Tern function parameters: how do I specify an object with keys?

Question

I have a Button function that accepts a few paramaters (name, label, onClick). I can set Button !type to be fn(name: string, label: string, onClick: fn()), but really it should be something like fn(config: {name: string, label: string, onClick: fn()}). The problem is when I try that second example I get the error Unrecognized type spec. Is there a correct way to specify an object with keys as a function argument?

Just for some context, I am using an autocomplete plugin for Brackets called Ternific. No issues with the plugin, just with my config.

Here is my .turn-project file which is throwing the error: (scroll to the bottom to see Button)

{
  "!name": "mb-core",
  "ComponentOfType": {
    "InteractiveValidated": {
        "prototype": {
          "enable": {
            "!type": "fn()",
            "!doc": "Enable component."
          },
          "disable": {
            "!type": "fn()",
            "!doc": "Disable component."
          },
          "isFilledOut": {
            "!type": "fn() -> boolean",
            "!doc": "Check if component's is filled out."
          },
          "isCorrect": {
            "!type": "fn() -> boolean",
            "!doc": "Check if component's value is correct."
          },
          "value": {
            "!type": "fn()",
            "!doc": "Get components value."
          },
          "reset": {
            "!type": "fn()",
            "!doc": "Reset component."
          },
          "show": {
            "!type": "fn()",
            "!doc": "Show component."
          },
          "hide": {
            "!type": "fn()",
            "!doc": "Hide component."
          }
        }
    }
  },
  "Button": {
    "!type": "fn(config: {name: string, label: string, onClick: fn()}) -> +ComponentType.InteractiveValidated",
    "!url": "https://docs.mathbrainius.com/problem-development/shared-components#button",
    "!doc": "Creates a button."
  }
}