[refactor] remove redundant typeslass constraints

This review commit removes a bunch of redundant typeclass constraints,
especially the ones on the data declarations, generally considered a
codesmell.

src/Async/Worker.hs

@@ -154,8 +154,7 @@ handleMessage state@(State { .. }) brokerMessage = do
 --         )
 
 
-callWorkerJobEvent :: (HasWorkerBroker b a)
-                   => WorkerJobEvent b a
+callWorkerJobEvent :: WorkerJobEvent b a
                    -> State b a
                    -> BrokerMessage b (Job a)
                    -> IO ()
@@ -223,7 +222,7 @@ handleJobError _state@(State { .. }) brokerMessage = do
 
         void $ sendJob broker queueName (job { metadata = mdata { readCount = readCt + 1 } })
 
-handleUnknownError :: (HasWorkerBroker b a) => State b a -> SomeException -> IO ()
+handleUnknownError :: State b a -> SomeException -> IO ()
 handleUnknownError state err = do
   let _ = traceStack ("unknown error: " <> show err)
   putStrLn $ formatStr state $ "unknown error: " <> show err
@@ -242,7 +241,7 @@ microsecond = 10^(6 :: Int)
 -}
 
 -- | Wraps parameters for the 'sendJob' function
-data (HasWorkerBroker b a) => SendJob b a =
+data SendJob b a =
   SendJob { broker       :: Broker b (Job a)
           , queue        :: Queue
           , msg          :: a
@@ -254,8 +253,7 @@ data (HasWorkerBroker b a) => SendJob b a =
           , resendOnKill :: Bool}
 
 -- | Create a 'SendJob' data with some defaults
-mkDefaultSendJob :: HasWorkerBroker b a
-                 => Broker b (Job a)
+mkDefaultSendJob :: Broker b (Job a)
                  -> Queue
                  -> a
                  -> Timeout
@@ -276,8 +274,7 @@ mkDefaultSendJob broker queue msg timeout =
 
 
 -- | Like 'mkDefaultSendJob' but with default timeout
-mkDefaultSendJob' :: HasWorkerBroker b a
-                  => Broker b (Job a)
+mkDefaultSendJob' :: Broker b (Job a)
                   -> Queue
                   -> a
                   -> SendJob b a

src/Async/Worker/Types.hs

@@ -238,7 +238,7 @@ jobTimeout (Job { metadata }) = timeout metadata
 --
 -- Note that our underlying 'Broker' handles messages of type 'Job'
 -- 'a'.
-data (HasWorkerBroker b a) => State b a =
+data State b a =
   State { broker            :: Broker b (Job a)
         -- | Queue associated with this worker. If you want to support
         -- more queues, spawn more workers.
@@ -259,7 +259,7 @@ data (HasWorkerBroker b a) => State b a =
 
 -- | Helper function to call an action for given worker, for a
 -- 'BrokerMessage'.
-runAction :: (HasWorkerBroker b a) => State b a -> BrokerMessage b (Job a) -> IO ()
+runAction :: State b a -> BrokerMessage b (Job a) -> IO ()
 runAction state brokerMessage = (performAction state) state brokerMessage
 
 type WorkerJobEvent b a = Maybe (State b a -> BrokerMessage b (Job a) -> IO ())
@@ -274,7 +274,7 @@ type PerformAction b a =
 type HasWorkerBroker b a = ( MessageBroker b (Job a), Typeable a, Typeable b, Show a )
 
 -- | Helper function to format a string with worker name (for logging)
-formatStr :: (HasWorkerBroker b a) => State b a -> String -> String
+formatStr :: State b a -> String -> String
 formatStr (State { name }) msg =
   "[" <> name <> "] " <> msg
 
@@ -282,5 +282,5 @@ formatStr (State { name }) msg =
 data JobTimeout b a =
   JobTimeout { jtBMessage  :: BrokerMessage b (Job a)
              , jtTimeout   :: Timeout }
-deriving instance (HasWorkerBroker b a) => Show (JobTimeout b a)
-instance (HasWorkerBroker b a) => Exception (JobTimeout b a)
+deriving instance (Show (BrokerMessage b (Job a))) => Show (JobTimeout b a)
+instance (Show (BrokerMessage b (Job a)), Typeable a, Typeable b) => Exception (JobTimeout b a)

tests/Test/Integration/Utils.hs

@@ -112,7 +112,7 @@ waitUntilTVarEq tvar expected (TimeoutMs timeoutMs) = do
           performTest
 
 -- | Similar to 'waitUntilTVarEq' but with predicate checking
-waitUntilTVarPred :: (HasCallStack, Show a, Eq a) => TVar a -> (a -> Bool) -> TimeoutMs -> Expectation
+waitUntilTVarPred :: (HasCallStack, Show a) => TVar a -> (a -> Bool) -> TimeoutMs -> Expectation
 waitUntilTVarPred tvar predicate (TimeoutMs timeoutMs) = do
   _mTimeout <- Timeout.timeout (timeoutMs * 1000) performTest
   -- shortcut for testing mTimeout