Cabal woes

Simon Peyton Jones simonpj at
Mon Apr 15 22:00:48 UTC 2019

Thanks.  But alas I have no clue about whether I want a v1-install or a v2-install, nor how to achieve them if I knew what they were.  I just want to install ‘hspec’ so that I can use it when compiling a program.  How would I do that?

The instructions here just say “cabal install hspec” which is what I tried.  Those instructions are pointed to from here, which in turn are pointed to from the main Cabal home page

I must be missing something.


From: Brandon Allbery <allbery.b at>
Sent: 15 April 2019 22:54
To: Simon Peyton Jones <simonpj at>
Cc: ghc-devs at
Subject: Re: Cabal woes

I think you wanted v1-install to install a library into the user package database, since your cabal is 3.x and the v2-* commands are now the default (that is, you did what used to be cabal new-install or cabal v2-install).

On Mon, Apr 15, 2019 at 5:47 PM Simon Peyton Jones via ghc-devs <ghc-devs at<mailto:ghc-devs at>> wrote:
I’m trying to install ‘hspec’ on my WSL (Windows subsystem for Linux) system.
But I fail; see below.
For some reason cabal complains about installing a library.  (That seems peculiar – isn’t that what cabal is for?)  But it helpfully suggests adding –lib.
Alas, cabal then crashes outright, which should never happen.
So I’m stuck.  What should I do?

simonpj at MSRC-9870733:~$ cabal --version

cabal-install version

compiled using version of the Cabal library

simonpj at MSRC-9870733:~$ cabal install hspec

Resolving dependencies...

Up to date

Warning: You asked to install executables, but there are no executables in

target: hspec. Perhaps you want to use --lib to install libraries instead.

simonpj at MSRC-9870733:~$ cabal install --lib hspec

Resolving dependencies...

Up to date

Distribution/Simple/GHC.hs:1959:5-56: Irrefutable pattern failed for pattern Just ghcPkgProg

simonpj at MSRC-9870733:~$ which ghc


simonpj at MSRC-9870733:~$ which ghc-pkg


simonpj at MSRC-9870733:~$

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