{"ast_node_type":"variable","tokens":[{"end":52,"kind":"keyword","start":0,"text":"let"}]}
        let mut found_str = DiagStyledString::new();
        expected_str.push(self.expected.fn_sig(self.tcx).to_string(), false);
        found_str.push(self.found.fn_sig(self.tcx).to_string(), true);