{"ast_node_type":"variable","tokens":[{"end":66,"kind":"keyword","start":0,"text":"let"}]}
    let usize = cx.path_ident(span, Ident::new(sym::usize, span));
fn generate_handler(cx: &ExtCtxt<'_>, handler: Ident, span: Span, sig_span: Span) -> Stmt {
    let ty_usize = cx.ty_path(usize);