And in fact, I think I saw a paper / blog post that showed exactly this, and then... nothing. For the last few years, the tech world became crazy with code generation, with forks of VSCode hooked to LLMs worth billions of dollars and all that. But AI-based code analysis is remarkably poor. The only thing I have seen resembling this is bug report generators, which is I believe is one of the worst approach.
The idea you have, that I also had and I am sure many thousands of other people had seem so obvious, why is no one talking about it? Is there something wrong with it?
The thing is, using such a feature requires a brain between the keyboard and the chair. A "surprising" token can mean many things: a bug, but also a unique feature, anyways, something you should pay attention to. Too much "green" should also be seen as a signal. Maybe you reinvented the wheel and you should use a library instead, or maybe you failed to take into account a use case specific to your application.
Maybe such tools don't make good marketing. You need to be a competent programmer to use them. It won't help you write more lines faster. It doesn't fit the fantasy of making anyone into a programmer with no effort (hint: learning a programming language is not the hard part). It doesn't generate the busywork of AI 1 introducing bugs for AI 2 to create tickets for.