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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: ambiguities for class wide types
Date: 1997/03/09
Message-ID: <dewar.857918005@merv>#1/1
X-Deja-AN: 224179215
Organization: New York University
Newsgroups: comp.lang.ada
Date: 1997-03-09T00:00:00+00:00
List-Id: <comp.lang.ada>


ince this bug was discussed a while ago, I thought the following output
from GNAT would be of interest (GNAT as you see agrees that this is
ambiguous. This is version 3.10 of GNAT, which will be available publicly
some time in the future:

     1. package P is
     2.
     3.    type T is tagged limited null record;
     4.
     5.    procedure Op (L : in     T;
     6.                  R : in out T'Class);
     7.
     8.    procedure Op (L : in     T'Class;
     9.                  R : in out T);
    10.
    11. end;


     1. with P;
     2. procedure test_p is
     3.
     4.    procedure Q (L : in     P.T'Class;
     5.                 R : in out P.T'Class) is
     6.    begin
     7.       P.Op (L, R);  -- this should not compile
               |
        >>> ambiguous expression (cannot resolve "Op")
        >>> possible interpretation at p.ads:8
        >>> possible interpretation at p.ads:5

     8.    end;
     9.
    10.    O1, O2 : P.T;
    11.
    12. begin
    13.    Q (P.T'Class (O1), P.T'Class (O2));
    14. end;