definition module sem

import qualified Data.Map as Map
from Data.Either import :: Either
from AST import :: AST, :: Pos, :: Type, :: FieldSelector, :: Op2
from StdOverloaded import class toString

:: SemError 
:: Gamma
:: SemOutput :== Either [SemError] (AST, Gamma)
:: Constraints :== [(Type, Type)]

instance toString SemError
instance toString Gamma

sem :: AST -> Either [SemError] (AST, Gamma)