respect createElement return type for JSX

[LongTengDao]

🔍 Search Terms

JSX createElement

✅ Viability Checklist

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• This isn't a request to add a new utility type: https://github.com/microsoft/TypeScript/wiki/No-New-Utility-Types
• This feature would agree with the rest of our Design Goals: https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals

⭐ Suggestion

respect type information for:

declare namespace React {
    function createElement<Ret extends JSX.Element, Props extends object> (
        component: (props: Props) => Ret,
        props: Props,
    ): Ret;
    namespace JSX {
        interface Element { o: null }
    }
}

function Component (x: {}) { return { o: null, a: null }; }

<Component /> satisfies { o: null, a: null };

📃 Motivating Example

to support framework write limit for children types, i.e. <ul> can only contain <li>;

even algebraic effect handler programming for required provide/inject context.

💻 Use Cases

1. What do you want to use this for?
2. What shortcomings exist with current approaches?
3. What workarounds are you using in the meantime?

[MartinJohns]

Duplicate of #21699.