syntax_data: {"ast_node_type":"impl","tokens":[{"end":59,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:             // This is where impl overlap checking happens:
context_before:         if let Some(impl_def_id) = impl_def_id.as_local() {
context_after:             let insert_result = sg.insert(tcx, impl_def_id.to_def_id(), overlap_mode);