syntax_data: {"ast_node_type":"function","tokens":[{"end":74,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn insert_none_ret_block(&self, body: &mut Body<'tcx>) -> BasicBlock {
context_before: impl<'tcx> TransformVisitor<'tcx> {
context_after:         let block = body.basic_blocks.next_index();