syntax_data: {"ast_node_type":"variable","tokens":[{"end":29,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let orig_span = span;
context_before:     fn walk_chain(&self, mut span: Span, to: SyntaxContext) -> Span {
context_after:         debug!("walk_chain({:?}, {:?})", span, to);