components/jstraceable_derive/lib.rs


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/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */

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

decl_derive!([JSTraceable] => js_traceable_derive);

fn js_traceable_derive(s: synstructure::Structure) -> proc_macro2::TokenStream {
    let match_body = s.each(|binding| Some(quote!(#binding.trace(tracer);)));

    let ast = s.ast();
    let name = &ast.ident;
    let (impl_generics, ty_generics, where_clause) = ast.generics.split_for_impl();
    let mut where_clause = where_clause.unwrap_or(&parse_quote!(where)).clone();
    for param in ast.generics.type_params() {
        let ident = &param.ident;
        where_clause
            .predicates
            .push(parse_quote!(#ident: crate::dom::bindings::trace::JSTraceable))
    }

    let tokens = quote! {
        #[allow(unsafe_code)]
        unsafe impl #impl_generics crate::dom::bindings::trace::JSTraceable for #name #ty_generics #where_clause {
            #[inline]
            #[allow(unused_variables, unused_imports)]
            unsafe fn trace(&self, tracer: *mut js::jsapi::JSTracer) {
                use crate::dom::bindings::trace::JSTraceable;
                match *self {
                    #match_body
                }
            }
        }
    };

    tokens
}