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Unsound calls allowed on a function coming from a deferred indexed access when intersection is involvedΒ #54824
Description
Bug Report
π Search Terms
deferred index access unsound call union intersection
π Version & Regression Information
- This is the behavior in every version I tried
β― Playground Link
Playground link with relevant code
π» Code
type A = {
type: "A";
value: string;
};
type B = {
type: "B";
value: number;
};
type Message = A | B;
export function handle<M extends Message>(callbacks: {
[K in M["type"]]: (msg: (M & { type: K })["value"]) => unknown;
}) {
window.addEventListener("message", (event) => {
const msg = event.data as M;
// should be an error because it's too permissive
callbacks[msg.type as keyof typeof callbacks](msg.value);
// one or the other must be wrong here
callbacks[msg.type as keyof typeof callbacks]("");
callbacks[msg.type as keyof typeof callbacks](100);
});
}π Actual behavior
There is no error even though it should be based on Ander's comment here. Note that the comment is about a different variant of this signature, one using Extract. Both the Extract and intersection variants are essentially the same though - one errors today and one doesn't.
π Expected behavior
I would expect to get an error here, just like in the Extract-based variant (TS playground)
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