"use" after "limited with" (GNAT bug?)

"use" after "limited with" (GNAT bug?)

[Victor Porton]

-- p1.ads
package P1 is

end P1;

-- p2.ads
limited with P1;
use P1;

package P2 is

end P2;

$ gnatmake -q -c -gnatc -u -P/home/porton/t/p/default.gpr p2.ads
p2.ads:2:05: "P1" is undefined
gnatmake: "/home/porton/t/p/p2.ads" compilation error

Why "use" does not work? Is it a bug of gnatgcc (Debian 4.9.1-4) 4.9.1?

-- 
Victor Porton - http://portonvictor.org

Re: "use" after "limited with" (GNAT bug?)

[Adam Beneschan]

On Thursday, August 14, 2014 11:08:47 AM UTC-7, Victor Porton wrote:
> -- p1.ads
> 
> package P1 is
> 
> end P1;
> 
> -- p2.ads
> 
> limited with P1;
> use P1;
> 
> package P2 is
> 
> end P2;
> 
> 
> 
> $ gnatmake -q -c -gnatc -u -P/home/porton/t/p/default.gpr p2.ads
> p2.ads:2:05: "P1" is undefined
> gnatmake: "/home/porton/t/p/p2.ads" compilation error
> 
> Why "use" does not work? Is it a bug of gnatgcc (Debian 4.9.1-4) 4.9.1?

It's illegal.  You just can't USE a LIMITED WITH'ed package.

RM 10.1.2, paragraphs 19, 22:

A limited_with_clause that names a library package shall not appear:

within a context_clause for a library_item that is within the scope of a use_clause that names an entity declared within the declarative region of the library package.

From the AARM:

Reason: This prevents visibility issues, where whether an entity is an incomplete or full view depends on how the name of the entity is written. The limited_with_clause cannot be useful, as we must have the full view available in the parent in order for the use_clause to be legal. 

                               -- Adam

Re: "use" after "limited with" (GNAT bug?)

[Victor Porton]

Adam Beneschan wrote:

> On Thursday, August 14, 2014 11:08:47 AM UTC-7, Victor Porton wrote:
>> -- p1.ads
>> 
>> package P1 is
>> 
>> end P1;
>> 
>> -- p2.ads
>> 
>> limited with P1;
>> use P1;
>> 
>> package P2 is
>> 
>> end P2;
>> 
>> 
>> 
>> $ gnatmake -q -c -gnatc -u -P/home/porton/t/p/default.gpr p2.ads
>> p2.ads:2:05: "P1" is undefined
>> gnatmake: "/home/porton/t/p/p2.ads" compilation error
>> 
>> Why "use" does not work? Is it a bug of gnatgcc (Debian 4.9.1-4) 4.9.1?
> 
> It's illegal.  You just can't USE a LIMITED WITH'ed package.
> 
> RM 10.1.2, paragraphs 19, 22:
> 
> A limited_with_clause that names a library package shall not appear:
> 
> within a context_clause for a library_item that is within the scope of a
> use_clause that names an entity declared within the declarative region of
> the library package.
> 
> From the AARM:
> 
> Reason: This prevents visibility issues, where whether an entity is an
> incomplete or full view depends on how the name of the entity is written.
> The limited_with_clause cannot be useful, as we must have the full view
> available in the parent in order for the use_clause to be legal.

Not a language lawyer, but may be it makes sense to introduced "limited use" 
clauses?

-- 
Victor Porton - http://portonvictor.org

Re: "use" after "limited with" (GNAT bug?)

[Shark8]

On 14-Aug-14 12:41, Victor Porton wrote:
> Not a language lawyer, but may be it makes sense to introduced "limited use"
> clauses?

How would it work?