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 let body_visit = s.each(|bind| {
16 ::rustc_middle::ty::fold::TypeFoldable::visit_with(#bind, __folder)?;
19 s.bind_with(|_| synstructure::BindStyle::Move);
20 let body_fold = s.each_variant(|vi| {
21 let bindings = vi.bindings();
22 vi.construct(|_, index| {
23 let bind = &bindings[index];
25 ::rustc_middle::ty::fold::TypeFoldable::try_fold_with(#bind, __folder)?
31 quote!(::rustc_middle::ty::fold::TypeFoldable<'tcx>),
33 fn try_super_fold_with<__F: ::rustc_middle::ty::fold::FallibleTypeFolder<'tcx>>(
36 ) -> Result<Self, __F::Error> {
37 Ok(match self { #body_fold })
40 fn super_visit_with<__F: ::rustc_middle::ty::fold::TypeVisitor<'tcx>>(
43 ) -> ::std::ops::ControlFlow<__F::BreakTy> {
44 match *self { #body_visit }
45 ::std::ops::ControlFlow::CONTINUE