[Bug c++/12216] Bad "implicit typename" warning

[igodard at pacbell dot net]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12216



------- Additional Comments From igodard at pacbell dot net  2003-09-09 07:02 -------
Subject: Re:  Bad "implicit typename" warning

Understood. Thanks.

Ivan

----- Original Message ----- 
From: "bangerth at dealii dot org" <gcc-bugzilla@gcc.gnu.org>
To: <igodard@pacbell.net>
Sent: Monday, September 08, 2003 2:41 PM
Subject: [Bug c++/12216] Bad "implicit typename" warning


> PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12216
>
>
> bangerth at dealii dot org changed:
>
>            What    |Removed                     |Added
> --------------------------------------------------------------------------
--
>              Status|UNCONFIRMED                 |RESOLVED
>          Resolution|                            |INVALID
>
>
> ------- Additional Comments From bangerth at dealii dot org  2003-09-08
21:41 -------
> No. Given your code
> -------------------------
> template<typename I>
> class C : public std::iterator<
>               typename std::iterator_traits<I>::Category,
>               typename std::iterator_traits<I>::value_type,
>               typename std::iterator_traits<I>::difference_type,
>               typename std::iterator_traits<I>::pointer,
>               typename std::iterator_traits<I>::reference
>                                                         > {
> public:
>                                 C(I i) : iter(i) {}
>
>         value_type operator*() const { return *iter; }
> private:
>         I iter;
>         };
>
> int main() {
>         }
>
> ---------------------------------
> the typedef value_type is not visible with two-stage lookup. Your code
> is thus invalid, but gcc up to and including 3.3.x accepts it. You
> really need to write the thing with the typename, but including the
> classname, i.e.
>   typename C<I>::value_type
> or
>   typename std::iterator<...>::value_type
>
> The point is that you need to make the name of the type dependent, so
> that it is looked up on instantiation, rather than declaration time. So
> the thing before :: must be template dependent, but then you also need
> the typename.
>
> W.
>
>
>
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