{"ast_node_type":"variable","tokens":[{"end":47,"kind":"keyword","start":0,"text":"let"}]}
        let (src_pointee_ty, dest_pointee_ty) =
        // A<Struct> -> A<Trait> conversion
            self.tcx.struct_lockstep_tails_for_codegen(source_ty, cast_ty, self.typing_env);