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From: Barry on 26 Jan 2008 02:24
wasosa(a)sbcglobal.net wrote:
> Consider the following code:
>
> class A
> {
> friend class B& foo(class B&, A&);
> };
>
> Now consider the slightly different
>
> class A
> {
> friend class B& foo(B&, A&);
> };
>
> My question is, are both of these valid c++ code?
> Specifically, do we still need to specify 'class B&' in the parameter
> list?
>

<std>
3.3/3
The names declared by a declaration are introduced into the scope in
which the declaration occurs, except that the presence of a friend
specifier (11.4), certain uses of the elaborated-type-specifier (3.3.1),
and using-directives (7.3.4) alter this general behavior.

3.3/4
[Note: ... In particular, elaborated-type-specifiers (3.3.1) and friend
declarations (11.4) may introduce a (possibly not visible) name into an
enclosing namespace; these restrictions apply to that region. Local
extern declarations (3.5) may introduce a name into the declarative
region where the declaration appears and also introduce a (possibly not
visible) name into an enclosing namespace; these restrictions apply to
both regions. ]
</std>

the above somehow supports your code(both).
but it said "may" and "possibly not visible"

<std>
3.3.1/5
� for an elaborated-type-specifier of the form
class-key identifier
if the elaborated-type-specifier is used in the decl-specifier-seq or
parameter-declaration-clause of a function defined in namespace scope,
the identifier is declared as a class-name in the namespace that
contains the declaration; otherwise, except as a friend declaration, the
identifier is declared in the smallest non-class, non-function-prototype
scope that contains the declaration.
</std>

this one does NOT support your code.
since it means "function defined in namespace scope" only.

<std>
3.3.1/6
[Note: friend declarations refer to functions or classes that are
members of the nearest enclosing namespace, but they do not introduce
new names into that namespace (7.3.1.2). Function declarations at block
scope and object declarations with the extern specifier at block scope
refer to delarations that are members of an enclosing namespace, but
they do not introduce new names into that scope. ]
</std>

this one said "refer to", but not "introduce"


I think to accept your code or not is by design.
Note that forward declaration in the enclosing namespace is a better
solution.


--
Best Regards
Barry




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