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

        override fun visitFileTreeBackedByFile(file: File, fileTree: FileTreeInternal, sourceTree: FileSystemMirroringFileTree) {
            elements.add(file)
        }

        fun simplify(): FileCollectionInternal = fileCollectionFactory.resolving(elements)