It really depends on the domain. E.g. I wrote a parser and copilot was tremendously useful, presumably because there are a gazillion examples on the internet.
Another case where it saved me literally hours was spawning a subprocess in C++ and capturing stdin/out. It didn’t get it 100% right but it saved me so much time looking up how to do it and the names of functions etc.
Today I’m trying to write a custom image format, and it is pretty useless for that task, presumably because nobody else has done it before.
Me too, but this was C++ where there isn’t a strong culture of making high quality libraries available for everything (because it doesn’t have a proper package manager, at least until very recently), so you do end up having to reinvent the wheel a fair bit.
And sometimes you just need things a bit different to what other people have done. So even though there are a gazillion expression parsers out there (so the LLM understood it pretty well) there are hardly any that support 64-bit integers. But that’s a small enough difference that it can deal with it.