I...did say that it doesn't have a full semantic understanding of your code. Copilot uses tree-sitter under the covers to be able to figure out several things t

I...did say that it doesn't have a full semantic understanding of your code. Copilot uses tree-sitter under the covers to be able to figure out several things that you can get by analyzing syntax alone, which is actually quite far. It lets you identify what kinds of declarations (e.g., a type) and what kind of expressions (e.g., pattern matching on that type) exist, provided there's a grammar for it, and then lets that influence the suggested code. This isn't perfect because indeed, you need a full language service to actually understand things, especially in resolving ambiguities in symbols (like shadowing in some languages), but, like I said...it's good enough.