Add assertion of recordable list (#76272)

packages/flutter/lib/src/material/reorderable_list.dart

@@ -457,6 +457,14 @@ class _ReorderableListContentState extends State<_ReorderableListContent> {
 
   Widget _itemBuilder(BuildContext context, int index) {
     final Widget item = widget.itemBuilder(context, index);
+    assert(() {
+      if (item.key == null) {
+        throw FlutterError(
+          'Every item of ReorderableListView must have a key.'
+        );
+      }
+      return true;
+    }());
 
     // TODO(goderbauer): The semantics stuff should probably happen inside
     //   _ReorderableItem so the widget versions can have them as well.

packages/flutter/test/material/reorderable_list_test.dart

@@ -1326,6 +1326,22 @@ void main() {
     }
     expect(items.take(8), orderedEquals(<int>[0, 1, 2, 3, 4, 5, 6, 7]));
   });
+
+  testWidgets('ReorderableListView throws an error when key is not passed to its children', (WidgetTester tester) async {
+    final Widget reorderableListView = ReorderableListView.builder(
+      itemBuilder: (BuildContext context, int index) {
+        return SizedBox(child: Text('Item $index'));
+      },
+      itemCount: 3,
+      onReorder: (int oldIndex, int newIndex) { },
+    );
+    await tester.pumpWidget(MaterialApp(
+      home: reorderableListView,
+    ));
+    final dynamic exception = tester.takeException();
+    expect(exception, isFlutterError);
+    expect(exception.toString(), contains('Every item of ReorderableListView must have a key.'));
+  });
 }
 
 Future<void> longPressDrag(WidgetTester tester, Offset start, Offset end) async {