GHC 7.4.2 on Ubuntu Trusty

[Edward Z. Yang]

For transformers, I needed:

diff --git a/Control/Monad/Trans/Error.hs b/Control/Monad/Trans/Error.hs
index 0158a8a..0dea478 100644
--- a/Control/Monad/Trans/Error.hs
+++ b/Control/Monad/Trans/Error.hs
@@ -57,6 +57,10 @@ instance MonadPlus IO where
     mzero       = ioError (userError "mzero")
     m `mplus` n = m `catchIOError` \_ -> n
 
+instance Alternative IO where
+    empty = mzero
+    (<|>) = mplus
+
 #if !(MIN_VERSION_base(4,4,0))
 -- exported by System.IO.Error from base-4.4
 catchIOError :: IO a -> (IOError -> IO a) -> IO a

For hpc, I needed:

     Build-Depends:
-        base       >= 4.4.1 && < 4.8,
+        base       >= 4.4.1 && < 4.9,
         containers >= 0.4.1 && < 0.6,
         directory  >= 1.1   && < 1.3,
-        time       >= 1.2   && < 1.5
+        time       >= 1.2   && < 1.6

For hoopl, I needed:

-  Build-Depends:     base >= 4.3 && < 4.8
+  Build-Depends:     base >= 4.3 && < 4.9

For the latter two, I think this should be a perfectly acceptable
point release.  For transformers, we could also just ifdef the
Alternative into the GHC sources.

Edward

Excerpts from Herbert Valerio Riedel's message of 2015-01-04 00:22:28 -0800:
> Hello Edward,
> 
> On 2015-01-04 at 08:54:58 +0100, Edward Z. Yang wrote:
> 
> [...]
> 
> > There are also some changes to hoopl, transformers and hpc (mostly
> > because their bootstrap libraries.)
> 
> ...what kind of changes specifically? 
> 
> Once thing that needs to be considered is that we'd require to upstream
> changes to transformers (it's not under GHC HQ's direct control) for a
> transformers point(?) release ... and we'd need that as we can't release
> any source-tarball that contains libraries (which get installed into the
> pkg-db) that don't match their upstream version on Hackage.
> 
> Cheers,
>   hvr