servo/components/jstraceable_derive/lib.rs
2018-11-30 17:48:41 +01:00

41 lines
1.4 KiB
Rust

/* 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
}