Getting a setter-only property is typed as the setter's parameter's type instead of undefined

🔎 Search Terms

setter only

🕗 Version & Regression Information

• This is the behavior in every version I tried, from 5.7.3 down to 3.3.3333

⏯ Playground Link

https://www.typescriptlang.org/play/?ts=5.7.3#code/MYewdgzgLgBANgQzAcwK4OQUxgXhgbwCgYYJNZhUAnKzMKACjAQFtMAuUqKgSxQEoCxEjCgALHhAB0cEMikAHVBDFNWmfgG5hAXwA0w2ck4BtALowEELrxTmDO7YUQp0WKZRp1YeAEQAxACVfJ1BIClx4JDQMTA9qWnptIA

💻 Code

const language = {
  set current(name: string) {
    this.log.push(name);
  },
  log: [] as string[],
};

language.current = "FR";

const c = language.current;

🙁 Actual behavior

Variable c is said to be of type string.

🙂 Expected behavior

As clearly stated here, it should be undefined.

Note that current is not defined, and any attempts to access it will result in undefined.

Additional information about the issue

No response

Inizia con l’esempio collegato di TypeScript Playground e conferma che la lettura della proprietà con il solo setter sia tipizzata come string anziché undefined. Segui la logica del compilatore che determina il tipo di una lettura di accessor, quindi aggiungi la coverage per questo caso di setter in un object literal e verifica che il tipo inferito sia undefined senza introdurre regressioni nel comportamento valido di getter/setter.