Compacting StaticPtr of a function doesn't work

I think we should be able to compact a StaticPtr of a function, but it currently doesn't work. Reproducer:

{-# LANGUAGE StaticPointers #-}

import GHC.StaticPtr
import Data.Compact

foo :: Int -> Int
foo x = x^2

main = do
    c <- compact (static foo :: StaticPtr (Int -> Int))
    return ()

Output:

./compact_test
compact_test: compaction failed: cannot compact functions

Tried with 8.4.3 (compact on hackage doesn't build with 8.6).

Trac metadata

Trac field	Value
Version	8.4.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	bgamari, simonmar
Operating system
Architecture