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Re: Question about argument-dependent-lookup for namespace-scope friend function

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On 2012-03-04 23:25, neverhoodboy wrote:
>  We know that argument-dependent-lookup can be used to find namespace-
>  scope friend function defined in some class which is otherwise not
>  visible using an ordinary lookup.  My question is, can the argument be
>  of some class in the same namespace other the enclosing class of the
>  friend function?  Please see the following code snippet:
>
>  namespace NNN
>  {
>      class BBB {};
>      class AAA
>      {
>      public:
>          friend void func() {}
>          friend void funca(AAA&) {}
>          friend void funcb(BBB&) {}
>      };
>  }
>
>  int main()
>  {
>      NNN::AAA a;
>      NNN::BBB b;
>      NNN::func();  // this will fail to compile for sure
>      funca(a);  // this will compile with no problem because of ADL
>      funcb(b);  // will this compile?
>  }

IMO the call of funcb is supposed to be ill-formed. According to 3.4.2
p4 b2:

"Any namespace-scope friend functions or friend function templates
declared in associated classes are visible [..]"

but for a non-template class BBB, only BBB itself (and not AAA) is an
associated class.

HTH&  Greetings from Bremen,

Daniel Krügler


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Question about argument-dependent-lookup for namespace-scope friend function neverhoodboy <xinjie.wang@gmail.com> - 2012-03-04 14:25 -0800
  Re: Question about argument-dependent-lookup for namespace-scope friend function Daniel Krügler<daniel.kruegler@googlemail.com> - 2012-03-06 08:50 -0800

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