syntax_data: {"ast_node_type":"other","tokens":[{"end":84,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:                 // If the arm is followed by a comma, extend the span to include it.
context_before:             let whole_arm_span = if is_match_arm {
context_after:                 let with_whitespace = sm.span_extend_while_whitespace(arm_span);