From 3a432fad8639dcaf623f6d6def93dcdd6cfc8fda Mon Sep 17 00:00:00 2001
From: Justus Adam <dev@justus.science>
Date: Thu, 21 Feb 2019 13:03:15 +0100
Subject: [PATCH] [#32] Added a check for empty and unused ctrl operators

---
 core/src/Ohua/ALang/Passes/Control.hs | 29 ++++++++++++++++-----------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/core/src/Ohua/ALang/Passes/Control.hs b/core/src/Ohua/ALang/Passes/Control.hs
index 6248480..8894ce2 100644
--- a/core/src/Ohua/ALang/Passes/Control.hs
+++ b/core/src/Ohua/ALang/Passes/Control.hs
@@ -177,15 +177,20 @@ liftIntoCtrlCtxt ::
        (Monad m, MonadGenBnd m) => Binding -> Expression -> m Expression
 liftIntoCtrlCtxt ctrlIn e = do
     (lam', actuals) <- lambdaLifting e
-    let (originalFormals, _) = lambdaArgsAndBody e
-    let (allFormals, e) = lambdaArgsAndBody lam'
-    ctrlOut <- generateBindingWith "ctrl"
-    let formals = reverse $ take (length actuals) $ reverse allFormals
-    let actuals' = [Var ctrlIn] ++ actuals
-    let ie = mkDestructured formals ctrlOut e
-    return $
-        mkLambda originalFormals $
-        Let
-            ctrlOut
-            (fromListToApply (FunRef "ohua.lang/ctrl" Nothing) actuals')
-            ie
+    if null actuals
+        then do
+            dAssertM $ lam' == e
+            pure lam'
+        else do
+            let (originalFormals, _) = lambdaArgsAndBody e
+            let (allFormals, e) = lambdaArgsAndBody lam'
+            ctrlOut <- generateBindingWith "ctrl"
+            let formals = reverse $ take (length actuals) $ reverse allFormals
+            let actuals' = [Var ctrlIn] ++ actuals
+            let ie = mkDestructured formals ctrlOut e
+            return $
+                mkLambda originalFormals $
+                Let
+                    ctrlOut
+                    (fromListToApply (FunRef "ohua.lang/ctrl" Nothing) actuals')
+                    ie