Re: argument of conversion cannot be an allocator

["John G. Volan" <johnvolan@sprintmail.com>]

Dale Stanbrough wrote:
> 
> I came across the following problem...
> 
>         type a is tagged private;
>         type a_ptr is access all a'class;
> 
>         type b is new a with private;
>         type b_ptr is acces all b'class;
> 
>         ...
> 
> 
>         return a'(new b);

I assume you meant:

          return a_ptr(new b);
> 
> which results in the error message (from GNAT)
> 
>         "argument of conversion cannot be an allocator"

Just so everyone's clear on this, if you're trying to generate an a_ptr,
there is no need to do a type conversion at all:

   Your_A_Ptr : A_Ptr := new B;

This is perfectly legal, and it makes perfect sense, too. An A_Ptr
points at any object in type A'Class, which is a classwide type that
covers all objects of type A as well as all types derived from A.  This
includes type B.

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