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The following program crashes in 8.2.2 and HEAD (8.5.20171228).

{-# LANGUAGE ForeignFunctionInterface, CApiFFI, GHCForeignImportPrim,
             QuasiQuotes, TemplateHaskell, JavaScriptFFI, MagicHash,
             UnliftedFFITypes #-}

module TH_foreignCallingConventions where

import GHC.Prim
import Control.Applicative
import Language.Haskell.TH
import System.IO
import Foreign.Ptr

$( do let fi cconv safety lbl name ty =
            ForeignD (ImportF cconv safety lbl name ty)
      dec1 <- fi CCall      Interruptible "&"   (mkName "foo") <$> [t| Ptr () |]
      dec2 <- fi CApi       Safe          "bar" (mkName "bar") <$> [t| Int# -> Int# |]
      -- the declarations below would result in warnings or errors when returned
      dec3 <- fi CApi       Unsafe        "baz" (mkName "baz") <$> [t| Double -> IO () |]
      dec4 <- fi StdCall    Safe          "bay" (mkName "bay") <$> [t| (Int -> Bool) -> IO Int |]
      dec5 <- fi JavaScript Unsafe        "bax" (mkName "bax") <$> [t| Ptr Int -> IO String |]
      runIO $
        mapM_ (putStrLn . pprint) [dec1, dec2, dec3, dec4, dec5] >> hFlush stdout
      return [dec1, dec2]
 )

This program is derived by mutating test TH_foreignCallingConventions.hs.

diff --git a/testsuite/tests/th/TH_foreignCallingConventions.hs b/testsuite/tests/th/TH_foreignCallingConventions.hs
index ee39510..16789af 100644
--- a/testsuite/tests/th/TH_foreignCallingConventions.hs
+++ b/testsuite/tests/th/TH_foreignCallingConventions.hs
@@ -13,7 +13,7 @@ import Foreign.Ptr
 $( do let fi cconv safety lbl name ty =
             ForeignD (ImportF cconv safety lbl name ty)
       dec1 <- fi CCall      Interruptible "&"   (mkName "foo") <$> [t| Ptr () |]
-      dec2 <- fi Prim       Safe          "bar" (mkName "bar") <$> [t| Int# -> Int# |]
+      dec2 <- fi CApi       Safe          "bar" (mkName "bar") <$> [t| Int# -> Int# |]
       -- the declarations below would result in warnings or errors when returned
       dec3 <- fi CApi       Unsafe        "baz" (mkName "baz") <$> [t| Double -> IO () |]
       dec4 <- fi StdCall    Safe          "bay" (mkName "bay") <$> [t| (Int -> Bool) -> IO Int |]

Log:

foreign import capi safe "bar" bar :: GHC.Prim.Int# ->
                                      GHC.Prim.Int#
foreign import capi unsafe "baz" baz :: GHC.Types.Double ->
                                        GHC.Types.IO ()
foreign import stdcall safe "bay" bay :: (GHC.Types.Int ->
                                          GHC.Types.Bool) ->
                                         GHC.Types.IO GHC.Types.Int
foreign import javascript unsafe "bax" bax :: GHC.Ptr.Ptr GHC.Types.Int ->
                                              GHC.Types.IO GHC.Base.String
ghc: panic! (the 'impossible' happened)
  (GHC version 8.5.20171228 for x86_64-unknown-linux):
	toCType
  Int#
  Call stack:
      CallStack (from HasCallStack):
        callStackDoc, called at compiler/utils/Outputable.hs:1150:37 in ghc:Outputable
        pprPanic, called at compiler/deSugar/DsForeign.hs:730:17 in ghc:DsForeign

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

Trac metadata

Trac field	Value
Version	8.2.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system	Linux
Architecture	x86_64 (amd64)