Kotlin type inference failure.

RxScheduling.java

public class RxScheduling {
    private final Scheduler io;
    private final Scheduler ui;
    private final Observable.Transformer ioThenUiTransform;
    private final Observable.Transformer thenUiTransform;

    public RxScheduling(Scheduler io, Scheduler ui) {
        this.io = io;
        this.ui = ui;
        ioThenUiTransform = new Observable.Transformer<Object, Object>() {
            @Override
            public Observable call(Observable observable) {
                return observable.subscribeOn(io).observeOn(ui);
            }
        };
        thenUiTransform = new Observable.Transformer<Object, Object>() {
            @Override
            public Observable call(Observable observable) {
                return observable.observeOn(ui);
            }
        };
    }

    public <T> Observable.Transformer<T, T> ioThenUi() {
        return ioThenUiTransform;
    }

    /**
     * Workaround for https://youtrack.jetbrains.com/issue/KT-10250
     */
    public <T> Observable.Transformer<? super T, ? extends T> ioThenUi_() {
        return ioThenUiTransform;
    }

    public <T> Observable.Transformer<T, T> thenUi() {
        return thenUiTransform;
    }

    /**
     * Workaround for https://youtrack.jetbrains.com/issue/KT-10250
     */
    public <T> Observable.Transformer<? super T, ? extends T> thenUi_() {
        return thenUiTransform;
    }
}