Fix Type to solve issue found in #36008

[Josehower]

Bug

when using styled-components following the official integration example

It seems the DocumentInitialProps types are not right (i.e when a fragment is used)

Class static side 'typeof MyDocument' incorrectly extends base class static side 'typeof Document'.
  The types returned by 'getInitialProps(...)' are incompatible between these types.
    Type 'Promise<{ styles: Element; html: string; head?: (Element | null)[] | undefined; }>' is not assignable to type 'Promise<DocumentInitialProps>'.
      Type '{ styles: JSX.Element; html: string; head?: (JSX.Element | null)[] | undefined; }' is not assignable to type 'DocumentInitialProps'.
        Type '{ styles: JSX.Element; html: string; head?: (JSX.Element | null)[] | undefined; }' is not assignable to type '{ styles?: ReactElement<any, string | JSXElementConstructor<any>>[] | ReactFragment | undefined; }'.
          Types of property 'styles' are incompatible.
            Type 'Element' is not assignable to type 'ReactElement<any, string | JSXElementConstructor<any>>[] | ReactFragment | undefined'.

The issue is documented here #36008

• Related issues linked using fixes Custom _document file example for styled-components throws a TS bug after updating @types/react to ^18.0.0 #36008
• I have implemented this patch successfully to update a portfolio project into latest next.js version

In advance thanks for your attention.

Good energy 👍👍👍👍

[timneutkens]

Can you add a test for this change?

[Josehower]

Sure I would be open to creating that, Just I have never created a test for a type. Can you maybe give some hints on where to start and what is the workflow for tests in Next.js?

added

[ijjk]

Hi, updated type was landed in another PR so landing test here, thanks for looking into this!