Options -no-hs-main -debug cause 'impossible' to happen

Here's the command line:

ghc -c ForeignTest.hs -fglasgow-exts -package text
-no-hs-main

And here's the module:
-----------------------
module ForeignTest (reduce) where

import Foreign.StablePtr
import GensDef
import GensCoreIO

foreign export ccall "reduce"
   reduceMain ::
      StablePtr LookupFun -> StablePtr ReduceFun -> IO
(StablePtr Environment)

reduceMain _ _ = newStablePtr emptyEnv
------------------------

Let me know if you need the modules GensDef and
GensCoreIO imported from above. I expect the problem is
more generic than that.

Trac metadata

Trac field	Value
Version	None
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	ResolvedNoReason
Component	Compiler (FFI)
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