From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from neon.ruby-lang.org (neon.ruby-lang.org [221.186.184.75]) by dcvr.yhbt.net (Postfix) with ESMTP id 550E81F66E for ; Mon, 31 Aug 2020 09:00:40 +0000 (UTC) Received: from neon.ruby-lang.org (localhost [IPv6:::1]) by neon.ruby-lang.org (Postfix) with ESMTP id 5E9F71209FA; Mon, 31 Aug 2020 18:00:05 +0900 (JST) Received: from xtrwkhkc.outbound-mail.sendgrid.net (xtrwkhkc.outbound-mail.sendgrid.net [167.89.16.28]) by neon.ruby-lang.org (Postfix) with ESMTPS id E7BE8120910 for ; Mon, 31 Aug 2020 18:00:03 +0900 (JST) Received: by filterdrecv-p3iad2-787bb5c9bc-z28f8 with SMTP id filterdrecv-p3iad2-787bb5c9bc-z28f8-18-5F4CBC31-17F 2020-08-31 09:00:33.856805807 +0000 UTC m=+313248.237881692 Received: from herokuapp.com (unknown) by geopod-ismtpd-2-1 (SG) with ESMTP id RtC0kM-aRBCw7zcLuXi2SA for ; Mon, 31 Aug 2020 09:00:33.848 +0000 (UTC) Date: Mon, 31 Aug 2020 09:00:33 +0000 (UTC) From: matz@ruby.or.jp Message-ID: References: Mime-Version: 1.0 X-Redmine-MailingListIntegration-Message-Ids: 75627 X-Redmine-Project: ruby-master X-Redmine-Issue-Tracker: Bug X-Redmine-Issue-Id: 17105 X-Redmine-Issue-Author: Eregon X-Redmine-Sender: matz X-Mailer: Redmine X-Redmine-Host: bugs.ruby-lang.org X-Redmine-Site: Ruby Issue Tracking System X-Auto-Response-Suppress: All Auto-Submitted: auto-generated X-SG-EID: =?us-ascii?Q?bXEIHGfdFwsIlBTndiToCp=2Fmc2rfxRD2sZAksRKJIHXFUdHxtrm8jsSsk2Xjah?= =?us-ascii?Q?iPNYp=2Fc=2Fo6RfW2KyL+jPhQUBJZdRYJK=2F+EUQyLC?= =?us-ascii?Q?B87D=2FDeXGifASYOwyyro=2FltqLpLV6nc3yNiSZLC?= =?us-ascii?Q?jYFB54vpFvk8SwfcYpwAQb2jIZ+MirVe2uV9D11?= =?us-ascii?Q?jFWJ4F7kpwK7ZRqaRgPRKfA4XXhJeq+75RYN+Xb?= =?us-ascii?Q?HGRL5+REOExUhBXJU=3D?= To: ruby-core@ruby-lang.org X-ML-Name: ruby-core X-Mail-Count: 99794 Subject: [ruby-core:99794] [Ruby master Bug#17105] A single `return` can return to two different places in a proc inside a lambda inside a method X-BeenThere: ruby-core@ruby-lang.org X-Mailman-Version: 2.1.15 Precedence: list Reply-To: Ruby developers List-Id: Ruby developers List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ruby-core-bounces@ruby-lang.org Sender: "ruby-core" Issue #17105 has been updated by matz (Yukihiro Matsumoto). It is intentional since 1.6.0. But I am OK with making `m2` raise `LocalJumpError`. Ask @ko1 about migration. Matz. ---------------------------------------- Bug #17105: A single `return` can return to two different places in a proc inside a lambda inside a method https://bugs.ruby-lang.org/issues/17105#change-87311 * Author: Eregon (Benoit Daloze) * Status: Open * Priority: Normal * Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN ---------------------------------------- A single `return` in the source code might return to 2 different lexical places. That seems wrong to me, as AFAIK all other control flow language constructs always jump to a single place. ```ruby def m(call_proc) r = -> { # This single return in the source might exit the lambda or the method! proc = Proc.new { return :return } if call_proc proc.call :after_in_lambda else proc end }.call # returns here if call_proc if call_proc [:after_in_method, r] else r.call :never_reached end end p m(true) # => [:after_in_method, :return] p m(false) # :return ``` We're trying to figure out the semantics of `return` inside a proc in https://github.com/oracle/truffleruby/issues/1488#issuecomment-669185675 and this behavior doesn't seem to make much sense. @headius also seems to agree: > I would consider that behavior to be incorrect; once the proc has escaped from the lambda, its return target is no longer valid. It should not return to a different place. > https://github.com/jruby/jruby/issues/6350#issuecomment-669603740 So: * is this behavior intentional? or is it a bug? * what are actually the semantics of `return` inside a proc? The semantics seem incredibly complicated to a point developers have no idea where `return` actually goes. Also it must get even more complicated if one defines a `lambda` method as the block in `lambda { return }` is then non-deterministically a proc or lambda. -- https://bugs.ruby-lang.org/