How to fix cabal installation error
I am getting the following error when trying to install the contravariant library (which is required for the lens) using Cabal:
`` Src / data / functor / Contravariant.hs: 96: 1: StateVar-1.1.0.0: Data.StateVar cannot be safely imported! The module itself is insecure. '
I didn't have any google search solutions and tried to fix some fixes (like getting rid of all my Haskell packages (with `` rm -r ~ / .ghc '') and starting over) m not clear that causes this error. I am using ghc 7.4.1 - could there be a problem?
Thank,
Reuben
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Posting correct answer from comments as community-wiki:
It looks like you suffered from interoperability between the old GHC and the lack of Safe Haskell annotations (in the library), which are redundant with newer versions of GHC. Wed http://github.com/ekmett/ersatz/issues/13
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