{"ast_node_type":"function","tokens":[{"end":96,"kind":"keyword","start":0,"text":"fn"}]}
    fn total_fields_in_tuple(&self, pat_hir_id: HirId, span: Span) -> Result<usize, Cx::Error> {
    /// Here `pat_hir_id` is the HirId of the pattern itself.
        let ty = self.cx.typeck_results().node_type(pat_hir_id);