syntax_data: {"ast_node_type":"function","tokens":[{"end":46,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn diverge_cleanup(&mut self) -> DropIdx {
context_before:     /// this point. The `DropIdx` will be created if it doesn't already exist.
context_after:         // It is okay to use dummy span because the getting scope index on the topmost scope