Add missing top-level type signatures

Add `-Wmissing-signatures` to `ghc-options`.

ihaskell.cabal

@@ -49,7 +49,7 @@ data-files:
 library
   hs-source-dirs:      src
   default-language:    Haskell2010
-  ghc-options:         -Wincomplete-patterns
+  ghc-options:         -Wincomplete-patterns -Wmissing-signatures
   build-depends:
                        aeson                >=1.0,
                        base                 >=4.9,
@@ -125,7 +125,7 @@ executable ihaskell
 
   -- Other library packages from which modules are imported.
   default-language:    Haskell2010
-  ghc-options:         -Wincomplete-patterns
+  ghc-options:         -Wincomplete-patterns -Wmissing-signatures
   build-depends:
                        ihaskell -any,
                        base                 >=4.9 && < 4.13,
@@ -152,7 +152,7 @@ Test-Suite hspec
         IHaskell.Test.Util
         IHaskell.Test.Parser
     default-language: Haskell2010
-    ghc-options:         -Wincomplete-patterns
+    ghc-options:         -Wincomplete-patterns -Wmissing-signatures
     build-depends:
         base,
         ihaskell,

main/IHaskellPrelude.hs

-{-# language NoImplicitPrelude, DoAndIfThenElse, OverloadedStrings, ExtendedDefaultRules #-}{-# LANGUAGE CPP #-}
+{-# language NoImplicitPrelude, DoAndIfThenElse, OverloadedStrings, ExtendedDefaultRules #-}
+{-# LANGUAGE CPP #-}
 module IHaskellPrelude (
   module IHaskellPrelude,
   module X,
@@ -64,7 +65,8 @@ module IHaskellPrelude (
 
 import           Prelude
 
-import           Data.Monoid            as X
+import           Data.Semigroup         as X
+import           Data.Monoid            as X hiding ((<>), First(..), Last(..))
 import           Data.Tuple             as X
 import           Control.Monad          as X
 import           Data.Maybe             as X
@@ -83,7 +85,7 @@ import           Data.List              as X hiding (head, last, tail, init, tra
                                         elemIndices, elemIndex, findIndex, findIndices, zip5, zip6,
                                         zip7, zipWith5, zipWith6, zipWith7, unzip5, unzip6, unzip6,
                                         delete, union, lookup, intersect, insert, deleteBy,
-                                        deleteFirstBy, unionBy, intersectBy, group, groupBy, insertBy,
+                                        unionBy, intersectBy, group, groupBy, insertBy,
                                         maximumBy, minimumBy, genericLength, genericDrop, genericTake,
                                         genericSplitAt, genericIndex, genericReplicate, inits, tails)
 
@@ -111,13 +113,27 @@ type LByteString = Data.ByteString.Lazy.ByteString
 
 type LText = Data.Text.Lazy.Text
 
-(headMay, tailMay, lastMay, initMay, maximumMay, minimumMay) =
-  (wrapEmpty head, wrapEmpty tail, wrapEmpty last,
-   wrapEmpty init, wrapEmpty maximum, wrapEmpty minimum)
-  where
-    wrapEmpty :: ([a] -> b) -> [a] -> Maybe b
-    wrapEmpty _ [] = Nothing
-    wrapEmpty f xs = Just (f xs)
+headMay :: [a] -> Maybe a
+headMay = wrapEmpty head
+
+tailMay :: [a] -> Maybe [a]
+tailMay = wrapEmpty tail
+
+lastMay :: [a] -> Maybe a
+lastMay = wrapEmpty last
+
+initMay :: [a] -> Maybe [a]
+initMay = wrapEmpty init
+
+maximumMay :: Ord a => [a] -> Maybe a
+maximumMay = wrapEmpty maximum
+
+minimumMay :: Ord a => [a] -> Maybe a
+minimumMay = wrapEmpty minimum
+
+wrapEmpty :: ([a] -> b) -> [a] -> Maybe b
+wrapEmpty _ [] = Nothing
+wrapEmpty f xs = Just (f xs)
 
 maximumByMay :: (a -> a -> Ordering) -> [a] -> Maybe a
 maximumByMay _ [] = Nothing

src/IHaskell/Display.hs

@@ -201,6 +201,7 @@ printDisplay disp = display disp >>= atomically . writeTChan displayChan
 
 -- | Convenience function for client libraries. Switch to a temporary directory so that any files we
 -- create aren't visible. On Unix, this is usually /tmp.
+switchToTmpDir :: IO ()
 switchToTmpDir = void (try switchDir :: IO (Either SomeException ()))
   where
     switchDir =

src/IHaskell/Eval/Completion.hs

@@ -69,6 +69,7 @@ exposedName :: (a, b) -> a
 exposedName = fst
 #endif
 
+extName (FlagSpec { flagSpecName = name }) = name
 extName (FlagSpec { flagSpecName = name }) = name
 
 complete :: String -> Int -> Interpreter (String, [String])

src/IHaskell/Eval/Evaluate.hs

@@ -1110,6 +1110,7 @@ doLoadModule name modName = do
 
       return $ displayError $ "Failed to load module " ++ modName ++ ": " ++ show exception
 
+objTarget :: DynFlags -> HscTarget
 objTarget flags = defaultObjectTarget $ targetPlatform flags
 
 keepingItVariable :: Interpreter a -> Interpreter a

src/IHaskell/Eval/ParseShell.hs

@@ -28,6 +28,7 @@ manyTillEnd p end = scan
              xs <- scan
              return $ x : xs
 
