regression: acceptable foreign result types

The following short file is rejected:

import Foreign.Ptr
foreign import ccall "wrapper" foo :: IO (FunPtr ())

The error is:

test.hs:2:1:
    Unacceptable type in foreign declaration: IO (FunPtr ())
    When checking declaration:
      foreign import ccall safe "wrapper" foo :: IO (FunPtr ())

However, my reading of the 2010 Report suggests this should be acceptable. Specifically:

• Prelude.IO t is a marshallable foreign result type when t is a marshallable foreign type,[[BR]]
• all basic foreign types are marshallable foreign types, and[[BR]]
• FunPtr a is a basic foreign type for all a.

(Political note: I include this chain of reasoning not because I think others too stupid to recreate it, but because I think it likely that I am not reading the Report correctly, and want to make it easy to detect and correct any misconceptions I have.)

Trac metadata

Trac field	Value
Version	7.6.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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