# ghc Test1.hs -c -fglasgow-exts -fallow-undecidable-instances -fallow-overlapping-instances # ghc Test2.hs -c -fglasgow-exts -fallow-undecidable-instances -fallow-overlapping-instances
works.
But for ghc6.3.20031201 the second compilation produces the message:
> Test2.hs:6: > No instance for (FormValue (Maybe [Char])) > arising from use of `isFormValue' at Test2.hs:6 > In the definition of `is': is = isFormValue (Just "")
Oddly enough the compilation works if you do it in one step using
# ghc --make Test2.hs -fglasgow-exts -fallow-undecidable-instances -fallow-overlapping-instances
module Test1 where
class FormValue value where isFormValue :: value -> () isFormValue _ = () class FormTextField value instance FormTextField String instance FormTextField value => FormTextFieldIO value class FormTextFieldIO value instance FormTextFieldIO value => FormValue value instance FormTextFieldIO value => FormTextFieldIO (Maybe value)
module Test2 where import Test1 is :: () is = isFormValue (Just "")
_______________________________________________ Glasgow-haskell-bugs mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs