Implementation signatures that do not contain all overloaded signatures are allowed in class definitions

🔎 Search Terms

implementation contain overloaded class member

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about overloading class member functions

⏯ Playground Link

https://www.typescriptlang.org/play?ts=5.2.2#code/FAYwNghgzlAEDCwDexZtgMwPZYBSwgH5YAuWAOwFcBbAIwFMAnWASlNgDcsBLAEwG5U6bHgLsqdJgBpYtcTQbM2ZLn0HpMOfBHmTGM2sTITFrdqt5C0KDRpBZyULGHoA6MFgDm+AC4BPAAd6LAwxFn5YAHpI2H8gkLFuOBMmK1gAX2BM4HJ6AHcEXBZXESKIqJiAxm5yHzgAIkpyXnoMGvpeeuAgA

💻 Code

class C
{
    foo( a? : number ) : void;
    foo( a : number, b : number ) : void;
    foo( a : number, b? : number ) : void
    {
        console.log( typeof a ); // typeof a is number
    }
}

new C().foo();  // prints "undefined"

🙁 Actual behavior

The compilation succeeded.

The type of argument "a" in function foo is number but prints "undefined" which is wrong.

Because the implementation signature of foo does not include all overload signatures, so compilation should fail.

🙂 Expected behavior

The compilation should fail.

Additional information about the issue

This bug is only reproduced with class member functions.

Inizia con la riproduzione collegata in TypeScript Playground e conferma che gli overload dei membri della classe vengono compilati nonostante la firma di implementazione ometta il caso senza argomenti. Traccia il percorso di verifica degli overload dei membri della classe, aggiungi un test di regressione per questo esempio e verifica che la compilazione ora fallisca come previsto.