[Git][ghc/ghc][master] Reject nested foralls in foreign imports (#16702)
Marge Bot
gitlab at gitlab.haskell.org
Sat Jun 1 03:56:32 UTC 2019
Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC
Commits:
45f88494 by Ryan Scott at 2019-06-01T03:56:27Z
Reject nested foralls in foreign imports (#16702)
This replaces a panic observed in #16702 with a simple error message
stating that nested `forall`s simply aren't allowed in the type
signature of a `foreign import` (at least, not at present).
Fixes #16702.
- - - - -
5 changed files:
- compiler/typecheck/TcForeign.hs
- docs/users_guide/ffi-chap.rst
- + testsuite/tests/ffi/should_fail/T16702.hs
- + testsuite/tests/ffi/should_fail/T16702.stderr
- testsuite/tests/ffi/should_fail/all.T
Changes:
=====================================
compiler/typecheck/TcForeign.hs
=====================================
@@ -64,7 +64,6 @@ import Hooks
import qualified GHC.LanguageExtensions as LangExt
import Control.Monad
-import Data.Maybe
-- Defines a binding
isForeignImport :: LForeignDecl name -> Bool
@@ -251,8 +250,7 @@ tcFImport (L dloc fo@(ForeignImport { fd_name = L nloc nm, fd_sig_ty = hs_ty
; let
-- Drop the foralls before inspecting the
-- structure of the foreign type.
- (bndrs, res_ty) = tcSplitPiTys norm_sig_ty
- arg_tys = mapMaybe binderRelevantType_maybe bndrs
+ (arg_tys, res_ty) = tcSplitFunTys (dropForAlls norm_sig_ty)
id = mkLocalId nm sig_ty
-- Use a LocalId to obey the invariant that locally-defined
-- things are LocalIds. However, it does not need zonking,
@@ -424,10 +422,9 @@ tcCheckFEType sig_ty (CExport (L l (CExportStatic esrc str cconv)) src) = do
checkForeignRes nonIOok noCheckSafe isFFIExportResultTy res_ty
return (CExport (L l (CExportStatic esrc str cconv')) src)
where
- -- Drop the foralls before inspecting n
+ -- Drop the foralls before inspecting
-- the structure of the foreign type.
- (bndrs, res_ty) = tcSplitPiTys sig_ty
- arg_tys = mapMaybe binderRelevantType_maybe bndrs
+ (arg_tys, res_ty) = tcSplitFunTys (dropForAlls sig_ty)
{-
************************************************************************
@@ -458,6 +455,11 @@ checkForeignRes non_io_result_ok check_safe pred_res_ty ty
= -- Got an IO result type, that's always fine!
check (pred_res_ty res_ty) (illegalForeignTyErr result)
+ -- We disallow nested foralls in foreign types
+ -- (at least, for the time being). See #16702.
+ | tcIsForAllTy ty
+ = addErrTc $ illegalForeignTyErr result (text "Unexpected nested forall")
+
-- Case for non-IO result type with FFI Import
| not non_io_result_ok
= addErrTc $ illegalForeignTyErr result (text "IO result type expected")
=====================================
docs/users_guide/ffi-chap.rst
=====================================
@@ -14,9 +14,10 @@ Foreign function interface (FFI)
Allow use of the Haskell foreign function interface.
-GHC (mostly) conforms to the Haskell Foreign Function Interface, whose
-definition is part of the Haskell Report on
-`http://www.haskell.org/ <http://www.haskell.org/>`__.
+GHC (mostly) conforms to the Haskell Foreign Function Interface as specified
+in the Haskell Report. Refer to the `relevant chapter
+<https://www.haskell.org/onlinereport/haskell2010/haskellch8.html>_`
+of the Haskell Report for more details.
FFI support is enabled by default, but can be enabled or disabled
explicitly with the :extension:`ForeignFunctionInterface` flag.
