From 2736b8776ee12640ebdd08b677b393afcafc313d Mon Sep 17 00:00:00 2001
From: Bodigrim <andrew.lelechenko@gmail.com>
Date: Sun, 21 Jun 2026 19:44:02 +0100
Subject: [PATCH] Monad of no Return

---
 Cabal-syntax/src/Distribution/Fields/LexerMonad.hs             | 1 -
 Cabal-syntax/src/Distribution/Fields/ParseResult.hs            | 1 -
 Cabal-syntax/src/Distribution/Parsec.hs                        | 2 --
 Cabal-syntax/src/Distribution/Types/Condition.hs               | 2 --
 Cabal/src/Distribution/Backpack/ReadyComponent.hs              | 1 -
 Cabal/src/Distribution/Backpack/UnifyM.hs                      | 1 -
 Cabal/src/Distribution/Simple/BuildTarget.hs                   | 2 --
 Cabal/src/Distribution/Utils/LogProgress.hs                    | 1 -
 Cabal/src/Distribution/Utils/Progress.hs                       | 1 -
 Cabal/src/Distribution/ZinzaPrelude.hs                         | 1 -
 cabal-install-solver/src/Distribution/Solver/Types/Progress.hs | 1 -
 cabal-install/src/Distribution/Client/Init/Types.hs            | 1 -
 cabal-install/src/Distribution/Client/TargetSelector.hs        | 1 -
 cabal-install/src/Distribution/Deprecated/ParseUtils.hs        | 1 -
 cabal-install/src/Distribution/Deprecated/ProjectParseUtils.hs | 1 -
 15 files changed, 18 deletions(-)

diff --git a/Cabal-syntax/src/Distribution/Fields/LexerMonad.hs b/Cabal-syntax/src/Distribution/Fields/LexerMonad.hs
index 4a9c5641db2..f239d39475a 100644
--- a/Cabal-syntax/src/Distribution/Fields/LexerMonad.hs
+++ b/Cabal-syntax/src/Distribution/Fields/LexerMonad.hs
@@ -55,7 +55,6 @@ instance Applicative Lex where
   (<*>) = ap
 
 instance Monad Lex where
-  return = pure
   (>>=) = thenLex
 
 data LexResult a = LexResult {-# UNPACK #-} !LexState a
diff --git a/Cabal-syntax/src/Distribution/Fields/ParseResult.hs b/Cabal-syntax/src/Distribution/Fields/ParseResult.hs
index b20d140c132..2842a89c90e 100644
--- a/Cabal-syntax/src/Distribution/Fields/ParseResult.hs
+++ b/Cabal-syntax/src/Distribution/Fields/ParseResult.hs
@@ -128,7 +128,6 @@ instance Applicative (ParseResult src) where
   {-# INLINE (<*) #-}
 
 instance Monad (ParseResult src) where
-  return = pure
   (>>) = (*>)
 
   m >>= k = PR $ \ !s fp failure success ->
diff --git a/Cabal-syntax/src/Distribution/Parsec.hs b/Cabal-syntax/src/Distribution/Parsec.hs
index 017e5e3573a..4420b3954f3 100644
--- a/Cabal-syntax/src/Distribution/Parsec.hs
+++ b/Cabal-syntax/src/Distribution/Parsec.hs
@@ -145,8 +145,6 @@ instance Alternative ParsecParser where
   {-# INLINE some #-}
 
 instance Monad ParsecParser where
-  return = pure
-
   m >>= k = PP $ \v -> unPP m v >>= \x -> unPP (k x) v
   {-# INLINE (>>=) #-}
   (>>) = (*>)
diff --git a/Cabal-syntax/src/Distribution/Types/Condition.hs b/Cabal-syntax/src/Distribution/Types/Condition.hs
index 0590cecf57e..6c764f1d9fe 100644
--- a/Cabal-syntax/src/Distribution/Types/Condition.hs
+++ b/Cabal-syntax/src/Distribution/Types/Condition.hs
@@ -73,8 +73,6 @@ instance Applicative Condition where
   (<*>) = ap
 
 instance Monad Condition where
-  return = pure
-
   -- Terminating cases
   (>>=) (Lit x) _ = Lit x
   (>>=) (Var x) f = f x
diff --git a/Cabal/src/Distribution/Backpack/ReadyComponent.hs b/Cabal/src/Distribution/Backpack/ReadyComponent.hs
index 08b4995db07..98c4d7a1d59 100644
--- a/Cabal/src/Distribution/Backpack/ReadyComponent.hs
+++ b/Cabal/src/Distribution/Backpack/ReadyComponent.hs
@@ -218,7 +218,6 @@ instance Applicative InstM where
      in (f' x', s'')
 
 instance Monad InstM where
-  return = pure
   InstM m >>= f = InstM $ \s ->
     let (x, s') = m s
      in runInstM (f x) s'
diff --git a/Cabal/src/Distribution/Backpack/UnifyM.hs b/Cabal/src/Distribution/Backpack/UnifyM.hs
index d4e1e1a0b0a..a6969986f6a 100644
--- a/Cabal/src/Distribution/Backpack/UnifyM.hs
+++ b/Cabal/src/Distribution/Backpack/UnifyM.hs
@@ -152,7 +152,6 @@ instance Applicative (UnifyM s) where
           Just x'' -> return (Just (f'' x''))
 
 instance Monad (UnifyM s) where
-  return = pure
   UnifyM m >>= f = UnifyM $ \r -> do
     x <- m r
     case x of
diff --git a/Cabal/src/Distribution/Simple/BuildTarget.hs b/Cabal/src/Distribution/Simple/BuildTarget.hs
index 1a1c9aaaeff..9c046100fee 100644
--- a/Cabal/src/Distribution/Simple/BuildTarget.hs
+++ b/Cabal/src/Distribution/Simple/BuildTarget.hs
@@ -908,8 +908,6 @@ instance Applicative Match where
   (<*>) = ap
 
