#11558: Using Cabal 1.22 against GHC 8.0 results in unhelpful errors -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.1 Component: Package system | Version: 8.0.1-rc1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D1892 Wiki Page: | -------------------------------------+------------------------------------- Description changed by bgamari: @@ -5,2 +5,2 @@ - isn't met. Namely, we complain about missing interface files for - dependencies. For instance, + isn't met. Namely, we complain about bad interface files for dependencies. + For instance, New description: GHC 8.0 will require Cabal >1.22 due to a variety of interface changes (see #10714, Phab:D1780, https://mail.haskell.org/pipermail/ghc- devs/2016-January/010978.html). Unfortunately things currently blow up late in compilation with a seemingly unrelated error when this requirement isn't met. Namely, we complain about bad interface files for dependencies. For instance, {{{ Text/Parsec/Prim.hs:85:1: error: Bad interface file: /root/.cabal/lib/x86_64-linux- ghc-8.0.0.20160204/mtl-2.2.1-9wMhzcfsAXi7cNtl9n7svO/Control/Monad/Cont/Class.hi Something is amiss; requested module mtl-2.2.1@mtl-2.2.1-1af5dabd2d7abb688f2145aec87badc4:Control.Monad.Cont.Class differs from name found in the interface file mtl_9wMhzcfsAXi7cNtl9n7svO:Control.Monad.Cont.Class }}} = For users seeing this error = The solution here is to install `Cabal` 1.23 or later and a `cabal- install` linking against it. Currently this requires installing `Cabal` and `cabal-install` from git. This is most easily done using GHC 7.10. Finally, you need to clear your package database. This can be done with, {{{ $ git clone git://github.com/haskell/cabal $ cd cabal $ cabal update $ cabal install Cabal/ cabal-install/ $ rm -R $HOME/.ghc/*-8.0.0* }}} -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11558#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler