foreign export doesn't deal with newtypes correctly

GHC does not accept foreign export dynamic where the result is not
Addr but a newtype for Addr. I think it should:

module M1 where
import Foreign
newtype FunPtr a = FunPtr Addr
foreign export dynamic f :: (Int -> Int) -> IO (FunPtr (Int -> Int))

Moreover, foreign export dynamic does not work with the NCG.

-- 
 __("<  Marcin Kowalczyk * qrczak@knm.org.pl http://qrczak.ids.net.pl/
 \__/            GCS/M d- s+:-- a23 C+++$ UL++>++++$ P+++ L++>++++$ E-
  ^^                W++ N+++ o? K? w(---) O? M- V? PS-- PE++ Y? PGP+ t
QRCZAK                5? X- R tv-- b+>++ DI D- G+ e>++++ h! r--%>++ y-

Trac metadata

Trac field	Value
Version	None
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	ResolvedFixed
Component	Compiler (FFI)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture

changed weight to 5

added FFI Tbug Trac import labels

It seems like this works fine these days. The syntax is different as "dynamic exports" have become "wrapper imports" that use FunPtr in place of Addr, but a newtype around FunPtr is accepted:

module M1 where
import Foreign.Ptr
newtype MyFunPtr a = MyFunPtr (FunPtr a)
foreign import ccall "wrapper" f :: (Int -> Int) -> IO (MyFunPtr (Int -> Int))

It looks like the checking is done by isFFIDynTy in TcType whose comments indicate that Ptr, FunPtr, or a newtype of either is acceptable. This is more permissive than Haskell2010 and doesn't seem to be documented anywhere, but...

Good to close this?

Thanks for testing @kabuhr, looks good to close to me.

closed

added obsolete label

As per Simon PJ's suggestion on ghc-dev, I'll add a regression test case for this.

Testsuite-tests: ffi/should_run/T493

mentioned in merge request !894 (merged)

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