[project @ 2000-11-01 17:15:28 by simonpj]

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

diff --git a/ghc/compiler/rename/RnNames.lhs b/ghc/compiler/rename/RnNames.lhs
index dd44505..f62fc86 100644 (file)
--- a/ghc/compiler/rename/RnNames.lhs
+++ b/ghc/compiler/rename/RnNames.lhs
@@ -88,9 +88,11 @@ getGlobalNames this_mod (HsModule _ _ exports imports decls _ mod_loc)
          (source, ordinary) = partition is_source_import all_imports
          is_source_import (ImportDecl _ ImportByUserSource _ _ _ _) = True
          is_source_import other                                     = False
+
+         get_imports = importsFromImportDecl this_mod_name rec_unqual_fn 
        in
-       mapAndUnzipRn (importsFromImportDecl rec_unqual_fn) ordinary    `thenRn` \ (imp_gbl_envs1, imp_avails_s1) ->
-       mapAndUnzipRn (importsFromImportDecl rec_unqual_fn) source      `thenRn` \ (imp_gbl_envs2, imp_avails_s2) ->
+       mapAndUnzipRn get_imports ordinary      `thenRn` \ (imp_gbl_envs1, imp_avails_s1) ->
+       mapAndUnzipRn get_imports source        `thenRn` \ (imp_gbl_envs2, imp_avails_s2) ->
 
                -- COMBINE RESULTS
                -- We put the local env second, so that a local provenance
@@ -141,12 +143,13 @@ getGlobalNames this_mod (HsModule _ _ exports imports decls _ mod_loc)
 \end{code}
        
 \begin{code}
-importsFromImportDecl :: (Name -> Bool)                -- OK to omit qualifier
+importsFromImportDecl :: ModuleName
+                     -> (Name -> Bool)         -- OK to omit qualifier
                      -> RdrNameImportDecl
                      -> RnMG (GlobalRdrEnv, 
                               ExportAvails) 
 
-importsFromImportDecl is_unqual (ImportDecl imp_mod_name from qual_only as_mod import_spec iloc)
+importsFromImportDecl this_mod_name is_unqual (ImportDecl imp_mod_name from qual_only as_mod import_spec iloc)
   = pushSrcLocRn iloc $
     getInterfaceExports imp_mod_name from      `thenRn` \ (imp_mod, avails_by_module) ->
 
@@ -158,7 +161,26 @@ importsFromImportDecl is_unqual (ImportDecl imp_mod_name from qual_only as_mod i
 
     let
        avails :: Avails
-       avails = concat (map snd avails_by_module)
+       avails = [ avail | (mod_name, avails) <- avails_by_module,
+                          mod_name /= this_mod_name,
+                          avail <- avails ]
+       -- 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.)  
+       --
+       -- Tiresome 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.  Oh well.
+
     in
     filterImports imp_mod_name import_spec avails      `thenRn` \ (filtered_avails, hides, explicits) ->