You could expose `IsDOMObject` as a `ChromeOnly` API, I think that'll give you "object implements interface". (Assuming that are the semantics you want, note that it doesn't include interface objects, interface prototype objects, named property objects, …)
Bug 1792524 Comment 8 Edit History
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You could expose `IsDOMObject` (https://searchfox.org/mozilla-central/rev/83b86005c6913c2062419efb8aabdf2e683aa47f/dom/bindings/BindingUtils.h#149) as a `ChromeOnly` API, I think that'll give you "object implements interface". (Assuming that are the semantics you want, note that it doesn't include interface objects, interface prototype objects, named property objects, …)