syntax_data: {"ast_node_type":"variable","tokens":[{"end":39,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:             let n = self.opaques.len();
context_before:             let mode = std::mem::replace(&mut self.mode, CollectionMode::Taits);
context_after:             super::sig_types::walk_types(self.tcx, define, self);