#data
callback foo = void ();
#parsed
{
  "definitions": [
    {
      "index": 0,
      "definition_type": "callback",
      "name": "foo",
      "type": "void",
      "arguments": []
    }
  ]
}

#data
callback foo = void (bac xx);
#parsed
{
  "definitions": [
    {
      "index": 0,
      "definition_type": "callback",
      "name": "foo",
      "type": "void",
      "arguments": [
        {
          "index": 21,
          "name": "xx",
          "type_name": "bac"
        }
      ]
    }
  ]
}