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

test/codegen/expect/fieldtest.js

Index: test/codegen/expect/fieldtest.js
diff --git a/test/codegen/expect/fieldtest.js b/test/codegen/expect/fieldtest.js
index 9354cf6742d7c7fd365d7343aeb536e991928128..ddbf5d5d92af9ea94adb5933e552adbb83d2fdab 100644
--- a/test/codegen/expect/fieldtest.js
+++ b/test/codegen/expect/fieldtest.js
@@ -3,15 +3,15 @@ var fieldtest;
   'use strict';
   class A extends core.Object {
     A() {
-      this.x = 42;
+      dart.initField(A, this, 'x', 42);
     }
   }
   let B$ = dart.generic(function(T) {
     class B extends core.Object {
       B() {
-        this.x = null;
-        this.y = null;
-        this.z = null;
+        dart.initField(B, this, 'x', null);
+        dart.initField(B, this, 'y', null);
+        dart.initField(B, this, 'z', null);
       }
     }
     return B;