{"ast_node_type":"other","tokens":[{"end":50,"kind":"keyword","start":0,"text":"iter::once(LocalDecl::new(sig.output(),"}]}
    iter::once(LocalDecl::new(sig.output(), span))
) -> IndexVec<Local, LocalDecl<'tcx>> {
        .chain(sig.inputs().iter().map(|ity| LocalDecl::new(*ity, span).immutable()))