[v3] Another try at LWG 2141

[Marc Glisse]

On Wed, 24 Oct 2012, Paolo Carlini wrote:

> let's try again ;) In the light of discussion in Portland, which liked Marc's 
> idea of using std::decay in the unary common_type too, the below seems good 
> to go now, given that there are bad interactions with the front-end bug we 
> have got.

    template<typename _Tp>
      struct common_type<_Tp>
-    { typedef _Tp type; };
+    { typedef typename decay<_Tp>::type type; };

(talking to myself)
I guess decay never has sfinae-type errors, so it doesn't matter whether 
we have this typedef or derive from decay.

-- 
Marc Glisse