Empty tuple not inferred from rest parameters of a generic array type

[fasttime]

TypeScript Version: 3.9.3

Search Terms: generic rest parameters empty tuple

Code

declare function requireAtLeast1Arg<T extends any[]>(...args: T extends [] ? never : T);

requireAtLeast1Arg();

Expected behavior: The code above should trigger the infamous compiler error 2345 as it used to do in TypeScript <= 3.8.

Actual behavior: The code compiles in current TypeScript 3.9.3.

I couldn't find a release note about the new behavior, so I'm assuming this was a kind of unintended breaking change.

Playground Link:

• Using TypeScript 3.8.3
• Using TypeScript 3.9.2

[ahejlsberg]

This is an intended change, see #35438. A better way to require at least one argument is

declare function requireAtLeast1Arg<T extends [any, ...any[]]>(...args: T): void;

requireAtLeast1Arg();  // Error
requireAtLeast1Arg(42);
requireAtLeast1Arg(42, 'hello');

This also produces a much better error message.

[fasttime]

I see, thanks. Missed that change.