+manyTillEnd1 :: Parser a -> Parser [a] -> Parser [a]
 manyTillEnd1 p end = do
   x <- p
   xs <- manyTillEnd p end
@@ -39,15 +40,18 @@ unescapedChar p = try $ do
   lookAhead p
   return [x]
 
+quotedString :: Parser [Char]
 quotedString = do
   quote <?> "expected starting quote"
   (manyTillEnd anyChar (unescapedChar quote) <* quote) <?> "unexpected in quoted String "
 
+unquotedString :: Parser [Char]
 unquotedString = manyTillEnd1 anyChar end
   where
     end = unescapedChar space
           <|> (lookAhead eol >> return [])
 
+word :: Parser [Char]
 word = quotedString <|> unquotedString <?> "word"
 
 separator :: Parser String

src/IHaskell/Eval/Util.hs

@@ -139,6 +139,7 @@ pprDynFlags show_all dflags =
     flgs1 = [Opt_PrintExplicitForalls]
     flgs2 = [Opt_PrintExplicitKinds]
 
+flgs3 :: [GeneralFlag]
 flgs3 = [Opt_PrintBindResult, Opt_BreakOnException, Opt_BreakOnError, Opt_PrintEvldWithShow]
 
 -- | Pretty-print the base language and active options (taken from `InteractiveUI` module of

src/IHaskell/Flags.hs

@@ -132,8 +132,10 @@ installPrefixFlag :: Flag Args
 installPrefixFlag = flagReq ["prefix"] (store KernelspecInstallPrefix) "<install-dir>"
                       "Installation prefix for kernelspec (see Jupyter's --prefix option)"
 
+helpFlag :: Flag Args
 helpFlag = flagHelpSimple (add Help)
 
+add :: Argument -> Args -> Args
 add flag (Args mode flags) = Args mode $ flag : flags
 
 store :: (String -> Argument) -> String -> Args -> Either String Args
@@ -204,6 +206,7 @@ ihaskellArgs =
   where
     add flag (Args mode flags) = Args mode $ flag : flags
 
+noArgs :: Arg a
 noArgs = flagArg unexpected ""
   where
     unexpected a = error $ "Unexpected argument: " ++ a

src/IHaskell/IPython.hs

@@ -106,6 +106,7 @@ ipython suppress args = do
                              else return ""
 
 -- | Run while suppressing all output.
+quietRun :: SH.FilePath -> [Text] -> SH.Sh ()
 quietRun path args = SH.runHandles path args handles nothing
   where
     handles = [SH.InHandle SH.Inherit, SH.OutHandle SH.CreatePipe, SH.ErrorHandle SH.CreatePipe]
@@ -267,7 +268,7 @@ getIHaskellPath = do
   -- If we have an absolute path, that's the IHaskell we're interested in.
   if FP.isAbsolute f
     then return f
-    else 
+    else
     -- Check whether this is a relative path, or just 'IHaskell' with $PATH resolution done by
     -- the shell. If it's just 'IHaskell', use the $PATH variable to find where IHaskell lives.
     if FP.takeFileName f == f

src/IHaskellPrelude.hs

@@ -85,7 +85,7 @@ import           Data.List              as X hiding (head, last, tail, init, tra
                                         elemIndices, elemIndex, findIndex, findIndices, zip5, zip6,
                                         zip7, zipWith5, zipWith6, zipWith7, unzip5, unzip6, unzip6,
                                         delete, union, lookup, intersect, insert, deleteBy,
-                                        deleteFirstBy, unionBy, intersectBy, group, groupBy, insertBy,
+                                        unionBy, intersectBy, group, groupBy, insertBy,
                                         maximumBy, minimumBy, genericLength, genericDrop, genericTake,
                                         genericSplitAt, genericIndex, genericReplicate, inits, tails)
 
@@ -113,13 +113,27 @@ type LByteString = Data.ByteString.Lazy.ByteString
 
 type LText = Data.Text.Lazy.Text
 
-(headMay, tailMay, lastMay, initMay, maximumMay, minimumMay) =
-  (wrapEmpty head, wrapEmpty tail, wrapEmpty last,
-   wrapEmpty init, wrapEmpty maximum, wrapEmpty minimum)
-  where
-    wrapEmpty :: ([a] -> b) -> [a] -> Maybe b
-    wrapEmpty _ [] = Nothing
-    wrapEmpty f xs = Just (f xs)
+headMay :: [a] -> Maybe a
+headMay = wrapEmpty head
+
+tailMay :: [a] -> Maybe [a]
+tailMay = wrapEmpty tail
+
+lastMay :: [a] -> Maybe a
+lastMay = wrapEmpty last
+
+initMay :: [a] -> Maybe [a]
+initMay = wrapEmpty init
+
+maximumMay :: Ord a => [a] -> Maybe a
+maximumMay = wrapEmpty maximum
+
+minimumMay :: Ord a => [a] -> Maybe a
+minimumMay = wrapEmpty minimum
+
+wrapEmpty :: ([a] -> b) -> [a] -> Maybe b
+wrapEmpty _ [] = Nothing
+wrapEmpty f xs = Just (f xs)
 
 maximumByMay :: (a -> a -> Ordering) -> [a] -> Maybe a
 maximumByMay _ [] = Nothing

src/tests/IHaskell/Test/Completion.hs

@@ -48,6 +48,7 @@ shouldHaveCompletionsInDirectory string expected = do
       unmatched = filter (not . existsInCompletion) expected
   expected `shouldBeAmong` completions
 
+completionHas :: String -> [String] -> IO ()
 completionHas string expected = do
   (matched, completions) <- ghc $ do
                               initCompleter