From 25036a92c10486f3c44b01961b4fd9fdc03ebf4d Mon Sep 17 00:00:00 2001
From: Soumik Sarkar <soumiksarkar.3120@gmail.com>
Date: Sun, 19 Jan 2025 11:38:11 +0530
Subject: [PATCH] Remove unnecessary return definitions (#1095)

The default return=pure works and we are long past the
Functor-Applicative-Monad Proposal.
---
 containers/src/Data/Graph.hs                      | 3 ---
 containers/src/Data/Sequence/Internal.hs          | 1 -
 containers/src/Data/Tree.hs                       | 1 -
 containers/src/Utils/Containers/Internal/State.hs | 2 --
 4 files changed, 7 deletions(-)

diff --git a/containers/src/Data/Graph.hs b/containers/src/Data/Graph.hs
index 409568931..3ab697833 100644
--- a/containers/src/Data/Graph.hs
+++ b/containers/src/Data/Graph.hs
@@ -587,8 +587,6 @@ newtype SetM s a = SetM { runSetM :: STArray  s Vertex Bool -> ST s a }
 #endif
 
 instance Monad (SetM s) where
-    return = pure
-    {-# INLINE return #-}
     SetM v >>= f = SetM $ \s -> do { x <- v s; runSetM (f x) s }
     {-# INLINE (>>=) #-}
 
@@ -621,7 +619,6 @@ include v     = SetM $ \ m -> writeArray m v True
 newtype SetM s a = SetM { runSetM :: IntSet -> (a, IntSet) }
 
 instance Monad (SetM s) where
-    return x     = SetM $ \s -> (x, s)
     SetM v >>= f = SetM $ \s -> case v s of (x, s') -> runSetM (f x) s'
 
 instance Functor (SetM s) where
diff --git a/containers/src/Data/Sequence/Internal.hs b/containers/src/Data/Sequence/Internal.hs
index 3835453e3..39b49e464 100644
--- a/containers/src/Data/Sequence/Internal.hs
+++ b/containers/src/Data/Sequence/Internal.hs
@@ -521,7 +521,6 @@ instance NFData1 Seq where
     liftRnf rnfx (Seq xs) = liftRnf (liftRnf rnfx) xs
 
 instance Monad Seq where
-    return = pure
     xs >>= f = foldl' add empty xs
       where add ys x = ys >< f x
     (>>) = (*>)
diff --git a/containers/src/Data/Tree.hs b/containers/src/Data/Tree.hs
index 4551f7207..7788b0c79 100644
--- a/containers/src/Data/Tree.hs
+++ b/containers/src/Data/Tree.hs
@@ -171,7 +171,6 @@ instance Applicative Tree where
         Node y (tys ++ map (*> ty) txs)
 
 instance Monad Tree where
-    return = pure
     Node x ts >>= f = case f x of
         Node x' ts' -> Node x' (ts' ++ map (>>= f) ts)
 
diff --git a/containers/src/Utils/Containers/Internal/State.hs b/containers/src/Utils/Containers/Internal/State.hs
index 7fd3dfc79..96b898b38 100644
--- a/containers/src/Utils/Containers/Internal/State.hs
+++ b/containers/src/Utils/Containers/Internal/State.hs
@@ -16,9 +16,7 @@ instance Functor (State s) where
     fmap = liftA
 
 instance Monad (State s) where
-    {-# INLINE return #-}
     {-# INLINE (>>=) #-}
-    return = pure
     m >>= k = State $ \ s -> case runState m s of
         (s', x) -> runState (k x) s'