Stream types have problems being inferred?

[thequailman]

When I define a stream type before using it, I regularly need to typecast the value when using stream():

interface MyType {
    [index: string]: string | undefined,
}

let s: Stream<MyType>;

s = Stream({
    hello: "world",
});

This will error, saying it's not assignable to MyType. Typecasting the object (adding } as MyType inside the stream) fixes it.

This works though:

interface MyType {
    [index: string]: string | undefined,
}

const s: Stream<MyType> = Stream({
    hello: "world",
});

This may be a typescript quirk that I'm not aware of. I'm using TypeScript 4.9.5.