Really nice flexible way of defining types.

& operator.ts

type QueueItem<T> =
    | { status: 'idle'; }
    | { status: 'uploading'; progress: number; }
    | { status: 'done'; url: string; file: T; }
    | { status: 'error'; error: Error; };

type QueueItem = {
    id: number;
} & (QueueItemUpload | QueueItemDone | QueueItemError);

type QueueItemUpload = {
    id: number;
    status: 'pending' | 'uploading';
    progress: number;
}

type QueueItemDone = {
    id: number;
    status: 'done';
    url: string; // download url
    file: File;
}

type QueueItemError = {
    id: number;
    status: 'error';
    error: Error;
}

const queue: QueueItem<File>[] = [{
    status: 'idle'
}, {
    status: 'uploading',
    progress: 0
}, {
    status: 'done',
    url: 'https://www.google.com',
    file: new File([], 'test')
}, {
    status: 'error',
    error: new Error('test')
}]

// can be checked like this
for (const item of queue) {
    switch (item.status) {
        case 'uploading':
            console.log(item.progress);
            break;
        case 'done':
            console.log(item.url);
            console.log(item.file);
            break;
        case 'error':
            console.log(item.error.message);
        default:
            break;
    }
}