From c699bee3df65e287cb5672541ee209a887f54ecd Mon Sep 17 00:00:00 2001
From: Joshua Potter <jrpotter2112@gmail.com>
Date: Sat, 2 Apr 2022 11:05:39 -0400
Subject: [PATCH] Drop IORef per
 https://github.com/fused-effects/fused-effects-exceptions/issues/18.

---
 fused-effects-exceptions.cabal     |  1 -
 src/Control/Carrier/State/IORef.hs | 81 ------------------------------
 test/Main.hs                       |  7 ---
 3 files changed, 89 deletions(-)
 delete mode 100644 src/Control/Carrier/State/IORef.hs

diff --git a/fused-effects-exceptions.cabal b/fused-effects-exceptions.cabal
index 851d8c7..6eceb2e 100644
--- a/fused-effects-exceptions.cabal
+++ b/fused-effects-exceptions.cabal
@@ -31,7 +31,6 @@ library
   import: common
   hs-source-dirs: src
   exposed-modules:
-    Control.Carrier.State.IORef
     Control.Effect.Exception
     Control.Effect.Exception.UnliftIO
   other-modules:
diff --git a/src/Control/Carrier/State/IORef.hs b/src/Control/Carrier/State/IORef.hs
deleted file mode 100644
index b60b1a0..0000000
--- a/src/Control/Carrier/State/IORef.hs
+++ /dev/null
@@ -1,81 +0,0 @@
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE GADTs #-}
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
-{-# LANGUAGE RankNTypes #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE TypeApplications #-}
-{-# LANGUAGE TypeOperators #-}
-{-# LANGUAGE UndecidableInstances #-}
-
-{- | A carrier for the 'State' effect. It uses an 'IORef' internally to handle its state, and thus is safe to use with "Control.Carrier.Resource". Underlying 'IORef' operations are performed with 'readIORef' and 'writeIORef'.
-
-Note that the parameter order in 'runState', 'evalState', and 'execState' is reversed compared the equivalent functions provided by @transformers@. This is an intentional decision made to enable the composition of effect handlers with '.' without invoking 'flip'.
--}
-module Control.Carrier.State.IORef
-( -- * Strict state carrier
-  runState
-, evalState
-, execState
-, StateC(..)
--- * State effect
-, module Control.Effect.State
-) where
-
-import           Control.Algebra
-import           Control.Applicative (Alternative(..))
-import           Control.Carrier.Reader
-import           Control.Effect.State
-import           Control.Monad (MonadPlus(..))
-import qualified Control.Monad.Fail as Fail
-import           Control.Monad.Fix
-import           Control.Monad.IO.Class
-import           Control.Monad.Trans.Class
-import           Data.IORef
-
--- | Run a 'State' effect starting from the passed value.
---
---   prop> run (runState a (pure b)) === (a, b)
---
--- @since 1.0.0.0
-runState :: MonadIO m => s -> StateC s m a -> m (s, a)
-runState s x = do
-  ref <- liftIO $ newIORef s
-  result <- runReader ref . runStateC $ x
-  final <- liftIO . readIORef $ ref
-  pure (final, result)
-{-# INLINE[3] runState #-}
-
--- | Run a 'State' effect, yielding the result value and discarding the final state.
---
---   prop> run (evalState a (pure b)) === b
---
--- @since 1.0.0.0
-evalState :: forall s m a . MonadIO m => s -> StateC s m a -> m a
-evalState s x = do
-  ref <- liftIO $ newIORef s
-  runReader ref . runStateC $ x
-{-# INLINE[3] evalState #-}
-
--- | Run a 'State' effect, yielding the final state and discarding the return value.
---
---   prop> run (execState a (pure b)) === a
---
--- @since 1.0.0.0
-execState :: forall s m a . MonadIO m => s -> StateC s m a -> m s
-execState s = fmap fst . runState s
-{-# INLINE[3] execState #-}
-
--- | @since 1.0.0.0
-newtype StateC s m a = StateC { runStateC :: ReaderC (IORef s) m a }
-  deriving (Alternative, Applicative, Functor, Monad, Fail.MonadFail, MonadFix, MonadIO, MonadPlus)
-
-instance (MonadIO m, Algebra sig m) => Algebra (State s :+: sig) (StateC s m) where
-  alg hdl sig ctx = case sig of
-    L act -> do
-      ref <- StateC (ask @(IORef s))
-      (<$ ctx) <$> case act of
-        Put s -> liftIO (writeIORef ref s)
-        Get   -> liftIO (readIORef ref)
-    R other -> StateC (alg (runStateC . hdl) (R other) ctx)
-  {-# INLINE alg #-}
diff --git a/test/Main.hs b/test/Main.hs
index 3cfa3d7..c84411f 100644
--- a/test/Main.hs
+++ b/test/Main.hs
@@ -6,7 +6,6 @@ module Main where
 import           Prelude hiding (ioError)
 
 import           Control.Carrier.Lift (runM)
-import qualified Control.Carrier.State.IORef as IOState
 import qualified Control.Carrier.State.Strict as State
 import           Control.Effect.Exception
 import           Control.Effect.State
@@ -23,16 +22,10 @@ testStateDropsWrites = HUnit.testCase "State.Strict drops writes" $ do
   result <- State.execState 'a' problematic
   result HUnit.@?= 'a' -- writes are lost
 
-testIOStatePreservesWrites :: Tasty.TestTree
-testIOStatePreservesWrites = HUnit.testCase "State.IORef preserves writes" $ do
-  result <- IOState.execState 'a' problematic
-  result HUnit.@?= 'x'
-
 tests :: Tasty.TestTree
 tests = Tasty.testGroup "Control.Carrier.Exception"
   [ Tasty.testGroup "finally"
     [ testStateDropsWrites
-    , testIOStatePreservesWrites
     ]
   ]