travis 12

.travis.yml

@@ -55,9 +55,11 @@ install:
   - stack setup --resolver=$RESOLVER
   - stack build --dependencies-only --resolver=$RESOLVER
 
+  # For verify_formatting.py
+  - if $FORMATTING; then stack install hindent; fi
+
 script:
   - export LD_LIBRARY_PATH=$HOME/zeromq/lib
-  - stack build --resolver=$RESOLVER
   - stack test --resolver=$RESOLVER
   - if $FORMATTING; then ./verify_formatting.py; fi
   - |

src/IHaskell/Eval/Evaluate.hs

@@ -30,6 +30,7 @@ import           Data.List (findIndex, and, foldl1, nubBy)
 import           Text.Printf
 import           Data.Char as Char
 import           Data.Dynamic
+import           Data.Typeable.Internal
 import           Data.Typeable
 import qualified Data.Serialize as Serialize
 import           System.Directory
@@ -356,11 +357,18 @@ evaluate kernelState code output widgetHandler = do
 -- | Compile a string and extract a value from it. Effectively extract the result of an expression
 -- from inside the notebook environment.
 extractValue :: Typeable a => String -> Interpreter a
-extractValue expr = do
-  compiled <- dynCompileExpr expr
-  case fromDynamic compiled of
-    Nothing     -> error "Error casting types in Evaluate.hs"
-    Just result -> return result
+extractValue expr = result
+  where
+    result = do
+      compiled <- dynCompileExpr expr
+      case fromDynamic compiled of
+        Nothing -> error $
+          "Error casting types in Evaluate.hs: " ++
+          showRep (dynTypeRep compiled) ++
+          " -> " ++
+          showRep (typeRep result)
+        Just result -> return result
+    showRep rep = show $ map (tyConPackage .typeRepTyCon) $ concatMap typeRepArgs (typeRepArgs rep)
 
 flushWidgetMessages :: KernelState
                     -> [WidgetMsg]

stack.yaml

@@ -4,5 +4,3 @@ packages:
 - './ipython-kernel'
 - './ghc-parser'
 resolver: lts-6.2
-extra-deps:
-    - system-argv0-0.1.1 # Necessary for LTS 2.22 (GHC 7.8)