*/
    public abstract RuntimeException getFailureOrNull();

    /**
     * Returns the value or rethrows the failures of this result.
     */
    public abstract T getValueOrRethrow();

    /**
     * Rethrows the failures in this result, if any, otherwise does nothing.
     */
    public abstract void rethrow();

    /**

     */
    public <S> S transition(T fromState, T toState, Supplier<? extends S> action) {
        return synchronizer.withLock(() -> doTransition(fromState, toState, () -> ExecutionResult.succeeded(action.get())).getValueOrRethrow());
    }

    /**
     * Transitions to the given "to" state, returning any failure in the result object.