Move the FreeVariables constraint into Evaluatable.

src/Analysis/Abstract/Evaluating.hs

@@ -72,6 +72,7 @@ evaluate :: forall v term.
          ( Ord v
          , Ord (LocationFor v)
          , Evaluatable (Evaluating v) term v (Base term)
+         , FreeVariables term
          , Recursive term
          )
          => term
@@ -82,6 +83,7 @@ evaluate = run @(Evaluating v) . foldSubterms eval
 evaluates :: forall v term.
           ( Ord v
           , Ord (LocationFor v)
+          , FreeVariables term
           , Evaluatable (Evaluating v) term v (Base term)
           , Recursive term
           )

src/Control/Monad/Effect/Evaluatable.hs

@@ -26,8 +26,8 @@ import qualified Data.Union as U
 
 -- | The 'Evaluatable' class defines the necessary interface for a term to be evaluated. While a default definition of 'eval' is given, instances with computational content must implement 'eval' to perform their small-step operational semantics.
 class Evaluatable es term v constr where
-  eval :: SubtermAlgebra constr term (Eff es v)
-  default eval :: (Fail :< es, Show1 constr) => SubtermAlgebra constr term (Eff es v)
+  eval :: FreeVariables term => SubtermAlgebra constr term (Eff es v)
+  default eval :: (Fail :< es, FreeVariables term, Show1 constr) => SubtermAlgebra constr term (Eff es v)
   eval expr = fail $ "Eval unspecialized for " ++ liftShowsPrec (const (const id)) (const id) 0 expr ""
 
 -- | If we can evaluate any syntax which can occur in a 'Union', we can evaluate the 'Union'.

src/Data/Syntax.hs

@@ -152,7 +152,6 @@ instance ( Ord (LocationFor (Value l t))
          , Show (LocationFor (Value l t))
          , Recursive t
          , Evaluatable es t (Value l t) (Base t)
-         , FreeVariables t
          , Member Fail es
          , Member (State (EnvironmentFor (Value l t))) es
          , Member (Reader (EnvironmentFor (Value l t))) es

src/Data/Syntax/Declaration.hs

@@ -39,8 +39,7 @@ instance Show1 Function where liftShowsPrec = genericLiftShowsPrec
 -- TODO: Filter the closed-over environment by the free variables in the term.
 -- TODO: How should we represent function types, where applicable?
 
-instance ( FreeVariables t
-         , Semigroup (Cell l (Value l t))
+instance ( Semigroup (Cell l (Value l t))
          , Addressable l es
          , Member (State (EnvironmentFor (Value l t))) es
          , Member (Reader (EnvironmentFor (Value l t))) es
@@ -63,7 +62,6 @@ instance Member Fail es => Evaluatable es t Type.Type Function
 --          , MonadFresh m
 --          , MonadEnv Type.Type m
 --          , MonadStore Type.Type m
---          , FreeVariables t
 --          )
 --          => Eval t Type.Type m Function where
 --   eval recur yield Function{..} = do
@@ -96,8 +94,7 @@ instance Show1 Method where liftShowsPrec = genericLiftShowsPrec
 
 -- Evaluating a Method creates a closure and makes that value available in the
 -- local environment.
-instance ( FreeVariables t                -- To get free variables from the function's parameters
-         , Semigroup (Cell l (Value l t)) -- lookupOrAlloc
+instance ( Semigroup (Cell l (Value l t)) -- lookupOrAlloc
          , Addressable l es              -- lookupOrAlloc
          , Member (State (EnvironmentFor (Value l t))) es
          , Member (Reader (EnvironmentFor (Value l t))) es

src/Data/Syntax/Expression.hs

@@ -62,7 +62,6 @@ instance Member Fail es => Evaluatable es t Type.Type Call
 --          , MonadFresh m
 --          , MonadGC Type m
 --          , MonadEnv Type m
---          , FreeVariables t
 --          )
 --          => Eval t Type m Call where
 --   eval recur yield Call{..} = do