diff options
Diffstat (limited to 'compiler/rename/RnNames.hs')
| -rw-r--r-- | compiler/rename/RnNames.hs | 231 |
1 files changed, 126 insertions, 105 deletions
diff --git a/compiler/rename/RnNames.hs b/compiler/rename/RnNames.hs index cf4c258d01..bfa7ee0e94 100644 --- a/compiler/rename/RnNames.hs +++ b/compiler/rename/RnNames.hs @@ -63,13 +63,11 @@ import qualified GHC.LanguageExtensions as LangExt import Control.Monad import Data.Either ( partitionEithers, isRight, rights ) --- import qualified Data.Foldable as Foldable import Data.Map ( Map ) import qualified Data.Map as Map import Data.Ord ( comparing ) import Data.List ( partition, (\\), find, sortBy ) import qualified Data.Set as S --- import qualified Data.Set as Set import System.FilePath ((</>)) import System.IO @@ -1094,8 +1092,8 @@ gresFromIE decl_spec (L loc ie, avail) = gresFromAvail prov_fn avail where is_explicit = case ie of - IEThingAll _ (L _ name) -> \n -> n == ieWrappedName name - _ -> \_ -> True + IEThingAll _ name -> \n -> n == ieLWrappedName name + _ -> \_ -> True prov_fn name = Just (ImpSpec { is_decl = decl_spec, is_item = item_spec }) where @@ -1217,44 +1215,11 @@ reportUnusedNames _export_decls gbl_env is_unused_local :: GlobalRdrElt -> Bool is_unused_local gre = isLocalGRE gre && isExternalName (gre_name gre) -{- -********************************************************* -* * -\subsection{Unused imports} -* * -********************************************************* - -This code finds which import declarations are unused. The -specification and implementation notes are here: - http://ghc.haskell.org/trac/ghc/wiki/Commentary/Compiler/UnusedImports --} - -type ImportDeclUsage - = ( LImportDecl GhcRn -- The import declaration - , [AvailInfo] -- What *is* used (normalised) - , [Name] ) -- What is imported but *not* used - -warnUnusedImportDecls :: TcGblEnv -> RnM () -warnUnusedImportDecls gbl_env - = do { uses <- readMutVar (tcg_used_gres gbl_env) - ; let user_imports = filterOut (ideclImplicit . unLoc) (tcg_rn_imports gbl_env) - -- This whole function deals only with *user* imports - -- both for warning about unnecessary ones, and for - -- deciding the minimal ones - rdr_env = tcg_rdr_env gbl_env - fld_env = mkFieldEnv rdr_env - - ; let usage :: [ImportDeclUsage] - usage = findImportUsage user_imports uses - - ; traceRn "warnUnusedImportDecls" $ - (vcat [ text "Uses:" <+> ppr uses - , text "Import usage" <+> ppr usage]) - ; whenWOptM Opt_WarnUnusedImports $ - mapM_ (warnUnusedImport Opt_WarnUnusedImports fld_env) usage - - ; whenGOptM Opt_D_dump_minimal_imports $ - printMinimalImports usage } +{- ********************************************************************* +* * + Missing signatures +* * +********************************************************************* -} -- | Warn the user about top level binders that lack type signatures. -- Called /after/ type inference, so that we can report the @@ -1312,29 +1277,48 @@ warnMissingSignatures gbl_env ; add_sig_warns } + {- -Note [The ImportMap] -~~~~~~~~~~~~~~~~~~~~ -The ImportMap is a short-lived intermediate data structure records, for -each import declaration, what stuff brought into scope by that -declaration is actually used in the module. +********************************************************* +* * +\subsection{Unused imports} +* * +********************************************************* -The SrcLoc is the location of the END of a particular 