From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 49DB1C0218C for ; Mon, 27 Jan 2025 08:23:11 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tcKO2-0002H7-BU; Mon, 27 Jan 2025 03:22:26 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tcKO0-0002GQ-0P; Mon, 27 Jan 2025 03:22:24 -0500 Received: from mgamail.intel.com ([198.175.65.11]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tcKNx-0004JO-Dn; Mon, 27 Jan 2025 03:22:23 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1737966142; x=1769502142; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=A6CWQx7dOOYy0iRH1Pi9Ekl4iJ390pJ2cTjmmpYgulg=; b=fJ2UR8bv6dcsBfc3hPoe5a5eN54qgPXo7Kyd9/FajjG8MBpczngVWxVT I6wR1F2iqeiHTV2D4wLpfIUWvugTJhNrgL8EA6Zsg/tDPsx32toVCsteB ZMY2r9mPFjvr60HWIeiEoG9lrgquDqE5cN1S7KO0TGENthTUDpqQNIUxp 8dPJm6lMgrpwoo8jUohIaH6ZJUIrble3yD9/Nua9MwugdEIJmm8reAz3H Kbw325gybMXhl9bdP2WDbCmH6NPiG32cgopY30JrQ3gBW9GqXNrm/dMWB FL2KAnGX+JrZVLjkjuPB+5Buu6vo4sI60GqtbqePNfVgItHhgiaFAd/Re Q==; X-CSE-ConnectionGUID: RprspQcRRTCXiS/adDzoPA== X-CSE-MsgGUID: y7lGvBm2QPiuFHw1iGHuWQ== X-IronPort-AV: E=McAfee;i="6700,10204,11327"; a="48921854" X-IronPort-AV: E=Sophos;i="6.13,237,1732608000"; d="scan'208";a="48921854" Received: from orviesa009.jf.intel.com ([10.64.159.149]) by orvoesa103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Jan 2025 00:22:18 -0800 X-CSE-ConnectionGUID: z7Ru6dXDTvOkoNZYZ4lfSw== X-CSE-MsgGUID: GQ7IprNCRhmp7sDNhtGyjQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.13,237,1732608000"; d="scan'208";a="108179328" Received: from liuzhao-optiplex-7080.sh.intel.com (HELO localhost) ([10.239.160.39]) by orviesa009.jf.intel.com with ESMTP; 27 Jan 2025 00:22:16 -0800 Date: Mon, 27 Jan 2025 16:41:40 +0800 From: Zhao Liu To: Paolo Bonzini Cc: qemu-devel@nongnu.org, qemu-rust@nongnu.org Subject: Re: [PATCH 04/10] rust: callbacks: allow passing optional callbacks as () Message-ID: References: <20250117194003.1173231-1-pbonzini@redhat.com> <20250117194003.1173231-5-pbonzini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250117194003.1173231-5-pbonzini@redhat.com> Received-SPF: pass client-ip=198.175.65.11; envelope-from=zhao1.liu@intel.com; helo=mgamail.intel.com X-Spam_score_int: -56 X-Spam_score: -5.7 X-Spam_bar: ----- X-Spam_report: (-5.7 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.299, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org > Date: Fri, 17 Jan 2025 20:39:57 +0100 > From: Paolo Bonzini > Subject: [PATCH 04/10] rust: callbacks: allow passing optional callbacks as > () > X-Mailer: git-send-email 2.47.1 > > In some cases, callbacks are optional. Using "Some(function)" and "None" > does not work well, because when someone writes "None" the compiler does > not know what to use for "F" in "Option". > > Therefore, adopt () to mean a "null" callback. It is possible to enforce > that a callback is valid by adding a "let _: () = F::ASSERT_IS_SOME" before > the invocation of F::call. > > Signed-off-by: Paolo Bonzini > --- > rust/qemu-api/src/callbacks.rs | 97 ++++++++++++++++++++++++++++++++++ > 1 file changed, 97 insertions(+) Awesome trick. Reviewed-by: Zhao Liu > + /// Referring to this constant asserts that the `Self` type is an actual > + /// function type, which can be used to catch incorrect use of `()` > + /// at compile time. An extra whitespace.