missing-private-fields.ts

// Creates a class object which is missing one of its private fields it's
// supposed to have, leading to issues with `#x in instance`.

class Abc {
    static #createWithAge = false
    static #instance?: Abc

    static create(withAge: boolean) {
        Abc.#createWithAge = withAge

        try {
            return new Abc()
        } catch {
            return Abc.#instance!
        }
    }

    #name = "sakawi"

    _ = ((Abc.#instance = this), void 0)

    #age =
        Abc.#createWithAge ? 48 : (
            ((): never => {
                throw new Error()
            })()
        )

    private constructor() {}

    hasName() {
        return #name in this
    }

    hasAge() {
        return #age in this
    }

    getName() {
        return this.#name
    }

    getAge() {
        return this.#age
    }

    setName(value: string) {
        this.#name = value
    }

    setAge(value: number) {
        this.#age = value
    }
}

const withoutAge = Abc.create(false)
const withAge = Abc.create(true)

export {}