docs: public Statement putInstanceField(final Expression instance, final Expression value) {
      checkState(!isStatic(), "This field is static!");
      instance.checkAssignableTo(owner().type());
      value.checkAssignableTo(type());
      return new Statement() {
        @Override
        protected void doGen(CodeBuilder adapter) {
          instance.gen(adapter);
          value.gen(adapter);
          putUnchecked(adapter);
        }
      };
    }