-- error messages

module Error where

import Id

data Diagnosis = Error String Pos

| Warning String Pos

newtype Result a = Result ([Diagnosis],Maybe a)

instance Monad Result where

return x = Result ([],Just x)

Result (errs, Nothing) >>= f = Result (errs,Nothing)

Result (errs1, Just x) >>= f = Result (errs1++errs2,y)

where Result (errs2,y) = f x

fail s = Result ([Error ("Fail: "++s) nullPos],Nothing)