return new CollectingSupplier(newCollector);
        }

        @Override
        public ExecutionTimeValue<? extends Map<K, V>> calculateExecutionTimeValue() {
            List<ExecutionTimeValue<? extends Map<? extends K, ? extends V>>> execTimeValues = collectExecutionTimeValues();
            ExecutionTimeValue<Map<K, V>> fixedOrMissing = fixedOrMissingValueOf(execTimeValues);
            return fixedOrMissing != null

        }

        @Override
        public void calculateExecutionTimeValue(Action<ExecutionTimeValue<? extends Map<? extends K, ? extends V>>> visitor) {
            ExecutionTimeValue<? extends V> value = providerOfValue.calculateExecutionTimeValue();
            if (value.isMissing()) {
                visitor.execute(ExecutionTimeValue.missing());
            } else if (value.hasFixedValue()) {

        }
    }

    private static <T> void visitValue(Action<? super ValueSupplier.ExecutionTimeValue<? extends Iterable<? extends T>>> visitor, ValueSupplier.ExecutionTimeValue<? extends T> value) {
        if (value.isMissing()) {
            visitor.execute(ValueSupplier.ExecutionTimeValue.missing());
        } else if (value.hasFixedValue()) {
            // transform preserving side effects

        @Nonnull
        private List<ExecutionTimeValue<? extends Iterable<? extends T>>> collectExecutionTimeValues() {
            List<ExecutionTimeValue<? extends Iterable<? extends T>>> values = new ArrayList<>();
            value.calculateExecutionTimeValue(values::add);
            return values;
        }

        given:
        def collection = new EmptyFileCollection("foo")

        when:
        def executionTimeValue = collection.calculateExecutionTimeValue()

        then:
        executionTimeValue.present

        when:
        def newCollection = executionTimeValue.get().toFileCollection(fileCollectionFactory())

        then:
        newCollection.isEmpty()

        }
    }

    @Override
    public ExecutionTimeValue<? extends T> calculateExecutionTimeValue() {
        try (EvaluationContext.ScopeContext ignored = openScope()) {
            ExecutionTimeValue<? extends T> value = provider.calculateExecutionTimeValue();
            if (value.isMissing()) {
                // Use fallback value
                return ExecutionTimeValue.fixedValue(fallbackValue);

        given:
        def collection = fileCollectionFactory().fixed("foo", new File("foo.txt"))

        when:
        def executionTimeValue = collection.calculateExecutionTimeValue()

        then:
        executionTimeValue.present

        and:
        def newCollection = executionTimeValue.get().toFileCollection(fileCollectionFactory())

        then:
        newCollection.files == [new File("foo.txt")] as Set

    @Override
    public ExecutionTimeValue<? extends T> calculateExecutionTimeValue() {
        try (EvaluationContext.ScopeContext ignored = openScope()) {
            ExecutionTimeValue<? extends T> leftValue = left.calculateExecutionTimeValue();
            if (leftValue.hasFixedValue()) {
                return leftValue;
            }
            ExecutionTimeValue<? extends T> rightValue = right.calculateExecutionTimeValue();

        }
    }

    @Override
    public ExecutionTimeValue<? extends OUT> calculateExecutionTimeValue() {
        try (EvaluationContext.ScopeContext context = openScope()) {
            ExecutionTimeValue<? extends IN> value = provider.calculateExecutionTimeValue();
            if (value.isChangingValue()) {

            }
        }
        def collection = new FilteredFileCollection(source, spec)

        when:
        def executionTimeValue = collection.calculateExecutionTimeValue()

        then:
        executionTimeValue.present

        when:
        def newCollection = executionTimeValue.get().toFileCollection(fileCollectionFactory())

        then: