visitor.visitFileTree(root, patterns, fileTree);
            }

            @Override
            public void visitFileTreeBackedByFile(File file, FileTreeInternal fileTree, FileSystemMirroringFileTree sourceTree) {
                visitor.visitFileTreeBackedByFile(file, fileTree, sourceTree);
            }
        });
    }

    @Override

            public void visitFileTree(File root, PatternSet patterns, FileTreeInternal fileTree) {
                addTreeContents(fileTree);
            }

            @Override
            public void visitFileTreeBackedByFile(File file, FileTreeInternal fileTree, FileSystemMirroringFileTree sourceTree) {
                addTreeContents(fileTree);
            }
        });
        return files;
    }

    @Override

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

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

    private

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

    override fun visitFileTreeBackedByFile(file: File, fileTree: FileTreeInternal, sourceTree: FileSystemMirroringFileTree) =
        unsupportedFileTree(fileTree)

    private
    fun unsupportedFileTree(fileTree: FileTreeInternal): Nothing =

                        filteredFileTreeTaskInputs.add(new FilteredTree(root.getAbsolutePath(), patterns));
                    }
                }

                @Override
                public void visitFileTreeBackedByFile(File file, FileTreeInternal fileTree, FileSystemMirroringFileTree sourceTree) {
                    taskInputs.add(file.getAbsolutePath());
                }
            }));

            }

            @Override
            public void visitFileTree(File root, PatternSet patterns, FileTreeInternal fileTree) {
            }

            @Override
            public void visitFileTreeBackedByFile(File file, FileTreeInternal fileTree, FileSystemMirroringFileTree sourceTree) {
            }
        });

        setFrom(Cast.castNullable(FileCollection.class, object));
    }

    @Override

        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)