{"ast_node_type":"other","tokens":[{"end":56,"kind":"keyword","start":0,"text":"#[instrument(level"}]}
    #[instrument(level = "debug", skip(self, relation))]
    /// other usecases (i.e. setting the value of a type var).
    pub fn instantiate_ty_var<R: PredicateEmittingRelation<InferCtxt<'tcx>>>(