syntax_data: {"ast_node_type":"variable","tokens":[{"end":35,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:     let span = sm.next_point(span);
context_before:     assert_eq!(sm.span_to_snippet(span), Ok("a".to_string()));
context_after:     assert_eq!(sm.span_to_snippet(span), Ok("…".to_string()));