syntax_data: {"ast_node_type":"other","tokens":[{"end":61,"kind":"keyword","start":0,"text":"for"}]}
source_snippet:                 for (pat, explanation) in redundant_subpats {
context_before:                 redundant_subpats.sort_unstable_by_key(|(pat, _)| pat.data().span);
context_after:                     report_unreachable_pattern(cx, arm.arm_data, pat, &explanation, None)