Bug Report

🔎 Search Terms

Number object
number primitive
binary operator <
ts2365
TypeScript 5.0-dev

🕗 Version & Regression Information

• This changed between versions 4.9.5 and 5.0.0-dev.20230210

⏯ Playground Link

Playground link with relevant code

💻 Code

const a = new Number(1); const b = 2; console.log(a < b)

🙁 Actual behavior

In TypeScript 5.0.0-dev.20230210, it reports error ts2365, but in TypeScript 4.9.5, it doesn't.

🙂 Expected behavior

I'm not sure whether this is a bug of 5.0-dev or a breaking change that which will be introduced in 5.0. If it's a breaking change by design, maybe it should be included in #51362? If not, it should not report any error since it's valid JavaScript code.

Actually, I run into this error when I try to extend Number.prototype for utility:

interface Number { [Symbol.iterator](): Generator<number>; } Number.prototype[Symbol.iterator] = function*() { for (let i = 0; i < this; i++) yield i; // ^^^^^^^^ ts2365 } for (const i of 10) console.log(i);