[Haskell-cafe] Skolems!

[evan@evan-borden.com]

A quick clarification. It s trac still the location to submit bugs or is
Phabricator more appropriate?

On Mon, Mar 2, 2015 at 1:49 PM, evan at evan-borden.com <
evan at evanrutledgeborden.dreamhosters.com> wrote:

> Thanks Richard, will do.
>
> On Mon, Mar 2, 2015 at 1:12 PM, Richard Eisenberg <eir at cis.upenn.edu>
> wrote:
>
>> This is admittedly a dark corner of the inference algorithm, but perhaps
>> these examples can shed some light. Post a bug report!
>>
>> Thanks for creating nice, small examples.
>>
>> Richard
>>
>> PS: I offer no strong guarantees that you've found bugs here... but in
>> any case, posting a bug report gets more serious attention than a
>> Haskell-cafe post.
>>
>> On Feb 27, 2015, at 1:23 PM, "evan at evan-borden.com" <
>> evan at evanrutledgeborden.dreamhosters.com> wrote:
>>
>> > An extension of the message Tom sent a little while back, we've
>> discovered a more in depth example of this possible GHC bug. It is
>> exacerbated by GADTs, but can be fixed with NoMonoLocalBinds. Without GADTs
>> and just leveraging ExistentialQuanitification it works fine. We've
>> included a pretty exhaustive set of examples.
>> >
>> >   {-# LANGUAGE ExistentialQuantification, GADTs #-}
>> >
>> >   {- removing MonoLocalBinds fixes all of these errors
>> >   {-# LANGUAGE ExistentialQuantification, GADTs, NoMonoLocalBinds #-}
>> >   -}
>> >
>> >   module PossibleGHCBug where
>> >
>> >   data SumType = SumFoo | SumBar
>> >
>> >   class SomeClass a where
>> >     someType :: a -> SumType
>> >
>> >   data SomeExistential = forall a. SomeClass a => SomeExistential a
>> >
>> >   noError :: String -> [SomeExistential] -> String
>> >   noError n st = n ++ concatMap cname st
>> >     where cname (SomeExistential p) = d p
>> >
>> >           d p = c $ someType p
>> >
>> >           c p = case p of
>> >                     SumFoo -> "foo"
>> >                     _ -> "asdf"
>> >
>> >   noError2 :: String -> [SomeExistential] -> String
>> >   noError2 n st = n ++ concatMap cname st
>> >     where cname (SomeExistential p) = d p
>> >
>> >           d p = c $ someType p
>> >
>> >           c :: SumType -> String
>> >           c p = case p of
>> >                     SumFoo -> "foo"
>> >                     _ -> "asdf" ++ n
>> >
>> >   noError3 :: String -> [SomeExistential] -> String
>> >   noError3 n st = n ++ concatMap cname st
>> >     where cname (SomeExistential p) = d p
>> >
>> >           d :: SomeClass a => a -> String
>> >           d p = c $ someType p
>> >
>> >           c p = case p of
>> >                     SumFoo -> "foo"
>> >                     _ -> "asdf" ++ n
>> >
>> >
>> >   partialTypedError :: String -> [SomeExistential] -> String
>> >   partialTypedError n st = n ++ concatMap cname st
>> >     where cname :: SomeExistential -> String
>> >           cname (SomeExistential p) = d p
>> >
>> >           d p = c $ someType p
>> >
>> >           c p = case p of
>> >                     SumFoo -> "foo"
>> >                     _ -> "asdf" ++ n
>> >
>> >   fullError :: String -> [SomeExistential] -> String
>> >   fullError n st = n ++ concatMap cname st
>> >     where cname (SomeExistential p) = d p
>> >
>> >           d p = c $ someType p
>> >
>> >           c p = case p of
>> >                     SumFoo -> "foo"
>> >                     _ -> "asdf" ++ n
>> >
>> >   justNError :: String -> [SomeExistential] -> String
>> >   justNError n st = n ++ concatMap cname st
>> >     where cname (SomeExistential p) = d p
>> >
>> >           d p = c $ someType p
>> >
>> >           c p = case p of
>> >                     SumFoo -> "foo"
>> >                     _ -> n
>> >
>> >   ignoreNError :: String -> [SomeExistential] -> String
>> >   ignoreNError n st = n ++ concatMap cname st
>> >     where cname (SomeExistential p) = d p
>> >
>> >           d p = c $ someType p
>> >
>> >           c p = case p of
>> >                     SumFoo -> "foo"
>> >                     _ -> fst ("foo", n)
>> >
>> >
>> > _______________________________________________
>> > Haskell-Cafe mailing list
>> > Haskell-Cafe at haskell.org
>> > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
>>
>>
>
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