Fix DDC errors on DDC

lib/src/codegen/side_effect_analysis.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.codegen.side_effect_analysis;
 
 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/error.dart' show ErrorReporter;
@@ skipping 18 matching lines @@
 ///
 /// This method is conservative: it should never return `true` unless it is
 /// certain the [node] is stateless, because generated code may rely on the
 /// correctness of a `true` value. However it may return `false` for things
 /// that are in fact, stateless.
 bool isStateless(Expression node, [AstNode context]) {
   // `this` and `super` cannot be reassigned.
   if (node is ThisExpression || node is SuperExpression) return true;
   if (node is SimpleIdentifier) {
     var e = node.staticElement;
-    if (e is PropertyAccessorElement) e = e.variable;
+    if (e is PropertyAccessorElement) e =
+        (e as PropertyAccessorElement).variable;
     if (e is VariableElement && !e.isSynthetic) {
       if (e.isFinal) return true;
       if (e is LocalVariableElement || e is ParameterElement) {
         // make sure the local isn't mutated in the context.
         return !_isPotentiallyMutated(e, context);
       }
     }
   }
   return false;
 }
@@ skipping 64 matching lines @@
     // ConstantEvaluator will not compute constants for non-const fields,
     // so run ConstantVisitor for those to figure out if the initializer is
     // actually a constant (and therefore side effect free to evaluate).
     assert(!field.isConst);
 
     var initializer = field.initializer;
     if (initializer == null) return null;
     return initializer.accept(_constantVisitor);
   }
 }