[Haskell-cafe] Why are these record accesses ambiguous

[John Ky]

Hi Luke,

You're right.  My code had a typo.  Unfortunately, I still get the same
error whichever way I do it.

For example:

> {-# LANGUAGE DisambiguateRecordFields #-}
> import A
> import B
>
> main = do
>    let xx = getA
>    print (x xx)

and:

#!/usr/bin/env runhaskell

> {-# LANGUAGE DisambiguateRecordFields #-}
> import A
> import B
>
> main = do
>    let xx = getA
>    putStrLn $ show (x xx)

both give me:

test.lhs:8:22:
    Ambiguous occurrence `x'
    It could refer to either `A.x', imported from A at test.lhs:3:2-9
                                      (defined at A.hs:5:5)
                          or `B.x', imported from B at test.lhs:4:2-9
                                      (defined at B.hs:5:5)

Any ideas?

$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 6.10.3

Thanks,

-John

On Sat, Jun 6, 2009 at 6:41 PM, Luke Palmer <lrpalmer at gmail.com> wrote:

> On Sat, Jun 6, 2009 at 1:48 AM, John Ky <newhoggy at gmail.com> wrote:
>
>> Hi Haskell Cafe,
>>
>> In the following code, I get an error saying Ambiguous occurrence `x'.
>> Why can't Haskell work out which x to call based on the type of getA?
>>
>> Thanks
>>
>> -John
>>
>> #!/usr/bin/env runhaskell
>>
>> > {-# LANGUAGE DisambiguateRecordFields #-}
>> > import A
>> > import B
>> >
>> > main = do
>> >    let xx = getA
>> >    putStrLn $ show x xx
>
>
> This is parsed as two arguments passed to the show function (which only
> takes one argument).
>
> putStrLn $ show (x xx)
>
> Or because putStrLn . show = print;
>
> print $ x xx
>
>
>>
>>
>> ----------------------
>>
>> module A where
>>
>> data TypeA = TypeA
>>    { a :: Int
>>    , x :: Int
>>    }
>>
>> getA = TypeA { a = 1, x = 2 }
>>
>> -------------------------
>>
>> module B where
>>
>> data TypeB = TypeB
>>    { b :: Int
>>    , x :: Int
>>    }
>>
>> getB = TypeB { b = 1, x = 3 }
>>
>> --------------------------
>>
>> ./test.lhs:8:21:
>>     Ambiguous occurrence `x'
>>     It could refer to either `A.x', imported from A at ./test.lhs:3:2-9
>>                                       (defined at A.hs:5:5)
>>                           or `B.x', imported from B at ./test.lhs:4:2-9
>>                                       (defined at B.hs:5:5)
>>
>>
>> _______________________________________________
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>> Haskell-Cafe at haskell.org
>> http://www.haskell.org/mailman/listinfo/haskell-cafe
>>
>>
>
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