syntax_data: {"ast_node_type":"variable","tokens":[{"end":75,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let block_span = tcx.sess.source_map().guess_head_span(block_span);
context_before:     for UnusedUnsafeWarning { hir_id, block_span, enclosing_unsafe } in warnings {
context_after:         tcx.emit_node_span_lint(