Using features from containers-0.5

[Joachim Breitner]

Hi, especially to Austin with his Release Manager hat on,

in my nested-cpr branch I have a few nice patches that clean up,
refactor and especially Note’ify the demand analyzer. I’d like to see
both my branch to be shorter, and to see those improvements in the
mainline independent of whether nested-cpr will turn out to be useful,
so I invested some time to rebase my branch and move all these patches
below those that actually change the code.

The result is the contents of the wip/nested-cpr branch up to and
including the patch “Make types of bothDmdType more precise”, which I
find especially useful (currently c26d31, but I tend to rebase while I
add more polish or remove typos). I am confident that this is a pure
refactoring (validate passes without changes to the testsuite, nofib
shows identical Allocation numbers), and I’d like to push this to
master.

But one of the patches, “Clarify the default demand on demand
environments” (currently 2b6a6a), uses a function from containers
(IntMap.mergeWithKey) which was only added in containers-0.5, which
ships with GHC 7.6, but not with 7.4. But especially that change is
nice, as removes the confusing modifyEnv function and makes the code
(IMHO) easier to understand.

What is the policy here? Is it ok to expect the user to upgrade the
containers package of the bootstrap compiler? Or can we start building
containers before stage-1, so that we can expect the new code (but when
I tried it seems that this needs some adjustments to the build system)?
Or should I add an alternative definition via CPP in
compiler/utils/UniqFM.lhs? Or is it not worth it and I should wait until
7.9 (which would then drop the requirement to be bootstrappable with
7.4, right?)


Thanks,
Joachim

-- 
Joachim “nomeata” Breitner
  mail at joachim-breitner.de • http://www.joachim-breitner.de/
  Jabber: nomeata at joachim-breitner.de  • GPG-Key: 0x4743206C
  Debian Developer: nomeata at debian.org
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