This is what I've been noticing. For C++ and Swift, it makes pretty unhelpful suggestions. For Python, its suggestions are fine.
Swift is especially frustrating because it will hallucinate the method name and/or the argument names (since you often have to specify the argument names when calling a method).
Ah I've had it hallucinate non-existing methods in python rather often.
Or when I say I need to do something, it invents a library that conveniently happens to just do that thing and writes code to import and use it. Except there's no such library of course.
Swift is especially frustrating because it will hallucinate the method name and/or the argument names (since you often have to specify the argument names when calling a method).