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From: "fchelnokov at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/113523] New: A conversion function template can have a
 deduced return type
Date: Sat, 20 Jan 2024 11:52:51 +0000
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X-Bugzilla-Version: 13.2.1
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113523

            Bug ID: 113523
           Summary: A conversion function template can have a deduced
                    return type
           Product: gcc
           Version: 13.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fchelnokov at gmail dot com
  Target Milestone: ---

Contrary to https://timsong-cpp.github.io/cppwp/n4861/class.conv.fct#6, GCC
allows  a conversion function template with a deduced return type:


struct A {
    template<class=3Dvoid>
    constexpr operator auto() const { return 1; }
};

constexpr int f() {
    return A{}.template operator auto();
}

static_assert( f() =3D=3D 1 );


Online demo: https://godbolt.org/z/s8oK6rnPY

In addition, the diagnostics "warning: use of 'auto' in member template
conversion operator can never be deduced" seems wrong.=