Re: Question about generic formal derived types

[Stephen Leake <Stephen.Leake@gsfc.nasa.gov>]

adam@irvine.com writes:

After adding a spec for Pack4, running this thru ObjectAda 7.1.2 gives
the error:

adam.adb: Error: line 32 col 67 LRM:8.3(26), Illegal to override
       declaration in same region, Introducing new declaration anyway
       (In instance of generic Pack2 at adam.adb: line 13 col 9)

I believe that answers all your questions :).

-- Stephe

> In this program fragment:
> 
> -------------------------------------------------------------------------------
> package Pack1 is
>     type Root_Type is tagged record
>         Field1 : Integer;
>         Field2 : Boolean;
>     end record;
> end Pack1;
> 
> with Pack1;
> generic
>     type Formal_Type is new Pack1.Root_Type with private;
> package Pack2 is
>     type New_Type is new Formal_Type with record
>         Field3 : Character;
>     end record;
> end Pack2;
> 
> with Pack1;
> package Pack3 is
>     type Root_Type_Extension is new Pack1.Root_Type with record
>         Field3 : Float;
>     end record;
> end Pack3;
> 
> . . .
> 
> with Pack2;
> with Pack3;
> package body Pack4 is
> 
>     package Instantiation is new Pack2 (Pack3.Root_Type_Extension);
> 
>     procedure Inner is
>         X : Character;
>         Y : Instantiation.New_Type;
>     begin
>         X := Y.Field3;
>     end Inner;
> 
> end Pack4;
> 
> -------------------------------------------------------------------------------
> 
> I can't believe that a record type can have two components of the same name,
> but it appears that Instantiation.New_Type would have two components named
> Field3.
> 
> When Y.Field3 is accessed, which Field3 is meant?
> 
> Which language rules in the RM govern this situation?
> 
> 				-- thanks, Adam
> 
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