Diff for speeding up grep-index(): well, it only speeds up 2x for the push-all case, the pull-one case is only marginally faster

gistfile1.txt

diff --git a/src/core/Any-iterable-methods.pm b/src/core/Any-iterable-methods.pm
index 84c6505..040cf67 100644
--- a/src/core/Any-iterable-methods.pm
+++ b/src/core/Any-iterable-methods.pm
@@ -378,27 +378,87 @@ augment class Any {
         }.new(self, $test))
     }
 
+    # This role is not actually used because of RT #126120.  Since most of
+    # the speed benefits are lost if we cannot use a native int for $!index,
+    # the contents of this role are copy-pasted for now
+    role GrepIndexer does Iterator {
+        has Mu $!iter;
+        has Mu $!test;
+        has int $!index;
+        method BUILD(\list,\test) {
+            $!iter  = as-iterable(list).iterator;
+            $!test := test;
+            $!index = -1;
+            self
+        }
+        method new(\list,\test) { nqp::create(self).BUILD(list,test) }
+    }
+
     proto method grep-index(|) is nodal { * }
     multi method grep-index(Bool:D $t) is rw {
         fail X::Match::Bool.new( type => '.grep-index' );
     }
     multi method grep-index(Regex:D $test) {
-        my int $index = -1;
-        self.map: {
-            $index = $index+1;
-            next unless .match($test);
-            nqp::box_i($index,Int);
-        };
+        Seq.new(class :: does Iterator {   # should be GrepIndexer
+            has Mu $!iter;
+            has Mu $!test;
+            has int $!index;
+            method BUILD(\list,\test) {
+                $!iter  = as-iterable(list).iterator;
+                $!test := test;
+                $!index = -1;
+                self
+            }
+            method new(\list,\test) { nqp::create(self).BUILD(list,test) }
+            method pull-one() {
+                my Mu $value;
+                until ($value := $!iter.pull-one) =:= IterationEnd {
+                    $!index = $!index + 1;
+                    return $!index if $value.match($!test);
+                }
+                IterationEnd
+            }
+            method push-all($target) {
+                my Mu $value;
+                until ($value := $!iter.pull-one) =:= IterationEnd {
+                    $!index = $!index + 1;
+                    $target.push(+$!index) if $value.match($!test);
+                }
+                IterationEnd
+            }
+        }.new(self, $test))
     }
     multi method grep-index(Callable:D $test) {
-        my int $index = -1;
-        self.map: {
-            $index = $index + 1;
-            next unless $test($_);
-            nqp::box_i($index,Int);
-        };
+        Seq.new(class :: does Iterator {   # should be GrepIndexer
+            has Mu $!iter;
+            has Mu $!test;
+            has int $!index;
+            method BUILD(\list,\test) {
+                $!iter  = as-iterable(list).iterator;
+                $!test := test;
+                $!index = -1;
+                self
+            }
+            method new(\list,\test) { nqp::create(self).BUILD(list,test) }
+            method pull-one() {
+                my Mu $value;
+                until ($value := $!iter.pull-one) =:= IterationEnd {
+                    $!index = $!index + 1;
+                    return $!index if $!test($value);
+                }
+                IterationEnd
+            }
+            method push-all($target) {
+                my Mu $value;
+                until ($value := $!iter.pull-one) =:= IterationEnd {
+                    $!index = $!index + 1;
+                    $target.push(+$!index) if $!test($value);
+                }
+                IterationEnd
+            }
+        }.new(self, $test))
     }
-    multi method grep-index(Mu $test) {
+     multi method grep-index(Junction:D $test) {
         my int $index = -1;
         self.map: {
             $index = $index + 1;
@@ -406,6 +466,36 @@ augment class Any {
             nqp::box_i($index,Int);
         };
     }
+    multi method grep-index(Mu $test) {
+        Seq.new(class :: does Iterator {   # should be GrepIndexer
+            has Mu $!iter;
+            has Mu $!test;
+            has int $!index;
+            method BUILD(\list,\test) {
+                $!iter  = as-iterable(list).iterator;
+                $!test := test;
+                $!index = -1;
+                self
+            }
+            method new(\list,\test) { nqp::create(self).BUILD(list,test) }
+            method pull-one() {
+                my Mu $value;
+                until ($value := $!iter.pull-one) =:= IterationEnd {
+                    $!index = $!index + 1;
+                    return $!index if $value ~~ $!test;
+                }
+                IterationEnd
+            }
+            method push-all($target) {
+                my Mu $value;
+                until ($value := $!iter.pull-one) =:= IterationEnd {
+                    $!index = $!index + 1;
+                    $target.push(+$!index) if $value ~~ $!test;
+                }
+                IterationEnd
+            }
+        }.new(self, $test))
+    }
 
     proto method first(|) is nodal { * }
     multi method first(Bool:D $t) is rw {