Make #[derive(JSTraceable)] a procedural macro

components/jstraceable_derive/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "jstraceable_derive"
+version = "0.0.1"
+authors = ["The Servo Project Developers"]
+license = "MPL-2.0"
+publish = false
+
+[lib]
+path = "lib.rs"
+proc-macro = true
+
+[dependencies]
+syn = "0.9"
+quote = "0.3"
+synstructure = "0.2"

components/jstraceable_derive/lib.rs

@@ -0,0 +1,58 @@
+/* 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 http://mozilla.org/MPL/2.0/. */
+
+#![feature(proc_macro, proc_macro_lib)]
+
+extern crate proc_macro;
+#[macro_use] extern crate quote;
+extern crate syn;
+extern crate synstructure;
+
+#[cfg(not(test))]
+#[proc_macro_derive(JSTraceable)]
+pub fn expand_token_stream(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    expand_string(&input.to_string()).parse().unwrap()
+}
+
+fn expand_string(input: &str) -> String {
+    let mut type_ = syn::parse_macro_input(input).unwrap();
+
+    let style = synstructure::BindStyle::Ref.into();
+    let match_body = synstructure::each_field(&mut type_, &style, |binding| {
+        Some(quote! { #binding.trace(tracer); })
+    });
+
+    let name = &type_.ident;
+    let (impl_generics, ty_generics, mut where_clause) = type_.generics.split_for_impl();
+    for param in &type_.generics.ty_params {
+        where_clause.predicates.push(syn::WherePredicate::BoundPredicate(syn::WhereBoundPredicate {
+            bound_lifetimes: Vec::new(),
+            bounded_ty: syn::Ty::Path(None, param.ident.clone().into()),
+            bounds: vec![syn::TyParamBound::Trait(
+                syn::PolyTraitRef {
+                    bound_lifetimes: Vec::new(),
+                    trait_ref: syn::parse_path("::dom::bindings::trace::JSTraceable").unwrap(),
+                },
+                syn::TraitBoundModifier::None
+            )],
+        }))
+    }
+
+    let tokens = quote! {
+        #type_
+
+        impl #impl_generics ::dom::bindings::trace::JSTraceable for #name #ty_generics #where_clause {
+            #[inline]
+            #[allow(unused_variables, unused_imports)]
+            fn trace(&self, tracer: *mut ::js::jsapi::JSTracer) {
+                use ::dom::bindings::trace::JSTraceable;
+                match *self {
+                    #match_body
+                }
+            }
+        }
+    };
+
+    tokens.to_string()
+}

components/plugins/jstraceable.rs

@@ -2,13 +2,10 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use syntax::ast::{Expr, MetaItem, Mutability};
+use syntax::ast::MetaItem;
 use syntax::codemap::Span;
 use syntax::ext::base::{Annotatable, ExtCtxt};
-use syntax::ext::build::AstBuilder;
 use syntax::ptr::P;
-use syntax_ext::deriving::generic::{Struct, Substructure, TraitDef, ty};
-use syntax_ext::deriving::generic::{combine_substructure, EnumMatching, FieldInfo, MethodDef};
 
 pub fn expand_dom_struct(cx: &mut ExtCtxt, sp: Span, _: &MetaItem, anno: Annotatable) -> Annotatable {
     if let Annotatable::Item(item) = anno {
@@ -29,63 +26,3 @@ pub fn expand_dom_struct(cx: &mut ExtCtxt, sp: Span, _: &MetaItem, anno: Annotat
         anno
     }
 }
-
-/// Provides the hook to expand `#[derive(JSTraceable)]` into an implementation of `JSTraceable`
-///
-/// The expansion basically calls `trace()` on all of the fields of the struct/enum, erroring if they do not
-/// implement the method.
-pub fn expand_jstraceable(cx: &mut ExtCtxt, span: Span, mitem: &MetaItem, item: &Annotatable,
-                          push: &mut FnMut(Annotatable)) {
-    let trait_def = TraitDef {
-        is_unsafe: false,
-        span: span,
-        attributes: Vec::new(),
-        path: ty::Path::new(vec!("dom", "bindings", "trace", "JSTraceable")),
-        additional_bounds: Vec::new(),
-        generics: ty::LifetimeBounds::empty(),
-        supports_unions: true,
-        methods: vec![
-            MethodDef {
-                name: "trace",
-                generics: ty::LifetimeBounds::empty(),
-                explicit_self: ty::borrowed_explicit_self(),
-                args: vec!(ty::Ptr(box ty::Literal(ty::Path::new(vec!("js", "jsapi", "JSTracer"))),
-                                   ty::Raw(Mutability::Mutable))),
-                ret_ty: ty::nil_ty(),
-                attributes: vec![quote_attr!(cx, #[inline])],
-                is_unsafe: false,
-                combine_substructure: combine_substructure(box jstraceable_substructure),
-                unify_fieldless_variants: true,
-            }
-        ],
-        associated_types: vec![],
-    };
-    trait_def.expand(cx, mitem, item, push)
-}
-
-// Mostly copied from syntax::ext::deriving::hash
-/// Defines how the implementation for `trace()` is to be generated
-fn jstraceable_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> P<Expr> {
-    let state_expr = if substr.nonself_args.len() == 1 {
-        &substr.nonself_args[0]
-    } else {
-        cx.span_bug(trait_span, "incorrect number of arguments in `jstraceable`")
-    };
-    let trace_ident = substr.method_ident;
-    let call_trace = |span, thing_expr| {
-        let expr = cx.expr_method_call(span, thing_expr, trace_ident, vec!(state_expr.clone()));
-        cx.stmt_expr(expr)
-    };
-    let mut stmts = Vec::new();
-
-    let fields = match *substr.fields {
-        Struct(_, ref fs) | EnumMatching(_, _, ref fs) => fs,
-        _ => cx.span_bug(trait_span, "impossible substructure in `jstraceable`")
-    };
-
-    for &FieldInfo { ref self_, span, .. } in fields {
-        stmts.push(call_trace(span, self_.clone()));
-    }
-
-    cx.expr_block(cx.block(trait_span, stmts))
-}

