Bas reports: When benchmarking my new vector-bytestring package I discovered that building the following program causes GHC to go into, what seems to be, an infinite loop:

import Data.Vector (Vector)
import qualified Data.Vector.Generic as VG

main = print $ VG.foldl f z (VG.fromList [] :: Vector Int)

f = flip (:)
z = []

I build it with:

$ ghc --make vectorGHCloop.hs -O2

It compiles fine without the -O2 or if you specify -fno-enable-rewrite-rules. So it's probably a loop in a rule somewhere.

Note that the program also builds fine when I change the 'f' and 'z' to:

f = (+)
z = 0

I use vector-0.9 and ghc-7.2.1.