From 5d59d0c7d725fe259b652bb9e9d17e6cbe1919af Mon Sep 17 00:00:00 2001
From: Peter Jaszkowiak <p.jaszkow@gmail.com>
Date: Tue, 23 Jan 2024 19:00:10 -0700
Subject: [PATCH] have `String` use `SliceIndex` impls from `str`

---
 library/alloc/src/lib.rs    |   1 +
 library/alloc/src/string.rs | 102 +++++-------------------------------
 2 files changed, 15 insertions(+), 88 deletions(-)

diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
index 45e93feb6c5b3..28695ade5bf55 100644
--- a/library/alloc/src/lib.rs
+++ b/library/alloc/src/lib.rs
@@ -152,6 +152,7 @@
 #![feature(set_ptr_value)]
 #![feature(sized_type_properties)]
 #![feature(slice_from_ptr_range)]
+#![feature(slice_index_methods)]
 #![feature(slice_ptr_get)]
 #![feature(slice_ptr_len)]
 #![feature(slice_range)]
diff --git a/library/alloc/src/string.rs b/library/alloc/src/string.rs
index 6dadbc8e36428..25991a91498f1 100644
--- a/library/alloc/src/string.rs
+++ b/library/alloc/src/string.rs
@@ -54,7 +54,7 @@ use core::ops::Add;
 use core::ops::AddAssign;
 #[cfg(not(no_global_oom_handling))]
 use core::ops::Bound::{Excluded, Included, Unbounded};
-use core::ops::{self, Index, IndexMut, Range, RangeBounds};
+use core::ops::{self, Range, RangeBounds};
 use core::ptr;
 use core::slice;
 use core::str::pattern::Pattern;
@@ -2433,100 +2433,26 @@ impl AddAssign<&str> for String {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl ops::Index<ops::Range<usize>> for String {
-    type Output = str;
+impl<I> ops::Index<I> for String
+where
+    I: slice::SliceIndex<str>,
+{
+    type Output = I::Output;
 
     #[inline]
-    fn index(&self, index: ops::Range<usize>) -> &str {
-        &self[..][index]
+    fn index(&self, index: I) -> &I::Output {
+        index.index(self.as_str())
     }
 }
-#[stable(feature = "rust1", since = "1.0.0")]
-impl ops::Index<ops::RangeTo<usize>> for String {
-    type Output = str;
 
-    #[inline]
-    fn index(&self, index: ops::RangeTo<usize>) -> &str {
-        &self[..][index]
-    }
-}
 #[stable(feature = "rust1", since = "1.0.0")]
-impl ops::Index<ops::RangeFrom<usize>> for String {
-    type Output = str;
-
-    #[inline]
-    fn index(&self, index: ops::RangeFrom<usize>) -> &str {
-        &self[..][index]
-    }
-}
-#[stable(feature = "rust1", since = "1.0.0")]
-impl ops::Index<ops::RangeFull> for String {
-    type Output = str;
-
-    #[inline]
-    fn index(&self, _index: ops::RangeFull) -> &str {
-        unsafe { str::from_utf8_unchecked(&self.vec) }
-    }
-}
-#[stable(feature = "inclusive_range", since = "1.26.0")]
-impl ops::Index<ops::RangeInclusive<usize>> for String {
-    type Output = str;
-
-    #[inline]
-    fn index(&self, index: ops::RangeInclusive<usize>) -> &str {
-        Index::index(&**self, index)
-    }
-}
-#[stable(feature = "inclusive_range", since = "1.26.0")]
-impl ops::Index<ops::RangeToInclusive<usize>> for String {
-    type Output = str;
-
-    #[inline]
-    fn index(&self, index: ops::RangeToInclusive<usize>) -> &str {
-        Index::index(&**self, index)
-    }
-}
-
-#[stable(feature = "derefmut_for_string", since = "1.3.0")]
-impl ops::IndexMut<ops::Range<usize>> for String {
-    #[inline]
-    fn index_mut(&mut self, index: ops::Range<usize>) -> &mut str {
-        &mut self[..][index]
-    }
-}
-#[stable(feature = "derefmut_for_string", since = "1.3.0")]
-impl ops::IndexMut<ops::RangeTo<usize>> for String {
-    #[inline]
-    fn index_mut(&mut self, index: ops::RangeTo<usize>) -> &mut str {
-        &mut self[..][index]
-    }
-}
-#[stable(feature = "derefmut_for_string", since = "1.3.0")]
-impl ops::IndexMut<ops::RangeFrom<usize>> for String {
-    #[inline]
-    fn index_mut(&mut self, index: ops::RangeFrom<usize>) -> &mut str {
-        &mut self[..][index]
-    }
-}
-#[stable(feature = "derefmut_for_string", since = "1.3.0")]
-impl ops::IndexMut<ops::RangeFull> for String {
-    #[inline]
-    fn index_mut(&mut self, _index: ops::RangeFull) -> &mut str {
-        unsafe { str::from_utf8_unchecked_mut(&mut *self.vec) }
-    }
-}
-#[stable(feature = "inclusive_range", since = "1.26.0")]
-impl ops::IndexMut<ops::RangeInclusive<usize>> for String {
-    #[inline]
-    fn index_mut(&mut self, index: ops::RangeInclusive<usize>) -> &mut str {
-        IndexMut::index_mut(&mut **self, index)
-    }
-}
-#[stable(feature = "inclusive_range", since = "1.26.0")]
-impl ops::IndexMut<ops::RangeToInclusive<usize>> for String {
+impl<I> ops::IndexMut<I> for String
+where
+    I: slice::SliceIndex<str>,
+{
     #[inline]
-    fn index_mut(&mut self, index: ops::RangeToInclusive<usize>) -> &mut str {
-        IndexMut::index_mut(&mut **self, index)
+    fn index_mut(&mut self, index: I) -> &mut I::Output {
+        index.index_mut(self.as_mut_str())
     }
 }