[project @ 2005-03-08 09:47:01 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 4b5bb26..8773732 100644 (file)
--- a/ghc/compiler/rename/RnNames.lhs
+++ b/ghc/compiler/rename/RnNames.lhs
@@ -273,7 +273,7 @@ exportsToAvails exports
        -- ensures that the subordinate names record their parent; 
        -- and that in turn ensures that the GlobalRdrEnv
        -- has the correct parent for all the names in its range.
-       -- For imported things, we only suck in the binding site later, if ever.
+       -- For imported things, we may only suck in the interface later, if ever.
        -- Reason for all this:
        --   Suppose module M exports type A.T, and constructor A.MkT
        --   Then, we know that A.MkT is a subordinate name of A.T,
@@ -762,8 +762,9 @@ gre_is_used used_names gre = gre_name gre `elemNameSet` used_names
 %*********************************************************
 
 \begin{code}
-reportUnusedNames :: TcGblEnv -> RnM ()
-reportUnusedNames gbl_env 
+reportUnusedNames :: Maybe [Located (IE RdrName)]      -- Export list
+                 -> TcGblEnv -> RnM ()
+reportUnusedNames export_decls gbl_env 
   = do { warnUnusedTopBinds   unused_locals
        ; warnUnusedModules    unused_imp_mods
        ; warnUnusedImports    unused_imports   
@@ -813,8 +814,10 @@ reportUnusedNames gbl_env
     -- To figure out the minimal set of imports, start with the things
     -- that are in scope (i.e. in gbl_env).  Then just combine them
     -- into a bunch of avails, so they are properly grouped
+    --
+    -- BUG WARNING: this does not deal properly with qualified imports!
     minimal_imports :: FiniteMap Module AvailEnv
-    minimal_imports0 = emptyFM
+    minimal_imports0 = foldr add_expall   emptyFM         expall_mods
     minimal_imports1 = foldr add_name     minimal_imports0 defined_and_used
     minimal_imports  = foldr add_inst_mod minimal_imports1 direct_import_mods
        -- The last line makes sure that we retain all direct imports
@@ -841,6 +844,27 @@ reportUnusedNames gbl_env
     add_name other acc 
        = acc
 
+       -- Modules mentioned as 'module M' in the export list
+    expall_mods = case export_decls of
+                   Nothing -> []
+                   Just es -> [m | L _ (IEModuleContents m) <- es]
+
+       -- This is really bogus.  The idea is that if we see 'module M' in 
+       -- the export list we must retain the import decls that drive it
+       -- If we aren't careful we might see
+       --      module A( module M ) where
+       --        import M
+       --        import N
+       -- and suppose that N exports everything that M does.  Then we 
+       -- must not drop the import of M even though N brings it all into
+       -- scope.
+       --
+       -- BUG WARNING: 'module M' exports aside, what if M.x is mentioned?!
+       --
+       -- The reason that add_expall is bogus is that it doesn't take
+       -- qualified imports into account.  But it's an improvement.
+    add_expall mod acc = addToFM_C plusAvailEnv acc mod emptyAvailEnv
+
        -- n is the name of the thing, p is the name of its parent
     mk_avail n (Just p)                                 = AvailTC p [p,n]
     mk_avail n Nothing | isTcOcc (nameOccName n) = AvailTC n [n]
@@ -863,6 +887,9 @@ reportUnusedNames gbl_env
     -- that are not mentioned in minimal_imports1
     -- [Note: not 'minimal_imports', because that includes directly-imported
     --       modules even if we use nothing from them; see notes above]
+    --
+    -- BUG WARNING: does not deal correctly with multiple imports of the same module
+    --             becuase direct_import_mods has only one entry per module
     unused_imp_mods = [(mod,loc) | (mod,imp,loc) <- direct_import_mods,
                       not (mod `elemFM` minimal_imports1),
                       mod /= pRELUDE,