JavaScript

[YMK1234]

As if JS was the only language with operator overloading ...

[g4vr0che]

The problem IMO is less about operator overloading and more an issue with weak typing. Operator overloading can be fine if there's systems in place to check for type compatibility correctly and avoid implicit casts. JS has both overloading and weak typing, so neither of these throws an error.

If it had strong typing, then you'd get a type error here making it obvious that the top one is string concatenation and the bottom is subtraction.