1 files changed, 20 insertions, 0 deletions
diff --git a/compiler/GHC/Data/Strict.hs b/compiler/GHC/Data/Strict.hs
index d028d51c64..c272f9cafa 100644
--- a/compiler/GHC/Data/Strict.hs
+++ b/compiler/GHC/Data/Strict.hs
@@ -9,6 +9,7 @@
 module GHC.Data.Strict (
     Maybe(Nothing, Just),
     fromMaybe,
+    catMaybes,
     Pair(And),
 
     -- Not used at the moment:
@@ -21,10 +22,20 @@ import GHC.Prelude hiding (Maybe(..), Either(..))
 import Control.Applicative
 import Data.Semigroup
 import Data.Data
+import Control.DeepSeq
+import GHC.Utils.Outputable (Outputable(..), text, (<+>))
 
 data Maybe a = Nothing | Just !a
   deriving (Eq, Ord, Show, Functor, Foldable, Traversable, Data)
 
+instance NFData a => NFData (Maybe a) where
+  rnf Nothing = ()
+  rnf (Just x) = rnf x
+
+instance Outputable a => Outputable (Maybe a) where
+    ppr Nothing  = text "Nothing"
+    ppr (Just x) = text "Just" <+> ppr x
+
 fromMaybe :: a -> Maybe a -> a
 fromMaybe d Nothing = d
 fromMaybe _ (Just x) = x
@@ -37,6 +48,12 @@ altMaybe :: Maybe a -> Maybe a -> Maybe a
 altMaybe Nothing r = r
 altMaybe l _ = l
 
+catMaybes :: [Maybe a] -> [a]
+catMaybes = foldr go []
+  where
+    go Nothing xs = xs
+    go (Just x) xs = x : xs
+
 instance Semigroup a => Semigroup (Maybe a) where
   Nothing <> b       = b
   a       <> Nothing = a
@@ -56,6 +73,9 @@ instance Alternative Maybe where
 data Pair a b = !a `And` !b
   deriving (Eq, Ord, Show, Functor, Foldable, Traversable, Data)
 
+instance (NFData a, NFData b) => NFData (Pair a b) where
+  rnf (And a b) = rnf a `seq` rnf b
+
 -- The definitions below are commented out because they are
 -- not used anywhere in the compiler, but are useful to showcase
 -- the intent behind this module (i.e. how it may evolve).