Fix #28120, strong mode allows field overrides

pkg/analyzer/test/src/context/context_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.
 
 library analyzer.test.src.context.context_test;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 4308 matching lines @@
         r'''
 class A {
   int foo;
   int get foo => 1;
 }
 class B extends A {
   int get foo => 2;
 }
 ''');
     _performPendingAnalysisTasks();
-    expect(context.getErrors(a).errors, hasLength(2));
+    expect(context.getErrors(a).errors, hasLength(1));
     // Update a.dart: rename "int foo" to "int bar".
-    // The strong mode "getter cannot override field" error is gone.
     context.setContents(
         a,
         r'''
 class A {
   int bar;
   int get foo => 1;
 }
 class B extends A {
   int get foo => 2;
 }
@@ skipping 1103 matching lines @@
    * Initialize the visitor.
    */
   _ElementGatherer();
 
   @override
   void visitElement(Element element) {
     elements[element] = element;
     super.visitElement(element);
   }
 }