I have the following: // FontFaceSource.webidl [NoInterfaceObject] interface FontFaceSource { readonly attribute FontFaceSet fonts; }; Document implements FontFaceSource; // FontFaceSet.webidl [Pref="..."] interface FontFaceSet { ... } But I find that the implements statement isn't heeded, and document objects don't get a .fonts property. If I move the implements statement into Document.webidl then it does work.

You did a dep, build, didn't you? The binding build system doesn't know about the comefrom setup you get with "implements" as being used here. We require "implements" statements to be placed in the .webidl file that defines the LHS interface of the "implements". We should probably just fail codegen in this situation with a helpful error message for now; this keeps biting people.

I filed bug 1071615 on failing codegen in this situation.

(In reply to Boris Zbarsky [:bz] from comment #1) > You did a dep, build, didn't you? Ah yes I would've. > The binding build system doesn't know about the comefrom setup you get with > "implements" as being used here. We require "implements" statements to be > placed in the .webidl file that defines the LHS interface of the > "implements". Ah. > We should probably just fail codegen in this situation with a helpful error > message for now; this keeps biting people. Sounds good, I'll just adjust my webidl files. Thanks!

https://bugzilla.mozilla.org/show_bug.cgi?id=1472046 Move all DOM bugs that haven’t been updated in more than 3 years and has no one currently assigned to P5. If you have questions, please contact :mdaly.