Qualify stdout/stderr references and handle operations.

Fixes #201.

CHANGES

@@ -1,3 +1,6 @@
+Unreleased
+  - Don't use unqualified references to `stderr` or `stdout` which may collide with definitions in user code. (#201)
+
 Changes in 0.17
   - #266:
     - doctest now annotates its internal marker string as a `String`, to prevent misbehaviour in `OverloadedStrings` environments. This has a theoretical chance of breakage; if you're affected, please open an issue.

ghci-wrapper/src/Language/Haskell/GhciWrapper.hs

@@ -54,20 +54,20 @@ new Config{..} args_ = do
   setMode stdin_
   setMode stdout_
   let interpreter = Interpreter {hIn = stdin_, hOut = stdout_, process = processHandle}
-  _ <- eval interpreter "import System.IO"
-  _ <- eval interpreter "import GHC.IO.Handle"
+  _ <- eval interpreter "import qualified System.IO"
+  _ <- eval interpreter "import qualified GHC.IO.Handle"
   -- The buffering of stdout and stderr is NoBuffering
-  _ <- eval interpreter "hDuplicateTo stdout stderr"
+  _ <- eval interpreter "GHC.IO.Handle.hDuplicateTo System.IO.stdout System.IO.stderr"
   -- Now the buffering of stderr is BlockBuffering Nothing
   -- In this situation, GHC 7.7 does not flush the buffer even when
   -- error happens.
-  _ <- eval interpreter "hSetBuffering stdout LineBuffering"
-  _ <- eval interpreter "hSetBuffering stderr LineBuffering"
+  _ <- eval interpreter "GHC.IO.Handle.hSetBuffering System.IO.stdout GHC.IO.Handle.LineBuffering"
+  _ <- eval interpreter "GHC.IO.Handle.hSetBuffering System.IO.stderr GHC.IO.Handle.LineBuffering"
 
   -- this is required on systems that don't use utf8 as default encoding (e.g.
   -- Windows)
-  _ <- eval interpreter "hSetEncoding stdout utf8"
-  _ <- eval interpreter "hSetEncoding stderr utf8"
+  _ <- eval interpreter "GHC.IO.Handle.hSetEncoding System.IO.stdout GHC.IO.Handle.utf8"
+  _ <- eval interpreter "GHC.IO.Handle.hSetEncoding System.IO.stderr GHC.IO.Handle.utf8"
 
   _ <- eval interpreter ":m - System.IO"
   _ <- eval interpreter ":m - GHC.IO.Handle"

test/integration/local-stderr-binding/A.hs

@@ -0,0 +1,11 @@
+module A where
+
+stderr :: Bool
+stderr = True
+
+stdout :: String
+stdout = "hello"
+
+-- |
+-- >>> 3 + 3
+-- 6

test/integration/system-io-imported/A.hs

@@ -0,0 +1,10 @@
+module A where
+
+import System.IO
+
+-- ghci-wrapper needs to poke around with System.IO itself, and unloads the module once it's done. Test to make sure legitimate uses of System.IO don't get lost in the wash.
+
+-- |
+-- >>> ReadMode
+-- ReadMode
+