IsString [Char] instance

[Michael Snoyman]

I'm in favor of this as well.

On Thu, Aug 13, 2015 at 6:44 AM, Edward Kmett <ekmett at gmail.com> wrote:

> I'm fully on board with just moving ahead with this simple change for now.
> It'd be nice to have a better defaulting story, but I'm not sure there _is_
> a perfect solution in the wings.
>
> -Edward
>
> On Wed, Aug 12, 2015 at 12:14 PM, Dan Doel <dan.doel at gmail.com> wrote:
>
>> So, I rather lost track of this. It has been (significantly) more than
>> the specified amount of time, though.
>>
>> No one has stepped up to specify/implement the new extended defaulting
>> to my knowledge. I'm not sure how much time is left before 7.12, but I
>> would guess it'd be tight for someone to start on this now. Perhaps
>> I'm wrong.
>>
>> Anyhow, I think we should modify the instance at this point. I think
>> it's even cool to say we can roll it back if someone decides to beef
>> up defaulting, in which case rolling it back should cause no
>> regressions. But it doesn't seem like defaulting is going to happen.
>>
>> -- Dan
>>
>> On Sun, May 17, 2015 at 8:08 PM, Dan Doel <dan.doel at gmail.com> wrote:
>> > Greetings,
>> >
>> > Today, someone came into #haskell and asked why they couldn't type the
>> > equivalent of:
>> >
>> >     > "hi" ++ "bye"
>> >
>> > into GHCi with OverloadedStrings enabled. The answer is that it's
>> ambiguous,
>> > because (++) only determines the strings to be [a], and not [Char].
>> >
>> > I noticed that this could actually be solved by making the instance:
>> >
>> >     instance (a ~ Char) => IsString [a] where ...
>> >
>> > Which causes [Char] to be inferred as soon as [a] is. I then searched my
>> > libraries mail and noticed that we'd discussed this two years ago. The
>> > proposal for this instance change was rejected based on
>> ExtendedDefaultRules
>> > being beefed up to solve this case. But then no one actually
>> implemented the
>> > better defaulting.
>> >
>> > So, I'm proposing that the issue be fixed for real. I'm not terribly
>> > concerned with how it gets fixed, but there's not a great reason for
>> this to
>> > not behave better than it currently does. If someone steps up and makes
>> > defaulting better, than that's great. But if not, then the libraries
>> > committee can fix this very easily for GHC 7.12, and I think it's
>> better to
>> > do so than to wait if there are no signs that the alternative is going
>> to
>> > happen.
>> >
>> > I don't think we need to nail down which of the two solutions we're
>> going to
>> > choose right now, but it'd be good to resolve that we're going to fix
>> it,
>> > one way or another, by some well defined date.
>> >
>> > Here's a link to the previous discussion:
>> >
>> >   http://comments.gmane.org/gmane.comp.lang.haskell.libraries/20088
>> >
>> > Discussion period: 2 weeks
>> >
>> > -- Dan
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>
>
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