Length not checked for spread operator in params

[JacobEvelyn]

TypeScript Version: 3.1.0-dev.20180830

Search Terms:
Spread length, Expected at least 1 arguments, but got 0 or more

Code

Porting this StackOverflow JS function into TypeScript, I got:

function *cartesian<T>(head: T[], ...tail: T[]): any {
  const remainder = tail.length > 0 ? cartesian(...tail) : [[]];
  for (let r of remainder) for (let h of head) yield [h, ...r];
}

Expected behavior:

The code compiles and works.

Actual behavior:

Expected at least 1 arguments, but got 0 or more.

Playground Link: http://www.typescriptlang.org/play/#src=function%20*cartesian%3CT%3E(head%3A%20T%5B%5D%2C%20...tail%3A%20T%5B%5D)%3A%20any%20%7B%0D%0A%20%20const%20remainder%20%3D%20tail.length%20%3E%200%20%3F%20cartesian(...tail)%20%3A%20%5B%5B%5D%5D%3B%0D%0A%20%20for%20(let%20r%20of%20remainder)%20for%20(let%20h%20of%20head)%20yield%20%5Bh%2C%20...r%5D%3B%0D%0A%7D

Related Issues:

I thought this might be #26350, but that seems slightly different. Various searches led me to #19419 and #4130, but those issues have been marked as fixed and closed.

[RyanCavanaugh]

We don't have the "range" types that would be needed to turn the length check into a resulting type narrowing. See #15480

[JacobEvelyn]

Ah interesting, I didn't realize "range" types would be required for something like this. Thanks for the info.

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.