Add a comment why Ref lens is necessary for arrays.

linebender · Sep 2, 2020 · 99b7865 · 99b7865
1 parent 71a4738
commit 99b7865
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/druid/src/lens/lens.rs b/druid/src/lens/lens.rs
@@ -128,6 +128,8 @@ pub trait LensExt<A: ?Sized, B: ?Sized>: Lens<A, B> {
     /// Invoke a type's `AsRef` and `AsMut` impl.
     ///
     /// It also allows indexing arrays with the [`index`] lens as shown in the example.
+    /// This is necessary, because the `Index` trait in Rust is only implemented
+    /// for slices (`[T]`), but not for arrays (`[T; N]`).
     ///
     /// # Examples
     ///