Actually Arch has been accommodating in other cases when there was a stable library and a new/developing.  It certainly keeps around two versions of python, autoconf, GTK, qt, gambas...  The solution I'm proposing would be a little different than those cases, but on the same principle.

Timothy
---------- Původní zpráva ----------
Od: Patrick Palka <patrick@parcs.ath.cx>
Datum: 28. 10. 2012
Předmět: Re: [Haskell-cafe] GHC maintenance on Arch

On Sun, Oct 28, 2012 at 5:54 PM, <timothyhobbs@seznam.cz> wrote:

  There seems to be a bit of a clash between ghc being a tool, and ghc being a toy.  There need not be.  Your works-for-me is great but it is meaningless to those of us who use ghc as a tool for larger projects.

This is not specific to GHC. Arch Linux, being a bleeding-edge Linux distribution, tends to prefer newer versions of software over more stable versions of software. I doubt that facet of Arch Linux will ever change, so perhaps you should reevaluate your choice of Linux distribution or avoid pacman/package updates for software whose stability and predictability is critical to you.