From 930464c05e9e77a555ff2c8f43b5ac3537e8af24 Mon Sep 17 00:00:00 2001
From: Ben Williamson <12386+benw@users.noreply.github.com>
Date: Thu, 11 Jun 2026 13:33:23 +1000
Subject: [PATCH] Remove ?Sized bound from Idx in Index and IndexMut

`Idx: ?Sized` is useless because the trait methods pass the index
by value, so it's impossible to impl with an unsized Idx type.

Removing this makes it a little easier for learners to understand
the intent of the Index and IndexMut traits.
---
 library/core/src/ops/index.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/library/core/src/ops/index.rs b/library/core/src/ops/index.rs
index 2c62a3930c281..d12e301aa1da7 100644
--- a/library/core/src/ops/index.rs
+++ b/library/core/src/ops/index.rs
@@ -56,7 +56,7 @@
 #[doc(alias = "[")]
 #[doc(alias = "[]")]
 #[rustc_const_unstable(feature = "const_index", issue = "143775")]
-pub const trait Index<Idx: ?Sized> {
+pub const trait Index<Idx> {
     /// The returned type after indexing.
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_diagnostic_item = "IndexOutput"]
@@ -167,7 +167,7 @@ see chapter in The Book <https://doc.rust-lang.org/book/ch08-02-strings.html#ind
 #[doc(alias = "]")]
 #[doc(alias = "[]")]
 #[rustc_const_unstable(feature = "const_index", issue = "143775")]
-pub const trait IndexMut<Idx: ?Sized>: [const] Index<Idx> {
+pub const trait IndexMut<Idx>: [const] Index<Idx> {
     /// Performs the mutable indexing (`container[index]`) operation.
     ///
     /// # Panics