more specific types in the generated *_stub.h files

Having a declaration like:

foreign export ccall "respond" respond :: CWString -> IO CWString

all the types in the corresponding _stub.h are HsPtr.

Wouldn't it be possible to write more specific types reflecting my expectations, i.e., wchar_t *?

It would be nice in order to signal automatically to the C code which uses the Haskell functions that the types of the Haskell functions changed. In simple cases, one could simply include the stub.h, and get automatically an error if the C code doesn't match the new types.

I've tried using a CTYPE pragma (cf. #2979 (closed) , #8222 (closed) , and https://mail.haskell.org/pipermail/haskell/2012-February/023155.html ) on a newtype to get such results:

newtype {-# CTYPE "wchar_t *" #-} CWString' = CWString' CWString
foreign export ccall "respond" respond :: CWString'  -> IO CWString

but that still produces HsPtr. (Well, I see, the CTYPE pragma was mostly intended for imports rather than exports.)

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The same problem and wish as mine are illustrated in http://stackoverflow.com/q/23629000/94687 by an attempt to use a Haskell function on Strings .

The solutions so far:

Either manual editing of the .h file (which may result in inconsistencies with the real code, and which is additional burden), or casting in the C code (which opens the door wide for inconsistencies with the real Haskell code).

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