type ActionType = ActionTypeA | ActionTypeB | ActionTypeC;


type ActionHandlerType<
  PayloadType extends Object,
  ActionParamType extends ActionType,
> = {
  isTypeOfAction: (action: ActionType) => action is ActionParamType;
  handleAction: (action?: ActionParamType, payload?: PayloadType) => void;
};

Considering the above example. I want to restructure the ActionHandlerType type in such a way that I don’t need to pass the second generic ActionParamType and the ‘action’ parameter type in the handleAction function should automatically infer from the return type (one of ActionType) from the isTypeOfAction.

Something like..

type PayloadType = { payload: 'test'}

// Not passing the second param.
export function someFunction(
): ActionHandlerType<PayloadType> {

  return {
    isTypeOfAction,
    handleAction,
  };

  function isTypeOfAction(action: ActionType): action is ActionTypeA {
    return action.type === 'A';
  }

  // It should automatically infer ActionTypeA from the isTypeOfAction function return type.
  function handleAction(action: ActionTypeA, record: {}): void {
    //..
  }
}