diff options
Diffstat (limited to 'compiler/utils/Maybes.hs')
| -rw-r--r-- | compiler/utils/Maybes.hs | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/compiler/utils/Maybes.hs b/compiler/utils/Maybes.hs index 56b6dab5d9..656f40a372 100644 --- a/compiler/utils/Maybes.hs +++ b/compiler/utils/Maybes.hs @@ -20,6 +20,9 @@ module Maybes ( import Control.Applicative import Control.Monad +#if __GLASGOW_HASKELL__ > 710 +import Control.Monad.Fail +#endif import Data.Maybe infixr 4 `orElse` @@ -85,6 +88,12 @@ instance (Monad m) => Monad (MaybeT m) where x >>= f = MaybeT $ runMaybeT x >>= maybe (pure Nothing) (runMaybeT . f) fail _ = MaybeT $ pure Nothing + +#if __GLASGOW_HASKELL__ > 710 +instance Monad m => MonadFail (MaybeT m) where + fail _ = MaybeT $ return Nothing +#endif + #if __GLASGOW_HASKELL__ < 710 -- Pre-AMP change instance (Monad m, Applicative m) => Alternative (MaybeT m) where |