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

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

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:async';
 
 import 'package:analysis_server/plugin/edit/fix/fix_core.dart';
 import 'package:analysis_server/plugin/edit/fix/fix_dart.dart';
 import 'package:analysis_server/src/services/correction/fix.dart';
 import 'package:analysis_server/src/services/correction/fix_internal.dart';
@@ skipping 2526 matching lines @@
 import 'package:pkg/a/a.dart';
 import 'package:pkg/b/b.dart';
 import 'package:pkg/c/c.dart';
 
 main() {
   A a;
   B b;
   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 {
     await resolveTestUnit('''
 main() {
   test = 42;
 }
 ''');
     await assertHasFix(DartFixKind.CREATE_LOCAL_VARIABLE, '''
 main() {
@@ skipping 3962 matching lines @@
   @override
   final AnalysisError error;
 
   _DartFixContextImpl(this.resourceProvider, this.analysisDriver,
       this.astProvider, this.unit, this.error);
 
   @override
   GetTopLevelDeclarations get getTopLevelDeclarations =>
       analysisDriver.getTopLevelNameDeclarations;
 }