Switch UnsafeMutableBufferPointer.subscript to use _modify (#19771)

airspeedswift · web-flow · commit 6a0fd51beb0f · 2018-10-08T16:23:01.000-07:00
diff --git a/stdlib/public/core/UnsafeBufferPointer.swift.gyb b/stdlib/public/core/UnsafeBufferPointer.swift.gyb
@@ -273,10 +273,10 @@ extension Unsafe${Mutable}BufferPointer: ${Mutable}Collection, RandomAccessColle
       return _position![i]
     }
 %if Mutable:
-    nonmutating set {
+    nonmutating _modify {
       _debugPrecondition(i >= 0)
       _debugPrecondition(i < endIndex)
-      _position![i] = newValue
+      yield &_position![i]
     }
 %end
   }

Original file line number	Diff line number	Diff line change
`@@ -273,10 +273,10 @@ extension Unsafe${Mutable}BufferPointer: ${Mutable}Collection, RandomAccessColle`
`273`	`273`	`return _position![i]`
`274`	`274`	`}`
`275`	`275`	`%if Mutable:`
`276`		`- nonmutating set {`
	`276`	`+ nonmutating _modify {`
`277`	`277`	`_debugPrecondition(i >= 0)`
`278`	`278`	`_debugPrecondition(i < endIndex)`
`279`		`- _position![i] = newValue`
	`279`	`+ yield &_position![i]`
`280`	`280`	`}`
`281`	`281`	`%end`
`282`	`282`	`}`