syntax_data: {"ast_node_type":"other","tokens":[{"end":51,"kind":"keyword","start":0,"text":"s.leave_ref(opt_old_mode_span);"}]}
source_snippet:                     s.leave_ref(opt_old_mode_span);
context_before:                 if let Some(s) = &mut self.rust_2024_migration {
context_after:                 }