lambda takes the set of free variables as a parameter.

src/Control/Abstract/Value.hs

@@ -137,8 +137,11 @@ class Show value => AbstractValue location value effects where
   -- | Extract the environment from any scoped object (e.g. classes, namespaces, etc).
   scopedEnvironment :: value -> Evaluator location term value effects (Maybe (Environment location value))
 
-  -- | Evaluate an abstraction (a binder like a lambda or method definition).
-  lambda :: FreeVariables term => [Name] -> Subterm term (Evaluator location term value effects value) -> Evaluator location term value effects value
+  -- | Build a closure (a binder like a lambda or method definition).
+  lambda :: [Name]                                      -- ^ The parameter names.
+         -> Set Name                                    -- ^ The set of free variables to close over.
+         -> Evaluator location term value effects value -- ^ The evaluator for the body of the closure.
+         -> Evaluator location term value effects value
   -- | Evaluate an application (like a function call).
   call :: value -> [Evaluator location term value effects value] -> Evaluator location term value effects value
 

src/Data/Abstract/Type.hs

@@ -92,7 +92,7 @@ instance ( Addressable location effects
          , Reducer (Type location) (Cell location (Type location))
          )
       => AbstractValue location (Type location) effects where
-  lambda names (Subterm _ body) = do
+  lambda names _ body = do
     (env, tvars) <- foldr (\ name rest -> do
       a <- alloc name
       tvar <- Var <$> raise fresh

src/Data/Abstract/Value.hs

@@ -349,9 +349,9 @@ instance ( Addressable location (Goto effects (Value location) ': effects)
     | otherwise = throwValueError (Bitwise2Error left right)
       where pair = (left, right)
 
-  lambda names (Subterm body bodyValue) = do
-    l <- label bodyValue
-    injValue . Closure names l . Env.bind (foldr Set.delete (Set.fromList (freeVariables body)) names) <$> getEnv
+  lambda parameters freeVariables body = do
+    l <- label body
+    injValue . Closure parameters l . Env.bind (foldr Set.delete freeVariables parameters) <$> getEnv
 
   call op params = do
     case prjValue op of

src/Data/Syntax/Declaration.hs

@@ -3,6 +3,7 @@ module Data.Syntax.Declaration where
 
 import qualified Data.Abstract.Environment as Env
 import Data.Abstract.Evaluatable
+import qualified Data.Set as Set (fromList)
 import Diffing.Algorithm
 import Prologue
 
@@ -22,7 +23,7 @@ instance Show1 Function where liftShowsPrec = genericLiftShowsPrec
 instance Evaluatable Function where
   eval Function{..} = do
     name <- either (throwEvalError . FreeVariablesError) pure (freeVariable $ subterm functionName)
-    (v, addr) <- letrec name (lambda (paramNames functionParameters) functionBody)
+    (v, addr) <- letrec name (lambda (paramNames functionParameters) (Set.fromList (freeVariables functionBody)) (subtermValue functionBody))
     modifyEnv (Env.insert name addr)
     pure v
     where paramNames = foldMap (freeVariables . subterm)
@@ -46,7 +47,7 @@ instance Show1 Method where liftShowsPrec = genericLiftShowsPrec
 instance Evaluatable Method where
   eval Method{..} = do
     name <- either (throwEvalError . FreeVariablesError) pure (freeVariable $ subterm methodName)
-    (v, addr) <- letrec name (lambda (paramNames methodParameters) methodBody)
+    (v, addr) <- letrec name (lambda (paramNames methodParameters) (Set.fromList (freeVariables methodBody)) (subtermValue methodBody))
     modifyEnv (Env.insert name addr)
     pure v
     where paramNames = foldMap (freeVariables . subterm)

test/Control/Abstract/Evaluator/Spec.hs

@@ -22,7 +22,7 @@ spec = parallel $ do
 
   it "calls functions" $ do
     (expected, _) <- evaluate $ do
-      identity <- lambda [name "x"] (term (variable (name "x")))
+      identity <- lambda [name "x"] lowerBound (variable (name "x"))
       call identity [integer 123]
     expected `shouldBe` Right (Value.injValue (Value.Integer (Number.Integer 123)))
 
@@ -47,9 +47,6 @@ reassociate :: Either String (Either (SomeExc exc1) (Either (SomeExc exc2) (Eith
 reassociate (Left s) = Left (SomeExc (injectSum (Const s)))
 reassociate (Right (Right (Right (Right a)))) = Right a
 
-term :: TermEvaluator Value -> Subterm Term (TermEvaluator Value)
-term eval = Subterm (Term eval) eval
-
 type TermEffects = Goto GotoEffects Value ': GotoEffects
 type GotoEffects
   = '[ LoopControl Value