[commit: ghc] ghc-7.6: Fix #7231: don't unload stable modules when there is an error later (772e6d2)

Repository : ssh://darcs.haskell.org//srv/darcs/ghc

On branch  : ghc-7.6

http://hackage.haskell.org/trac/ghc/changeset/772e6d20bcac691bcfe8528829d6ed100fd701bb

>---------------------------------------------------------------

commit 772e6d20bcac691bcfe8528829d6ed100fd701bb
Author: Simon Marlow <[email protected]>
Date:   Tue Nov 27 08:55:31 2012 +0000

    Fix #7231: don't unload stable modules when there is an error later

>---------------------------------------------------------------

 compiler/main/GhcMake.hs |   17 ++++++++++++-----
 1 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/compiler/main/GhcMake.hs b/compiler/main/GhcMake.hs
index 322c631..f563cd9 100644
--- a/compiler/main/GhcMake.hs
+++ b/compiler/main/GhcMake.hs
@@ -238,11 +238,18 @@ load how_much = do
         stable_mg = 
             [ AcyclicSCC ms
             | AcyclicSCC ms <- full_mg,
-              ms_mod_name ms `elem` stable_obj++stable_bco,
-              ms_mod_name ms `notElem` [ ms_mod_name ms' | 
-                                            AcyclicSCC ms' <- partial_mg ] ]
-
-        mg = stable_mg ++ partial_mg
+              ms_mod_name ms `elem` stable_obj++stable_bco ]
+ 
+        -- the modules from partial_mg that are not also stable
+        -- NB. also keep cycles, we need to emit an error message later
+        unstable_mg = filter not_stable partial_mg
+          where not_stable (CyclicSCC _) = True
+                not_stable (AcyclicSCC ms)
+                   = ms_mod_name ms `notElem` stable_obj++stable_bco
+
+        -- Load all the stable modules first, before attempting to load
+        -- an unstable module (#7231).
+        mg = stable_mg ++ unstable_mg
 
     -- clean up between compilations
     let cleanup hsc_env = intermediateCleanTempFiles dflags