{"ast_node_type":"variable","tokens":[{"end":98,"kind":"keyword","start":0,"text":"let"}]}
        let (Some(sub), Some(sup)) = (self.to_error_region(sub), self.to_error_region(sup)) else {
    fn suggest_adding_lifetime_params(&self, diag: &mut Diag<'_>, sub: RegionVid, sup: RegionVid) {
            return;