[project @ 2000-05-22 06:56:04 by simonpj]

*** NO NEED TO MERGE WITH 4.07, BUT POSSIBLE ***

Warn about completely unused imported modules (when -fwarn-unused-imports)

diff --git a/ghc/compiler/rename/Rename.lhs b/ghc/compiler/rename/Rename.lhs
index 3f27194..ee176e6 100644 (file)
--- a/ghc/compiler/rename/Rename.lhs
+++ b/ghc/compiler/rename/Rename.lhs
@@ -24,7 +24,8 @@ import RnIfaces               ( getImportedInstDecls, importDecl, getImportVersions, getInter
                          getImportedRules, loadHomeInterface, getSlurped, removeContext
                        )
 import RnEnv           ( availName, availsToNameSet, unitAvailEnv, availEnvElts, plusAvailEnv, 
-                         warnUnusedImports, warnUnusedLocalBinds, lookupImplicitOccRn, pprAvail,
+                         warnUnusedImports, warnUnusedLocalBinds, warnUnusedModules,
+                         lookupImplicitOccRn, pprAvail,
                          FreeVars, plusFVs, plusFV, unitFV, emptyFVs, isEmptyFVs
                        )
 import Module           ( Module, ModuleName, WhereFrom(..),
@@ -46,10 +47,10 @@ import Type         ( namesOfType, funTyCon )
 import ErrUtils                ( printErrorsAndWarnings, dumpIfSet, ghcExit )
 import BasicTypes      ( NewOrData(..) )
 import Bag             ( isEmptyBag, bagToList )
-import FiniteMap       ( FiniteMap, eltsFM, fmToList, emptyFM, addToFM_C )
+import FiniteMap       ( FiniteMap, eltsFM, fmToList, emptyFM, lookupFM, addToFM_C )
 import UniqSupply      ( UniqSupply )
 import UniqFM          ( lookupUFM )
-import Maybes          ( maybeToBool )
+import Maybes          ( maybeToBool, expectJust )
 import Outputable
 import IO              ( openFile, IOMode(..) )
 \end{code}
@@ -146,11 +147,6 @@ rename this_mod@(HsModule mod_name vers _ imports local_decls mod_deprec loc)
     getImportVersions mod_name export_env      `thenRn` \ my_usages ->
     getNameSupplyRn                            `thenRn` \ name_supply ->
 
-       -- REPORT UNUSED NAMES
-    reportUnusedNames mod_name gbl_env global_avail_env
-                     export_env
-                     source_fvs                        `thenRn_`
-
        -- RETURN THE RENAMED MODULE
     let
        has_orphans        = any isOrphanDecl rn_local_decls
@@ -161,7 +157,13 @@ rename this_mod@(HsModule mod_name vers _ imports local_decls mod_deprec loc)
                                  mod_deprec
                                  loc
     in
-    rnDump rn_imp_decls        rn_all_decls            `thenRn` \ dump_action ->
+       -- REPORT UNUSED NAMES, AND DEBUG DUMP 
+    reportUnusedNames mod_name direct_import_mods
+                     gbl_env global_avail_env
+                     export_env
+                     source_fvs                        `thenRn_`
+    rnDump rn_imp_decls        rn_all_decls                    `thenRn` \ dump_action ->
+
     returnRn (Just (mkThisModule mod_name,
                    renamed_module, 
                    (InterfaceDetails has_orphans my_usages export_env deprecs),
@@ -528,8 +530,12 @@ getInstDeclGates other                                 = emptyFVs
 %*********************************************************
 
 \begin{code}
-reportUnusedNames :: ModuleName -> GlobalRdrEnv -> AvailEnv -> ExportEnv -> NameSet -> RnMG ()
-reportUnusedNames mod_name gbl_env avail_env (ExportEnv export_avails _ _) mentioned_names
+reportUnusedNames :: ModuleName -> [ModuleName] 
+                 -> GlobalRdrEnv -> AvailEnv
+                 -> ExportEnv -> NameSet -> RnMG ()
+reportUnusedNames mod_name direct_import_mods 
+                 gbl_env avail_env 
+                 (ExportEnv export_avails _ _) mentioned_names
   = let
        used_names = mentioned_names `unionNameSets` availsToNameSet export_avails
 
