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Subject: [Bug c++/54890] New: Incorrect SFINAE Rejection
Date: Wed, 10 Oct 2012 15:19:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D54890

             Bug #: 54890
           Summary: Incorrect SFINAE Rejection
    Classification: Unclassified
           Product: gcc
           Version: 4.7.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: pmenso57@comcast.net


When explicitly specifying the template parameters to a function template in
the following context, the compiler incorrectly removes the function from t=
he
overload set for a substitution failure which should not exist.

struct A {
    template<class T> struct apply { };
};

template<class T, class... U>
void f(typename T::template apply<U...>*) { }

int main() {
    f<A, int>(nullptr);
    return 0;
}

Output from the compiler is:

In function =E2=80=98int main()=E2=80=99:
error: no matching function for call to =E2=80=98f(std::nullptr_t)=E2=80=99
note: candidate is:
note: template<class T, class ... U> void f(typename T::apply<U ...>*)
note:   template argument deduction/substitution failed:
note:   mismatched types =E2=80=98A::apply<U ...>*=E2=80=99 and =E2=80=98st=
d::nullptr_t=E2=80=99

Which I believe is incorrect.