FYI: add strong mode checking to error verifier's task

pkg/analyzer/test/src/task/dart_test.dart

 // Copyright (c) 2015, 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 test.src.task.dart_test;
 
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/constant.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/engine.dart'
     show AnalysisOptionsImpl, CacheState;
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/resolver.dart';
 import 'package:analyzer/src/generated/scanner.dart';
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/services/lint.dart';
 import 'package:analyzer/src/task/dart.dart';
 import 'package:analyzer/src/task/html.dart';
+import 'package:analyzer/src/task/strong/info.dart';
 import 'package:analyzer/task/dart.dart';
 import 'package:analyzer/task/general.dart';
 import 'package:analyzer/task/model.dart';
 import 'package:unittest/unittest.dart';
 
 import '../../generated/resolver_test.dart';
 import '../../generated/test_support.dart';
 import '../../reflective_tests.dart';
 import '../../utils.dart';
 import '../context/abstract_context.dart';
@@ skipping 3977 matching lines @@
         '/test.dart',
         '''
 const topLevel = 3;
 class C {
   String field = topLevel;
 }
 ''');
     computeResult(new LibrarySpecificUnit(source, source), VERIFY_ERRORS);
     // validate
     _fillErrorListener(VERIFY_ERRORS);
-    errorListener.assertErrorsWithCodes(
-        <ErrorCode>[StaticTypeWarningCode.INVALID_ASSIGNMENT]);
+
+    // TODO(jmesserly): DDC errors do not hash correctly.
+    // TODO(jmesserly): also we have a duplicate error message here.
+    var errors = errorListener.errors;
+    expect(errors.length, 2);
+    expect(errors[0].errorCode.name, 'dev_compiler.StaticTypeError');
+    expect(errors[0].message,
+        'Type check failed: topLevel (int) is not of type String');
+    expect(errors[1].errorCode, StaticTypeWarningCode.INVALID_ASSIGNMENT);
   }
 
   test_perform_verifyError() {
     Source source = newSource(
         '/test.dart',
         '''
 main() {
   if (42) {
     print('Not bool!');
   }
@@ skipping 218 matching lines @@
   /**
    * Fill [errorListener] with [result] errors in the current [task].
    */
   void _fillErrorListener(ResultDescriptor<List<AnalysisError>> result) {
     List<AnalysisError> errors = task.outputs[result];
     expect(errors, isNotNull, reason: result.name);
     errorListener = new GatheringErrorListener();
     errorListener.addAll(errors);
   }
 }