{"ast_node_type":"variable","tokens":[{"end":58,"kind":"keyword","start":0,"text":"if"}]}
        if let hir::ExprKind::Closure(closure) = expr.kind
    fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
            && let Some(upvars) = self.tcx.upvars_mentioned(closure.def_id)