[Haskell-cafe] Downsides to disabling unticked-promoted-constructor warning?

Richard Eisenberg lists at richarde.dev
Mon Oct 18 02:19:43 UTC 2021

As its author, I think -Wunticked-promoted-constructors is a misfeature. It was motivated by the fact that writing [True] when you mean '[True] produces a cascade of obscure kind errors, and so I thought it was good to encourage people to always write the ticks. But the feature does not achieve its goal: because errors squelch warnings, we do not see the warnings if there are any errors. Furthermore, I agree with Adam's post that I've come to prefer a style where we leave off the ticks (where possible).

Bottom line: feel free to turn this warning off.


> On Oct 16, 2021, at 5:55 AM, Markus Läll <markus.l2ll at gmail.com> wrote:
> Hi!
> Is there any consensus on unticked promoted constructors -- are they generally safe to use?
> Currently the warning is part of -Wall, but having promoted constructors unticked is just aesthetically nicer.
> Thanks,
> -- 
> Markus Läll
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