ENH use better types for wait

bin/vbox-start.hs

@@ -21,6 +21,7 @@ import RIO
 import RIO.Process
 import qualified RIO.Text as T
 import System.Environment
+import System.Process (Pid)
 import Text.XML.Light
 import XMonad.Internal.Concurrent.VirtualBox
 import XMonad.Internal.IO
@@ -54,7 +55,7 @@ vmLaunch i = do
         "Failed to start VM: "
           <> displayBytesUtf8 (encodeUtf8 i)
 
-vmPID :: T.Text -> RIO SimpleApp (Maybe Int)
+vmPID :: T.Text -> RIO SimpleApp (Maybe Pid)
 vmPID vid = do
   (rc, out) <- proc "pgrep" ["-f", "VirtualBoxVM.*" ++ T.unpack vid] readProcessStdout
   return $ case rc of

lib/XMonad/Internal/IO.hs

@@ -31,6 +31,7 @@ import RIO.Directory
 import RIO.FilePath
 import qualified RIO.Text as T
 import System.IO.Error
+import System.Process
 
 --------------------------------------------------------------------------------
 -- read
@@ -161,7 +162,7 @@ getPermissionsSafe f = do
 -- | Block until a PID has exited.
 -- Use this to control flow based on a process that was not explicitly started
 -- by the Haskell runtime itself, and thus has no data structures to query.
-waitUntilExit :: (MonadIO m, Show t, Num t) => t -> m ()
+waitUntilExit :: (MonadIO m) => Pid -> m ()
 waitUntilExit pid = do
   res <- doesDirectoryExist $ "/proc" </> show pid
   when res $ do