#2176: H98 module Array exports non-H98 instance Functor ((->) a)
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Reporter: duncan | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: libraries/haskell98 | Version: 6.8.2
Severity: normal | Resolution:
Keywords: | Testcase:
Architecture: Unknown | Os: Unknown
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Comment (by ross):
Here's a test for this bug:
{{{
module ShouldCompile where
-- import all Haskell 98 modules
import Array
import Char
import Complex
import CPUTime
import Directory
import IO
import Ix
import List
import Locale
import Maybe
import Monad
import Numeric
import Random
import Ratio
import System
import Time
-- This will fail if any of the Haskell 98 modules indirectly import
-- Control.Monad.Instances
instance Functor ((->) r) where
fmap = (.)
}}}
This can be used to show that Array is the only H98 module where this
bites. The problem is that it defines Foldable and Traversable instances
for the Array type, and thus needs those modules and Control.Applicative,
which they import. (Another vector is Control.Monad.Fix, imported by
Control.Arrow, but that doesn't seem to lead to H98 modules.)
I believe that these instances are a Good Thing, and we want them
everywhere, except in H98 modules.
I think the fix is to have an extra version of Data.Array, without the
Foldable and Traversable instances (which are orphans anyway), and have
Array import that.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2176#comment:1>
GHC <http://www.haskell.org/ghc/>
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