Correctly update positions when adding edits before them (issue 30444)

pkg/analysis_server/test/services/correction/fix_test.dart

Index: pkg/analysis_server/test/services/correction/fix_test.dart
diff --git a/pkg/analysis_server/test/services/correction/fix_test.dart b/pkg/analysis_server/test/services/correction/fix_test.dart
index c8801213929ed53b4dcfd8e0266bf85ee294b361..42f4d3dacebe5110e9f5422f3e96a138052108eb 100644
--- a/pkg/analysis_server/test/services/correction/fix_test.dart
+++ b/pkg/analysis_server/test/services/correction/fix_test.dart
@@ -2544,6 +2544,18 @@ main() {
   new C(a, b);
 }
 ''');
+
+    List<LinkedEditGroup> groups = change.linkedEditGroups;
+    expect(groups, hasLength(2));
+    LinkedEditGroup typeGroup = groups[0];
+    List<Position> typePositions = typeGroup.positions;
+    expect(typePositions, hasLength(1));
+    expect(typePositions[0].offset, 112);
+    LinkedEditGroup nameGroup = groups[1];
+    List<Position> groupPositions = nameGroup.positions;
+    expect(groupPositions, hasLength(2));
+    expect(groupPositions[0].offset, 114);
+    expect(groupPositions[1].offset, 128);
   }
 
   test_createLocalVariable_write_assignment() async {