Function is not a valid shorthand

[miroslavstastny]

Bug Report

Steps

<Menu
  items={[
    render => render(3, (Component, props) => <Component {...props} />)
  ]}
/>

Expected Result

Custom render function is used (as described in #355), no warning

Actual Result

Custom render function is used as expected,
There is warning in console: 💣

Warning: Failed prop type: Invalid prop `items[0]` supplied to `Menu`.
    in Menu (created by App)
    in App
    in ThemeProvider (created by FelaTheme)
    in Provider (created by FelaTheme)
    in FelaTheme (created by ProviderConsumer)
    in ProviderConsumer (created by Provider)
    in Provider

Version

0.15.0

Testcase

https://codesandbox.io/s/6jmvkyyz9w