4 pub fn type_foldable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::TokenStream {
5 if let syn::Data::Union(_) = s.ast().data {
6 panic!("cannot derive on union")
9 if !s.ast().generics.lifetimes().any(|lt| lt.lifetime.ident == "tcx") {
10 s.add_impl_generic(parse_quote! { 'tcx });
13 s.add_bounds(synstructure::AddBounds::Generics);
14 s.bind_with(|_| synstructure::BindStyle::Move);
15 let body_fold = s.each_variant(|vi| {
16 let bindings = vi.bindings();
17 vi.construct(|_, index| {
18 let bind = &bindings[index];
20 ::rustc_middle::ty::fold::TypeFoldable::try_fold_with(#bind, __folder)?
26 quote!(::rustc_middle::ty::fold::TypeFoldable<'tcx>),
28 fn try_fold_with<__F: ::rustc_middle::ty::fold::FallibleTypeFolder<'tcx>>(
31 ) -> Result<Self, __F::Error> {
32 Ok(match self { #body_fold })