1 files changed, 55 insertions, 4 deletions
diff --git a/components/domobject_derive/lib.rs b/components/domobject_derive/lib.rs
index 037ae597e8b..c718b514fc5 100644
--- a/components/domobject_derive/lib.rs
+++ b/components/domobject_derive/lib.rs
@@ -14,17 +14,27 @@ pub fn expand_token_stream(input: proc_macro::TokenStream) -> proc_macro::TokenS
 fn expand_string(input: &str) -> String {
     let type_ = syn::parse_macro_input(input).unwrap();
 
-    let first_field_name = if let syn::Body::Struct(syn::VariantData::Struct(ref fields)) = type_.body {
-        let first_field = fields.first().expect("#[derive(DomObject)] should not be applied on empty structs");
-        first_field.ident.as_ref().unwrap()
+    let fields = if let syn::Body::Struct(syn::VariantData::Struct(ref fields)) = type_.body {
+        fields
     } else {
         panic!("#[derive(DomObject)] should only be applied on proper structs")
     };
 
+    let (first_field, fields) = fields
+        .split_first()
+        .expect("#[derive(DomObject)] should not be applied on empty structs");
+    let first_field_name = first_field.ident.as_ref().unwrap();
+    let mut field_types = vec![];
+    for field in fields {
+        if !field_types.contains(&&field.ty) {
+            field_types.push(&field.ty);
+        }
+    }
+
     let name = &type_.ident;
     let (impl_generics, ty_generics, where_clause) = type_.generics.split_for_impl();
 
-    let tokens = quote! {
+    let mut items = quote! {
         impl #impl_generics ::js::conversions::ToJSValConvertible for #name #ty_generics #where_clause {
             #[allow(unsafe_code)]
             unsafe fn to_jsval(&self,
@@ -49,5 +59,46 @@ fn expand_string(input: &str) -> String {
         }
     };
 
+    let mut params = quote::Tokens::new();
+    params.append_separated(type_.generics.ty_params.iter().map(|param| &param.ident), ", ");
+
+    // For each field in the struct, we implement ShouldNotImplDomObject for a
+    // pair of all the type parameters of the DomObject and and the field type.
+    // This allows us to support parameterized DOM objects
+    // such as IteratorIterable<T>.
+    items.append_all(field_types.iter().map(|ty| {
+        quote! {
+            impl #impl_generics ShouldNotImplDomObject for ((#params), #ty) #where_clause {}
+        }
+    }));
+
+    let bound = syn::TyParamBound::Trait(
+        syn::PolyTraitRef {
+            bound_lifetimes: vec![],
+            trait_ref: syn::parse_path("::dom::bindings::reflector::DomObject").unwrap(),
+        },
+        syn::TraitBoundModifier::None
+    );
+
+    let mut generics = type_.generics.clone();
+    generics.ty_params.push(syn::TyParam {
+        attrs: vec![],
+        ident: "__T".into(),
+        bounds: vec![bound],
+        default: None,
+    });
+    let (impl_generics, _, where_clause) = generics.split_for_impl();
+
+    items.append(quote! {
+        trait ShouldNotImplDomObject {}
+        impl #impl_generics ShouldNotImplDomObject for ((#params), __T) #where_clause {}
+    }.as_str());
+
+    let dummy_const = syn::Ident::new(format!("_IMPL_DOMOBJECT_FOR_{}", name));
+    let tokens = quote! {
+        #[allow(non_upper_case_globals)]
+        const #dummy_const: () = { #items };
+    };
+
     tokens.to_string()
 }