Looks like namespace.udecl#14
<https://eel.is/c++draft/namespace.udecl#14> makes
this ill-formed.

On Mon, 11 May 2026 at 23:04, Brian Bi via Std-Discussion <
std-discussion_at_[hidden]> wrote:

> I think it's valid per the wording of the standard. Per
> [class.access.base]/5 <https://eel.is/c++draft/class.access.base#5>, the
> designating class is `Base`, and the member we are trying to access is
> public when considered as a member of that designating class, therefore
> access is granted.
>
> It does seem to me like this shouldn't be valid, and I'm not sure if we
> have the wording to make it so. Since [namespace.udecl]/3
> <https://eel.is/c++draft/namespace.udecl#3> says that you must name a
> base class, it seems to me that there is some missing wording saying that
> it must be an accessible base class.
>
> That's because we treat *using-declarations* (with the only exception
> being when they name constructors) as if they declared a name in a new
> scope that happens to refer to the same entity as that name in the original
> scope. So if we say that `using ::Base::member;` is valid, then we cannot
> stop `Derived` from being able to use `member` without further
> qualification, since it would then be accessing its *own* member, not
> that of a base class. This doesn't seem like the right result, so the only
> option is to make the *using-declaration* illegal.
>
> On Mon, May 11, 2026 at 11:31 AM Yongwei Wu via Std-Discussion <
> std-discussion_at_[hidden]> wrote:
>
>> Is the following code valid?
>>
>> class Base { public: int member; };
>> class Middle : private Base {};
>> struct Derived : public Middle { public: using ::Base::member; };
>>
>> I am inclined to think it is not valid, as :Base::member is not really
>> accessible inside Derived. I believe accessibility is a requirement:
>> https://eel.is/c++draft/namespace.udecl#14.sentence-1.
>>
>> However, while GCC rejects the code, both Clang and EDG accept it:
>> https://godbolt.org/z/Y33drKb6n.
>>
>> Any comments?
>>
>> --
>> Yongwei Wu
>> URL: http://wyw.dcweb.cn/
>> --
>> Std-Discussion mailing list
>> Std-Discussion_at_[hidden]
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>>
>
>
> --
> *Brian Bi*
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>