Re: [C++] Unreviewed patches

[Nathan Sidwell <nathan at codesourcery dot com>]

Giovanni Bajo wrote:
> Hello,
>
> Allow 'template' within non dependent nested-specifiers:
> http://gcc.gnu.org/ml/gcc-patches/2003-12/msg01698.html
>
> A little bit of DR224
> http://gcc.gnu.org/ml/gcc-patches/2003-12/msg01722.html
>
> They both fix regressions on mainline. About the latter, I have some doubts
> about its correctness mainly because there is a part of DR224 which is not
> totally clear. Basically, should this be accepted?
>
> ------------------------------------
> struct B {
>   typedef int K;
> };
>
> template <class T> struct D : T {
>   typedef typename D::K K2;
> };
> ------------------------------------
I do not think this is valid. IIU 224 correctly, the nested-name-specifier
(which is D) is not dependent, therefore we do the lookup and definition
time (looking in D and any non-dependent bases), and in this case we
find nothing, so it is an error.

In addition, as D is non-dependent, the typename keyword should not be there.
But IIRC there is/may be a DR about relaxing the typename rule. Originally
it was either needed or not-allowed, there was no overlap.  If DR224 is
implemented, without relaxing the typename rule, a lot of code will become
ill-formed. See DR409.

nathan

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