[Ada] fix bug in handling of equality operator

[Arnaud Charlet <charlet at adacore dot com>]

Tested on i686-linux. Committed on mainline.

An implicit inequality operator is created whenever there is user-defined
equality operation, either inherited or explicit. The inequality is built
only for semantic analysis, and eventually rewritten as the negation of
the corresponding equality operation. Because of this transient nature,
it is handled in an abbreviated matter, and its declaration is not visible
to the back-end. Previous code simply set the Parent field of the operator
declaration. This is incorrect when the operation is declared in a private
part and overrides an inherited operation declared in the visible part
of a package. Because the declaration was not properly part of a list of
declarations, the predicate Is_Private_Operation could malfunction, either
aborting when built with assertions, or returning an incorrect result. The
new code ensures that Is_Private_Operation works properly.

The following procedure must compile and execute quietly:

with P; use P;
with text_io; use text_io;
procedure try is
  this, that: t;
  yes : boolean := this /= that;
begin if not yes then put_line ("FAILED"); end if; end;
package q is
  type t is null record;
  function "=" (this, that: t) return boolean;
end;
package body q is
  function "=" (this, that: t) return boolean is begin return False; end;
end;
with q;
package p is
   type t is new q.t;
private
   function "=" (this, that: t) return boolean;
end;
package body p is
   function "=" (this, that: t) return boolean is begin return True; end;
   this, that : t;
end;

2005-03-08  Ed Schonberg  <schonberg@adacore.com>

	* sem_ch6.adb (Is_Private_Declaration): Verify that the declaration is
	attached to a list before checking whether it appears in the private
	declarations of the current package.
	(Make_Inequality_Operator): Insert declaration in proper declarative
	list rather than just setting the Parent field, so that
	Is_Private_Declaration can handle it properly.

Attachment: difs.27
Description: Text document