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, FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY 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 240841F990 for ; Thu, 6 Aug 2020 14:34:35 +0000 (UTC) Received: from neon.ruby-lang.org (localhost [IPv6:::1]) by neon.ruby-lang.org (Postfix) with ESMTP id 65BA8120B0E; Thu, 6 Aug 2020 23:33:59 +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 582E0120A12 for ; Thu, 6 Aug 2020 23:33:56 +0900 (JST) Received: by filterdrecv-p3iad2-d8cc6d457-tlvzw with SMTP id filterdrecv-p3iad2-d8cc6d457-tlvzw-19-5F2C14EB-38 2020-08-06 14:34:19.18288131 +0000 UTC m=+678353.897954901 Received: from herokuapp.com (unknown) by geopod-ismtpd-3-0 (SG) with ESMTP id Z7nmWaOKSZmG5OwL-kgAyg for ; Thu, 06 Aug 2020 14:34:19.062 +0000 (UTC) Date: Thu, 06 Aug 2020 14:34:19 +0000 (UTC) From: hanmac@gmx.de Message-ID: References: Mime-Version: 1.0 X-Redmine-MailingListIntegration-Message-Ids: 75328 X-Redmine-Project: ruby-master X-Redmine-Issue-Tracker: Bug X-Redmine-Issue-Id: 17105 X-Redmine-Issue-Author: Eregon X-Redmine-Sender: Hanmac 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?z6kUDlxbGclXLcwluHLUb5EO6uh6mW1Jn0ZSGyxj3H2Ua=2FQudPU96yYxGK0Pfb?= =?us-ascii?Q?obPOkGxfUbN+hOl6TJXR0ynF56lnhfOkY9n4r0=2F?= =?us-ascii?Q?7eWRzfm=2FQLzN2PoDnORPLoWDCPMv9HWg=2Fb+A9gh?= =?us-ascii?Q?5AtvNPmVkUmQ8fognPxhuzBpeoWpXM7xVYECyGw?= =?us-ascii?Q?BCmZVx6gNJPLR1Vo5mYequwaoZH0I+K5GXg=3D=3D?= To: ruby-core@ruby-lang.org X-ML-Name: ruby-core X-Mail-Count: 99502 Subject: [ruby-core:99502] [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 Hanmac (Hans Mackowiak). i think this is by design: https://www.rubyguides.com/2016/02/ruby-procs-and-lambdas/ > A lambda will return normally, like a regular method. > But a proc will try to return from the current context. > Procs return from the current method, while lambdas return from the lambda itself. ---------------------------------------- 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-86959 * 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/