import antlr.preprocessor.Hierarchy;

import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;

/**
 * Models cross-reference (x-ref) info about {@link GrammarFileMetadata grammar files} such as {@link #filesByPath}, {@link #filesByExportVocab} and {@link #filesByClassName}.
 */
public class XRef {
    private final Hierarchy antlrHierarchy;

     * by getName() is not unique in the hierarchy.
     *
     * @param element the element, cannot be null
     * @return the identity name of the element, never null
     */
    String getIdentityName(T element);

    /**
     * Returns the parent in this element's hierarchy.
     *
     * @param element the child element, cannot be null

     *
     * For example, this removes everything from the root which can't be kept after the current build finished.
     * This is anything which is not within a watchable hierarchy or in a cache directory.
     *
     * @return the snapshot hierarchy without snapshots which can't be kept till the next build.
     */
    @CheckReturnValue

        outputHierarchy.clear();
        destroyableHierarchy.clear();
    }

    /**
     * Create the input node access hierarchy.
     *
     * For performance reasons, we keep one input node access hierarchy per project,
     * so we only have a factory method here and this is used to create the hierarchy in {@link org.gradle.execution.ProjectExecutionServices}.
     */
    public InputNodeAccessHierarchy createInputHierarchy() {

 *     <dd>The list of file system hierarchies that we've activated a file system probe for.
 *     We list every hierarchy here, even if there are ones nested inside others.
 *     See {@link FileWatcherProbeRegistry}.</dd>
 * </dl>
 */
public interface FileWatcherUpdater {
    /**
     * Registers a watchable hierarchy.
     *
     * @see FileWatcherRegistry#registerWatchableHierarchy(File, SnapshotHierarchy)
     */

    }

    interface Iface {}

    class Child extends Base implements Serializable, Iface {
        @Nullable
        Object doSomething() { null }
    }

    def "walking type hierarchy happens breadth-first"() {
        def visitor = Mock(Types.TypeVisitor)
        when:
        Types.walkTypeHierarchy(Child, [Object, GroovyObject], visitor)

     */
    Stream<FileSystemLocationSnapshot> roots();

    /**
     * Walks the whole hierarchy represented by this snapshot.
     *
     * The walk is depth first.
     */
    SnapshotVisitResult accept(FileSystemSnapshotHierarchyVisitor visitor);

    /**
     * Walks the whole hierarchy represented by this snapshot.
     *
     * The walk is depth first.
     */

        ImmutableList<ModuleComponentArtifactMetadata> artifacts = configurationHelper.filterArtifacts(name, hierarchy);
        ImmutableList<ExcludeMetadata> excludesForConfiguration = configurationHelper.filterExcludes(hierarchy);

            if (watchedFiles.contains(watchableHierarchy)) {
                // Need to stop watching this hierarchy
                return !hasSnapshotsToWatch;
            } else {
                // Need to start watching this hierarchy
                return hasSnapshotsToWatch;
            }
        });
    }

    @Override

import static org.gradle.internal.snapshot.impl.SerializedLambdaQueries.serializedLambdaFor;

/**
 * Identifies a type in a classloader hierarchy. The type is identified by its name,
 * the classloader hierarchy by its hash code.
 */
public abstract class ImplementationSnapshot implements ValueSnapshot {

    protected final String classIdentifier;