{"ast_node_type":"variable","tokens":[{"end":43,"kind":"keyword","start":0,"text":"let"}]}
        let pat = self.lower_pat(&arm.pat);
    fn lower_arm(&mut self, arm: &Arm) -> hir::Arm<'hir> {
        let guard = arm.guard.as_ref().map(|cond| self.lower_expr(cond));