[Haskell] ambiguous record field names which actually aren’t ambigious

[Wolfgang Jeltsch]

Am Dienstag, 29. Mai 2007 17:19 schrieben Sie:
> [Redirecting to ghc-bugs]
>
> |     module A where
> |         data A = A { label :: Int }
> |
> |     module B where
> |         data B = B { label :: Int }
> |
> |         b :: B
> |         b = B { label = 0 }
> |
> |         x :: B -> ()
> |         x B { label = 0 } = ()
> |
> | GHC reports an ambiguity for both usages of label.
>
> Are you sure?  Module B doesn't even import A!

Oops, I forgot to include the import line.

> And if you mean that B does import A, then Haskell 98 indeed says it's
> ambiguous.

But wouldn’t it be worthwhile to allow this kind of stuff as a language 
extension?  It would make life easier in a couple of situations.  I don’t 
like the idea of using advanced record implemenations based on contended 
language extensions (undecidable instances, etc.), thereby probably loosing 
pattern matching, just to get rid of the need to qualify field names. :-( 

> […]

Best wishes,
Wolfgang
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