Issue with package "pretty"

[Duncan Coutts]

On Sun, 2008-04-27 at 22:07 +0100, David MacIver wrote:
> On Sun, Apr 27, 2008 at 9:52 PM, Duncan Coutts
> <duncan.coutts at worc.ox.ac.uk> wrote:
> >
> >  On Sun, 2008-04-27 at 21:29 +0100, David MacIver wrote:
> >
> >  > The main thing I'd like to borrow from the Nix approach is the ability
> >  > to back out of the package change. I'm really more bothered about the
> >  > fact that it left me with a nonfunctioning build system (until someone
> >  > pointed out runghc would compile everything from source) than anything
> >  > else. :-)
> >
> >  Yes, that's one of its great features, that installed packages are never
> >  modified, that you just add new ones and GC old ones.
> >
> >  Though in this case you didn't modify any package you just masked it. At
> >  least I assume that's what you did. In which case the solution was to
> >  unregister the version that was masking the normal one.
> 
> No, the problem seems to be that because the old and new copies of
> pretty have the same version number the installation of it overwrote
> the old one with an incompatible file.

So it depends if you installed 'pretty' as a global or user package. If
as global then you'd have replaced the registration for the pre-existing
instance. If as user then it's just the masking that I was mentioning
previously.

Duncan