Change in demand analysis results between 7.10.2 and RC1 (not fixed in RC2 and HEAD)

Joachim Breitner mail at
Sat Feb 27 08:49:25 UTC 2016

Am Freitag, den 26.02.2016, 22:12 -0500 schrieb Ömer Sinan Ağacan:
> While working on demand analyzer today we realized that there has
> been some changes in demand analysis results between GHC 7.10.2 and
> 8.0-rc2. 

a quick git log highlights this commit, as it relates to strict data
constructors: 0696fc6d4de28cb589f6c751b8491911a5baf774

commit 0696fc6d4de28cb589f6c751b8491911a5baf774
Author: Simon Peyton Jones <simonpj at>
Date:   Fri Jun 26 11:40:01 2015 +0100

    Improve CPR behavior for strict constructors
    When working on Trac #10482 I noticed that we could give constructor
    arguments the CPR property if they are use strictly.
    This is documented carefully in
        Note [CPR in a product case alternative]
    and also
        Note [Initial CPR for strict binders]
    There are a bunch of intersting examples in
        Note [CPR examples]
    which I have added to the test suite as T10482a.
    I also added a test for #10482 itself.

I did not investigate whether this could actually have effected¹ this


¹ How do you recognize a regular xkcd reader?
  He uses effect as an verb.

Joachim “nomeata” Breitner
  mail at joachim-breitner.de
  XMPP: nomeata at • OpenPGP-Key: 0xF0FBF51F
  Debian Developer: nomeata at

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