Each member of the union type (...) has signatures, but none of those signatures are compatible

[molten pumice]

https://tsplay.dev/N5VO0m

[burnt radish]

If you have a variable v of type T, where T is a union, and you want to call v v(), your call to v must be compatible with all options in the union

if each type has a different call signature, then you cannot call them all with the same call format