}
        }

        override fun visitCollection(source: FileCollectionInternal.Source, contents: Iterable<File>) =
            throw UnsupportedOperationException()

        override fun visitFileTree(root: File, patterns: PatternSet, fileTree: FileTreeInternal) {
            roots.add(DirectoryTreeSpec(root, patterns))
        }

private
class ResolutionBackedFileCollectionSpec(val displayName: String, val lenient: Boolean, val elements: List<Any>)


private
abstract class AbstractVisitor : FileCollectionStructureVisitor {
    override fun visitFileTree(root: File, patterns: PatternSet, fileTree: FileTreeInternal) =
        unsupportedFileTree(fileTree)

        override fun visitCollection(source: FileCollectionInternal.Source, contents: Iterable<File>) {
            elements.addAll(contents)
        }

        override fun visitFileTree(root: File, patterns: PatternSet, fileTree: FileTreeInternal) {
            elements.add(directoryFileTreeFactory.create(root, patterns))
        }