compiler/rustc_macros/src/type_visitable.rs

   1 use quote::quote;
   2 use syn::parse_quote;
   3
   4 pub fn type_visitable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::TokenStream {
   5     if let syn::Data::Union(_) = s.ast().data {
   6         panic!("cannot derive on union")
   7     }
   8
   9     if !s.ast().generics.lifetimes().any(|lt| lt.lifetime.ident == "tcx") {
  10         s.add_impl_generic(parse_quote! { 'tcx });
  11     }
  12
  13     s.add_bounds(synstructure::AddBounds::Generics);
  14     let body_visit = s.each(|bind| {
  15         quote! {
  16             ::rustc_middle::ty::visit::TypeVisitable::visit_with(#bind, __visitor)?;
  17         }
  18     });
  19     s.bind_with(|_| synstructure::BindStyle::Move);
  20
  21     s.bound_impl(
  22         quote!(::rustc_middle::ty::visit::TypeVisitable<'tcx>),
  23         quote! {
  24             fn visit_with<__V: ::rustc_middle::ty::visit::TypeVisitor<'tcx>>(
  25                 &self,
  26                 __visitor: &mut __V
  27             ) -> ::std::ops::ControlFlow<__V::BreakTy> {
  28                 match *self { #body_visit }
  29                 ::std::ops::ControlFlow::Continue(())
  30             }
  31         },
  32     )
  33 }