From eceeb6a33e33e3ad6b4a11c8ac6dc9e17f09f189 Mon Sep 17 00:00:00 2001
From: Lautaro Emanuel <emlautarom1@gmail.com>
Date: Thu, 15 Dec 2022 13:25:22 -0300
Subject: [PATCH 1/2] Add 'liftMaybe'

---
 Control/Monad/Error/Class.hs | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/Control/Monad/Error/Class.hs b/Control/Monad/Error/Class.hs
index b2465e7..3c5cc0f 100644
--- a/Control/Monad/Error/Class.hs
+++ b/Control/Monad/Error/Class.hs
@@ -45,6 +45,7 @@ The Error monad (also called the Exception monad).
 module Control.Monad.Error.Class (
     MonadError(..),
     liftEither,
+    liftMaybe,
     tryError,
     withError,
     handleError,
@@ -74,7 +75,7 @@ import Control.Monad.Trans.Class (lift)
 import Control.Exception (IOException, catch, ioError)
 import Control.Monad (Monad)
 import Data.Monoid (Monoid)
-import Prelude (Either (Left, Right), Maybe (Nothing), either, flip, (.), IO, pure, (<$>), (>>=))
+import Prelude (Either (Left, Right), Maybe (Nothing), either, maybe, flip, (.), IO, pure, (<$>), (>>=))
 
 {- |
 The strategy of combining computations that can throw exceptions
@@ -122,6 +123,16 @@ where @action1@ returns an 'Either' to represent errors.
 liftEither :: MonadError e m => Either e a -> m a
 liftEither = either throwError pure
 
+{- |
+Lifts a @'Maybe' a@ into any @'MonadError' e@, using @e@ as the error if the 'Maybe' is 'Nothing'.
+
+> do { val <- liftMaybe e =<< action1; action2 }
+
+where @action1@ returns an 'Maybe'.
+-}
+liftMaybe :: MonadError e m => e -> Maybe a -> m a
+liftMaybe e = maybe (throwError e) pure
+
 instance MonadError IOException IO where
     throwError = ioError
     catchError = catch

From dbc850fa68b54cf3a5c97977c95edf38aad3f894 Mon Sep 17 00:00:00 2001
From: Lautaro Emanuel <emlautarom1@gmail.com>
Date: Thu, 15 Dec 2022 13:28:23 -0300
Subject: [PATCH 2/2] Update docs

---
 Control/Monad/Error/Class.hs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Control/Monad/Error/Class.hs b/Control/Monad/Error/Class.hs
index 3c5cc0f..263b551 100644
--- a/Control/Monad/Error/Class.hs
+++ b/Control/Monad/Error/Class.hs
@@ -124,11 +124,11 @@ liftEither :: MonadError e m => Either e a -> m a
 liftEither = either throwError pure
 
 {- |
-Lifts a @'Maybe' a@ into any @'MonadError' e@, using @e@ as the error if the 'Maybe' is 'Nothing'.
+Lifts a @'Maybe'@ into any @'MonadError' e@, using a supplied @e@ as the error if the 'Maybe' is 'Nothing'.
 
 > do { val <- liftMaybe e =<< action1; action2 }
 
-where @action1@ returns an 'Maybe'.
+where @action1@ returns a 'Maybe'.
 -}
 liftMaybe :: MonadError e m => e -> Maybe a -> m a
 liftMaybe e = maybe (throwError e) pure