#1522: enumFrom* do not respect -fno-implicit-prelude
-------------------------+--------------------------------------------------
Reporter: guest | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 6.6.1
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Os: Multiple | Testcase:
Architecture: Multiple |
-------------------------+--------------------------------------------------
Old description:
> The [foo..], [foo..bar], [foo,bar..] and [foo,bar..baz] sugars do not
> obey -fno-implicit-prelude.
>
> {-# OPTIONS_GHC -fno-implicit-prelude #-}
> module ListSugar where
>
> import Control.Monad
> import Prelude hiding (Enum,enumFrom)
>
> class Enum a where
> enumFrom :: MonadPlus m => a -> m a
> instance Enum Int where
> enumFrom n = return n `mplus` enumFrom (n + 1)
>
> main = print $ ([1..] :: Maybe Int)
>
> ListSugar.hs:9:16:
> Couldn't match expected type `Maybe Int'
> against inferred type `[a]'
> In the expression: [1 .. ]
> In the second argument of `($)', namely `([1 .. ] :: Maybe Int)'
> In the expression: print $ ([1 .. ] :: Maybe Int)
>
> and even with the same signature as the original type, it invokes the
> version in the Prelude.
New description:
The [foo..], [foo..bar], [foo,bar..] and [foo,bar..baz] sugars do not obey
-fno-implicit-prelude.
{{{
{-# OPTIONS_GHC -fno-implicit-prelude #-}
module ListSugar where
import Control.Monad
import Prelude hiding (Enum,enumFrom)
class Enum a where
enumFrom :: MonadPlus m => a -> m a
instance Enum Int where
enumFrom n = return n `mplus` enumFrom (n + 1)
main = print $ ([1..] :: Maybe Int)
ListSugar.hs:9:16:
Couldn't match expected type `Maybe Int'
against inferred type `[a]'
In the expression: [1 .. ]
In the second argument of `($)', namely `([1 .. ] :: Maybe Int)'
In the expression: print $ ([1 .. ] :: Maybe Int)
}}}
and even with the same signature as the original type, it invokes the
version in the Prelude.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1522>
GHC <http://www.haskell.org/ghc/>
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