Is copilot not gpt3.5 now (before I think it was gpt3)? It performs well even on languages it doesn’t even know. I write weird languages for fun and in VScode it quickly starts giving elaborate slabs of code for languages it only knows from my personal projects. I don’t use regular syntax generally (we have enough of those); my last abomination was a Unicode char apl like and it picked it up pretty fast.
They announced Copilot X as using GPT-4 but its unclear to me whether it's just the new features (the chat, etc.) or the code completion that will move to GPT-4 as well.
If it isn't, then Copilot has previously used OpenAI Codex (which is based on GPT-3)
It goes beyond languages. Yesterday I was editing a markdown file that was to become a post on a static site with movies. After I entered the title of a Taiwanese movie from the eighties, I jumped to the frontmatter to add some metadata about it. It autocompleted the director even before I typed the first letter of his name.
It was so unexpected for me that I had to pause for a second to process what happened.