syntax_data: {"ast_node_type":"other","tokens":[{"end":58,"kind":"keyword","start":0,"text":"for"}]}
source_snippet:     for (bb, data) in traversal::reverse_postorder(body) {
context_before:     let mut dropline: DenseBitSet<BasicBlock> = DenseBitSet::new_empty(body.basic_blocks.len());
context_after:         if dropline.contains(bb) {