Move error checking from scope creation to error reporter

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 analyzer.test.src.task.dart_test;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
@@ skipping 5650 matching lines @@
 }
 
 main() {
   const Test();
 }
 ''');
     LibrarySpecificUnit target = new LibrarySpecificUnit(source, source);
     computeResult(target, VERIFY_ERRORS, matcher: isVerifyUnitTask);
     // validate
     _fillErrorListener(VERIFY_ERRORS);
-    errorListener.assertNoErrors();
+    errorListener
+        .assertErrorsWithCodes([CompileTimeErrorCode.DUPLICATE_DEFINITION]);
   }
 
   test_perform_ConstantValidator_noInitializer() {
     Source source = newSource(
         '/test.dart',
         '''
 const x;
 ''');
     LibrarySpecificUnit target = new LibrarySpecificUnit(source, source);
     computeResult(target, VERIFY_ERRORS, matcher: isVerifyUnitTask);
@@ skipping 190 matching lines @@
   /**
    * Fill [errorListener] with [result] errors in the current [task].
    */
   void _fillErrorListener(ResultDescriptor<List<AnalysisError>> result) {
     List<AnalysisError> errors = task.outputs[result] as List<AnalysisError>;
     expect(errors, isNotNull, reason: result.name);
     errorListener = new GatheringErrorListener();
     errorListener.addAll(errors);
   }
 }