Where they'd get training data?

Source code generation is possible due to large training set and effort put into reinforcing better outcomes.

I suspect debugging is not that straightforward to LLM'ize.

It's a non-sequential interaction - when something happens, it's not necessarily caused the problem, timeline may be shuffled. LLM would need tons of examples where something happens in debugger or logs and associate it with another abstraction.

I was debugging something in gdb recently and it was a pretty challenging bug. Out of interest I tried chatgpt, and it was hopeless - try this, add this print etc. That's not how you debug multi-threaded and async code. When I found the root cause, I was analyzing how I did it and where did I learn that specific combination of techniques, each individually well documented, but never in combination - it was learning from other people and my own experience.