Singleton BlackHole value

unisonweb · Nov 27, 2024 · 700c33c · 700c33c
1 parent 37244aa
commit 700c33c
Showing 1 changed file with 8 additions and 1 deletion.
diff --git a/unison-runtime/src/Unison/Runtime/Stack.hs b/unison-runtime/src/Unison/Runtime/Stack.hs
@@ -279,6 +279,11 @@ data GClosure comb
   deriving stock (Show, Functor, Foldable, Traversable)
 {- ORMOLU_ENABLE -}
 
+-- Singleton black hole value to avoid allocation.
+blackHole :: Closure
+blackHole = Closure GBlackHole
+{-# NOINLINE blackHole #-}
+
 pattern PAp :: CombIx -> GCombInfo (RComb Val) -> Seg -> Closure
 pattern PAp cix comb seg = Closure (GPAp cix comb seg)
 
@@ -295,7 +300,9 @@ pattern Captured k a seg = Closure (GCaptured k a seg)
 
 pattern Foreign x = Closure (GForeign x)
 
-pattern BlackHole = Closure GBlackHole
+pattern BlackHole <- Closure GBlackHole
+  where
+    BlackHole = blackHole
 
 pattern UnboxedTypeTag t <- Closure (GUnboxedTypeTag t)
   where