TestJdk12Regression.java

public class TestJdk12Regression {
    @FunctionalInterface
    interface HandleCallback<T, X extends Exception> {
        T withHandle(Handle handle) throws X;
    }
    @FunctionalInterface
    interface HandleConsumer<X extends Exception> {
        void useHandle(Handle handle) throws X;
    }

    interface Handle {}

    interface Jdbi {
        <R, X extends Exception> R withHandle(HandleCallback<R, X> callback) throws X;
        <X extends Exception> void useHandle(final HandleConsumer<X> callback) throws X;
    }

    interface ObjectAssert<ACTUAL> {
        void isSameAs(ACTUAL t);
    }

    static <T> ObjectAssert<T> assertThat(T actual) {
        return null;
    }

    private Jdbi jdbi;

    public void nestedUseHandle() {
        jdbi.withHandle(h1 -> {
            jdbi.useHandle(h2 ->
                assertThat(h1).isSameAs(h2));
            return null;
        });
    }
}