syntax_data: {"ast_node_type":"function","tokens":[{"end":61,"kind":"keyword","start":0,"text":"pub"}]}
source_snippet:     pub fn typeck_root_def_id(self, def_id: DefId) -> DefId {
context_before:     /// fetching the `typeck` the enclosing fn item.
context_after:         let mut def_id = def_id;