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

        public void visitCollection(FileCollectionInternal.Source source, Iterable<File> contents) {
            cannotInferSourceRoots(contents);
        }

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

        @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

                    }
                }

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

                @Override

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

                assert patterns.getIncludes() == includes
                assert patterns.getExcludes() == excludes
            }

            @Override
            void visitFileTreeBackedByFile(File file, FileTreeInternal fileTree, FileSystemMirroringFileTree sourceTree) {
                throw new IllegalArgumentException()
            }
        })
    }

    private void configureTask() {

        }


        @Override
        void visitFileTree(File root, PatternSet patterns, FileTreeInternal fileTree) {
            Assert.fail()
        }

        @Override
        void visitFileTreeBackedByFile(File file, FileTreeInternal fileTree, FileSystemMirroringFileTree sourceTree) {
            Assert.fail()
        }
    }

        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)