Arg

        pub const Arg = struct {
            flags: @This().Flags,
            prefix: Storage.FlagOptional(.flags, .prefix, String),
            suffix: Storage.FlagOptional(.flags, .suffix, String),
            basename: Storage.FlagOptional(.flags, .basename, String),
            path: Storage.FlagOptional(.flags, .path, LazyPath.Index),
            /// Always a compile step.
            producer: Storage.FlagOptional(.flags, .producer, Step.Index),
            generated: Storage.FlagOptional(.flags, .generated, GeneratedFileIndex),

            pub const Flags = packed struct(u32) {
                tag: Arg.Tag,
                prefix: bool,
                suffix: bool,
                basename: bool,
                path: bool,
                producer: bool,
                generated: bool,
                dep_file: bool,
                make_absolute: bool,
                _: u20 = 0,
            };

            pub const Tag = enum(u4) {
                artifact,
                /// `path` contains the file.
                path_file,
                path_directory,
                /// `prefix` contains the string.
                string,
                file_content,
                output_file,
                output_directory,
                passthru,
                /// `prefix` contains the enabled string.
                /// `suffix` contains the disabled string.
                enable_darling,
                enable_qemu,
                enable_rosetta,
                enable_wasmtime,
                enable_wine,
            };

            pub const Index = IndexType(@This());
        }