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[176.9.126.58]) by mx.google.com with ESMTPS id n4si6991658wrf.267.2017.09.26.00.55.49 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 26 Sep 2017 00:55:49 -0700 (PDT) Received-SPF: pass (google.com: domain of marc.mutz@kdab.com designates 176.9.126.58 as permitted sender) client-ip=176.9.126.58; X-Virus-Scanned: amavisd-new at kdab.com Original-Sender: marc@kdab.com X-Sender: marc.mutz@kdab.com X-Original-Sender: marc.mutz@kdab.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of marc.mutz@kdab.com designates 176.9.126.58 as permitted sender) smtp.mailfrom=marc.mutz@kdab.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:34490 Archived-At: Hi, Why do these semantically identical pieces of code have different syntax rules? template auto find(Map &map, const Lookup &key) { const auto it = map.find(key); if (it == map.end()) return std::nullopt; else return std::optional{*it}; // error: inconsistent deduction for auto return type } template auto find(Map &map, const Lookup &key) { const auto it = map.find(key); return it == map.end() ? std::nullopt : std::optional{*it}; // OK, -> std::optional } iow: Why do auto return types have to have identical types, and don't just use the rules for the ternary operator? And why, in the first case, can I not say auto find(Map &map, const Lookup &key) -> std::optional { iow: why doesn't ctor template argument deduction work for trailing return types? Is/was this a conscious decision against, or would a proposal adding/changing these be welcome? Thanks, Marc -- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an email to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/7bf0d2563477e89a8faa3ca2daa18f67%40kdab.com. .