fun inputFile(file: File) =
            InputFile(
                file,
                host.hashCodeOf(file)
            )

        fun inputFileSystemEntry(file: File) =
            InputFileSystemEntry(file, fileSystemEntryType(file))
    }

    private
    class BuildScopedSink(
        host: Host,
        private val writer: ScopedFingerprintWriter<ConfigurationCacheFingerprint>

    ) : ConfigurationCacheFingerprint()

    data class DirectoryChildren(
        val file: File,
        val hash: HashCode
    ) : ConfigurationCacheFingerprint()

    data class InputFileSystemEntry(
        val file: File,
        val fileType: FileType
    ) : ConfigurationCacheFingerprint()

    data class ValueSource(
        val obtainedValue: ObtainedValue
    ) : ConfigurationCacheFingerprint()

                if (hasDirectoryChanged(file, hash)) {
                    return "directory '${displayNameOf(file)}' has changed"
                }
            }
            is ConfigurationCacheFingerprint.InputFileSystemEntry -> input.run {
                val newType = fileSystemEntryType(file)
                if (newType != fileType) {
                    val prefix = "the file system entry '${displayNameOf(file)}'"

                    on { displayNameOf(inputFile) } doReturn "displayNameOf(inputFile)"
                },
                ConfigurationCacheFingerprint.InputFileSystemEntry(
                    inputFile,
                    FileType.RegularFile
                )
            ),
            equalTo("the file system entry 'displayNameOf(inputFile)' has been removed")
        )