syntax_data: {"ast_node_type":"function","tokens":[{"end":54,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn make_block(cfg: &mut CFG<'tcx>) -> BasicBlock {
context_before: impl<'tcx> DropTreeBuilder<'tcx> for ExitScopes {
context_after:         cfg.start_new_block()