Fix DDC errors on DDC

lib/src/checker/checker.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 dev_compiler.src.checker.checker;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/scanner.dart' show Token, TokenType;
@@ skipping 209 matching lines @@
   ///
   /// The [errorLocation] node indicates where errors are reported, see
   /// [_checkSingleOverride] for more details.
   _checkIndividualOverridesFromClass(
       ClassDeclaration node, InterfaceType baseType, Set<String> seen) {
     for (var member in node.members) {
       if (member is ConstructorDeclaration) continue;
       if (member is FieldDeclaration) {
         if (member.isStatic) continue;
         for (var variable in member.fields.variables) {
-          var name = variable.element.name;
+          var element = variable.element as PropertyInducingElement;
+          var name = element.name;
           if (seen.contains(name)) continue;
-          var getter = variable.element.getter;
-          var setter = variable.element.setter;
+          var getter = element.getter;
+          var setter = element.setter;
           bool found = _checkSingleOverride(getter, baseType, variable, member);
           if (!variable.isFinal &&
               _checkSingleOverride(setter, baseType, variable, member)) {
             found = true;
           }
           if (found) seen.add(name);
         }
       } else {
-        assert(member is MethodDeclaration);
-        if (member.isStatic) continue;
+        if ((member as MethodDeclaration).isStatic) continue;
         var method = member.element;
         if (seen.contains(method.name)) continue;
         if (_checkSingleOverride(method, baseType, member, member)) {
           seen.add(method.name);
         }
       }
     }
   }
 
   /// Checks that [element] correctly overrides its corresponding member in
@@ skipping 586 matching lines @@
   void _recordDynamicInvoke(AstNode node) {
     _reporter.log(new DynamicInvoke(_rules, node));
   }
 
   void _recordMessage(StaticInfo info) {
     if (info == null) return;
     if (info.level >= logger.Level.SEVERE) _failure = true;
     _reporter.log(info);
   }
 }