syntax_data: {"ast_node_type":"variable","tokens":[{"end":88,"kind":"keyword","start":0,"text":"if"}]}
source_snippet:                 if let Some(comma) = sm.span_look_ahead(with_whitespace, ",", Some(1)) {
context_before:                 let with_whitespace = sm.span_extend_while_whitespace(arm_span);
context_after:                     Some(arm_span.to(comma))