The main problem that prevented us from reusing the ASTContext was that we weren’t remapping the `LocToResolve` in the temporary buffer that only contains the re-parsed function back to the original buffer. Thus `NodeFinder` couldn’t find the node that we want to get cursor info for.
Getting AST reuse to work for top-level items is harder because it currently heavily relies on the `HasCodeCompletion` state being set on the parser result. I’ll try that in a follow-up PR.
rdar://103251263
a5f85ee10c