Inability to use typeof on an ES private property

Bug Report

🔎 Search Terms

• typeof
• private

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about private and typeof

⏯ Playground Link

Playground link with relevant code

💻 Code

class Example {
  #privateProp = 'hello';

  constructor() {
    const p: typeof this.#privateProp = 'world';
    const p2: Example['#privateProp'] = 'world';
  }
}

The example is kept short for reproduction, but in practice this is more for cases where you would want to use keyof this.#someProperty and similar constructs (since here the type could just be inferred).

🙁 Actual behavior

Specifying a type using const name: typeof this.#anESprivateProperty is not possible.

For p, the error is that an identifier is expected (because it’s a PrivateIdentifier and not an Identifier from the compiler’s pov?).

For p2, the error is that the property does not exist on the type, which is logical when done from “outside” the class where the property should not be visible.

🙂 Expected behavior

Having the ability to use typeof on an ES private property from “inside” the class itself where that property is visible, e.g. like in the example code above.

[RyanCavanaugh]

For now I would not support indexed access lookup (const p: C["#p"] or variants thereof); it’s very messy. Accessing the type of a private property from outside the class is a huge code smell since it breaks under declaration emit, and should really be avoided.

typeof this.#p (from inside the class) should be the only way to get at it.

[dnalborczyk]

@RyanCavanaugh Do we need to support this syntax?

const p2: Example['#privateProp'] = 'world';

already in use with public properties.

class Example {
  #privateProp = 'hello';

  ['#publicProp']: number
}

type Prop = Example['#publicProp']

https://www.typescriptlang.org/play?#code/MYGwhgzhAECiAeYC2AHEBTaBvAsAKGmgGIUAnASwDcwAXdABVIHsVoBeaAcgAt0QQmnANz58hANqcSAVwBGIcsEYtOAXQBc0AHbSks9KXwBfUXhoBPFJmWsOCZGnSSZ8xTbVA