code: private JSType getJSType(Node n) {
      JSType jsType = n.getJSType();
      if (jsType == null) {
        // TODO(nicksantos): This branch indicates a compiler bug, not worthy of
        // halting the compilation but we should log this and analyze to track
        // down why it happens. This is not critical and will be resolved over
        // time as the type checker is extended.
        return unknownType;
      } else {
        return jsType;
      }
    }
docs: This method gets the JSType from the Node argument and verifies that it is
  present.