Is deprecation as bad as removal?

Niklas Haas haskell at
Wed Feb 25 00:01:40 UTC 2015

I disagree, since nobody's forcing you to turn on -Werror. If you're not
in the mood to maintain your packages, you don't need to use that
particular flag. You can also silence the warning on a case-by-case

The way I see it, -Werror exists for those who want to make sure their
code does not contain deprecated functionality. I don't think this is
the status quo.

On Tue, 24 Feb 2015 23:35:04 +0000, Ben Millwood <haskell at> wrote:
> I'm going to grab this quotation from a recent thread discussing removal 
> of fromJust:
> On Tue, Feb 24, 2015 at 02:32:08PM -0500, Edward Kmett wrote:
> >I'm personally pretty strongly against removing this function on mere
> >proscriptive grounds and a deprecation is effectively removal for most
> >users who care about warnings.
> This strikes me as troubling. Are we considering deprecations to be 
> equivalent to removals, in terms of stability impact? I've heard more 
> than one person suggest that we are, or should. The argument for it is 
> reasonably clear: with -Werror enabled, as many people do, as many would 
> encourage, even, either removal or deprecation of something you use will 
> break your build.
> But surely the *entire purpose* of deprecations is to be *less* damaging 
> than removals, and so if we're implicitly considering them equally bad, 
> that suggests to me that our deprecation mechanism is totally broken, 
> and needs to be fixed.
> I can think of several potential fixes, but I'd first like to see if 
> others agree that there is a problem :)
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