Statecharts

or can we use assign in another way that makes it easier for typescript?

on: {
  SOME_EVENT: {
    // just like normal assign
    assign: { count: 0 },
    assign: { count: (context) => context.count + 1 },
    assign: (context) => ({ count: context.count + 1 }),
    assign: [
      { count: 0 },
      { otherCount: (context) => context.count + 10 }
    ]
  }
}

export type SpecificEvent<
  X extends XEventObject,
  T extends X["type"]
> = X extends Event<T, infer U> ? Event<T, U> : never
type Event = 
    { type: "AUTH.LOGGED_IN"; token?: Token } 
  | { type: "AUTH.LOGGED_OUT" }
export type AuthEvent<T extends Event["type"]> =
  SpecificEvent<Event, T>
assign((ctx, ev:  AuthEvent<"AUTH.LOGGED_IN">) => ({token: ev.token}))

export type Event<T = string, D = {}> = { type: T } & D

ActionFunction<PanContext, Event<"PARENT_DATA", PARENT_DATA>>' is not assignable to type 'ActionFunction<PanContext, Events>