{"ast_node_type":"function","tokens":[{"end":100,"kind":"keyword","start":0,"text":"let"}]}
            let decl = node.fn_decl().unwrap_or_else(|| bug!("expected fn decl, found {:?}", node));
            let node = tcx.expect_hir_owner_node(fn_id);
            decl.inputs.iter().map(|t| t.span).chain(std::iter::once(decl.output.span()))