syntax_data: {"ast_node_type":"variable","tokens":[{"end":26,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let mut sp = span;
context_before:     pub fn span_look_ahead(&self, span: Span, expect: &str, limit: Option<usize>) -> Option<Span> {
context_after:         for _ in 0..limit.unwrap_or(100_usize) {