Enabling TypeHoles by default

[Edward Kmett]

Heck if we wanted to bikeshed the name, even 'Holes' would do. ;)


On Mon, Jan 13, 2014 at 4:30 PM, Daniil Frumin <difrumin at gmail.com> wrote:

> On ghc-dev Dominique Devriese has actually proposed changing TypeHoles
> to TypedHoles or to something similar, because "TypeHoles" sounds like
> you can have holes in types, just like in your example.
>
> But what error message do you want to get if you have a hole in your
> type? GHC won't be able to tell you much
>
> On Tue, Jan 14, 2014 at 12:54 AM, Mateusz Kowalczyk
> <fuuzetsu at fuuzetsu.co.uk> wrote:
> > On 13/01/14 18:42, Krzysztof Gogolewski wrote:
> >> Hello,
> >>
> >> As discussed on ghc-devs, I propose to enable -XTypeHoles in GHC by
> >> default. Rationale:
> >>
> >> (1) This way holes are far easier to use; just entering "_" allows to
> check
> >> type of a subexpression, no need of adding "-XTypeHoles".
> >>
> >> (2) This affects error messages only; i.e. the set of programs that
> compile
> >> stays the same - Haskell 2010. The only exception is that if you use
> >> -fdefer-type-errors, then a program with a hole compiles, but this seems
> >> fine with philosophy of -fdefer-type-errors.
> >>
> >> If so: would you like it to be in 7.8 or wait a cycle? My preference is
> >> 7.8, two people (John and Richard) suggested 7.10.
> >>
> >> -KG
> >>
> >
> > Sounds good. Are there plans to allow TypeHoles to actually sit in place
> > of types? In the past I did
> >
> > ```
> > data Hole
> >
> > hole :: Hole
> > hole = undefined
> >
> > foo :: Integer -> Integer
> > foo x = hole
> >
> > bar :: Integer -> Hole
> > bar x y = x + y
> > ```
> >
> > to cause type errors that could guide me. I now don't have to resort to
> > the first use in ‘foo’ but I still have to define my own Hole type in
> ‘bar’.
> >
> >
> > --
> > Mateusz K.
> > _______________________________________________
> > Glasgow-haskell-users mailing list
> > Glasgow-haskell-users at haskell.org
> > http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
>
>
>
> --
> Sincerely yours,
> -- Daniil
> _______________________________________________
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>
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