function castFixed(name, func, n) {
    if (config.fixed && (forceFixed || !mapping.skipFixed[name])) {
      var data = mapping.methodSpread[name],
          start = data && data.start;

      return start  === undefined ? ary(func, n) : flatSpread(func, start);
    }
    return func;
  }
Casts `func` to a fixed arity function if needed.

@private
@param {string} name The name of the function to inspect.
@param {Function} func The function to inspect.
@param {number} n The arity cap.
@returns {Function} Returns the cast function.