Re: Dynamically tagged expression not allowed. Why?

[Adam Beneschan <adam@irvine.com>]

On Jun 2, 7:36 pm, Yannick Duchêne (Hibou57)
<yannick_duch...@yahoo.fr> wrote:
> Le Wed, 02 Jun 2010 01:36:17 +0200, Randy Brukardt <ra...@rrsoftware.com>  
> a écrit:> You have to explicitly use a
> > type conversion here:
>
> >     Conn : Class_Type := Class_Type (New_Class_Instance);
>
> This one is not legal, as Class_Type is limited and conversion are not  
> allowed on limited type due to their copy based semantic.
> [ARM 2005 4.6] says about type conversions
> “Neither the target type nor the operand type shall be limited”

Umm, no, that sentence (4.6(24.7)) applies only to array types.  (And,
I think, only in cases where there is no common ancestor of the
operand and target type.)  However, 7.5(2.1-2.2) makes it illegal.
Type conversions on limited types are allowed in some cases; e.g. if
T1 is a limited tagged type, and T2 is a type extension, and X2 is an
object of type T2, you can use T1(X2) as an actual parameter to a
procedure that takes an IN OUT parameter of type T1.  This is a view
conversion and doesn't involve a copy.

                               -- Adam