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extern crate proc_macro;
extern crate syn;
extern crate synstructure;
#[macro_use]
extern crate quote;

use proc_macro::TokenStream;
use synstructure::BindStyle;

#[proc_macro_derive(Trace, attributes(unsafe_ignore_trace))]
pub fn derive_trace(input: TokenStream) -> TokenStream {
    let source = input.to_string();
    let ast = syn::parse_derive_input(&source).unwrap();

    let trace = synstructure::each_field(&ast, &BindStyle::Ref.into(), |bi| {
        // Check if this field is annotated with an #[unsafe_ignore_trace]
        if bi.field.attrs.iter().any(|attr| attr.name() == "unsafe_ignore_trace") {
            quote::Tokens::new()
        } else {
            quote!(mark(#bi);)
        }
    });

    // Build the output tokens
    let name = &ast.ident;
    let (impl_generics, ty_generics, where_clause) = ast.generics.split_for_impl();
    let result = quote! {
        unsafe impl #impl_generics ::gc::Trace for #name #ty_generics #where_clause {
            #[inline] unsafe fn trace(&self) {
                #[allow(dead_code)]
                #[inline]
                unsafe fn mark<T: ::gc::Trace>(it: &T) {
                    ::gc::Trace::trace(it);
                }
                match *self { #trace }
            }
            #[inline] unsafe fn root(&self) {
                #[allow(dead_code)]
                #[inline]
                unsafe fn mark<T: ::gc::Trace>(it: &T) {
                    ::gc::Trace::root(it);
                }
                match *self { #trace }
            }
            #[inline] unsafe fn unroot(&self) {
                #[allow(dead_code)]
                #[inline]
                unsafe fn mark<T: ::gc::Trace>(it: &T) {
                    ::gc::Trace::unroot(it);
                }
                match *self { #trace }
            }
            #[inline] fn finalize_glue(&self) {
                #[allow(dead_code)]
                #[inline]
                fn mark<T: ::gc::Trace>(it: &T) {
                    ::gc::Trace::finalize_glue(it);
                }
                match *self { #trace }
                ::gc::Finalize::finalize(self);
            }
        }

        // We also implement drop to prevent unsafe drop implementations on this
        // type and encourage people to use Finalize. This implementation will
        // call `Finalize::finalize` if it is safe to do so.
        impl #impl_generics ::std::ops::Drop for #name #ty_generics #where_clause {
            fn drop(&mut self) {
                if ::gc::finalizer_safe() {
                    ::gc::Finalize::finalize(self);
                }
            }
        }
    };

    // Generate the final value as a TokenStream and return it
    result.to_string().parse().unwrap()
}

#[proc_macro_derive(Finalize)]
pub fn derive_finalize(input: TokenStream) -> TokenStream {
    let source = input.to_string();
    let ast = syn::parse_derive_input(&source).unwrap();

    let name = &ast.ident;
    let (impl_generics, ty_generics, where_clause) = ast.generics.split_for_impl();
    let result = quote! {
        impl #impl_generics ::gc::Finalize for #name #ty_generics #where_clause { }
    };

    result.to_string().parse().unwrap()
}