diff for making BagHash<unknown_key>-- return Int rather than 0

gistfile1.txt

diff --git a/src/core/BagHash.pm b/src/core/BagHash.pm
index 21a35b8..960ea99 100644
--- a/src/core/BagHash.pm
+++ b/src/core/BagHash.pm
@@ -1,39 +1,31 @@
-my class BagHash does Baggy {
+my class BagValue is Int {
+    has $!hash;
+    has $!key;
+
+    submethod BUILD (:$!hash,:$!key) {}
 
-    method at_key($k) {
-        Proxy.new(
-          FETCH => {
-              my $key   := $k.WHICH;
-              %!elems.exists_key($key) ?? %!elems{$key}.value !! 0;
-          },
-          STORE => -> $, $value is copy {
-              if $value > 0 {
-                  (%!elems{$k.WHICH} //= ($k => 0)).value = $value;
-              }
-              elsif $value == 0 {
-                  self.delete_key($k);
-              }
-              else {
-                  $value = 0;
-              }
-              $value;
-          }
-        );
+    method STORE ($value) {
+        ($!hash{$!key.WHICH} //= ($!key => 0)).value = $value;
     }
+}
+
+my class BagHash does Baggy {
+
+    method at_key($key) { BagValue.new(:hash(%!elems),:$key) }
 
     method delete($k) {  # is DEPRECATED doesn't work in settings
         DEPRECATED("the :delete adverb");
         self.delete_key($k);
     }
     method delete_key($k) {
-        my $key   := $k.WHICH;
-        if %!elems.exists_key($key) {
-            my $value = %!elems{$key}.value;
-            %!elems.delete_key($key);
+        my $keyw := $k.WHICH;
+        if %!elems.exists_key($keyw) {
+            my $value = %!elems{$keyw}.value;
+            %!elems.delete_key($keyw);
             $value;
         }
         else {
-            0;
+            Int;
         }
     }
 
@@ -52,4 +44,34 @@ my class BagHash does Baggy {
     method MixHash { MixHash.new-fp(%!elems.values) }
 }
 
+multi postcircumfix:<{ }> (BagHash:D $self, $key) {
+    my $hash := nqp::getattr($self,BagHash,'%!elems');
+    my $keyw := $key.WHICH;
+    $hash.exists_key($keyw) ?? $hash{$keyw}.value !! Int;
+}
+multi prefix:<++> (BagValue:D $self) {
+    my $hash := nqp::getattr($self,BagValue,'$!hash');
+    my $key  := nqp::getattr($self,BagValue,'$!key');
+    ($hash{$key.WHICH} //= ($key => 1)).value;
+}
+multi prefix:<--> (BagValue:D $self) {
+    my $hash := nqp::getattr($self,BagValue,'$!hash');
+    my $keyw := nqp::getattr($self,BagValue,'$!key').WHICH;
+    my $value = $hash.exists_key($keyw) ?? --($hash{$keyw}.value) !! Int;
+    $hash.delete_key($keyw) if $value.defined and $value == 0;
+    $value;
+}
+multi postfix:<++> (BagValue:D $self) {
+    my $hash := nqp::getattr($self,BagValue,'$!hash');
+    my $key  := nqp::getattr($self,BagValue,'$!key');
+    ($hash{$key.WHICH} //= ($key => 0)).value++ || Int;
+}
+multi postfix:<--> (BagValue:D $self) {
+    my $hash := nqp::getattr($self,BagValue,'$!hash');
+    my $keyw := nqp::getattr($self,BagValue,'$!key').WHICH;
+    my $value = $hash.exists_key($keyw) ?? ($hash{$keyw}.value)-- !! Int;
+    $hash.delete_key($keyw) if $value.defined and $value == 1;
+    $value;
+}
+
 # vim: ft=perl6 expandtab sw=4