rustc-ap-rustc_macros 644.0.0

Automatically published version of the package `rustc_macros` in the rust-lang/rust repository from commit 0176a9eef845e7421b7e2f7ef015333a41a7c027 The publishing script for this crate lives at: https://github.com/alexcrichton/rustc-auto-publish
Documentation 
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use quote::quote;

pub fn type_foldable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::TokenStream {
    if let syn::Data::Union(_) = s.ast().data {
        panic!("cannot derive on union")
    }

    s.add_bounds(synstructure::AddBounds::Generics);
    let body_fold = s.each_variant(|vi| {
        let bindings = vi.bindings();
        vi.construct(|_, index| {
            let bind = &bindings[index];
            quote! {
                ::rustc::ty::fold::TypeFoldable::fold_with(#bind, __folder)
            }
        })
    });
    let body_visit = s.fold(false, |acc, bind| {
        quote! { #acc || ::rustc::ty::fold::TypeFoldable::visit_with(#bind, __folder) }
    });

    s.bound_impl(
        quote!(::rustc::ty::fold::TypeFoldable<'tcx>),
        quote! {
            fn super_fold_with<__F: ::rustc::ty::fold::TypeFolder<'tcx>>(
                &self,
                __folder: &mut __F
            ) -> Self {
                match *self { #body_fold }
            }

            fn super_visit_with<__F: ::rustc::ty::fold::TypeVisitor<'tcx>>(
                &self,
                __folder: &mut __F
            ) -> bool {
                match *self { #body_visit }
            }
        },
    )
}