String(number) does not return `${number}` type

Bug Report

🔎 Search Terms

string constructor number type template literal

🕗 Version & Regression Information

4.2.3

⏯ Playground Link

Playground link with relevant code

💻 Code

const stringNumber: `${number}` = String(123)

🙁 Actual behavior

Error: Type 'string' is not assignable to type '${number}'.(2322)

🙂 Expected behavior

No error.

Why

String, according to ES (String(value), and ToString(argument)), uses toString method on passed in values, so ideally the fix should include only changes on Number interface, but currently it's String's def does not care about toString, so these two signature would have to be generic:

// lib.es5.d.ts
interface StringConstructor {
    new(value?: any): String;
    (value?: any): string;
}

And this one would need to be generic as well as the type of returned string would depend on the radix.

// lib.es5.d.ts
interface Number {
    toString(radix?: number): string;
}

This approach would make String easily extensible and compatible with template literal types, but I'm not sure how drastic of a change it is.

Most likely would be related to https://github.com/microsoft/TypeScript/issues/42996

Inizia riproducendo l'assegnazione nel TypeScript Playground collegato, poi esamina le definizioni di StringConstructor e Number in lib.es5.d.ts e leggi la issue correlata #42996. Il lavoro è completato quando si raggiunge un comportamento type-safe concordato per String(123) e Number.toString con i tipi di literal template, supportato da test appropriati del compilatore.