#1259: Accessing undefined value in DiffArray returns misleading error message
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Reporter: guest | Owner:
Type: bug | Status: new
Priority: low | Milestone: 6.10
Component: libraries/base | Version: 6.6
Severity: normal | Resolution:
Keywords: | Difficulty: Easy (1 hr)
Os: Unknown | Testcase:
Architecture: Multiple |
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Changes (by igloo):
* milestone: => 6.10
Old description:
> Prelude> :m + Data.Array.Diff
> Prelude Data.Array.Diff> :t array
> array :: (Ix i, IArray a e) => (i, i) -> [(i, e)] -> a i e
> Prelude Data.Array.Diff> array (1,1) [] :: DiffArray Int Int
> array (1,1) [(1,*** Exception: MArray: undefined array element
>
> Since DiffArray isn't a MArray(it implements IArray), this is misleading.
> It should either say IArray or better DiffArray: undefined array element.
New description:
{{{
Prelude> :m + Data.Array.Diff
Prelude Data.Array.Diff> :t array
array :: (Ix i, IArray a e) => (i, i) -> [(i, e)] -> a i e
Prelude Data.Array.Diff> array (1,1) [] :: DiffArray Int Int
array (1,1) [(1,*** Exception: MArray: undefined array element
}}}
Since DiffArray isn't a MArray(it implements IArray), this is misleading.
It should either say IArray or better DiffArray: undefined array element.
Comment:
I think the right way to fix this is to wait until we have extensible
exceptions, so MArray throws a structured exception. DiffArray can then
s/MArray/DiffArray/ without having to duplicate all the checks.
As such, it's probably something for 6.10.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1259>
GHC <http://www.haskell.org/ghc/>
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