syntax_data: {"ast_node_type":"other","tokens":[{"end":64,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// Create a new block for the tree. This should call either
context_before: trait DropTreeBuilder<'tcx> {
context_after:     /// `cfg.start_new_block()` or `cfg.start_new_cleanup_block()`.