Hello again Ian,
I noticed that in December, Bas van Dijk reported a bug in the
implementation of ConstraintKinds/associated type defaults, and the
fix wasn't merged to 7.4.1.
The relevant email thread is archived here:
http://www.haskell.org/pipermail/glasgow-haskell-users/2011-December/021318....
The relevant trac ticket is #5719 here:
http://hackage.haskell.org/trac/ghc/ticket/5719
The example in the ticket does not type-check with GHC 7.4.1-rc2, but
it does with a copy of HEAD. There seem to be 2 commits that are
relevant to this issue:
https://github.com/ghc/ghc/commit/416c5903f3b8cf4cdd4a03c8949489df18cd790a
https://github.com/ghc/ghc/commit/8785726b57ccd44c5451385de61913a79fe02eb7
Would it be possible to have these merged into the 7.4 branch before
release? They fix the issue Bas reported, and eliminate the need for
his kludgy fix which uses an Empty typeclass to get around the issue.
It makes turning Set into a Functor much cleaner in this case, IMO.
On Fri, Jan 27, 2012 at 5:15 PM, Ian Lynagh
We are pleased to announce the first release candidate for GHC 7.4.1:
http://www.haskell.org/ghc/dist/7.4.1-rc2/
This includes the source tarball, installers for OS X and Windows, and bindists for amd64/Linux, i386/Linux, amd64/FreeBSD and i386/FreeBSD.
Please test as much as possible; bugs are much cheaper if we find them before the release!
We expect this to be the last release candidate, with the final release in approximately 1 week's time.
Thanks Ian, on behalf of the GHC team
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-- Regards, Austin