Relational operations on discrete types / visibility

[concert!samba!usenet@gatech.edu (Frank Prindle)]

In the following simple example, the second if statement fails because the
"=" is not visible, but the semantically equivalent case statement compiles
without error (yet still implicitly requires the "=" or some combination of
relational operations on the discrete type color_type).  

Since the compiler can generate code for the case statement, it can clearly
generate code for the second if statement (i.e. there is no ambiguity to
resolve).  So why the inconsistency? (personally, I don't think either
statement should fail, but if one must, both should).  The compiler is
VADS 6.0.3.

Sincerely,
Frank Prindle
Prindle@NADC.navy.mil

-------------------------------example follows--------------------------
package color_pkg is
        type color_type is (RED, GREEN);
end color_pkg;

with color_pkg;
with text_io;
procedure color_test is
        color:color_pkg.color_type:=color_pkg.GREEN;
begin
        if(color_pkg."="(color,color_pkg.GREEN))
        then
                text_io.put_line("GREEN");
        end if;

        if(color = color_pkg.GREEN)			--ERROR HERE (EXPECTED)
        then
                text_io.put_line("GREEN");
        end if;

        case color is					--WHY NO ERROR HERE?
                when color_pkg.GREEN=>text_io.put_line("GREEN");
                when others=>null;
        end case;
end color_test;
--
   The opinions expressed are not necessarily those of the University of
     North Carolina at Chapel Hill, the Campus Office for Information
        Technology, or the Experimental Bulletin Board Service.
           internet:  bbs.oit.unc.edu or 152.2.22.80