[Bug c++/25006] New: failure "using" a name contained in a class

[Bug c++/25006] New: failure "using" a name contained in a class

[fp at mc dot com]

The following code fails to compile:

namespace Foo {
  struct Bar {
    struct FooBar {};
  };
}

using ::Foo::Bar::FooBar; // line 7

The error message being:
using.cpp:7: error: `Foo::Bar' is not a namespace

In the ISO C++ grammar [7.3.3], the using-declaration references a
"nested-name-specifier unqualified-id", not stating any restrictions
on the nested-name-specifier, which is composed of a sequence of
class-or-namespace-name [5.1].


-- 
           Summary: failure "using" a name contained in a class
           Product: gcc
           Version: 3.4.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: fp at mc dot com
 GCC build triplet: mingw-special
  GCC host triplet: mingw-special
GCC target triplet: mingw-special


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25006

[Bug c++/25006] failure "using" a name contained in a class

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2005-11-23 18:51 -------
ICC rejects it as invalid too:
t.cc(7): error: a class-qualified name is not allowed
  using ::Foo::Bar::FooBar; // line 7

So does  Comeau with the same error message.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25006

[Bug c++/25006] failure "using" a name contained in a class

[gdr at integrable-solutions dot net]

------- Comment #2 from gdr at integrable-solutions dot net  2005-11-23 19:36 -------
Subject: Re:  failure "using" a name contained in a class

"pinskia at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org> writes:

| ICC rejects it as invalid too:
| t.cc(7): error: a class-qualified name is not allowed
|   using ::Foo::Bar::FooBar; // line 7
| 
| So does  Comeau with the same error message.

The construct is ill-formed -- sorry, someone needs to quote
chapter and verse. I'll do that later if no one beats me at it.

-- Gaby


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25006

[Bug c++/25006] failure "using" a name contained in a class

[reichelt at gcc dot gnu dot org]

------- Comment #3 from reichelt at gcc dot gnu dot org  2005-11-30 21:09 -------
This is really invalid code.

Paragraph [7.3.3]/6 states:
  A using-declaration for a class member shall be a member-declaration.

In your code snippet "using ::Foo::Bar::FooBar;" is a using-declaration
for "FooBar" which is a class member of the class "::Foo::Bar". But since
the using-declaration is not inside a class, it is not a member-declaration
- which violates [7.3.3]/6.

Or the other way round: Because the using-declaration for "FooBar" is not
inside a class, it cannot be a member-declaration according to [7.3.3]/6.
Therefore "::Foo::Bar" cannot be a class-name - it has to be a
namespace-name. And that's what GCC's error message says.


-- 

reichelt at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |reichelt at gcc dot gnu dot
                   |                            |org
             Status|UNCONFIRMED                 |RESOLVED
  GCC build triplet|mingw-special               |
   GCC host triplet|mingw-special               |
 GCC target triplet|mingw-special               |
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25006

[Bug c++/25006] failure "using" a name contained in a class

[reichelt at gcc dot gnu dot org]

------- Comment #4 from reichelt at gcc dot gnu dot org  2005-11-30 21:13 -------
> Or the other way round: Because the using-declaration for "FooBar" is not
> inside a class, it cannot be a member-declaration according to [7.3.3]/6.
> Therefore "::Foo::Bar" cannot be a class-name - it has to be a
> namespace-name. And that's what GCC's error message says.

Sorry, the "according to" is at the wrong place.
This should read:

Or the other way round: Because the using-declaration for "FooBar" is not
inside a class, it cannot be a member-declaration. Therefore "::Foo::Bar"
cannot be a class-name according to [7.3.3]/6. Which means it has to be
a namespace-name. And that's what GCC's error message says.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25006