1 files changed, 8 insertions, 0 deletions
diff --git a/compiler/basicTypes/UniqSupply.hs b/compiler/basicTypes/UniqSupply.hs
index da1a924736..664600147e 100644
--- a/compiler/basicTypes/UniqSupply.hs
+++ b/compiler/basicTypes/UniqSupply.hs
@@ -29,7 +29,10 @@ module UniqSupply (
         initUniqSupply
   ) where
 
+import GhcPrelude
+
 import Unique
+import Panic (panic)
 
 import GHC.IO
 
@@ -37,6 +40,7 @@ import MonadUtils
 import Control.Monad
 import Data.Bits
 import Data.Char
+import Control.Monad.Fail
 
 #include "Unique.h"
 
@@ -145,6 +149,10 @@ instance Applicative UniqSM where
                               (# xx, us'' #) -> (# ff xx, us'' #)
     (*>) = thenUs_
 
+-- TODO: try to get rid of this instance
+instance MonadFail UniqSM where
+    fail = panic
+
 -- | Run the 'UniqSM' action, returning the final 'UniqSupply'
 initUs :: UniqSupply -> UniqSM a -> (a, UniqSupply)
 initUs init_us m = case unUSM m init_us of { (# r, us #) -> (r,us) }