Remapping a tuple constraint fails to provide a contextual type for the tuple elements

[Andarist]

Bug Report

🔎 Search Terms

tuple constraint infer type parameter remapped reverse mapped contextual type

🕗 Version & Regression Information

• This is the behavior in every version I tried

⏯ Playground Link

Playground link with relevant code

💻 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
    },
  },
]);

🙁 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.

🙂 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)