c2hs should derive and use default marshallers from enum and pointer hooks

[ian-ross]

Bug imported from C2HS Trac

Trac ticket created: 2010-05-27T17:26:12-0700

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This is a FIXME in the source code, and I'm working on bindings that would really benefit from the DRY aspect of this feature.

Specifically, c2hs should derive the following in/out marshallers:

• fromIntegral . fromEnum and toEnum . fromIntegral from an enum hook
• id and id from both naked and newtype pointer hooks
• withForeignPtr and newForeignPtr_ for foreign pointer hooks
• withPointerType (the generated function) and PointerType . newForeignPtr_ for foreign newtype pointer hooks. The out marshaller is not great here, a !ForeignPtr with no finalizers is not terribly useful concealed inside the newtype. Perhaps foreign newtype should be left naked, or furnished with an 'in' default marshaller only.

Since I don't enjoy giving work to other people, I volunteer to add this functionality and submit a patch. This ticket is created for tracking purposes.