Array prototype extensions fail circularly with `...args: T[]`, but not `args: T[]`

🔎 Search Terms

Typescript array prototype extension spread rest variadic parameter circular failure TS2310 version 5.4.3

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about circular compilation failures

I've added two playground links; the first works, the second fails. The only difference between the snippets is receiving an array T[] as a spread argument vs a single argument.

⏯ Playground Link

Working: https://www.typescriptlang.org/play?#code/PTAEBUAsEsGdQO4HsBOBrWAuAUAYyQHawAuoBApggLLnGRIAm8AvKAN7ahegCGDDAHnAA+ABR04mCAG0AugBpQANx4AbAK7ksM2QEop4dqAmwAdAAd1sSKNN2VGrboDcoFLXUoCytZtjSABllXAF9sEOdsYgBPc3JQADlKAEEUFB5omjpGFmNY8iQAMzJKLPomSOgCYnIUQp5ceNT06KFhUHIADxqCJkSUtIyynPYI7GwAeQAjACtyXGJTBnJCqvIABRQkOJQY0WaMiy3iJBi4xQByPgYLxTYOgnUAW1qeKdVyKXrVWHJFBBQ0GIbw+UmIKE0igcmikFGotHKZmuoBCLnG+CIpCe0WaUhIgIIAHM5KBWHJItjmqZrqJpKArlNcLd6ctCsyLoSYBdQHpInhCLAkB9TKokITRPdKWkUS4gA

Failing: https://www.typescriptlang.org/play?#code/PTAEBUAsEsGdQGYENoBtYC4BQBjA9gHawAuoBApgO4Cy5xkeAJvALygDeWo3oSjjAHnAA+ABT04GCAG0AugBpQAOhUA3JKgCu5TDNkBKKeA6gJsJQAdNsSKJVL1WnfoDcoAE51N7gqEfbYaQAGWTcAXywwlyxiAE8LclAAOSoAQXd3JFjaeiZWU3jyPAQyKhyGZmjoAmJyd2QcRPTM2KFhUHIAD1qCZmS0jKzyvI4orCwAeQAjACtyHGIlRnIEavIABXc8BPc40Wasyy3iPDiExQByPkYLxXYOgk0AWzqkKdRyKWR0ckVKd2gxDeHykxHc2kU-k+pRodAq5muoDCrnG+CIpCesWaUhIAIIAHM5KA2HJopjmkprqIrlMcLdQBdlgh6Rd8TALijcIRYHgPkpUHh8aJ7uSMkjXEA

💻 Code

Failing:

const newMethods = {
    add<T>(this: T[], ...values: T[]): T { this.push(...values); return values[0]; }
};
type NewArrayMethods = typeof newMethods;
interface Array<T> extends NewArrayMethods {};

Object.defineProperty(Array.prototype, 'add', { enumerable: false, writable: true, value: newMethods.add });

const myArr: string[] = [];
myArr.add('abc', 'def', 'ghi');

console.log({ myArr });

Working (only difference is ...values: T[] is now values: T[] - without ...):

const newMethods = {
    add<T>(this: T[], values: T[]): T { this.push(...values); return values[0]; }
};
type NewArrayMethods = typeof newMethods;
interface Array<T> extends NewArrayMethods {};

Object.defineProperty(Array.prototype, 'add', { enumerable: false, writable: true, value: newMethods.add });

const myArr: string[] = [];
myArr.add([ 'abc', 'def', 'ghi' ]);

console.log({ myArr });

🙁 Actual behavior

Example using ...values: T[] fails to compile!

🙂 Expected behavior

Both examples should compile successfully.

Additional information about the issue

No response

Beginnen Sie mit dem fehlschlagenden TypeScript Playground-Link und vergleichen Sie ihn anhand der TypeScript-5.4.3-Reproduktion im Issue mit dem funktionierenden Link. Verfolgen Sie, warum der Spread-Rest-Parameter TS2310 erzeugt, der Array-Parameter jedoch nicht; abgeschlossen ist die Aufgabe, wenn beide gezeigten Beispiele erfolgreich ohne den Zirkularitätsfehler kompiliert werden.