}

    @Override
    public void visitLeafElement(FileSystemLeafSnapshot snapshot) {
        collectEntry(snapshot);
    }

    @Override
    public void visitDirectory(DirectorySnapshot directorySnapshot) {
        collectEntry(directorySnapshot);
    }

    @Override
    public FileSystemLocationSnapshot leaveDirectory() {
        FileSystemLocationSnapshot snapshot = directoryStack.removeLast().fold();

        def outputFile = fileSnapshot("outputs", TestHashCodes.hashCodeFrom(345))

        def emptyDirectory = directorySnapshot()
        def directoryWithStaleFile = directorySnapshot(staleFile)
        def directoryWithStaleFileAndOutput = directorySnapshot(outputFile, staleFile)
        def directoryWithOutputFile = directorySnapshot(outputFile)

        def previousOutputs = ImmutableSortedMap.<String, FileSystemSnapshot> of(

 */
public interface FileSystemSnapshotHierarchyVisitor {

    /**
     * Called before visiting the contents of a directory.
     */
    default void enterDirectory(DirectorySnapshot directorySnapshot) {}

    /**
     * Called for each regular file/directory/missing/unavailable file.
     *
     * @return how to continue visiting the rest of the snapshot hierarchy.
     */

                entrySnapshot.accept(new FileSystemLocationSnapshotVisitor() {
                    @Override
                    public void visitDirectory(DirectorySnapshot directorySnapshot) {
                        recordOutputSnapshot(directorySnapshot);
                    }

                    @Override
                    public void visitRegularFile(RegularFileSnapshot fileSnapshot) {

    }

    def "detects overlap when there is a stale #type in an output directory"() {
        def emptyDirectory = new DirectorySnapshot("/absolute", "absolute", AccessType.DIRECT, TestHashCodes.hashCodeFrom(0x1234), [])
        def directoryWithStaleBrokenSymlink = new DirectorySnapshot("/absolute", "absolute", AccessType.DIRECT, TestHashCodes.hashCodeFrom(0x5678), [
            staleEntry
        ])

                        AtomicBoolean symlinkHasBeenFiltered = new AtomicBoolean();
                        DirectorySnapshot targetSnapshot = followSymlink(file, internedFileName, symlinkHasBeenFiltered);
                        if (targetSnapshot != null) {
                            DirectorySnapshot directorySnapshotAccessedViaSymlink = new DirectorySnapshot(
                                targetSnapshot.getAbsolutePath(),

        snapshot.absolutePath == rootDir.absolutePath

        def link2 = snapshot.children[0].children[0] as DirectorySnapshot
        link2.accessType == AccessType.VIA_SYMLINK
        link2.name == "linked"

        def link3 = link2.children[1].children[0] as DirectorySnapshot
        link3.accessType == AccessType.VIA_SYMLINK
        link3.name == "linked3"

        default void visitDirectory(DirectorySnapshot directorySnapshot) {};
        default void visitRegularFile(RegularFileSnapshot fileSnapshot) {};
        default void visitMissing(MissingFileSnapshot missingSnapshot) {};
    }

    interface FileSystemLocationSnapshotTransformer<T> {
        T visitDirectory(DirectorySnapshot directorySnapshot);
        T visitRegularFile(RegularFileSnapshot fileSnapshot);

                @Override
                public Boolean visitDirectory(DirectorySnapshot directorySnapshot) {
                    // Check if a new directory appeared. For matching directories don't check content
                    // hash as we should detect individual entries that are different instead)
                    return hasNewContent(relativePath, directorySnapshot);
                }

                @Override

                @Override
                public SnapshotVisitResult visitDirectory(DirectorySnapshot directorySnapshot) {
                    if (watchableHierarchies.ignoredForWatching(directorySnapshot)) {
                        return SnapshotVisitResult.SKIP_SUBTREE;
                    } else {
                        subDirectoryToWatchConsumer.accept(directorySnapshot.getAbsolutePath());
                        return SnapshotVisitResult.CONTINUE;