feat: instances for Arbitrary

src/Language/Scalie/Ast/Expression.hs

@@ -1,12 +1,23 @@
 {-# LANGUAGE Safe #-}
+{-# LANGUAGE InstanceSigs #-}
 module Language.Scalie.Ast.Expression (Expression(..)) where
 
 import Prelude (Integer)
 import Data.Kind (Type)
 import Text.Show (Show)
 import Text.Read (Read)
+import Data.Eq (Eq)
+import Test.QuickCheck (Arbitrary (arbitrary), Gen, oneof)
+import Data.Functor ((<$>))
 
 type Expression :: Type
 data Expression
   = RawInt Integer
-  deriving stock (Show, Read)
+  deriving stock (Show, Read, Eq)
+
+instance Arbitrary Expression where
+  arbitrary :: Gen Expression
+  arbitrary = oneof
+    [ RawInt <$> arbitrary
+    ]
+