From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on yquem.inria.fr X-Spam-Level: * X-Spam-Status: No, score=1.5 required=5.0 tests=AWL,SPF_SOFTFAIL autolearn=disabled version=3.1.3 X-Original-To: caml-list@yquem.inria.fr Delivered-To: caml-list@yquem.inria.fr Received: from concorde.inria.fr (concorde.inria.fr [192.93.2.39]) by yquem.inria.fr (Postfix) with ESMTP id 4679FBC6B for ; Fri, 23 Feb 2007 21:51:41 +0100 (CET) Received: from smtp.janestcapital.com (janestcapital.com [66.155.124.107]) by concorde.inria.fr (8.13.6/8.13.6) with ESMTP id l1NKpe2Z007169 for ; Fri, 23 Feb 2007 21:51:40 +0100 Received: from [192.168.250.217] [209.213.205.130] by janestcapital.com with ESMTP (SMTPD-9.10) id A3D70120; Fri, 23 Feb 2007 15:51:35 -0500 Message-ID: <45DF53D7.4090007@gnu.org> Date: Fri, 23 Feb 2007 15:51:35 -0500 From: Sam Steingold User-Agent: Thunderbird 1.5.0.8 (X11/20061107) MIME-Version: 1.0 To: Jacques Garrigue Cc: caml-list@inria.fr Subject: Re: warning on value shadowing References: <45DCAE89.1050904@gnu.org> <20070222.095436.125900161.garrigue@math.nagoya-u.ac.jp> In-Reply-To: <20070222.095436.125900161.garrigue@math.nagoya-u.ac.jp> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Miltered: at concorde with ID 45DF53DC.001 by Joe's j-chkmail (http://j-chkmail . ensmp . fr)! X-Spam: no; 0.00; foo:01 quux:01 foo:01 quux:01 overkill:01 overkill:01 refactor:01 pervasives:01 printf:01 baz:01 bug:01 compiler:01 defines:01 unix:01 wrote:01 Jacques Garrigue wrote: > From: Sam Steingold >> Proposal: >> When both foo.ml and bar.ml define zot and quux.ml opens both Foo and >> Bar, there should be a warning (when compiling quux) about Foo.zot being >> shadowed by Bar.zot (or vice versa, depending on the order of the open >> statements). >> If you think this is an overkill, please at least consider issuing the >> warning when zot is used in quux.ml. >> If you think that is also an overkill, please at least consider issuing >> the warning when foo=quux. > > The first one is clearly overkill: if nobody uses zot, then who cares? you are not using it NOW, but you might in the future, at which point you will all of a sudden have to refactor your code to avoid the warning. I would rather see the shadowing warning the moment I add "open Foo" for the first time. > The second one might be useful, but it creates some problems. > For instance, it is common practice to open Format or Unix, and have > them intentionally shadow definitions from Pervasives. Should we make > an exception for that? But it is not so infrequent to do it with > other modules too (for instance open Printf, then Format). For this to > be practical, the language would have to be enriched with finer grain > control on imports. you should be able to say something like shadow Foo.bar with Baz.bar > How bad is the problem in practice? horrible. silent shadowing is one of those "low probability -- high consequences" situations. the fact that you personally have never had to spend hours chasing a stupid bug that should have been uncovered by the compiler does not mean that silent shadowing is good practice. > As for the 3rd case, I'm not sure what you are pointing at. bar.ml defines zot. foo.ml contains this: open Bar let zot = 1 compiling foo.ml should warn me that foo shadows Bar.zot. Sam.