Case-inspecting unboxed unit causes codegen crash

Here is a minimal test case:

foo :: (() -> (# #)) -> Int
foo f = case f () of (# #) -> 5

GHC crashes with:

ghc.exe: panic! (the 'impossible' happened)
  (GHC version 7.6.1 for i386-unknown-mingw32):
        compiler\codeGen\CgCase.lhs:572:15-61: Irrefutable pattern failed for pattern ((CoreSyn.DEFAULT,
                                        deflt_absC) : others)

Here is the actual function (simplified) that triggered the bug:

foo :: [a] -> Int
foo xs = foldl' (flip seq) () xs `seq` 5

Trac metadata

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