fixes #147, add more cases to isStateless

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/element.dart';
 
 /// True is the expression can be evaluated multiple times without causing
@@ skipping 10 matching lines @@
 ///
 /// This method is used to avoid creating temporaries in cases where we know
 /// we can safely re-evaluate [node] multiple times in [context]. This lets
 /// us generate prettier code.
 ///
 /// 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 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);
       }
     }
@@ skipping 36 matching lines @@
     if (parent is MethodInvocation &&
         identical(parent.methodName, node)) return;
     if (parent is ConstructorName) return;
     if (parent is Label) return;
 
     if (node.inSetterContext() && node.staticElement == _variable) {
       _potentiallyMutated = true;
     }
   }
 }