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Remapping a tuple constraint fails to provide a contextual type for the tuple elementsΒ #52650
Description
Bug Report
π Search Terms
tuple constraint infer type parameter remapped reverse mapped contextual type
π Version & Regression Information
- This is the behavior in every version I tried
β― Playground Link
Playground link with relevant code
π» Code
type Tuple<T> = readonly [T, ...T[]];
declare function bindAll<
TTarget extends EventTarget,
TTypes extends Tuple<keyof TTarget & `on${any}`>
>(
target: TTarget,
bindings: {
[K in keyof TTypes]: {
type: TTypes[K];
listener: (
ev: Parameters<Extract<TTarget[TTypes[K]], (...args: any[]) => any>>[0]
) => void;
};
}
): void;
bindAll({} as HTMLButtonElement, [
{
type: "onclick",
listener: (event) => {
event
// ^? actual: string | Event | MouseEvent | ..., expected: MouseEvent
},
},
{
type: "onkeydown",
listener: (event) => {
event
// ^? actual: string | Event | MouseEvent | ..., expected: KeyboardEvent
},
},
]);π Actual behavior
It should be possible to provide per element types using reverse mapped types when mapping over a type parameter with a tuple constraint. It works OK when at the argument position we use [...{ [K in keyof TTypes]: { /*...*/ } }] instead of { [K in keyof TTypes]: { /*...*/ } }. That is a weird workaround though.
π Expected behavior
I would expect the contextual types to be correctly provided for each element separately, just like in the case of [...{ [K in keyof TTypes]: { /*...*/ } }] (TS playground)
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