If you tried GPT4, you probably understood it's not about feeding all the code in the world. GPT4 analyzes and "understands" your code and will answer based on this. Clearly, it will read the variable names and make deductions based on this. It will actually read the comments, the function names and make decisions based on this. And it knows the rules of the language. I mean, I'm writing this because this is what I've witnessed since the time I spent playing with it.

The problem I've seen is that, maybe like the author has been writing, it's making sh*t up. That's not untrue, sometimes I didn't give it all dependent classes and it tried to think sometimes correctly, sometimes incorrectly what those were (such as method signatures, instance members, etc.) I wish it would have asked me some details rather than trying to figure things out. The guys at OpenAI have still a lot to do, but the current status is very impressive