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Subject: [Bug ada/55324] New: diagnostic about abstract new in type derivation misleading due to being overly terse
Date: Wed, 14 Nov 2012 12:53:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55324

             Bug #: 55324
           Summary: diagnostic about abstract new in type derivation
                    misleading due to being overly terse
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: ada
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: georggcc@googlemail.com


When deriving an abstract type from a tagged type but omitting the record
extension part, GNAT says that "abstract" is not allowed here. Actually it is,
following LRM 3.4 about derived_type_definition (similarly, 12.5.1), but only
if followed by the record extension part.
Maybe the "here" of the message could be expanded a bit, "here[, only for ...]"

package x is

   type T is abstract tagged null record;

   type S is abstract new T;  -- with null record;

end x;

$ gnatmake -gnatwa -gnaty -gnatv x.ads
gcc -c -gnatwa -gnaty -gnatv x.ads

GNAT 4.8.0 20120611 (experimental)
Copyright 1992-2012, Free Software Foundation, Inc.

Compiling: x.ads (source file time stamp: 2012-11-14 12:13:28)

     5.    type S is abstract new T;  -- with null record;
                     |
        >>> "abstract" not allowed here, ignored

 7 lines: 1 error
gnatmake: "x.ads" compilation error