Hello!
I like to have the warnings about non-exhaustive pattern matches
etc. turned on: I find them very useful. Unfortunately, this
prevents me from taking full advantage of field labels.
Here is an (artificial) example:
module See ( D, foo ) where
data D = U | D{ value :: Int }
foo :: D -> D
foo d = case d
of
D{} -> d{ value = value d + 1 }
U -> D{ value = 0 }
GHC complains as follows:
ghc --make -odir../ghc -hidir../ghc -Wall -fno-warn-missing-signatures See.hs
ghc-5.02.2: chasing modules from: See.hs
Compiling See ( See.hs, ../ghc/See.o )
See.hs:9: Warning: Pattern match(es) are non-exhaustive
In a record-update construct (D ds_dpd): Patterns not matched: U
This is not quite as it should be, is it?
Is there any work-around other than abandoning the use of field
labels or turning off the warnings? (In my real application there
are quite a few more cases in the union, and more fields.)
Regards,
-- Feliks
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