compiler/rustc_macros/src/type_foldable.rs

   1 use quote::quote;
   2
   3 pub fn type_foldable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::TokenStream {
   4     if let syn::Data::Union(_) = s.ast().data {
   5         panic!("cannot derive on union")
   6     }
   7
   8     s.add_bounds(synstructure::AddBounds::Generics);
   9     let body_visit = s.each(|bind| {
  10         quote! {
  11             ::rustc_middle::ty::fold::TypeFoldable::visit_with(#bind, __folder)?;
  12         }
  13     });
  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];
  19             quote! {
  20                 ::rustc_middle::ty::fold::TypeFoldable::fold_with(#bind, __folder)
  21             }
  22         })
  23     });
  24
  25     s.bound_impl(
  26         quote!(::rustc_middle::ty::fold::TypeFoldable<'tcx>),
  27         quote! {
  28             fn super_fold_with<__F: ::rustc_middle::ty::fold::TypeFolder<'tcx>>(
  29                 self,
  30                 __folder: &mut __F
  31             ) -> Self {
  32                 match self { #body_fold }
  33             }
  34
  35             fn super_visit_with<__F: ::rustc_middle::ty::fold::TypeVisitor<'tcx>>(
  36                 &self,
  37                 __folder: &mut __F
  38             ) -> ::std::ops::ControlFlow<__F::BreakTy> {
  39                 match *self { #body_visit }
  40                 ::std::ops::ControlFlow::CONTINUE
  41             }
  42         },
  43     )
  44 }