[pmc] Object.invoke as vtable override: fix unstable self heuristic

Change experimental usage of vtable overridden subs.
Only push self if the sub is a method, otherwise replace it.

Closes #1013. Thanks to Zefram

ChangeLog

@@ -24,6 +24,9 @@
         + Unescape double-quoted .lex string constants. #1095, perl6 RT#116643
         + Downgrade external ascii strings on multi-byte platform encodings
           to ascii. #1098
+        + Fix self heuristic with vtable overridden method calls.
+          $P0() instead of $P0($P0) is now stable, push if $P0 is a :method, otherwise set.
+          https://trac.parrot.org/parrot/ticket/103 #1013
     - Build
         + Set -mabi=64 for gcc --m=64 on mips, -m64 on powerpc #1110
         + Add --{en,dis}able-static #1104

api.yaml

@@ -198,12 +198,14 @@
   ticket:  'https://trac.parrot.org/parrot/ticket/852'
 -
   name:  'Overriding vtable invoke in PIR objects'
-  note:  'The VTABLE invoke in object.pmc puts SELF at the start of the signature call arguments when there is no current object and is not already here. This allows the usage of $P0() instead of $P0($P0).'
+  note:  'The VTABLE invoke in object.pmc pushes or replaces SELF at the start of the signature call arguments. It pushes when the vtable method is marked as :method. This allows the usage of $P0() instead of $P0($P0). This changed with 6.10.0'
   tags:
     - 'PMC'
     - 'experimental'
     - 'completed'
-  ticket:  'https://trac.parrot.org/parrot/ticket/103'
+  ticket:
+    - 'https://trac.parrot.org/parrot/ticket/103'
+    - 'https://github.com/parrot/parrot/issues/1013'
 -
   name:  'PARROT_LIBRARY and PARROT_INCLUDE environment variables'
   note:  'A way to provide an equivalent of -L and -I parrot command line options to language that doesn''t support it.'

src/pmc/object.pmc

@@ -22,6 +22,7 @@ Parrot_ext_call, which creates a new interp, task and calls a new runloop.
 
 #include "parrot/oo_private.h"
 #include "pmc/pmc_class.h"
+#include "pmc/pmc_sub.h"
 
 /* HEADERIZER HFILE: none */
 /* HEADERIZER BEGIN: static */
@@ -828,10 +829,11 @@ Invokes the object (if this vtable function is overridden).
                 PMC * const call_sig =
                     Parrot_pcc_get_signature(INTERP, CURRENT_CONTEXT(INTERP));
 
-                if ((VTABLE_elements(INTERP, call_sig) == 0
-                ||   VTABLE_get_pmc_keyed_int(INTERP, call_sig, 0) != SELF))
+                /* Check for :method if to add or set SELF. GH #1013 */
+                if (Sub_comp_flag_TEST(METHOD, PARROT_SUB(meth)))
                     VTABLE_unshift_pmc(INTERP, call_sig, SELF);
-
+                else
+                    VTABLE_set_pmc_keyed_int(INTERP, call_sig, 0, SELF);
                 return VTABLE_invoke(INTERP, meth, next);
             }
 

t/pmc/object-meths.t

@@ -1,11 +1,11 @@
 #! perl
-# Copyright (C) 2001-2010, Parrot Foundation.
+# Copyright (C) 2001-2014, Parrot Foundation.
 
 use strict;
 use warnings;
 use lib qw( . lib ../lib ../../lib );
 use Test::More;
-use Parrot::Test tests => 38;
+use Parrot::Test tests => 39;
 
 =head1 NAME
 
@@ -1138,6 +1138,31 @@ CODE
 1
 OUTPUT
 
+pir_output_is( <<'CODE', <<'OUTPUT', "vtable invoke self", todo => 'GH #1013' );
+.sub "" :anon :init :load
+    $P0 = newclass "MyFunc"
+.end
+.namespace ["MyFunc"]
+.sub invoke :vtable
+    .param pmc a
+    say "ok"
+    .return ()
+.end
+.namespace []
+.sub main :main
+    $P0 = new "MyFunc"
+    $P1 = new "MyFunc"
+    $P0("a")
+    $P0($P1)
+    $P0($P0)
+.end
+CODE
+ok
+ok
+ok
+OUTPUT
+
+
 # Local Variables:
 #   mode: cperl
 #   cperl-indent-level: 4