components/plugins/lib.rs

@@ -25,7 +25,6 @@ extern crate rustc;
 extern crate rustc_plugin;
 #[macro_use]
 extern crate syntax;
-extern crate syntax_ext;
 
 use rustc_plugin::Registry;
 use syntax::ext::base::*;
@@ -44,8 +43,6 @@ mod utils;
 #[plugin_registrar]
 pub fn plugin_registrar(reg: &mut Registry) {
     reg.register_syntax_extension(intern("dom_struct"), MultiModifier(box jstraceable::expand_dom_struct));
-    reg.register_syntax_extension(intern("derive_JSTraceable"),
-                                  MultiDecorator(box jstraceable::expand_jstraceable));
     reg.register_syntax_extension(intern("_generate_reflector"),
                                   MultiDecorator(box reflector::expand_reflector));
     reg.register_late_lint_pass(box lints::unrooted_must_root::UnrootedPass::new());

components/script/Cargo.toml

@@ -42,6 +42,7 @@ hyper_serde = "0.1.4"
 image = "0.10"
 ipc-channel = "0.5"
 js = {git = "https://github.com/servo/rust-mozjs", features = ["promises"]}
+jstraceable_derive = {path = "../jstraceable_derive"}
 libc = "0.2"
 log = "0.3.5"
 mime = "0.2.1"

components/script/dom/validitystate.rs

@@ -10,7 +10,7 @@ use dom::element::Element;
 use dom::window::Window;
 
 // https://html.spec.whatwg.org/multipage/#validity-states
-#[derive_JSTraceable]
+#[derive(JSTraceable)]
 #[derive(HeapSizeOf)]
 pub enum ValidityStatus {
     ValueMissing,

components/script/lib.rs

@@ -54,6 +54,8 @@ extern crate image;
 extern crate ipc_channel;
 #[macro_use]
 extern crate js;
+#[macro_use]
+extern crate jstraceable_derive;
 extern crate libc;
 #[macro_use]
 extern crate log;

components/servo/Cargo.lock

@@ -1118,6 +1118,15 @@ dependencies = [
  "num-traits 0.1.35 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "jstraceable_derive"
+version = "0.0.1"
+dependencies = [
+ "quote 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "synstructure 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "kernel32-sys"
 version = "0.2.2"
@@ -1970,6 +1979,7 @@ dependencies = [
  "image 0.10.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "ipc-channel 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "js 0.1.3 (git+https://github.com/servo/rust-mozjs)",
+ "jstraceable_derive 0.0.1",
  "libc 0.2.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "mime 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",

ports/cef/Cargo.lock

@@ -1025,6 +1025,15 @@ dependencies = [
  "num-traits 0.1.35 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "jstraceable_derive"
+version = "0.0.1"
+dependencies = [
+ "quote 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "synstructure 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "kernel32-sys"
 version = "0.2.2"
@@ -1821,6 +1830,7 @@ dependencies = [
  "image 0.10.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "ipc-channel 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "js 0.1.3 (git+https://github.com/servo/rust-mozjs)",
+ "jstraceable_derive 0.0.1",
  "libc 0.2.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "mime 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",