Bug: [Typescript] event target doesn't get restricted to declared state

[BrandonTing]

XState version

XState version 5

Description

I created the following state machine. However, when I tried declaring a non-existant state Non exist state, no type error is generated. (Refer to code snippet)

import { setup } from "xstate";

const loginMachine = setup({
    types: {
        context: {} as { userId: string, name: string },
        events: {} as
            | { type: "Login" }
            | { type: "Log out" }
            | { type: "Test" },
    },
}).createMachine({
    context: {
        userId: "",
        name: "",
    },
    id: "Simple Login",
    initial: "Guest",
    states: {
        "Guest": {
            on: {
                "Test": {
                    // @ts-expect-error
                    target: "Non exist state"
                },
                Login: {
                    target: "Login Success"
                }
            },
        },
        "Login Success": {
            on: {
                "Log out": {
                    target: "Guest"
                }
            }
        },
    },
});

export default loginMachine

Expected result

Typescript error to be shown for target: "Non exist state"

Actual result

No type error shown

Reproduction

https://stackblitz.com/edit/github-4b6ck8

Additional context

No response

[davidkpiano]

This is currently as designed (i.e., not implemented yet).

[BrandonTing]

Hi David,

Thanks for clarification! I believe this will improve DX a ton. Is this feature on the roadmap? Really appreciated.

[davidkpiano]

No problem! That would be a question for @Andarist to see if this is even possible.