Proposal: Improving the IsString String instance

[Oren Ben-Kiki]

Changing the defaulting, if that is possible, would be my preference - this
way one can still use OverloadedString for list types. Disallowing them to
allow for the default case to work doesn't seem quite right, though I guess
it is acceptable if defaulting turns out to be impossible.


On Mon, Aug 26, 2013 at 1:24 AM, Edward Kmett <ekmett at gmail.com> wrote:

> If that can be done in such a way that defaulting fires for FromString
> (say, even without EDR turned on) it could ensure OverloadedStrings has
> nearly zero impact on users.
>
> This may not be an issue but you may need to check that just adding
> FromString to the list of classes for which defaulting is done is
> sufficient to make cases like (length "hello") work as unlike the other
> defaulting cases, you get situations where it is partially known. e.g.
> we've determined that the argument is [a], but not String. This can't
> happen with the Int, Integer, (), cases, which either unify or don't.
>
> If you're looking at hacking up that part of the compiler,
> http://ghc.haskell.org/trac/ghc/ticket/8171 would also be really nice to
> clean up at the same time. ;)
>
> -Edward
>
>
> On Sun, Aug 25, 2013 at 6:16 PM, Ian Lynagh <igloo at earth.li> wrote:
>
>> On Sun, Aug 25, 2013 at 05:02:10PM -0400, Edward Kmett wrote:
>> >
>> > The issue is that length "abc", splitAt 2 "abc", and dozens of other
>> tools
>> > just stop working for anyone who turns on OverloadedStrings right now.
>>
>> Would/could this be better addressed by changing
>> ghci/ExtendedDefaultRules such that the ambiguous uses would be
>> defaulted to String?
>>
>>
>> Thanks
>> Ian
>>
>>
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