You’re basically arguing that whole books aren’t copyrightable because after you filter out all the words which aren’t individually copyrightable there isn’t anything left to copyright. Which obviously doesn’t make any sense.

The tests exist as a way of determining if someone did the action of copying which is the important thing at the core of it. And in this case the facts aren’t really in dispute, it’s whether what GH is doing counts as copying.

If you had a really really good memory and remembered almost exactly how your former company implemented something and when faced with a similar problem unknowingly produced similar code. It’s iffy as to whether this is copying. Because it really probably isn’t — you’re allowed to learn from copyrighted works — but the courts aren’t omniscient and when presented with the code they very well may rule that copying was more likely than not.

But we are omniscient in this case so we don’t really need the tests. Is what GH does more like copying or learning? This isn’t something that can be determined purely from the output of the tool.

Code elements like conditionals, loops, arithmetic or Boolean expressions, assignment statements, etc. are not copyrightable, but not because they’re insignificant (like individual words in a novel), but because they’re useful articles. Copyright protects expression, not utility, which is the domain of patent law.

That's nonsense though. If we filter out the non-copyrightable parts of music we'd remove all the pitches, eighth notes, quarter notes, half notes...

We could remove the non-copyrightable parts of text works too. Just take out all the basic building blocks of language like verbs, nouns, stop words...

Individual notes, like individual words, are not copyrightable. Longer sequences, however, can be if they are original.

The problem of API copyrightability was not resolved by Google v. Oracle, the ruling was that no matter whether or not APIs are copyrightable, copying APIs is fair use (which is a concept in the USA but not in many other countries around the world).

I’d wager you’d get rid of over 90% of most codebases by removing all that.

But perhaps there could be a way to make something that automatically converts these "non-expressive elements" into copyrightable elements?

Output would probably be maddening to figure out though.