@@ -102,6 +103,25 @@ OK: ::
foreign import foo :: Int -> MyIO Int
foreign import "dynamic" baz :: (Int -> MyIO Int) -> CInt -> MyIO Int
+.. _ffi-foralls:
+
+Explicit ``forall``s in foreign types
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The type variables in the type of a foreign declaration may be quantified with
+an explicit ``forall`` by using the :extension:`ExplicitForAll` language
+extension, as in the following example: ::
+
+ {-# LANGUAGE ExplicitForAll #-}
+ foreign import ccall "mmap" c_mmap :: forall a. CSize -> IO (Ptr a)
+
+Note that an explicit ``forall`` must appear at the front of the type signature
+and is not permitted to appear nested within the type, as in the following
+(erroneous) examples: ::
+
+ foreign import ccall "mmap" c_mmap' :: CSize -> forall a. IO (Ptr a)
+ foreign import ccall quux :: (forall a. Ptr a) -> IO ()
+
.. _ffi-prim:
Primitive imports
=====================================
testsuite/tests/ffi/should_fail/T16702.hs
=====================================
@@ -0,0 +1,24 @@
+{-# LANGUAGE ForeignFunctionInterface #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE UnliftedFFITypes #-}
+{-# LANGUAGE RankNTypes #-}
+
+module T16702 where
+
+import Foreign.C.Types
+import Foreign.Ptr
+import Data.Kind (Type)
+
+foreign import ccall "math.h pow"
+ c_pow :: CDouble
+ -> forall (a :: Type). CDouble
+ -> forall (b :: Type). CDouble
+
+foreign import ccall "malloc"
+ malloc1 :: CSize -> forall a. IO (Ptr a)
+
+foreign import ccall "malloc"
+ malloc2 :: Show a => CSize -> IO (Ptr a)
+
+foreign import ccall "malloc"
+ malloc3 :: CSize -> Show a => IO (Ptr a)
=====================================
testsuite/tests/ffi/should_fail/T16702.stderr
=====================================
@@ -0,0 +1,29 @@
+
+T16702.hs:12:1: error:
+ • Unacceptable result type in foreign declaration:
+ Unexpected nested forall
+ • When checking declaration:
+ foreign import ccall safe "math.h pow" c_pow
+ :: CDouble
+ -> forall (a :: Type). CDouble -> forall (b :: Type). CDouble
+
+T16702.hs:17:1: error:
+ • Unacceptable result type in foreign declaration:
+ Unexpected nested forall
+ • When checking declaration:
+ foreign import ccall safe "malloc" malloc1
+ :: CSize -> forall a. IO (Ptr a)
+
+T16702.hs:20:1: error:
+ • Unacceptable argument type in foreign declaration:
+ ‘Show a’ cannot be marshalled in a foreign call
+ • When checking declaration:
+ foreign import ccall safe "malloc" malloc2
+ :: Show a => CSize -> IO (Ptr a)
+
+T16702.hs:23:1: error:
+ • Unacceptable argument type in foreign declaration:
+ ‘Show a’ cannot be marshalled in a foreign call
+ • When checking declaration:
+ foreign import ccall safe "malloc" malloc3
+ :: CSize -> Show a => IO (Ptr a)
=====================================
testsuite/tests/ffi/should_fail/all.T
=====================================
@@ -14,6 +14,7 @@ test('T5664', normal, compile_fail, ['-v0'])
test('T7506', normal, compile_fail, [''])
test('T7243', normal, compile_fail, [''])
test('T10461', normal, compile_fail, [''])
+test('T16702', normal, compile_fail, [''])
# UnsafeReenter tests implementation of an undefined behavior (calling Haskell
# from an unsafe foreign function) and only makes sense in non-threaded way
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/commit/45f88494293bea20cc3aca025ee6fe84087987ce
--
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/commit/45f88494293bea20cc3aca025ee6fe84087987ce
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