{"ast_node_type":"variable","tokens":[{"end":75,"kind":"keyword","start":0,"text":"let"}]}
                let layout_val = self.layout_of(instance_args.type_at(0))?;
                // rotate_right: (X << ((BW - S) % BW)) | (X >> (S % BW))
                let val = self.read_scalar(&args[0])?;