On Wed, Jan 4, 2012 at 1:07 AM, Yves Parès
Try to put a totally wrong type to subsome, like subsome :: Int and tell us from the error what type is actually inferred.
The error is like
Couldn't match type `nt' with `Int' `nt' is a rigid type variable bound by the type signature for legSome :: LegGram nt t s -> nt -> Either String ([t], s) at xx.hs:35:1 Expected type: [RRule Int t s] Actual type: [RRule nt t s] In the first argument of `subsome', namely `l' In the expression: subsome l
However, this error cannot be resolved by a use of ScopedTypeVariable, while the original error can be resolved. I still don't see where the mismatch happens in the original error. Any help is appreciated.