{"ast_node_type":"other","tokens":[{"end":52,"kind":"keyword","start":0,"text":"debug_assert!(self.probe(vid).is_unknown());"}]}
        debug_assert!(self.probe(vid).is_unknown());
        debug_assert!(!ty.is_ty_var(), "instantiating ty var with var: {vid:?} {ty:?}");
        debug_assert!(