Implement function type?

[Kreijstal]

Something like

var cftype = function(rtype,args){return {
  size: ref.sizeof.pointer,
  alignment: ref.alignof.pointer,
  rtype,
  args,
  indirection: 1,
  get: function get (buf, offset) {
    const _buf = ref.readPointer(buf, offset)
    if (ref.isNull(_buf)) {
      return null;
    }
    return ffi.ForeignFunction(_buf,rtype,args);
  },
  set: function set (buf, offset, val) {
    let _buf
    if (Buffer.isBuffer(val)) {
      _buf = val;
    } else {
      // assume fn
      _buf = ffi.Callback(rtype,args,val);
	  val._buf=_buf;//make lifetime valid as long as val is valid.
    }
    return ref.writePointer(buf, offset, _buf);
  }
}
}

However this solution polutes the function, I guess