The spread syntax is native to JavaScript. TS wouldn't complain about the first case, because as the parent said, it is a valid operation. TS only complains ab

The spread syntax is native to JavaScript. TS wouldn't complain about the first case, because as the parent said, it is a valid operation. TS only complains about valid operations if there's some potential mistake due to ambiguity, usually when relying on to strong conversions such as adding a string and an array together or some other nonsense.