[addon-docs] TS code generation for a story doesn't render if a JSX element is typed

Describe the bug Typing a JSX element will prevent the documentation to render the story code.

To Reproduce

https://github.com/lgraziani2712/sb-8827

Steps to reproduce the behavior:

1. Create a story in a TSX file.
2. Type a generic JSX element.
3. Open storybook and see the error.

Expected behavior To render the story code the same way as if the JSX element wouldn’t have been typed.

Code snippets

// Wrapper

interface Props<P> {
  initial?: P;
  children(val: P): JSX.Element;
}

function Wrapper<P>({ initial, children }: Props<P>) {
  const [state, setState] = useState(initial || null);

  return children({state, setState });
}

// Story
import Component, { ComponentProps } from '.';

export const someStory = () => (
  // Since I'm not setting a default value, TS doesn't know the type.
  // Typing the element makes TS stop complaining but the story code doesn't render.
  // If I delete the typing, the code starts rendering but TS complains.
  <Wrapper<ComponentProps>>
    {(props) => (<Component {...props} />)}
  </Wrapper>
);

System:

  System:
    OS: Linux 4.15 Ubuntu 18.04.3 LTS (Bionic Beaver)
    CPU: (4) x64 Intel(R) Core(TM) i7-4510U CPU @ 2.00GHz
  Binaries:
    Node: 10.16.0 - ~/.nvm/versions/node/v10.16.0/bin/node
    Yarn: 1.19.1 - /usr/bin/yarn
    npm: 6.9.0 - ~/.nvm/versions/node/v10.16.0/bin/npm
  Browsers:
    Chrome: 78.0.3904.97
    Firefox: 71.0b8
  npmPackages:
    @storybook/addon-actions: 5.2.5 => 5.2.5 
    @storybook/addon-docs: 5.2.5 => 5.2.5 
    @storybook/addon-knobs: 5.2.5 => 5.2.5 
    @storybook/preset-typescript: 1.1.0 => 1.1.0 
    @storybook/react: 5.2.5 => 5.2.5

[shilman]

We’ve just released zero-config typescript support in 6.0-beta. Please upgrade and test it!

• Release 6.0.0-beta.12+
• Migration instructions
• Updated docs

Thanks for your help and support getting this stable for release!

[lgraziani2712]

I can confirm this is partially fixed in v6-beta (I’m using beta-25). It’s partially fixed because although it renders the code now, most of the code is being grayed out:

Specifying the generic:

Without specifying it: