[GHC] #7436: Derived Foldable and Traversable instances become extremely inefficient due to eta-expansion

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[GHC] #7436: Derived Foldable and Traversable instances become extremely inefficient due to eta-expansion

Ian Lynagh-2

Hi Simon,

On Tue, Apr 16, 2013 at 03:55:16PM -0000, GHC wrote:
> #7436: Derived Foldable and Traversable instances become extremely inefficient due
> to eta-expansion
>
> Comment(by simonpj):
>
>  This one is fixed, just awaiting merging into 7.6.3

My suggestion was that we only fix #7748 in 7.6.3, as that seems to be a
show-stopper. There are several other fixes that we would ordinarily
merge into 7.6.3, but every change has a risk of causing a regression
(after all, 7.6.2 made #7748 worse), and we want to get 7.6.3 out as
quickly as possible (so as not to hold up the HP release) so we don't
have the luxury of being able to have a long testing/RC phase.

But if you think it's important enough, and the fix safe enough, please
let me know and I'll merge it.


Thanks
Ian



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[GHC] #7436: Derived Foldable and Traversable instances become extremely inefficient due to eta-expansion

Simon Peyton Jones
It was ready to merge 3 months ago... but perhaps just got lost in the press of events.   liyang said then " Since this issue affects a large number of users and doesn't seem too contentious, could this fix be included in 7.6.2?"  

But we are where we are.  I honestly don't know if it's worth the risk, though it seems very slight, and certainly only affects 'deriving Foldable/Traversable".

Simon

|  -----Original Message-----
|  From: Ian Lynagh [mailto:ian at well-typed.com]
|  Sent: 17 April 2013 14:54
|  To: Simon Peyton-Jones; ghc-devs at haskell.org
|  Subject: Re: [GHC] #7436: Derived Foldable and Traversable instances become
|  extremely inefficient due to eta-expansion
|  
|  
|  Hi Simon,
|  
|  On Tue, Apr 16, 2013 at 03:55:16PM -0000, GHC wrote:
|  > #7436: Derived Foldable and Traversable instances become extremely
|  inefficient due
|  > to eta-expansion
|  >
|  > Comment(by simonpj):
|  >
|  >  This one is fixed, just awaiting merging into 7.6.3
|  
|  My suggestion was that we only fix #7748 in 7.6.3, as that seems to be a
|  show-stopper. There are several other fixes that we would ordinarily
|  merge into 7.6.3, but every change has a risk of causing a regression
|  (after all, 7.6.2 made #7748 worse), and we want to get 7.6.3 out as
|  quickly as possible (so as not to hold up the HP release) so we don't
|  have the luxury of being able to have a long testing/RC phase.
|  
|  But if you think it's important enough, and the fix safe enough, please
|  let me know and I'll merge it.
|  
|  
|  Thanks
|  Ian