Function getSetter

test/angular/1.6/angular.js:24173–24179

(expression)

    return formDirective;

    function getSetter(expression) {
      if (expression === '') {
        //create an assignable expression, so forms with an empty name can be renamed later
        return $parse('this[""]').assign;
      }
      return $parse(expression).assign || noop;
    }
  }];
};