Hi all,

Is the following valid C++ or not?

   void f(int, int) {}
   class X {};
   template< typename T > void f(X const &, T const &);
   enum { E };
   int main() { f(1, E); }

Specifically, when determining the set of canditate functions for the
call to f in main, should the compiler complain that the template f is
instantiated with an unnamed type (14.3.1/2: "[...] an unnamed type
[...] shall not be used as a template-argument for a template
type-parameter."), or should it just ignore the template f, a la SFINAE?

If SFINAE does not apply here, is a compiler still allowed to accept the
above program, on the grounds that the template f is never a viable
overload for the call (since 1 cannot be converted to X), so
instantiating it for the unnamed enum can be "short circuited" away?
No, right?

-Stephan

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Good morning Stephan Bergmann,

Stephan Bergmann schrieb:

> Hi all,
>
> Is the following valid C++ or not?
>
>   void f(int, int) {}
>   class X {};
>   template< typename T > void f(X const &, T const &);
>   enum { E };
>   int main() { f(1, E); }
>
> Specifically, when determining the set of canditate functions for the=20
> call to f in main, should the compiler complain that the template f is=20
> instantiated with an unnamed type (14.3.1/2: "[...] an unnamed type=20
> [...] shall not be used as a template-argument for a template=20
> type-parameter."), or should it just ignore the template f, a la SFINAE=
?
>
> If SFINAE does not apply here, is a compiler still allowed to accept=20
> the above program, on the grounds that the template f is never a=20
> viable overload for the call (since 1 cannot be converted to X), so=20
> instantiating it for the unnamed enum can be "short circuited" away?=20
> No, right?=20

I think, a similar problem has been described in the following open issue=
s:

http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#488
http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#489

Greetings from Bremen,

Daniel Kr=FCgler

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