[Bug ada/24480] New: subtype declared in generic child fails to match actual

["gaedba at comcast dot net" <gcc-bugzilla at gcc dot gnu dot org>]

(This bug report is just one example of a category of bugs that may all revolve
around one bug in the compiler.  I've run into this situation in various
guises.  The sample code below is the smallest example of the problem I've
encounted so far.)

The bug manifests when:
a) a generic child package declares a subtype that is simply a rename of one of
its generic formal types, (the problem doesn't show up when this is done with
an ordinary library level generic, only when the generic is a child) eg.
    generic
        type a is private;
    package x.y is
        subtype b is a;
    end x.y;
b) the child is instantiated with any type (type seems to have no affect, eg.
range<>, mod<>, (<>), record, etc), eg.
    package x_y is x.y (a => integer);
c) reference the child's public subtype in a generic formal of another generic,
such as the argument type for a generic formal subroutine, eg.
    generic
        with package x_y is new x.y (<>);
        with procedure q (r : x_y.a);
    package xxx is ...;
d) now try to instantiate this new generic.  You will have great difficulty
matching q.  I've found a few tricks but it is nearly impossible.  The new
generic can be a separate generic (such as in the example below) or it can be a
child of the child, both fail.  

In the example below there are three compiler errors.  All three are incorrect.
 They are each three different ways of saying the same thing.

gcc (GCC) 4.0.1

------------------------------------------------------------------------------

cd /a/projects/geb/prolib.ada/test/
gnat compile -P test.gpr -gnatc  levelx.2.ada
gcc -c -gnata -gnatE -fstack-check -gnatef -gnatf -gnatm50 -gnatn -gnato -gnatU
-gnatwa -gnatwe -gnatwi -gnatwj -gnatwK -gnatwl -Wuninitialized -gnatVa
-pass-exit-codes -O -g -gnatc -I- -gnatA -x ada
/a/projects/geb/prolib.ada/test/levelx.2.ada
/a/projects/geb/prolib.ada/test/levelx.2.ada:24:51: error: no visible
subprogram matches the specification for "Any_Image3"
/a/projects/geb/prolib.ada/test/levelx.2.ada:25:51: error: no visible
subprogram matches the specification for "Any_Image3"
/a/projects/geb/prolib.ada/test/levelx.2.ada:26:47: error: no visible
subprogram matches the specification for "Any_Image3"
/a/projects/geb/prolib.ada/test/level1.level2.level3.1.ada:5:22: error:
"Level2" not declared in "Level2"
gnatmake: "/a/projects/geb/prolib.ada/test/levelx.2.ada" compilation error

Process compilation exited abnormally with code 4

------------------------------------------------------------------------------

with Level1.Level2.Level3;
procedure Levelx is

    type Type1 is new Integer;
    function Image1 (X : Type1) return String renames Type1'Image;

    package Our2 is new Level1.Level2 (Type1, Image1);
    package Our3 is new Our2.Level3;

    generic
        with package Any3 is new Level1.Level2.Level3 (<>);
        with function Any_Image3 (X : Any3.Interfaces.Level2.Level2_Type)
           return String is Type1'Image;
    procedure Do_Something (X : Any3.Interfaces.Level2.Level2_Type);

    procedure Do_Something (X : Any3.Interfaces.Level2.Level2_Type) is
        A : String := Any3.Interfaces.Level2.Level2_Image (X);
        B : String := Any_Image3 (X);
    begin
        if A = B then null; end if;
    end Do_Something;    

    procedure Do_W is new Do_Something (Our3, Our3.Level3_Image);
    procedure Do_X is new Do_Something (Our3, Our2.Level2_Image);
    procedure Do_Y is new Do_Something (Our3, Image1);

begin
    null;
end Levelx;
------------------------------------------------------------------------------
package Level1 is
end Level1;
------------------------------------------------------------------------------
generic
    type Arg_Type is private;
    with function Arg_Image (X : Arg_Type) return String;
package Level1.Level2 is

    subtype Level2_Type is Arg_Type;
    function Level2_Image (X : Level2_Type) return String renames Arg_Image;

    package Rename is
        subtype Our_Arg_Type is Arg_Type;
    end Rename;
    package Interfaces is
        subtype Arg_Type is Rename.Our_Arg_Type;
    end Interfaces;

end Level1.Level2;
------------------------------------------------------------------------------
generic
package Level1.Level2.Level3 is

    function Level3_Image (X : Level2_Type) return String
       renames Level2.Level2_Image;

    package Rename is
        package Our_Level2 renames Level2;
    end Rename;
    package Interfaces is
        package Level2 renames Rename.Our_Level2;
    end Interfaces;

end Level1.Level2.Level3;
------------------------------------------------------------------------------


-- 
           Summary: subtype declared in generic child fails to match actual
           Product: gcc
           Version: 4.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: ada
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: gaedba at comcast dot net
  GCC host triplet: i686-pc-cygwin-gcc-4.0.1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24480