microsoft / microsoft/TypeScript
Issue with 'this' Parameter and JSX Component Generics
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Since Aug 18, 2023.
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Description
🔎 Search Terms
"jsx component with this", "jsx component ThisParameterType"
🕗 Version & Regression Information
- This is the behavior in every version I tried, and I reviewed the FAQ for entries about JSX
⏯ Playground Link
💻 Code
declare namespace JSX {
type LibraryManagedAttributes<C, P> = ThisParameterType<C>;
interface IntrinsicElements {
div: {};
}
}
function Test<T>(this: { value: T }) {
return <div>{ this.value }</div>
}
<Test<number> value={5} /> // value is unknown
🙁 Actual behavior
TypeScript is incorrectly inferring props types for JSX functional components with generic templates when props are derived from the 'this' parameter.
Even when explicitly typed as <number>, the Test component still exhibits the issue where the type of value remains unknown.
🙂 Expected behavior
It should infer the type from the passed data or at least accept that you explicitly type it with <Test<number> ...
Additional information about the issue
If you define a separate variable and assign the component with <Test<number>>, the value prop's type gets correctly inferred as number.
const TypedTest = Test<number>;
<TypedTest value={5} /> // value is number
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Assessment
This issue has not been assessed yet.