DfltProb1(optasm): panic CoreToStg.myCollectArgs
The program looks like this:
module DfltProb1 where
import Control.Monad.ST
import Prelude hiding (traverse)
traverse :: a -> ST s [a]
traverse = undefined
-- WORKS with signature test :: Num a => [a]
test = runST (traverse 1)
main = print testThis is the failure:
$ ghc-7.11.20151225 -O DfltProb1.hs
ghc-stage2: panic! (the 'impossible' happened)
(GHC version 7.11.20151224 for x86_64-unknown-linux):
CoreToStg.myCollectArgs
(case traverse of _ [Occ=Dead] { }) realWorld#