         let x: HistoryBuf<u8, 4> = HistoryBuf::new_with(1);
         assert_eq!(x.len(), 4);
         assert_eq!(x.as_slice(), [1; 4]);
-        assert_eq!(*x, [1; 4]);
         assert!(x.is_full());
 
         let x: HistoryBuf<u8, 4> = HistoryBuf::new();
@@ -910,8 +900,8 @@ mod tests {
                 x,
                 y,
                 "{:?} {:?}",
-                x.iter().collect::<Vec<_>>(),
-                y.iter().collect::<Vec<_>>()
+                x.as_slice().iter().collect::<Vec<_>>(),
+                y.as_slice().iter().collect::<Vec<_>>()
             );
         }
     }