Issue 5052. Analyzer should treat assert as a keyword

compiler/java/com/google/dart/compiler/resolver/TopLevelElementBuilder.java

 // Copyright (c) 2012, 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.
 
 package com.google.dart.compiler.resolver;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
 import com.google.dart.compiler.DartCompilationError;
@@ skipping 209 matching lines @@
       reportDuplicateDeclaration(listener, oldElement, newElement);
       reportDuplicateDeclaration(listener, newElement, oldElement);
     }
     scope.declareElement(name, newElement);
   }
 
   private static boolean shouldReportDuplicateDeclaration(Element oldElement, Element newElement) {
     if (oldElement == null) {
       return false;
     }
-    // ignore "assert"
-    if (Elements.isArtificialAssertMethod(oldElement)) {
-      return false;
-    }
     // Getter/setter can shared same name, but not setter/setter and getter/getter.
     if (newElement.getModifiers().isAbstractField()
         && oldElement.getModifiers().isAbstractField()) {
       if (newElement.getModifiers().isGetter() && !oldElement.getModifiers().isGetter()) {
         return false;
       }
       if (newElement.getModifiers().isSetter() && !oldElement.getModifiers().isSetter()) {
         return false;
       }
     }
@@ skipping 54 matching lines @@
     }
 
     @Override
     public Void visitField(DartField node) {
       Modifiers modifiers = node.getModifiers();
       node.setElement(Elements.fieldFromNode(node, library, node.getObsoleteMetadata(), modifiers));
       return null;
     }
   }
 }