Fix recompilation checking.

One-shot compilation was throwing away the old iface read by
checkOldIface, with the result that version numbers were never being
incremented.  Fixes the recomp001 test too.

diff --git a/compiler/main/HscMain.lhs b/compiler/main/HscMain.lhs
index 986d2ce..fdad852 100644 (file)
--- a/compiler/main/HscMain.lhs
+++ b/compiler/main/HscMain.lhs
@@ -217,6 +217,9 @@ data CompState
 get :: Comp CompState
 get = Comp $ \s -> return (s,s)
 
+modify :: (CompState -> CompState) -> Comp ()
+modify f = Comp $ \s -> return ((), f s)
+
 gets :: (CompState -> a) -> Comp a
 gets getter = do st <- get
                  return (getter st)
@@ -253,6 +256,10 @@ hscMkCompiler norecomp messenger frontend backend
              <- {-# SCC "checkOldIface" #-}
                 liftIO $ checkOldIface hsc_env mod_summary
                               source_unchanged mbOldIface
+        -- save the interface that comes back from checkOldIface.
+        -- In one-shot mode we don't have the old iface until this
+        -- point, when checkOldIface reads it from the disk.
+        modify (\s -> s{ compOldIface = mbCheckedIface })
          case mbCheckedIface of 
            Just iface | not recomp_reqd
                -> do messenger mbModIndex False