type T = {
    foo: string
string
    bar: number
    baz: boolean
}
type A = `{ keyof T }_changed`

type WatchCallback = (newValue: any) => void
type WatchEventId = `${string & keyof Type}_changed`
type WatchEvent<Type> = {
    on(eventName: `${string & keyof Type}_changed`, callback: WatchCallback): void
}
type WatchedObject<Type> = Type & WatchEvent<Type>
function makeWatchedObject<Type>(obj: Type): WatchedObject<Type> {
    const watched = obj as WatchedObject<Type>
    watched.on = (eventName: string, callback) => {
        
    }
    return watched
}

type WrapWithNewlines<T extends string> = `\n${T}\n`

type NumericString<T extends string> = `${T}` extends `${number}` ? T : never
type Absolute<T extends number | string> = `${T}` extends `-${infer R}` ? NumericString<R> : NumericString<`${T}`>