@@ -565,28 +571,42 @@ reportUnusedNames mod_name gbl_env avail_env (ExportEnv export_avails _ _) menti
           nameSetToList (defined_names `minusNameSet` really_used_names)
 
        -- Filter out the ones only defined implicitly
-       bad_locals = [n | n <- defined_but_not_used, isLocallyDefined             n]
-       bad_imps   = [n | n <- defined_but_not_used, isUserImportedExplicitlyName n]
+       bad_locals     = [n | n <- defined_but_not_used, isLocallyDefined             n]
+       bad_imp_names  = [n | n <- defined_but_not_used, isUserImportedExplicitlyName n,
+                                                        not (module_unused n)]
 
        deprec_used deprec_env = [ (n,txt)
                                  | n <- nameSetToList mentioned_names,
                                    not (isLocallyDefined n),
                                    Just txt <- [lookupNameEnv deprec_env n] ]
 
-       minimal_imports :: FiniteMap Module AvailEnv
+       minimal_imports :: FiniteMap ModuleName AvailEnv
        minimal_imports = foldNameSet add emptyFM really_used_names
        add n acc = case maybeUserImportedFrom n of
                        Nothing -> acc
-                       Just m  -> addToFM_C plusAvailEnv acc m
+                       Just m  -> addToFM_C plusAvailEnv acc (moduleName m)
                                             (unitAvailEnv (mk_avail n))
        mk_avail n = case lookupNameEnv avail_env n of
                        Just (AvailTC m _) | n==m      -> AvailTC n [n]
                                           | otherwise -> AvailTC m [n,m]
                        Just avail         -> Avail n
                        Nothing            -> pprPanic "mk_avail" (ppr n)
+
+       -- unused_imp_mods are the directly-imported modules 
+       -- that are not mentioned in minimal_imports
+       unused_imp_mods = [m | m <- direct_import_mods, 
+                               not (maybeToBool (lookupFM minimal_imports m))]
+
+       module_unused :: Name -> Bool
+       -- Name is imported from a module that's completely unused,
+       -- so don't report stuff about the name (the module covers it)
+       module_unused n = moduleName (expectJust "module_unused" (maybeUserImportedFrom n))
+                         `elem` unused_imp_mods
+                               -- module_unused is only called if it's user-imported
     in
+    warnUnusedModules unused_imp_mods                          `thenRn_`
     warnUnusedLocalBinds bad_locals                            `thenRn_`
-    warnUnusedImports bad_imps                                 `thenRn_`
+    warnUnusedImports bad_imp_names                            `thenRn_`
     printMinimalImports mod_name minimal_imports               `thenRn_`
     getIfacesRn                                                        `thenRn` \ ifaces ->
     (if opt_WarnDeprecations
@@ -613,7 +633,7 @@ printMinimalImports mod_name imps
                            parens (fsep (punctuate comma (map ppr ies)))
 
     to_ies (mod, avail_env) = mapRn to_ie (availEnvElts avail_env)     `thenRn` \ ies ->
-                             returnRn (moduleName mod, ies)
+                             returnRn (mod, ies)
 
     to_ie :: AvailInfo -> RnMG (IE Name)
     to_ie (Avail n)       = returnRn (IEVar n)

diff --git a/ghc/compiler/rename/RnEnv.lhs b/ghc/compiler/rename/RnEnv.lhs
index 118267f..7cef968 100644 (file)
--- a/ghc/compiler/rename/RnEnv.lhs
+++ b/ghc/compiler/rename/RnEnv.lhs
@@ -763,8 +763,15 @@ mapFvRn f xs = mapRn f xs  `thenRn` \ stuff ->
 
 
 \begin{code}
-warnUnusedLocalBinds, warnUnusedImports, warnUnusedMatches :: [Name] -> RnM d ()
+warnUnusedModules :: [ModuleName] -> RnM d ()
+warnUnusedModules mods
+  | not opt_WarnUnusedImports = returnRn ()
+  | otherwise                = mapRn_ (addWarnRn . unused_mod) mods
+  where
+    unused_mod m = ptext SLIT("Module") <+> quotes (ppr m) <+> 
+                  ptext SLIT("is imported, but nothing from it is used")
 
+warnUnusedLocalBinds, warnUnusedImports, warnUnusedMatches :: [Name] -> RnM d ()
 warnUnusedImports names
   | not opt_WarnUnusedImports
   = returnRn ()        -- Don't force names unless necessary