{"ast_node_type":"variable","tokens":[{"end":80,"kind":"keyword","start":0,"text":"let"}]}
                let var = ty::BoundVar::from_usize(self.still_bound_vars.len());
                // Allocate a new var idx, and insert a new bound ty.
                self.still_bound_vars.push(ty::BoundVariableKind::Ty(old_bound.kind));