Further wibbles to checkBootIface (fixed HEAD build)

diff --git a/compiler/typecheck/TcRnDriver.lhs b/compiler/typecheck/TcRnDriver.lhs
index f428853..a4a94ed 100644 (file)
--- a/compiler/typecheck/TcRnDriver.lhs
+++ b/compiler/typecheck/TcRnDriver.lhs
@@ -514,28 +514,34 @@ checkHiBootIface
        ; return (tcg_env { tcg_binds = binds `unionBags` unionManyBags dfun_binds }) }
   where
     check_export name  -- Name is exported by the boot iface
-      | name `elem` dfun_names       = return ()       
-      | isWiredInName name          = return ()        -- No checking for wired-in names.  In particular,
-                                                       -- 'error' is handled by a rather gross hack
-                                                       -- (see comments in GHC.Err.hs-boot)
-      | isImplicitTyThing boot_thing = return ()
-      | Just real_thing <- lookupTypeEnv local_type_env name
-      = do { checkTc (name `elemNameSet` local_export_set)
-                    (missingBootThing boot_thing "exported by")
+      | name `elem` dfun_names = return ()     
+      | isWiredInName name     = return ()     -- No checking for wired-in names.  In particular,
+                                               -- 'error' is handled by a rather gross hack
+                                               -- (see comments in GHC.Err.hs-boot)
+
+       -- Check that the actual module exports the same thing
+      | not (name `elemNameSet` local_export_set)
+      = addErrTc (missingBootThing name "exported by")
+
+       -- If the boot module does not *define* the thing, we are done
+       -- (it simply re-exports it, and names match, so nothing further to do)
+      | isNothing mb_boot_thing = return ()
 
-          ; let boot_decl = tyThingToIfaceDecl boot_thing
+       -- Check that the actual module also defines the thing, and 
+       -- then compare the definitions
+      | Just real_thing <- lookupTypeEnv local_type_env name
+      = do { let boot_decl = tyThingToIfaceDecl (fromJust mb_boot_thing)
                 real_decl = tyThingToIfaceDecl real_thing
           ; checkTc (checkBootDecl boot_decl real_decl)
-                    (bootMisMatch boot_thing boot_decl real_decl) }
+                    (bootMisMatch real_thing boot_decl real_decl) }
                -- The easiest way to check compatibility is to convert to
                -- iface syntax, where we already have good comparison functions
 
       | otherwise
-      = addErrTc (missingBootThing boot_thing "defined in")
+      = addErrTc (missingBootThing name "defined in")
       where
-       boot_thing = lookupTypeEnv boot_type_env name
-                    `orElse` pprPanic "checkHiBootIface" (ppr name)
-
+       mb_boot_thing = lookupTypeEnv boot_type_env name
+                
     dfun_names = map getName boot_insts
 
     local_export_set :: NameSet