Assert that the incoming elements have a correct count implementation

Catfish-Man · lorentey · Catfish-Man · commit 71a8c89026b7 · 2024-12-06T16:24:28.000-08:00
Co-authored-by: Karoy Lorentey &lt;klorentey@apple.com&gt;
diff --git a/stdlib/public/core/Array.swift b/stdlib/public/core/Array.swift
@@ -1240,7 +1240,8 @@ extension Array: RangeReplaceableCollection {
                 start: startNewElements,
                 count: _buffer.mutableCapacity - oldCount)
 
-    _ = buf.initialize(fromContentsOf: newElements)
+    let end = buf.initialize(fromContentsOf: newElements)
+    _precondition(end == buf.endIndex)
     _buffer.mutableCount = _buffer.mutableCount + newElementsCount
   }
 

Original file line number	Diff line number	Diff line change
`@@ -1240,7 +1240,8 @@ extension Array: RangeReplaceableCollection {`
`1240`	`1240`	`start: startNewElements,`
`1241`	`1241`	`count: _buffer.mutableCapacity - oldCount)`
`1242`	`1242`
`1243`		`- _ = buf.initialize(fromContentsOf: newElements)`
	`1243`	`+ let end = buf.initialize(fromContentsOf: newElements)`
	`1244`	`+ _precondition(end == buf.endIndex)`
`1244`	`1245`	`_buffer.mutableCount = _buffer.mutableCount + newElementsCount`
`1245`	`1246`	`}`
`1246`	`1247`