@Override
    public Iterator<File> iterator() {
        return getFiles().iterator();
    }

    @Override
    public String getAsPath() {
        showGetAsPathDeprecationWarning();
        return GUtil.asPath(this);
    }

    private void showGetAsPathDeprecationWarning() {
        List<String> filesAsPaths = this.getFiles().stream()
            .map(File::getPath)

    final library = new SwiftGreeterWithOptionalFeature()
    final application = new SwiftMainWithOptionalFeature(library.withFeatureDisabled()) {
        @Override
        List<SourceFile> getFiles() {
            return super.getFiles().collect {
                sourceFile(it.path, it.name, "import Greeter\n${it.content}")
            }
        }
    }

    AppElement withFeatureEnabled() {

            .willBecomeAnErrorInGradle9()
            .withUpgradeGuideSection(8, "deprecate_self_resolving_dependency")
            .nagUser();

        return source.getFiles();
    }

    @Override
    @Deprecated
    public Set<File> resolve(boolean transitive) {
        DeprecationLogger.deprecate("Directly resolving a file collection dependency's files")

            listener.visitArtifacts(new EndCollection(this));
            return;
        }

        FileCollectionInternal fileCollection = dependencyMetadata.getFiles();
        Set<File> files;
        try {
            files = fileCollection.getFiles();
        } catch (Exception throwable) {
            listener.visitArtifacts(new BrokenArtifacts(throwable));
            return;
        }

        FileTree scriptPluginFiles = pluginSourceSet.getAllSource().matching(PrecompiledGroovyScript::filterPluginFiles);

        List<PrecompiledGroovyScript> scriptPlugins = scriptPluginFiles.getFiles().stream()
            .map(file -> new PrecompiledGroovyScript(file, getTextFileResourceLoader()))
            .peek(scriptPlugin -> validateScriptPlugin(project, scriptPlugin))
            .collect(Collectors.toList());

    SourceElement getGreeter() {
        return app.greeter
    }

    SourceElement getLogger() {
        return app.logger
    }

    @Override
    List<SourceFile> getFiles() {
        return Lists.newArrayList(Iterables.concat(super.getFiles(), app.greeter.files, app.logger.files, sum.files, multiply.files))
    }

        when:
        Set<File> files = collection.getFiles()

        then:
        collection.toString() == 'test files'
        files == [tmpDir.file('abc')] as Set
    }

    def 'resolving collection source #description can return null'() {
        def collection = factory.resolving('test files', input)

        when:
        Set<File> files = collection.getFiles()

        then:
        files.isEmpty()

        for (int i = 0; i < artifactSets.length; i++) {
            fileCollections[i] = (FileCollectionInternal) artifactSets[i].getFiles();
        }
        files = new UnionFileCollection(taskDependencyFactory, fileCollections);
    }

    @Override
    public FileCollection getFiles() {
        return files;
    }

        left.visitDependencies(context);
    }

    @Override
    protected Set<File> getIntrinsicFiles() {
        Set<File> files = new LinkedHashSet<File>(left.getFiles());
        files.removeAll(right.getFiles());
        return files;
    }

    @Override
    public boolean contains(File file) {
        return left.contains(file) && !right.contains(file);
    }

            for (NativeDependencySet nativeDependencySet : binary.getLibs()) {
                runtimeFiles.add(getFiles(nativeDependencySet));
            }
            return runtimeFiles;
        }

        protected abstract FileCollection getFiles(NativeDependencySet nativeDependencySet);
    }