It can't? I could've sworn I've seen (cherry-picked) examples of it doing exactly that, when prompted. It even explains what the bug is and why the fix works.
Those are cherry picked, and most importantly, all of the examples where it can fix a bug are examples where it's working with a stack trace, or with an extremely small section of code (<200 lines). At what point will it be able to fix a bug in a 20,000 line codebase, with only "When the user does X, Y unintended consequence happens" to go off of?
It's obvious how an expert at regurgitating StackOverflow would be able to correct an NPE or an off-by-one error when given the exact line of code that error is on. Going any deeper, and actually being able to find a bug, requires understanding of the codebase as a whole and the ability to map the code to what the code actually does in real life. GPT has shown none of this.
"But it will get better over time" arguments fail for this because the thing that's needed is a fundamentally new ability, not just "the same but better." Understanding a codebase is a different thing from regurgitating StackOverflow. It's the same thing as saying in 1980, "We have bipedal robots that can hobble, so if we just improve on that enough we'll eventually have bipedal robots that beat humans at football."
It can't? I could've sworn I've seen (cherry-picked) examples of it doing exactly that, when prompted. It even explains what the bug is and why the fix works.