Hi, The document of GHC API says that "desugarModule" displays warnings of pattern matching even if HscNothing is specified: http://www.haskell.org/ghc/docs/latest/html/libraries/ghc/GHC.html#t:HscTarg... Unfortunately, I cannot get warnings of pattern matching. To demonstrate this, I attached two files: - Main.hs -- using "desugarModule" - B.hs -- a target file: top level signature is missing, pattern is imcompleted When I run "Main.hs" with: % runghc -- -package --ghc-arg=ghc -Wall Main I only got: B.hs:6:1: Warning: Top-level binding with no type signature: main :: IO () Does anyone know how to display warnings of pattern matching with HscNothing? --Kazu <Main> -- runghc -- -package --ghc-arg=ghc A module Main where import GHC import GHC.Paths (libdir) import DynFlags main :: IO () main = defaultErrorHandler defaultFatalMessager defaultFlushOut $ runGhc (Just libdir) $ getWarings "B.hs" "B" getWarings :: String -> String -> Ghc () getWarings targetFile targetModule = do dflags <- getSessionDynFlags let dflags' = dflags { ghcLink = NoLink , hscTarget = HscNothing } dflags'' = foldl wopt_set dflags' [Opt_WarnMissingSigs,Opt_WarnIncompletePatterns] _ <- setSessionDynFlags dflags'' target <- guessTarget targetFile Nothing setTargets [target] _ <- load LoadAllTargets modSum <- getModSummary $ mkModuleName targetModule p <- parseModule modSum t <- typecheckModule p _ <- desugarModule t return () </Main> <B> module B where myHead :: [Int] -> Int myHead (x:_) = x main = do print $ myHead [1,2,3] </B>