Re: making a son benefit access ton an instanciation of a generic package required as a formal parameter to his father and instanciated by him

["J-P. Rosen" <rosen@adalog.fr>]

Le 21/01/2018 à 21:15, Mehdi Saada a écrit :
> Thanks Dmitry. I just stumpled against another exemple of your point 1, RM's paragraph 11.2.8:
> An exception_name of a choice shall not denote an exception declared in a generic formal package.
Right, and there is a good reason.
Assuming exception E is declared in generic package GP1:

Imagine this:
generic
   package P1 is new GP1 (<>);
   package P2 is new GP1 (<>);
package GP2 is... end GP2;

package body GP2 is
   ...
begin
   exception
      when P1.E =>  -- not allowed by Ada
         ...
      when P2.E =>  -- not allowed by Ada
         ...
end GP2;

So far, so good. But then, if you instantiate:
package Inst1 is new GP1;

package Inst2 is new GP2 (Inst1, Inst1);

then you would end up with two different handlers for the same exception
(since formals P1 and P2 are actually the same package Inst1). And
that's a no-no!

I agree with Dmitry (It happens sometimes ;-) ) that normally,
exceptions are better declared outside of generics.
-- 
J-P. Rosen
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