Relax Flatten constraint

Author: garyb

src/Control/Promise.purs

@@ -19,7 +19,7 @@ import Promise as Promise
 import Promise.Rejection as Rejection
 
 -- | Convert an Aff into a Promise.
-fromAff :: forall a. Promise.Flatten a a => Aff a -> Effect (Promise.Promise a)
+fromAff :: forall a b. Promise.Flatten a b => Aff a -> Effect (Promise.Promise b)
 fromAff aff = Promise.new (\succ err -> runAff_ (either (err <<< Rejection.fromError) succ) aff)
 
 coerce :: Promise.Rejection -> Error

test/Main.purs

@@ -84,8 +84,8 @@ main = launchAff_ $ flip runReaderT "" do
         res <- Promise.toAffE $ Promise.fromAff $ pure 123
         assert "round-trip result for toAffE is 123" $ res == 123
     test "error" do
-      promise <- liftEffect $ Promise.fromAff (throwError (error "err123"))
-      res <- attempt $ Promise.toAff (promise :: Promise Unit)
+      promise <- liftEffect $ Promise.fromAff (throwError (error "err123") :: Aff Unit)
+      res <- attempt $ Promise.toAff promise
       shouldEqual "err123" $ either message (const "-") res
   where
   errorCodeCoerce v =