impl<Target: FromEvent<A> + FromEvent<B>, A: Widget2<Ctx = C>, B: Widget2<Ctx = C>, C: for<'a> CtxFamily<'a>> Widget2 for WidgetEventLifter<Target, A, B> { type Ctx = C; type Event = Vec<Target>; } mod foo { impl<Target: FromEvent<A> + FromEvent<B>, A: Widget2<Ctx = C>, B: Widget2<Ctx = C>, C: for<'a> CtxFamily<'a>> Widget2 for WidgetEventLifter<Target, A, B> { type Ctx = C; type Event = Vec<Target>; } }