Do not fully saturate the type synonyms

If we define type Serial a = SerialT IO a, then we cannot use Serial where we
need SerialT IO.

src/Streamly/Streams/Ahead.hs

@@ -625,7 +625,7 @@ newtype AheadT m a = AheadT {getAheadT :: Stream m a}
 -- 'AheadT' documentation for more details.
 --
 -- @since 0.3.0
-type Ahead a = AheadT IO a
+type Ahead = AheadT IO
 
 -- | Fix the type of a polymorphic stream as 'AheadT'.
 --

src/Streamly/Streams/Async.hs

@@ -641,7 +641,7 @@ newtype AsyncT m a = AsyncT {getAsyncT :: Stream m a}
 -- type @a@.  See 'AsyncT' documentation for more details.
 --
 -- @since 0.2.0
-type Async a = AsyncT IO a
+type Async = AsyncT IO
 
 -- | Fix the type of a polymorphic stream as 'AsyncT'.
 --
@@ -768,7 +768,7 @@ newtype WAsyncT m a = WAsyncT {getWAsyncT :: Stream m a}
 -- See 'WAsyncT' documentation for more details.
 --
 -- @since 0.2.0
-type WAsync a = WAsyncT IO a
+type WAsync = WAsyncT IO
 
 -- | Fix the type of a polymorphic stream as 'WAsyncT'.
 --

src/Streamly/Streams/Parallel.hs

@@ -331,7 +331,7 @@ newtype ParallelT m a = ParallelT {getParallelT :: Stream m a}
 -- See 'ParallelT' documentation for more details.
 --
 -- @since 0.2.0
-type Parallel a = ParallelT IO a
+type Parallel = ParallelT IO
 
 -- | Fix the type of a polymorphic stream as 'ParallelT'.
 --

src/Streamly/Streams/Serial.hs

@@ -127,7 +127,7 @@ newtype SerialT m a = SerialT {getSerialT :: Stream m a}
 -- for more details.
 --
 -- @since 0.2.0
-type Serial a = SerialT IO a
+type Serial = SerialT IO
 
 -- |
 -- @since 0.1.0
@@ -247,7 +247,7 @@ newtype WSerialT m a = WSerialT {getWSerialT :: Stream m a}
 -- documentation for more details.
 --
 -- @since 0.2.0
-type WSerial a = WSerialT IO a
+type WSerial = WSerialT IO
 
 -- |
 -- @since 0.1.0

src/Streamly/Streams/Zip.hs

@@ -82,7 +82,7 @@ type ZipStream = ZipSerialM
 -- | An IO stream whose applicative instance zips streams serially.
 --
 -- @since 0.2.0
-type ZipSerial a = ZipSerialM IO a
+type ZipSerial = ZipSerialM IO
 
 -- | Fix the type of a polymorphic stream as 'ZipSerialM'.
 --
@@ -171,7 +171,7 @@ newtype ZipAsyncM m a = ZipAsyncM {getZipAsyncM :: Stream m a}
 -- | An IO stream whose applicative instance zips streams wAsyncly.
 --
 -- @since 0.2.0
-type ZipAsync a = ZipAsyncM IO a
+type ZipAsync = ZipAsyncM IO
 
 -- | Fix the type of a polymorphic stream as 'ZipAsyncM'.
 --