syntax_data: {"ast_node_type":"other","tokens":[{"end":70,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // RETURN_PLACE then is a fresh unused local with type ret_ty.
context_before:         // We rename RETURN_PLACE which has type mir.return_ty to old_ret_local
context_after:         let old_ret_local = replace_local(RETURN_PLACE, new_ret_ty, body, tcx);