 instance Monad Match where
-  return = pure
-
   NoMatch d ms >>= _ = NoMatch d ms
   ExactMatch d xs >>= f =
     addDepth d $
diff --git a/Cabal/src/Distribution/Utils/LogProgress.hs b/Cabal/src/Distribution/Utils/LogProgress.hs
index dce540df985..3fc34604e2a 100644
--- a/Cabal/src/Distribution/Utils/LogProgress.hs
+++ b/Cabal/src/Distribution/Utils/LogProgress.hs
@@ -41,7 +41,6 @@ instance Applicative LogProgress where
   LogProgress f <*> LogProgress x = LogProgress $ \r -> f r `ap` x r
 
 instance Monad LogProgress where
-  return = pure
   LogProgress m >>= f = LogProgress $ \r -> m r >>= \x -> unLogProgress (f x) r
 
 -- | Run 'LogProgress', outputting traces according to 'Verbosity',
diff --git a/Cabal/src/Distribution/Utils/Progress.hs b/Cabal/src/Distribution/Utils/Progress.hs
index c6edf87d558..903007f38d9 100644
--- a/Cabal/src/Distribution/Utils/Progress.hs
+++ b/Cabal/src/Distribution/Utils/Progress.hs
@@ -57,7 +57,6 @@ foldProgress step err done = fold
     fold (Done r) = done r
 
 instance Monad (Progress step fail) where
-  return = pure
   p >>= f = foldProgress Step Fail f p
 
 instance Applicative (Progress step fail) where
diff --git a/Cabal/src/Distribution/ZinzaPrelude.hs b/Cabal/src/Distribution/ZinzaPrelude.hs
index 81ef5170c1a..5fe1d49e641 100644
--- a/Cabal/src/Distribution/ZinzaPrelude.hs
+++ b/Cabal/src/Distribution/ZinzaPrelude.hs
@@ -33,7 +33,6 @@ instance Applicative Writer where
   (<*>) = ap
 
 instance Monad Writer where
-  return = pure
   m >>= k = W $ \s1 ->
     let (s2, x) = unW m s1
      in unW (k x) s2
diff --git a/cabal-install-solver/src/Distribution/Solver/Types/Progress.hs b/cabal-install-solver/src/Distribution/Solver/Types/Progress.hs
index b70e12a26e3..aac29a4a23f 100644
--- a/cabal-install-solver/src/Distribution/Solver/Types/Progress.hs
+++ b/cabal-install-solver/src/Distribution/Solver/Types/Progress.hs
@@ -36,7 +36,6 @@ foldProgress step' fail' done' = fold
         fold (Done r)   = done' r
 
 instance Monad (Progress step fail) where
-  return   = pure
   p >>= f  = foldProgress Step Fail f p
 
 instance MonadFail (Progress step String) where
diff --git a/cabal-install/src/Distribution/Client/Init/Types.hs b/cabal-install/src/Distribution/Client/Init/Types.hs
index 893323535d9..eb0951c0f2b 100644
--- a/cabal-install/src/Distribution/Client/Init/Types.hs
+++ b/cabal-install/src/Distribution/Client/Init/Types.hs
@@ -330,7 +330,6 @@ instance Applicative PurePrompt where
       Right (a, s'') -> Right (f a, s'')
 
 instance Monad PurePrompt where
-  return = pure
   PurePrompt a >>= k = PurePrompt $ \s -> case a s of
     Left e -> Left e
     Right (a', s') -> runPromptState (k a') s'
diff --git a/cabal-install/src/Distribution/Client/TargetSelector.hs b/cabal-install/src/Distribution/Client/TargetSelector.hs
index 306cb629302..efba01d1b05 100644
--- a/cabal-install/src/Distribution/Client/TargetSelector.hs
+++ b/cabal-install/src/Distribution/Client/TargetSelector.hs
@@ -2365,7 +2365,6 @@ instance Alternative Match where
   (<|>) = matchPlus
 
 instance Monad Match where
-  return = pure
   NoMatch d ms >>= _ = NoMatch d ms
   Match m d xs >>= f =
     -- To understand this, it needs to be read in context with the
diff --git a/cabal-install/src/Distribution/Deprecated/ParseUtils.hs b/cabal-install/src/Distribution/Deprecated/ParseUtils.hs
index 54d19932ea7..cdbf548d21d 100644
--- a/cabal-install/src/Distribution/Deprecated/ParseUtils.hs
+++ b/cabal-install/src/Distribution/Deprecated/ParseUtils.hs
@@ -124,7 +124,6 @@ instance Applicative ParseResult where
   (<*>) = ap
 
 instance Monad ParseResult where
-  return = pure
   ParseFailed err >>= _ = ParseFailed err
   ParseOk ws x >>= f = case f x of
     ParseFailed err -> ParseFailed err
diff --git a/cabal-install/src/Distribution/Deprecated/ProjectParseUtils.hs b/cabal-install/src/Distribution/Deprecated/ProjectParseUtils.hs
index 790b7b6b352..f7d6bc1f981 100644
--- a/cabal-install/src/Distribution/Deprecated/ProjectParseUtils.hs
+++ b/cabal-install/src/Distribution/Deprecated/ProjectParseUtils.hs
@@ -41,7 +41,6 @@ instance Applicative ProjectParseResult where
   (<*>) = ap
 
 instance Monad ProjectParseResult where
-  return = pure
   ProjectParseFailed err >>= _ = ProjectParseFailed err
   ProjectParseOk ws x >>= f = case f x of
     ProjectParseFailed err -> ProjectParseFailed err