Merge pull request #330 from cje/th

Permit use of inline template haskell

ihaskell.cabal

@@ -85,6 +85,7 @@ library
                        system-argv0         -any,
                        system-filepath      -any,
                        tar                  -any,
+                       template-haskell     -any, 
                        text                 >=0.11,
                        transformers         -any,
                        unix                 >= 2.6,

src/IHaskell/Eval/Evaluate.hs

@@ -20,6 +20,7 @@ import Data.Char as Char
 import Data.Dynamic
 import Data.Typeable
 import qualified Data.Serialize as Serialize
+import qualified Language.Haskell.TH as TH  
 import System.Directory
 import Filesystem.Path.CurrentOS (encodeString)
 import System.Posix.IO
@@ -704,9 +705,28 @@ evalCommand output (Expression expr) state = do
   let widgetExpr = printf "(IHaskell.Display.Widget (%s))" expr :: String
   isWidget <- attempt $ exprType widgetExpr
 
+  -- Check if this is a template haskell declaration 
+  let declExpr = printf "((id :: DecsQ -> DecsQ) (%s))" expr::String
+  isTHDeclaration <- attempt $ exprType declExpr  
+
   write $ "Can Display: " ++ show canRunDisplay
-  write $ "  Is Widget: " ++ show canRunDisplay
+  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.
@@ -716,7 +736,6 @@ evalCommand output (Expression expr) state = do
         if isWidget
         then registerWidget out
         else return out
-
       else do
         -- Evaluate this expression as though it's just a statement.
         -- The output is bound to 'it', so we can then use it.