我有一个Gulp 3文件，我试图升级到Gulp 4。当我这样做时，一些任务工作，其他人不工作。我得到的三个错误如下：
清爽型：

gulp.task('clean-styles', function (done) {
    var files = config.temp + '**/*.css';
    clean(files, done);
});

[23:47:05] The following tasks did not complete: clean-styles 
[23:47:05] Did you forget to signal async completion?

scss观察程序：

gulp.task('scss-watcher', function () {
    gulp.watch([config.scss], ['styles']);
});

[23:51:27] 'scss-watcher' errored after 2.46 ms
[23:51:27] Error: watching ./src/client/styles/styles.scss: watch task has to be a function (optionally generated by using gulp.parallel or gulp.series)

styles：（如果我删除clean-styles系列，这将起作用）

gulp.task('styles', gulp.series('clean-styles', function () {
log('Compiling SCSS --> CSS');

return gulp
    .src(config.scss)
    .pipe($.scss())
    .pipe($.autoprefixer({ browsers: ['last 2 versions', '> 5%'] }))
    .pipe(gulp.dest(config.temp));
}));

[23:52:42] The following tasks did not complete: styles, clean-styles
[23:52:42] Did you forget to signal async completion?

（作品）

gulp.task('vet', function () {
    log('Analyzing source with ESLint');
    return gulp
        .src(config.js)
        .pipe($.if(args.verbose, $.print()))
        .pipe($.eslint())
        .pipe($.eslint.format())
        .pipe($.eslint.failOnError());
});

功能：

function clean(path, done) {
    log('Cleaning: ' + $.util.colors.blue(path));
    del(path, done);
}

function log(msg) {
    if (typeof(msg) === 'object') {
        for (var item in msg) {
            if (msg.hasOwnProperty(item)) {
                $.util.log($.util.colors.blue(msg[item]));
            }
        }
    }
    else {
        $.util.log($.util.colors.blue(msg));
    }
}

我一定是错过了什么。有人能告诉我我错过了什么吗？