fixes #52, fields shadowing getters/setters or other fields

test/codegen/expect/cascade.js

Index: test/codegen/expect/cascade.js
diff --git a/test/codegen/expect/cascade.js b/test/codegen/expect/cascade.js
index 97bdf1eefb46de54e114d384f6a4fbbb9d2497aa..5edb9527fdb7906d118fd0535cebcefbf6a801be 100644
--- a/test/codegen/expect/cascade.js
+++ b/test/codegen/expect/cascade.js
@@ -1,9 +1,16 @@
 var cascade;
 (function(exports) {
   'use strict';
+  let x = Symbol('x');
   class A extends core.Object {
     A() {
-      this.x = null;
+      this[x] = null;
+    }
+    get x() {
+      return this[x];
+    }
+    set x(value) {
+      this[x] = value;
     }
   }
   // Function test_closure_with_mutate: () → void
@@ -82,10 +89,14 @@ var cascade;
       return a;
     })());
   }
+  let x$ = Symbol('x');
   let Base$ = dart.generic(function(T) {
     class Base extends core.Object {
       Base() {
-        this.x = new core.List$(T).from([]);
+        this[x$] = new core.List$(T).from([]);
+      }
+      get x() {
+        return this[x$];
       }
     }
     return Base;