Add test to reproduce #5

hood.cabal

@@ -25,6 +25,12 @@ Library
   Exposed-modules:
       Debug.Hood.Observe
 
+Test-Suite hood-test
+  Type:                exitcode-stdio-1.0
+  Hs-Source-Dirs:      test
+  Main-Is:             test.hs
+  Build-Depends:       base, hood
+
 source-repository head
     type:     git
     location: https://github.com/ku-fpg/hood

test/test.hs

@@ -0,0 +1,26 @@
+#!/usr/bin/env stack
+{-# LANGUAGE DeriveGeneric #-}
+-- stack --resolver lts-8.4 runghc --package hood
+-- Minimum program to reproduce https://github.com/ku-fpg/hood/issues/5
+
+import           Debug.Hood.Observe
+import           GHC.Generics
+
+
+data Hoge =
+  Hoge
+    { hoge1 :: Int
+    , hoge2 :: String
+    } deriving Generic
+
+instance Observable Hoge
+
+
+main :: IO ()
+main = runO $ print $ f undefined
+
+
+f :: Hoge -> Bool
+f = observe "f" f'
+f' :: Hoge -> Bool
+f' h@(Hoge _h1 _h2) = error "ERROR"