import java.util.function.Function;

public class Playbook {

    static class A {
    }

    static class B {
    }

    static class Property<T> {
    }

    static class Var<T> {
        static <T, U> Var<U> mapBidirectional(final Property<T> src, final Function<? super T, ? extends U> f, final Function<? super U, ? extends T> g) {
            return null;
        }

        void bindBidirectional(final Property<T> other) {

        }
    }

    private static A f(final B x) {
        return null;
    }

    private static B g(final A x) {
        return null;
    }

    public void bindTimeString1(final Property<A> timepoint, final Property<B> textProperty) {
        Var.mapBidirectional(textProperty, s -> new A(), t -> new B()).bindBidirectional(timepoint);
    }

    public void bindTimeString2(final Property<A> timepoint, final Property<B> textProperty) {
        Var.mapBidirectional(textProperty, Playbook::f, Playbook::g).bindBidirectional(timepoint);
    }

    void f(final Property<Integer> p) {

    }
}

[ERROR]Playbook.java:[35,90] incompatible types: main.java.Playbook.Property<main.java.Playbook.A> cannot be converted to main.java.Playbook.Property<java.lang.Object>