syntax_data: {"ast_node_type":"variable","tokens":[{"end":45,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:             let before = &src[..start_index];
context_before:         self.span_to_source(sp, |src, start_index, _| {
context_after:             let last_line = before.rsplit_once('\n').map_or(before, |(_, last)| last);