From -2440770295702202820 X-Google-Thread: f78e5,d9fe358a73c69991 X-Google-Attributes: gidf78e5,public X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news1.google.com!news3.google.com!news2.google.com!newsread.com!news-xfer.newsread.com!nntp.abs.net!news-FFM2.ecrc.net!news.m-online.net!newsfeed.stueberl.de!peer-uk.news.demon.net!kibo.news.demon.net!news.demon.co.uk!demon!stump.algebra.com!devnull From: pavel@despammed.com ("Pavel Kuznetsov") Newsgroups: comp.std.c++ Subject: Re: Should failure to instantiate a function template abort compilation during overload resolution? Date: Thu, 11 Aug 2005 14:33:37 GMT Lines: 77 Sender: mail2news@demon.net Approved: fjh@cs.mu.oz.au (Fergus Henderson , moderator of comp.std.c++) Message-ID: References: <1123485075.096196.242990@g44g2000cwa.googlegroups.com> <3ltsd1F14jf4hU1@individual.net> NNTP-Posting-Host: news.news.demon.net Mime-Version: 1.0 Content-Type: text/plain; format=flowed; delsp=yes; charset=windows-1251 Content-Transfer-Encoding: 8bit X-Trace: news.demon.co.uk 1123770831 19868 158.152.254.254 (11 Aug 2005 14:33:51 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Thu, 11 Aug 2005 14:33:51 +0000 (UTC) X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-User-Agent: Opera M2(BETA1)/8.02 (Win32, build 7668) X-Virus-Scanned: amavisd-new at cs.mu.OZ.AU X-Received: (from fjh@localhost) by mulga.cs.mu.OZ.AU (8.12.10+Sun/8.12.9/Submit) id j7BEXbn5028801; Fri, 12 Aug 2005 00:33:37 +1000 (EST) X-Path: comp-std-cpp-robomod!not-for-mail X-Delivered-To: std-c++@ucar.edu X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-Newsgroups: comp.std.c++ Xref: g2news1.google.com comp.std.c++:1762 Richard, > template > struct A > { > friend class B; > }; > > template > typename T::TYPE foo (T); // Does use SFNAE > > template > typename A::TYPE foo (T); // Does not use SFNAE > > void foo (int); > > void bar () > { > foo (0); > } > > // ... > > typedef int B; I fail to see why you're saying that SFINAE does not take place in the second case, and in fact the standard contains a similar example: 14.8.2/2 <...> Type deduction may fail for the following reasons: <...> - Attempting to use a type in the qualifier portion of a qualified name that names a type when that type does not contain the specified member, or if the specified member is not a type where a type is required. [Example: template int f(typename T::B*); struct A {}; struct C { int B; }; int i = f(0); int j = f(0); ] 14.8.3/1 <...> If, for a given function template, argument deduction fails, no such function is added to the set of candidate functions for that template. > If the compiler did allow you to instantiate class bodies, it would then > have a lot of difficulty back tracking. In this example, a completely > unrelated typedef would now generate an error since there is already a > 'class B' declared in the namespace. This is exactly what Comeau Online and VC++8 beta 2 has to say for your example: ==== "ComeauTest.c", line 23: error: invalid redeclaration of type name "B" (declared at line 4) typedef int B; ^ 1 error detected in the compilation of "ComeauTest.c". === .\test.cpp(36) : error C2371: 'B' : redefinition; different basic types .\test.cpp(17) : see declaration of 'B' -- Pavel --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ]