Re: [Haskell-cafe] Cabal hell (8.2.1,/Haskell Package/MacOS X)

On 2017-10-05 11:47 AM, Mikhail Glushenkov wrote:

Hi,

On 5 October 2017 at 16:29, Stuart A. Kurtz wrote:

...

I have problems around trying to install some standard packages: hlint, aeson. A typical error reported by cabal is

<command line>: cannot satisfy -package-id hashable-1.2.6.1-14fEJP30YhAG9w115PODz0: hashable-1.2.6.1-14fEJP30YhAG9w115PODz0 is unusable due to shadowed dependencies: text-1.2.2.2-EGUst8sqNAZCw1xLPcmcMH

This looks like a known Cabal 2.0 bug, which I haven't yet got around to fix:

https://github.com/haskell/cabal/issues/4728

IIUC, this affects both Stack and Cabal, but only when used with GHC 8.2.1. Downgrading to GHC 8.0.2 should help for now.

I have found the cause (first-order cause anyway) and wrote it up on the cabal issue and the haskell-platform issue, and explained why the stack issue is unrelated, all on github. Please refer to those issues separately for details. Oh too bad the Haskell Platform people closed theirs, because it is totally a Haskell Platform build error for some builds. In short, while I don't have Mac and so I need you to do the following checks, I have Linux and checked it. Best to start with a fresh install, full binary version, for minimum doubt: 1. "ghc -v" to see you already have shadowing messages right from the start with a clean slate. 2. "ghc-pkg field hashable abi-depends" for example and look at the oddity "text-...=inplace" in contrast to more common ones like "base-...=hexstring". This is why GHC says it can't find the right text for hashable. (See also "ghc-pkg field base abi" and "ghc-pkg field text abi", these are what GHC checks against.) The Windows version doesn't have this problem because the abi-depends fields don't even exist there. This is probably because the Windows versions was built by Cabal 1.x. The core versions don't have this problem.