async deepmap

The code below seems ok on simple tests but there's spectest
fallout and one of my modules (Data::Selector) also breaks.
Seems the return has changed somehow but I can't figure it
out. I had to change line 241 of lib/Data/Selector.pm like
so:

-       make $/.<selector_group>>>.ast.hash;
+       make $/.<selector_group>>>.ast.[0].hash;

to make it work again.

I'm using:

[jdv@wieldy rakudo]$ perl6 -v 
This is perl6 version 2015.07.1-45-g31a083f built on MoarVM version 2015.07-5-gbbe6231
[jdv@wieldy rakudo]$

with this patch:

[jdv@wieldy rakudo]$ git diff
diff --git a/src/core/metaops.pm b/src/core/metaops.pm
index 3bf9fe5..bababde 100644
--- a/src/core/metaops.pm
+++ b/src/core/metaops.pm
@@ -425,37 +425,39 @@ multi sub HYPER(\op, \obj) {
 proto sub deepmap(|) { * }
 
 multi sub deepmap(\op, \obj) {
+    my $lock = nqp::create(Lock);
+    my $cond = $lock.condition;
+    my int $todo = 0;
+    my int $done = 0;
+    my Exception $ex;
+    my int $batch_size = (%*ENV<RAKUDO_HYPER_BATCH_SIZE> // 10).Int;
+
     my Mu $rpa := nqp::list();
     my Mu $items := nqp::p6listitems(obj.flat.eager);
-    my Mu $o;
-    # We process the elements in two passes, end to start, to
-    # prevent users from relying on a sequential ordering of hyper.
-    # Also, starting at the end pre-allocates $rpa for us.
+
     my int $i = nqp::elems($items) - 1;
-    nqp::while(
-        nqp::isge_i($i, 0),
-        nqp::stmts(
-            ($o := nqp::atpos($items, $i)),
-            nqp::bindpos($rpa, $i,
-                nqp::if(nqp::istype($o, Iterable),
-                        $o.new(deepmap(op, $o)).item,
-                        op.($o))),
-            $i = nqp::sub_i($i, 2)
-        )
-    );
-    $i = nqp::elems($items) - 2;
-    nqp::while(
-        nqp::isge_i($i, 0),
-        nqp::stmts(
-            ($o := nqp::atpos($items, $i)),
-            nqp::bindpos($rpa, $i,
-                nqp::if(nqp::istype($o, Iterable),
-                        $o.new(deepmap(op, $o)).item,
-                        op.($o))),
-            $i = nqp::sub_i($i, 2)
-        )
-    );
-    nqp::p6parcel($rpa, Nil);
+    while $i > -1 {
+        my int $from = $i;
+        my int $to = $i -= $batch_size;
+        $to = -1 if $to < -1;
+        $*SCHEDULER.cue( {
+            while $from > $to {
+                my Mu $o := nqp::atpos($items, $from);
+                my Mu $r = nqp::if(nqp::istype($o, Iterable),
+                  $o.new(deepmap(op, $o)).item,
+                  op.($o));
+                $lock.protect: { nqp::bindpos($rpa, $from, $r) }
+                $from--;
+            }
+            $lock.protect: { $cond.signal if ++$done == $todo }
+        }, catch => sub ($e) { $ex = $e; $cond.signal } );
+        $lock.protect: { $todo++ }
+    }
+
+    $lock.protect: { $cond.wait unless $done == $todo || $ex }
+    die $ex if $ex;
+
+    nqp::p6parcel(nqp::decont($rpa), Nil);
 }
 
 multi sub deepmap(\op, Associative \h) {
diff --git a/tools/build/moar_core_sources b/tools/build/moar_core_sources
index f283053..ae20c33 100644
--- a/tools/build/moar_core_sources
+++ b/tools/build/moar_core_sources
@@ -115,11 +115,11 @@ src/core/ObjAt.pm
 src/core/Version.pm
 src/core/ForeignCode.pm
 src/core/operators.pm
-src/core/metaops.pm
 src/core/precedence.pm
 src/core/Deprecations.pm
 src/core/Thread.pm
 src/core/Lock.pm
+src/core/metaops.pm
 src/core/Semaphore.pm
 src/core/Cancellation.pm
 src/core/Scheduler.pm
[jdv@wieldy rakudo]$