[Haskell-cafe] Why are these record accesses ambiguous

6 Jun 2009

      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
----------------------

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)

[Haskell-cafe] Why are these record accesses ambiguous

John Ky