[project @ 1999-01-28 14:22:15 by simonpj]

[ghc-hetmet.git] / ghc / compiler / rename / RnIfaces.lhs

diff --git a/ghc/compiler/rename/RnIfaces.lhs b/ghc/compiler/rename/RnIfaces.lhs
index 0407764..5010eed 100644 (file)
--- a/ghc/compiler/rename/RnIfaces.lhs
+++ b/ghc/compiler/rename/RnIfaces.lhs
@@ -203,16 +203,21 @@ loadInterface doc_str load_mod
 
        -- LOAD IT INTO Ifaces
        -- First set the module
-    setModuleRn load_mod       $
 
        -- NB: *first* we do loadDecl, so that the provenance of all the locally-defined
        ---    names is done correctly (notably, whether this is an .hi file or .hi-boot file).
        --     If we do loadExport first the wrong info gets into the cache (unless we
        --      explicitly tag each export which seems a bit of a bore)
+
+    getModuleRn                `thenRn` \ this_mod ->
+    setModuleRn load_mod  $    -- First set the module name of the module being loaded,
+                               -- so that unqualified occurrences in the interface file
+                               -- get the right qualifer
     foldlRn loadDecl (iDecls ifaces) rd_decls          `thenRn` \ new_decls ->
     foldlRn loadFixDecl (iFixes ifaces) rd_decls       `thenRn` \ new_fixities ->
-    mapRn   loadExport exports                         `thenRn` \ avails_s ->
     foldlRn loadInstDecl insts rd_insts                        `thenRn` \ new_insts ->
+
+    mapRn (loadExport this_mod) exports                        `thenRn` \ avails_s ->
     let
         mod_details = (new_hif, mod_vers, concat avails_s)
 
@@ -229,8 +234,26 @@ loadInterface doc_str load_mod
     returnRn new_ifaces
     }}
 
-loadExport :: ExportItem -> RnMG [AvailInfo]
-loadExport (mod, entities)
+loadExport :: Module -> ExportItem -> RnMG [AvailInfo]
+loadExport this_mod (mod, entities)
+  | mod == this_mod = returnRn []
+       -- If the module exports anything defined in this module, just ignore it.
+       -- Reason: otherwise it looks as if there are two local definition sites
+       -- for the thing, and an error gets reported.  Easiest thing is just to
+       -- filter them out up front. This situation only arises if a module
+       -- imports itself, or another module that imported it.  (Necessarily,
+       -- this invoves a loop.)  Consequence: if you say
+       --      module A where
+       --         import B( AType )
+       --         type AType = ...
+       --
+       --      module B( AType ) where
+       --         import {-# SOURCE #-} A( AType )
+       --
+       -- then you'll get a 'B does not export AType' message.  A bit bogus
+       -- but it's a bogus thing to do!
+
+  | otherwise
   = mapRn load_entity entities
   where
     new_name occ = newImportedGlobalName mod occ