Re: library level required or not?

["Robert I. Eachus" <rieachus@comcast.net>]

Simon Wright wrote:

> (I also see (4), "A type extension shall not be declared in a generic
> body if the parent type is declared outside that body." I think ISNBAL
> -- I shall never be a lawyer)

This rule seems very mysterious, but it is actually a simple rule! 
Well, simple compared to the alternative.  There are many weird things 
that you could do if this rule wasn't there.  Rather than have a dozen 
exceptions to other rules, this one rule takes care of all of them.

If you really need a type extension in a generic body, you can put the 
extension declaration in the private part of the package specification. 
  This way (necessary) checks can be made at the point of any 
instantiation.  If they succeed, fine.  If not the instantiation is 
illegal.  But the Ada model doesn't allow rejecting an instantiation 
because of declarations in the body of the generic.

Extending a type declared in the generic body itself can never cause a 
problem because the legality of those declarations can't depend on the 
characteristics of a generic formal parameter.

-- 
                                           Robert I. Eachus

"The only thing necessary for the triumph of evil is for good men to do 
nothing." --Edmund Burke