Fix to permit use of future IHaskellDisplay instance.

See comments at https://github.com/gibiansky/IHaskell/pull/330

src/IHaskell/Eval/Evaluate.hs

@@ -699,27 +699,35 @@ evalCommand output (Expression expr) state = do
   -- typeclass instance, this will throw an exception and thus `attempt` will
   -- return False, and we just resort to plaintext.
   let displayExpr = printf "(IHaskell.Display.display (%s))" expr :: String
+  write displayExpr 
   canRunDisplay <- attempt $ exprType displayExpr
 
   -- Check if this is a widget.
   let widgetExpr = printf "(IHaskell.Display.Widget (%s))" expr :: String
   isWidget <- attempt $ exprType widgetExpr
 
-  -- Check if this is a declaration  
- -- let declExpr = printf "((id :: Q [Dec] -> Q [Dec]) (%s))" expr::String
+  -- Check if this is a template haskell declaration 
   let declExpr = printf "((id :: DecsQ -> DecsQ) (%s))" expr::String
-  isDeclaration <- attempt $ exprType declExpr  
+  isTHDeclaration <- attempt $ exprType declExpr  
 
   write $ "Can Display: " ++ show canRunDisplay
-  write $ "  Is Widget: " ++ show isWidget 
-  if isDeclaration 
-  then do 
-      write $ "  Is Declaration: " ++ show isDeclaration 
-      (GHC.runDecls expr) >> return ()  
-  else  
-      write $ "  Is Declaration:" ++ show isDeclaration 
-
+  write $ "Is Widget: " ++ show isWidget 
+  write $ "Is Declaration: " ++ show isTHDeclaration 
 
+  if isTHDeclaration 
+    -- If it typechecks as a DecsQ, we do not want to display the DecsQ, 
+    -- we just want the declaration made. 
+  then do 
+          write $ "Suppressing display for template haskell declaration"  
+          GHC.runDecls expr  
+          return EvalOut {
+                    evalStatus = Success,
+                    evalResult = mempty,  
+                    evalState = state,
+                    evalPager = "",
+                    evalComms = []
+                }
+  else do  
       if canRunDisplay
       then do
         -- Use the display. As a result, `it` is set to the output.
@@ -729,18 +737,6 @@ evalCommand output (Expression expr) state = do
         if isWidget
         then registerWidget out
         else return out
-  else do
-    if isDeclaration 
-    -- We do not want to display the DecsQ, we just want the 
-    -- declaration made. 
-    then do write $ "Suppressing display for template haskell declaration"  
-            return EvalOut {
-                    evalStatus = Success,
-                    evalResult = mempty,  
-                    evalState = state,
-                    evalPager = "",
-                    evalComms = []
-                }
       else do
         -- Evaluate this expression as though it's just a statement.
         -- The output is bound to 'it', so we can then use it.