From f6498110591ad13e490724e1c6cc59c5c2aa0429 Mon Sep 17 00:00:00 2001
From: Ben Cohen <ben_cohen@apple.com>
Date: Thu, 29 Nov 2018 16:49:21 -0800
Subject: [PATCH] Change Slice and CollectionOfOne to use _read/_modify

---
 stdlib/public/core/CollectionOfOne.swift |  4 ++--
 stdlib/public/core/Slice.swift           | 12 ++++++------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/stdlib/public/core/CollectionOfOne.swift b/stdlib/public/core/CollectionOfOne.swift
index 98a9d5a5c23e9..1086a661a1290 100644
--- a/stdlib/public/core/CollectionOfOne.swift
+++ b/stdlib/public/core/CollectionOfOne.swift
@@ -127,9 +127,9 @@ extension CollectionOfOne: RandomAccessCollection, MutableCollection {
   ///   valid position in a `CollectionOfOne` instance is `0`.
   @inlinable // trivial-implementation
   public subscript(position: Int) -> Element {
-    get {
+    _read {
       _precondition(position == 0, "Index out of range")
-      return _element
+      yield _element
     }
     _modify {
       _precondition(position == 0, "Index out of range")
diff --git a/stdlib/public/core/Slice.swift b/stdlib/public/core/Slice.swift
index 01cf1d675e445..e4d695ce6f5e0 100644
--- a/stdlib/public/core/Slice.swift
+++ b/stdlib/public/core/Slice.swift
@@ -156,9 +156,9 @@ extension Slice: Collection {
 
   @inlinable // generic-performance
   public subscript(index: Index) -> Base.Element {
-    get {
+    _read {
       _failEarlyRangeCheck(index, bounds: startIndex..<endIndex)
-      return _base[index]
+      yield _base[index]
     }
   }
 
@@ -235,13 +235,13 @@ extension Slice: BidirectionalCollection where Base: BidirectionalCollection {
 extension Slice: MutableCollection where Base: MutableCollection {
   @inlinable // generic-performance
   public subscript(index: Index) -> Base.Element {
-    get {
+    _read {
       _failEarlyRangeCheck(index, bounds: startIndex..<endIndex)
-      return _base[index]
+      yield _base[index]
     }
-    set {
+    _modify {
       _failEarlyRangeCheck(index, bounds: startIndex..<endIndex)
-      _base[index] = newValue
+      yield &_base[index]
       // MutableSlice requires that the underlying collection's subscript
       // setter does not invalidate indices, so our `startIndex` and `endIndex`
       // continue to be valid.