turn lack of equality support into runtime error
turn lack of equality support into runtime error

ReactiveX/RxCpp,ReactiveX/RxCpp,Reactive-Extensions/RxCpp,alexeymarkov/RxCpp,ReactiveX/RxCpp,Reactive-Extensions/RxCpp,Reactive-Extensions/RxCpp,alexeymarkov/RxCpp,alexeymarkov/RxCpp