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

test/codegen/expect/temps.js

Index: test/codegen/expect/temps.js
diff --git a/test/codegen/expect/temps.js b/test/codegen/expect/temps.js
index 821b41bedc879dfb63be527e110105ff9120f612..a44a46bc24fbad4f51d71d6ec68545cea3a71e85 100644
--- a/test/codegen/expect/temps.js
+++ b/test/codegen/expect/temps.js
@@ -6,9 +6,9 @@ var temps;
   let _function = Symbol('_function');
   class FormalCollision extends core.Object {
     FormalCollision(x, _x$, func) {
-      this[_x] = x;
-      this[__x] = _x$;
-      this[_function] = func;
+      dart.initField(FormalCollision, this, _x, x);
+      dart.initField(FormalCollision, this, __x, _x$);
+      dart.initField(FormalCollision, this, _function, func);
     }
   }
   // Function main: () → dynamic