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|
use quote::quote;
use syn::parse_quote;
pub fn type_visitable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::TokenStream {
if let syn::Data::Union(_) = s.ast().data {
panic!("cannot derive on union")
}
// ignore fields with #[type_visitable(ignore)]
s.filter(|bi| {
let mut ignored = false;
bi.ast().attrs.iter().for_each(|attr| {
if !attr.path().is_ident("type_visitable") {
return;
}
let _ = attr.parse_nested_meta(|nested| {
if nested.path.is_ident("ignore") {
ignored = true;
}
Ok(())
});
});
!ignored
});
if !s.ast().generics.lifetimes().any(|lt| lt.lifetime.ident == "tcx") {
s.add_impl_generic(parse_quote! { 'tcx });
}
s.add_bounds(synstructure::AddBounds::Generics);
let body_visit = s.each(|bind| {
quote! {
::rustc_middle::ty::visit::TypeVisitable::visit_with(#bind, __visitor)?;
}
});
s.bind_with(|_| synstructure::BindStyle::Move);
s.bound_impl(
quote!(::rustc_middle::ty::visit::TypeVisitable<::rustc_middle::ty::TyCtxt<'tcx>>),
quote! {
fn visit_with<__V: ::rustc_middle::ty::visit::TypeVisitor<::rustc_middle::ty::TyCtxt<'tcx>>>(
&self,
__visitor: &mut __V
) -> ::std::ops::ControlFlow<__V::BreakTy> {
match *self { #body_visit }
::std::ops::ControlFlow::Continue(())
}
},
)
}
|
