Rollup merge of #51326 - sdroege:slice-iter-cleanup, r=dtolnay

Various minor slice iterator cleanups

See individual commits

src/libcore/slice/mod.rs

@@ -2541,6 +2541,12 @@ fn rfold<Acc, Fold>(mut self, init: Acc, mut f: Fold) -> Acc
                 accum
             }
         }
+
+        #[stable(feature = "fused", since = "1.26.0")]
+        impl<'a, T> FusedIterator for $name<'a, T> {}
+
+        #[unstable(feature = "trusted_len", issue = "37572")]
+        unsafe impl<'a, T> TrustedLen for $name<'a, T> {}
     }
 }
 
@@ -2667,12 +2673,6 @@ fn is_empty(&self) -> bool {
     }
 }
 
-#[stable(feature = "fused", since = "1.26.0")]
-impl<'a, T> FusedIterator for Iter<'a, T> {}
-
-#[unstable(feature = "trusted_len", issue = "37572")]
-unsafe impl<'a, T> TrustedLen for Iter<'a, T> {}
-
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T> Clone for Iter<'a, T> {
     fn clone(&self) -> Iter<'a, T> { Iter { ptr: self.ptr, end: self.end, _marker: self._marker } }
@@ -2734,9 +2734,7 @@ impl<'a, T> IterMut<'a, T> {
     /// View the underlying data as a subslice of the original data.
     ///
     /// To avoid creating `&mut` references that alias, this is forced
-    /// to consume the iterator. Consider using the `Slice` and
-    /// `SliceMut` implementations for obtaining slices with more
-    /// restricted lifetimes that do not consume the iterator.
+    /// to consume the iterator.
     ///
     /// # Examples
     ///
@@ -2795,13 +2793,6 @@ fn is_empty(&self) -> bool {
     }
 }
 
-#[stable(feature = "fused", since = "1.26.0")]
-impl<'a, T> FusedIterator for IterMut<'a, T> {}
-
-#[unstable(feature = "trusted_len", issue = "37572")]
-unsafe impl<'a, T> TrustedLen for IterMut<'a, T> {}
-
-
 // Return the number of elements of `T` from `start` to `end`.
 // Return the arithmetic difference if `T` is zero size.
 #[inline(always)]
@@ -3399,6 +3390,9 @@ fn next_back(&mut self) -> Option<&'a [T]> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T> ExactSizeIterator for Windows<'a, T> {}
 
+#[unstable(feature = "trusted_len", issue = "37572")]
+unsafe impl<'a, T> TrustedLen for Windows<'a, T> {}
+
 #[stable(feature = "fused", since = "1.26.0")]
 impl<'a, T> FusedIterator for Windows<'a, T> {}
 
@@ -3518,6 +3512,9 @@ fn next_back(&mut self) -> Option<&'a [T]> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T> ExactSizeIterator for Chunks<'a, T> {}
 
+#[unstable(feature = "trusted_len", issue = "37572")]
+unsafe impl<'a, T> TrustedLen for Chunks<'a, T> {}
+
 #[stable(feature = "fused", since = "1.26.0")]
 impl<'a, T> FusedIterator for Chunks<'a, T> {}
 
@@ -3634,6 +3631,9 @@ fn next_back(&mut self) -> Option<&'a mut [T]> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T> ExactSizeIterator for ChunksMut<'a, T> {}
 
+#[unstable(feature = "trusted_len", issue = "37572")]
+unsafe impl<'a, T> TrustedLen for ChunksMut<'a, T> {}
+
 #[stable(feature = "fused", since = "1.26.0")]
 impl<'a, T> FusedIterator for ChunksMut<'a, T> {}
 
@@ -3744,6 +3744,9 @@ fn is_empty(&self) -> bool {
     }
 }
 
+#[unstable(feature = "trusted_len", issue = "37572")]
+unsafe impl<'a, T> TrustedLen for ExactChunks<'a, T> {}
+
 #[unstable(feature = "exact_chunks", issue = "47115")]
 impl<'a, T> FusedIterator for ExactChunks<'a, T> {}
 
@@ -3841,6 +3844,9 @@ fn is_empty(&self) -> bool {
     }
 }
 
+#[unstable(feature = "trusted_len", issue = "37572")]
+unsafe impl<'a, T> TrustedLen for ExactChunksMut<'a, T> {}
+
 #[unstable(feature = "exact_chunks", issue = "47115")]
 impl<'a, T> FusedIterator for ExactChunksMut<'a, T> {}