@@ -16,7 +16,7 @@ import qualified System.IO as IO
1616
1717import Effectful
1818import Effectful.Error
19−import Effectful.State
19+import Effectful.State.Local
2020
2121-- | An effect for reading and writing files.
2222data FileSystem :: Effect where
@@ -30,11 +30,11 @@ newtype FsError = FsError String
3030-- Operations
3131
3232-- | Read contents of a file.
33−readFile :: FileSystem :> es => FilePath -> Eff es String
33+readFile :: (HasCallStack, FileSystem :> es) => FilePath -> Eff es String
3434readFile = send . ReadFile
3535
3636-- | Write contents to a file.
37−writeFile :: FileSystem :> es => FilePath -> String -> Eff es ()
37+writeFile :: (HasCallStack, FileSystem :> es) => FilePath -> String -> Eff es ()
3838writeFile path = send . WriteFile path
3939
4040----------------------------------------