Nested union variant not infered correctly

[jpqx]

🔎 Search Terms

"union type inference", "union type variant inference"

🕗 Version & Regression Information

This is the behavior in every version I tried (all the way back to 3.3.3333 in playground), and I reviewed the FAQ for entries about "common-bugs-that-arent-bugs".

⏯ Playground Link

https://www.typescriptlang.org/play/?#code/C4TwDgpgBAMg9gYwIYBsCCBXYALAysJYaAXgCgoKoAfKAbyiS2wgDtgBLZIgEwC4oAZqgDOEADRQA7knYcWAcwBicAE4AlCAFs4RTDlYcuEPlABGcOCghIWUAL7lKNeo31tOhY-2AqM4qCxImhD8wj7sCvakpKCQUBraukz4nlBklNR0DEwGHjz8QiiiURnO2W6GniY+fhKBwaHhkQ4x4NAAsjIsengERGmOFGWuzO5GJoXFDqVZI7nj3r7QdlAAZFAAFIMZmfQoiKj8AKIAHj5ICMAAPPDI6Ml9-i45Y1WLfvYAfBIqWjoh8T+SRwKX60x2Qyy+zu-FuqB6oP8v0SANO50uVwS-wRjwkzwqeS8UBqy0+JUoAEpogB6alQNAsHTMFRQbgQAQRWTsOC2ASqKCdCI41IbYRBaCxfwAKwwYSg2l+UAAbhAVOZinyVJpCBJJLJsHAsFBZRF5FAAAZolQXYDmikSUxGsXBKCqlSqAB0pGpACpWnFBd0Hql0k5Zi9KvlBCJltthhHCdUlvY1pttjM9gcUPx8aNI0SSXVxY0VKb7D8gQDc-M3sSlkWGlAwqXmuSIWVoYdwwSFnXagFi02mma7BWUTnynnEwUYynwe2oVmJ3NXlHJv5pFyFMp1JWejWo+ZLNZbKOoMj-suE73CwPG82yyt51AqT7qdEBBgWJdubZhCBv2FIhhA2bUhWDIh+EDICIApKCuhguhtnYARNjAoMQUeD0V3zbg1nWABCdCYI9TsUGw68qnw+UEIgiBSKzD1NzkJRVCxYEp3GCkkIhChfmADAVFsWh014j1xOIuixFEiEyKvHta1veoAUkzDPA9C8iA9ZSU1pKAAAlVWgABJKB5AgYAoAQOBNDAdgrFdFR3RZc0AAV3UgFRQCgAByZSfNZOAIGEAIdFdE52DlHliTaXz2IgGCfK9Xj7AAbm2FoMj0tAijgCQULMJlJwPYwJBEOBXRYYRBOgZSQu1YAEGwaIMn4wTbFU3pPHShwgA

💻 Code

type LocalAuthState =
    | { authenticated: false, waitingForRemoteAuthenticated: boolean }
    | { authenticated: true, name: string }

type RemoteAuthState =
    | { authenticated: false }
    | { authenticated: true, name: string }

type MainAuthState =
    | { authenticated: false }
    | { authenticated: true } & (
        | { local: Extract<LocalAuthState, { authenticated: true }>, remote: RemoteAuthState }
        | { local: LocalAuthState, remote: Extract<RemoteAuthState, { authenticated: true }> }
    )

// Another definition for MainAuthState (same type, just more verbose format, without using `Extract`), but same error.
/*
type MainAuthState =
    | { authenticated: false }
    | { authenticated: true } & (
        | { local: { authenticated: true, name: string }, remote: { authenticated: true, name: string } }
        | { local: { authenticated: true, name: string }, remote: { authenticated: false } }
        | { local: { authenticated: false, waitingForRemoteAuthenticated: boolean }, remote: { authenticated: true, name: string } }
    )
*/

function syncAuthStates(mainAuthState: MainAuthState): MainAuthState {
    if (mainAuthState.authenticated && !mainAuthState.local.authenticated && mainAuthState.local.waitingForRemoteAuthenticated) {
        return {
            ...mainAuthState,
            local: { authenticated: true, name: mainAuthState.remote.name } // Here I get compile error `Property 'name' does not exist on type 'RemoteAuthState'.
        };
    }

    // Also, if both authenticated, ensure names match

    return mainAuthState;
}

🙁 Actual behavior

I get compile error: Property 'name' does not exist on type 'RemoteAuthState'..

🙂 Expected behavior

If the condition mainAuthState.authenticated && !mainAuthState.local.authenticated is met, TS should infer that mainAuthState.remote is of type { authenticated: true, name: string }.

[jpqx]

I updated the title to "Nested ...". After posting, I thought maybe it has to do with checking for nested fields of the union. Then I found this issue from 2017, I think it's the same topic. Shall we mark this one as a duplicate of that?

[RyanCavanaugh]

Yeah, narrowing currently can't affect "sibling" properties unless it's a literal discriminant

[typescript-bot]

This issue has been marked as "Duplicate" and has seen no recent activity. It has been automatically closed for house-keeping purposes.