Re: Is that code valid ?

[Pal Engstad <engstad at hunt dot inmet dot com>]

Lassi A. Tuura wrote:
> 
> I believe you are confusing two things.  The name above is a
> qualified-id, where the nested-name-specifier nominates a class.  Hence,
> the following lookup rules apply:
[--snip--]

I stand corrected and I thank you for your explaination.

I've checked it and I've noticed that the use of Class::Class(arg0) can 
only be to construct a temporary. It is specified that what is on the
left
of the '(' can only be a simple-type-identifier:

simple-type-specifier:
                  ::opt nested-name-specifieropt type-name
                  char
          	  etc.

And the last Class in this context is obviously a type-name:

type-name:
                  class-name
                  enum-name
                  typedef-name
          
Having said this, I do not understand why the standard explicitely 
says that the constructor does not have a name, for instance in:

12.1  Constructors					[class.ctor]

2 A  constructor  is  used  to  initialize  objects  of  its class type.
  Because constructors do not have names, they are  never  found  during
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  name  lookup; however an explicit type conversion using the functional
  ^^^^^^^^^^^^
  notation (_expr.type.conv_) will cause a constructor to be  called  to
  initialize  an  object.  [Note: for initialization of objects of class
  type see _class.init_.  ]

So the question is now: Why is there such a requirement? I hope we are
not missing something obvious.

> Hence, the qualified-id `QDate::QDate::QDate::QDate' should be treated
> as `QDate' in a the above context.  Definition of a function with that
> name would be a different thing.  I am not sure it would be valid as a
> constructor name---in my reading it should be (the first two `QDate's
> would just be ignored).  In my interpretation it should, however, be
> valid as a type name in a context where a type name is allowed.  Anybody
> interpret the standard differently?

I am not sure but I think it is ok. For reference here's the important
descriptions:

  9.3  Member functions                                     [class.mfct]

2 A member function may be defined (_dcl.fct.def_) in its class  defini-
  tion,  in which case it is an inline member function (_dcl.fct.spec_),
  or it may be defined outside of its class definition if it has already
  been declared but not defined in its class definition.  A member func-
                                                          ^^^^^^^^^^^^^^
  tion definition that appears outside of  the  class  definition  shall
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  appear  in  a  namespace scope enclosing the class definition.  Except
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  for member function definitions that appear outside of a class defini-
  tion, and except for explicit specializations of template member func-
  tions (_temp.spec_) appearing outside of the class definition, a  mem-
  ber function shall not be redeclared.

5 If the definition of a member function is lexically outside its  class
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  definition,  the  member function name shall be qualified by its class
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  name using the :: operator.
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^

Since the definition of the constructor _is_ a member function, the 
name has to be Class::Class(). Since the definition has to be in the 
namescope enclosing the class definition, putting a namespace in front 
of this would not make sense. If 

	Class::Class::Class() {} 

is legal is however not so clear, but I agree. Since this is outside 
the class' namespace and the class-name has put in the namespace's 
scope, I would assume that 
	Class::Class::Class() {}
	       ^
at this point, we are in the class' name scope. Also, since the class 
name is also put into the scope of the class itself, the next 
'Class::' is a scope resolution to itself and in the end specifying 
the constructor.

But is that really what is intended with "shall be qualified by its
class
name using the :: operator" in 9.3.5?

If anyone have access to the final standard I'd appreciate if anyone
can comment on this. Has there been changes?

PKE.