Add note about handle leak and fix warning

core/Test/Framework/Runners/ThreadPool.hs

@@ -48,7 +48,12 @@ executeOnPool n actions = do
     -- that are unrunnable.
     -- See also the ticket where SimonM (semi-cryptically) explains this:
     -- http://hackage.haskell.org/trac/ghc/ticket/3291
-    stablePtr <- myThreadId >>= newStablePtr
+    --
+    -- NB: this actually leaks stable pointers. We could prevent this by making
+    -- takeWhileWorkersExist do |unsafePerformIO newStablePtr| when returning the
+    -- lazily-demanded tail of the list, but its a bit of a pain. For now, just
+    -- grit our teeth and accept the leak.
+    _stablePtr <- myThreadId >>= newStablePtr
 
     -- Return the results generated by the worker threads lazily and in
     -- the same order as we got the inputs