diff --git a/src/Data/Syntax/Type.hs b/src/Data/Syntax/Type.hs
index ba6a51186..b6fb31ad9 100644
--- a/src/Data/Syntax/Type.hs
+++ b/src/Data/Syntax/Type.hs
@@ -16,6 +16,13 @@ instance Eq1 Annotation where liftEq = genericLiftEq
 instance Ord1 Annotation where liftCompare = genericLiftCompare
 instance Show1 Annotation where liftShowsPrec = genericLiftShowsPrec
 
+data Alias a = Alias { aliasSubject :: !a, aliasType :: !a }
+  deriving (Diffable, Eq, Foldable, Functor, GAlign, Generic1, Mergeable, Ord, Show, Traversable)
+
+instance Eq1 Alias where liftEq = genericLiftEq
+instance Ord1 Alias where liftCompare = genericLiftCompare
+instance Show1 Alias where liftShowsPrec = genericLiftShowsPrec
+
 data Function a = Function { functionParameters :: [a], functionReturn :: a }
   deriving (Diffable, Eq, Foldable, Functor, GAlign, Generic1, Mergeable, Ord, Show, Traversable)