vector: ‘ANN type’ without GHCi

Nikita Karetnikov nikita at
Sun Mar 30 22:05:18 UTC 2014

The latest Hackage version and HEAD fail to build on mips64el due to the
ANN pragma in ‘Data/Vector/Fusion/Stream/Monadic.hs’:

[ 5 of 21] Compiling Data.Vector.Fusion.Stream.Monadic ( Data/Vector/Fusion/Stream/Monadic.hs, dist/build/Data/Vector/Fusion/Stream/Monadic.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 7.6.3 for mipsel-unknown-linux):
	Cant do annotations without GHCi
    base:GHC.Exts.ForceSpecConstr{d r2i8}

Please report this as a GHC bug:

Here’s the relevant part of the code:

data SPEC = SPEC | SPEC2
#if __GLASGOW_HASKELL__ >= 700
{-# ANN type SPEC ForceSpecConstr #-}

Is it possible to use CPP along with some configure flag to determine if
GHCi is available, and if it is not, skip the said pragma?  I tested the
Hackage version, and it builds fine if I comment out the mentioned

Does the lack of the pragma make a big difference?  (The relevant
section of the GHC manual is very brief.)
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