I'm currently experimenting with typescript generics and I'm trying to automatically infer the type of fn, also known as P, but it doesn't seem to be working as intended.
If you want to check out the code yourself, visit this interactive Playground link
Below is a snippet of the code I'm working on:
type Callback = (...args: any[]) => any
interface Route<
T extends Callback
> {
fn: T
}
function route <
P extends Callback,
R extends Route<P>
> (pathname: string, handler: R) {
return handler.fn
}
const x = route('/hi', {fn: (name: string) => `hi ${name}`})
// ^?
My expectation was for x to have the type (name: string) => string, however, it instead returned Callback.