[ghc-steering-committee] #380 GHC2021: Forth status update / kialo.com

[Simon Marlow]

On Thu, 17 Dec 2020 at 16:42, Spiwack, Arnaud <arnaud.spiwack at tweag.io>
wrote:

> On Thu, Dec 17, 2020 at 5:24 PM Simon Marlow marlowsd at gmail.com
> <http://mailto:marlowsd@gmail.com> wrote:
>
>> In the case of partial type signatures *you can't use the feature
>> without generating a warning*, which is quite a different matter, I
>> think. It would be even stranger if it was an error!
>>
> I’m not sure I follow, I can certainly use PartialTypeSignature without
> generating a warning:
>
> > :set -XPartialTypeSignatures
> > :set -Wno-partial-type-signatures
> > f :: _ -> _ ; f = (+) 1
>
> You disabled the warning!

I'm sorry I'm not making this point very well, let me try to clarify.  I'm
saying that it would be strange to enable PartialTypeSignatures by default
*and* leave the warning turned on by default, because it would be
impossible to use the feature without generating a warning (unless of
course you disable the warning explicitly, but it's silly to have to do
that just to use a feature that is enabled by default). It would be fine to
leave the extension disabled, or better (in my view) to enable the
extension and disable the warning.

Cheers
Simon




> Unless you are saying that the feature *is* the warning. Which is
> debatable.
>
> If you think that the warning is the feature, though, then you have the
> same feature without PartialTypeSignature, but as an error instead
>
> > f :: _ -> _ ; f = (+) 1
>
> <interactive>:2:6: error:
>     * Found type wildcard `_' standing for `Integer'
>       To use the inferred type, enable PartialTypeSignatures
>     * In the type `_ -> _'
>       In the type signature: f :: _ -> _
>
> <interactive>:2:11: error:
>     * Found type wildcard `_' standing for `Integer'
>       To use the inferred type, enable PartialTypeSignatures
>     * In the type `_ -> _'
>       In the type signature: f :: _ -> _
>
>
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