@@ -136,7 +136,7 @@ data CheckState = CheckState {
136136-- The type checking monad, which provides the state of the type checker, and error reporting capabilities
137137--
138138newtype Check a = Check { unCheck :: StateT CheckState (Either ErrorStack) a }
139− deriving (Functor, Monad, Applicative, MonadPlus, MonadState CheckState, MonadError ErrorStack)
139+ deriving (Functor, Monad, Applicative, Alternative, MonadPlus, MonadState CheckState, MonadError ErrorStack)
140140
141141-- |
142142-- Get the current @Environment@