Storybook build fails mysteriously

[cinnamennen]

Describe the bug
Whenever I try to build storybook, I simply get

ERR! Unexpected token (18:4)
ERR! | try {
ERR! |     // @ts-ignore
ERR! |     default.Header.displayName = "default.Header";
ERR! |     // @ts-ignore
ERR! |     default.Header.__docgenInfo = { "description": "", "displayName": "default.Header", "props": {} };

To Reproduce
I've created https://github.com/cinnamennen/storybook-broken-example as a minimal example of what's going on. I suspect that the subcomponent doesn't play nice with the docgen, but don't have any concrete proof.

Expected behavior
The build to succeed.

System

Environment Info:

  System:
    OS: macOS 11.1
    CPU: (12) x64 Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
  Binaries:
    Node: 14.15.3 - ~/.nvm/versions/node/v14.15.3/bin/node
    npm: 6.14.9 - ~/.nvm/versions/node/v14.15.3/bin/npm
  Browsers:
    Chrome: 88.0.4324.96
    Firefox: 72.0.2
    Safari: 14.0.2
  npmPackages:
    @storybook/addon-actions: 6.1.15 => 6.1.15
    @storybook/addon-essentials: 6.1.15 => 6.1.15
    @storybook/addon-knobs: 6.1.15 => 6.1.15
    @storybook/addon-links: 6.1.15 => 6.1.15
    @storybook/core: 6.1.15 => 6.1.15
    @storybook/node-logger: 6.1.15 => 6.1.15
    @storybook/preset-create-react-app: 3.1.5 => 3.1.5
    @storybook/preset-typescript: 3.0.0 => 3.0.0
    @storybook/react: 6.1.15 => 6.1.15
    ```

[shilman]

Closing as a duplicate of #9556

Possible workarounds:

• Use named exports instead of default exports, e.g. export class Modal ...
• Turn off react-docgen-typescript in main.js:

module.exports = {
  typescript: {
    reactDocgen: "react-docgen",
  },
};

I've confirmed both workarounds.