> ghc-4.01, linux, binary for i386 says
>
> panic! (the `impossible' happened):
> tcLookupGlobalValue: T.name{-r1n,x-} ...
It's a GHC bug all right...
> when compiling
> -------------------------------------------------------------
> data S a = S {longFieldName :: a}
>
> f :: S String -> S String
> f s =
> let S {name = x} = s in S {name = tail x}
>
> name = longFieldName -- local for this module
> -------------------------------------------------------------
>
>
> Otherwise, how can one introduce a short local synonym for
> longFieldName ?
You can't! When it's used as an ordinary *function* (i.e. selector) you
can,
but not when it's used as a field name in a pattern or record
construction or update. It's just an infelicity in Haskell I'm afraid.
You can use qualified names, though:
module L where
data A a = S { short :: a }
module Main where
import L
f s = let S {L.short = x} = s in S {L.short = tail x}
Simoin
> I thought, the record field is treated as a function ...
> And the long global names for the record fields, they look in-
> avoidible in Haskell-98. Because, as, say, in the above example, many
> different kinds of object modelled by records are likely to have a
> field called `name'.