'import' -declaration. Why *END*? Because we don't want to get confused -by the implicit Prelude import. Consider (Trac #7476) the module - import Foo( foo ) - main = print foo -There is an implicit 'import Prelude(print)', and it gets a SrcSpan -of line 1:1 (just the point, not a span). If we use the *START* of -the SrcSpan to identify the import decl, we'll confuse the implicit -import Prelude with the explicit 'import Foo'. So we use the END. -It's just a cheap hack; we could equally well use the Span too. +This code finds which import declarations are unused. The +specification and implementation notes are here: + http://ghc.haskell.org/trac/ghc/wiki/Commentary/Compiler/UnusedImports -The AvailInfos are the things imported from that decl (just a list, -not normalised). +See also Note [Choosing the best import declaration] in RdrName -} -type ImportMap = Map SrcLoc [AvailInfo] -- See [The ImportMap] +type ImportDeclUsage + = ( LImportDecl GhcRn -- The import declaration + , [GlobalRdrElt] -- What *is* used (normalised) + , [Name] ) -- What is imported but *not* used + +warnUnusedImportDecls :: TcGblEnv -> RnM () +warnUnusedImportDecls gbl_env + = do { uses <- readMutVar (tcg_used_gres gbl_env) + ; let user_imports = filterOut (ideclImplicit . unLoc) (tcg_rn_imports gbl_env) + -- This whole function deals only with *user* imports + -- both for warning about unnecessary ones, and for + -- deciding the minimal ones + rdr_env = tcg_rdr_env gbl_env + fld_env = mkFieldEnv rdr_env + + ; let usage :: [ImportDeclUsage] + usage = findImportUsage user_imports uses + + ; traceRn "warnUnusedImportDecls" $ + (vcat [ text "Uses:" <+> ppr uses + , text "Import usage" <+> ppr usage]) + + ; whenWOptM Opt_WarnUnusedImports $ + mapM_ (warnUnusedImport Opt_WarnUnusedImports fld_env) usage + + ; whenGOptM Opt_D_dump_minimal_imports $ + printMinimalImports usage } findImportUsage :: [LImportDecl GhcRn] -> [GlobalRdrElt] @@ -1344,16 +1328,17 @@ findImportUsage imports used_gres = map unused_decl imports where import_usage :: ImportMap - import_usage - = foldr extendImportMap Map.empty used_gres + import_usage = mkImportMap used_gres unused_decl decl@(L loc (ImportDecl { ideclHiding = imps })) - = (decl, nubAvails used_avails, nameSetElemsStable unused_imps) + = (decl, used_gres, nameSetElemsStable unused_imps) where - used_avails = Map.lookup (srcSpanEnd loc) import_usage `orElse` [] - -- srcSpanEnd: see Note [The ImportMap] - used_names = availsToNameSetWithSelectors used_avails - used_parents = mkNameSet [n | AvailTC n _ _ <- used_avails] + used_gres = Map.lookup (srcSpanEnd loc) import_usage + -- srcSpanEnd: see Note [The ImportMap] + `orElse` [] + + used_names = mkNameSet (map gre_name used_gres) + used_parents = mkNameSet (mapMaybe greParent_maybe used_gres) unused_imps -- Not trivial; see eg Trac #7454 = case imps of @@ -1362,19 +1347,16 @@ findImportUsage imports used_gres _other -> emptyNameSet -- No explicit import list => no unused-name list add_unused :: IE GhcRn -> NameSet -> NameSet - add_unused (IEVar _ (L _ n)) acc - = add_unused_name (ieWrappedName n) acc - add_unused (IEThingAbs _ (L _ n)) acc - = add_unused_name (ieWrappedName n) acc - add_unused (IEThingAll _ (L _ n)) acc - = add_unused_all (ieWrappedName n) acc - add_unused (IEThingWith _ (L _ p) wc ns fs) acc = - add_wc_all (add_unused_with (ieWrappedName p) xs acc) - where xs = map (ieWrappedName . unLoc) ns - ++ map (flSelector . unLoc) fs + add_unused (IEVar _ n) acc = add_unused_name (ieLWrappedName n) acc + add_unused (IEThingAbs _ n) acc = add_unused_name (ieLWrappedName n) acc + add_unused (IEThingAll _ n) acc = add_unused_all (ieLWrappedName n) acc + add_unused (IEThingWith _ p wc ns fs) acc = + add_wc_all (add_unused_with pn xs acc) + where pn = ieLWrappedName p + xs = map ieLWrappedName ns ++ map (flSelector . unLoc) fs add_wc_all = case wc of NoIEWildcard -> id - IEWildcard _ -> add_unused_all (ieWrappedName p) + IEWildcard _ -> add_unused_all pn add_unused _ acc = acc add_unused_name n acc @@ -1394,49 +1376,86 @@ findImportUsage imports used_gres -- Num is not itself mentioned. Hence the two cases in add_unused_with. unused_decl (L _ (XImportDecl _)) = panic "unused_decl" -extendImportMap :: GlobalRdrElt -> ImportMap -> ImportMap + +{- Note [The ImportMap] +~~~~~~~~~~~~~~~~~~~~~~~ +The ImportMap is a short-lived intermediate data structure records, for +each import declaration, what stuff brought into scope by that +declaration is actually used in the module. + +The SrcLoc is the location of the END of a particular 'import' +declaration. Why *END*? Because we don't want to get confused +by the implicit Prelude import. Consider (Trac #7476) the module + import Foo( foo ) + main = print foo +There is an implicit 'import Prelude(print)', and it gets a SrcSpan +of line 1:1 (just the point, not a span). If we use the *START* of +the SrcSpan to identify the import decl, we'll confuse the implicit +import Prelude with the explicit 'import Foo'. So we use the END. +It's just a cheap hack; we could equally well use the Span too. + +The [GlobalRdrElt] are the things imported from that decl. +-} + +type ImportMap = Map SrcLoc [GlobalRdrElt] -- See [The ImportMap] + -- If loc :-> gres, then + -- 'loc' = the end loc of the bestImport of each GRE in 'gres' + +mkImportMap :: [GlobalRdrElt] -> ImportMap -- For each of a list of used GREs, find all the import decls that brought -- it into scope; choose one of them (bestImport), and record -- the RdrName in that import decl's entry in the ImportMap -extendImportMap gre imp_map - = add_imp gre (bestImport (gre_imp gre)) imp_map +mkImportMap gres + = foldr add_one Map.empty gres where - add_imp :: GlobalRdrElt -> ImportSpec -> ImportMap -> ImportMap - add_imp gre (ImpSpec { is_decl = imp_decl_spec }) imp_map - = Map.insertWith add decl_loc [avail] imp_map - where - add _ avails = avail : avails -- add is really just a specialised (++) - decl_loc = srcSpanEnd (is_dloc imp_decl_spec) - -- For srcSpanEnd see Note [The ImportMap] - avail = availFromGRE gre + add_one gre@(GRE { gre_imp = imp_specs }) imp_map + = Map.insertWith add decl_loc [gre] imp_map + where + best_imp_spec = bestImport imp_specs + decl_loc = srcSpanEnd (is_dloc (is_decl best_imp_spec)) + -- For srcSpanEnd see Note [The ImportMap] + add _ gres = gre : gres warnUnusedImport :: WarningFlag -> NameEnv (FieldLabelString, Name) -> ImportDeclUsage -> RnM () warnUnusedImport flag fld_env (L loc decl, used, unused) + + -- Do not warn for 'import M()' | Just (False,L _ []) <- ideclHiding decl - = return () -- Do not warn for 'import M()' + = return () + -- Note [Do not warn about Prelude hiding] | Just (True, L _ hides) <- ideclHiding decl , not (null hides) , pRELUDE_NAME == unLoc (ideclName decl) - = return () -- Note [Do not warn about Prelude hiding] - | null used = addWarnAt (Reason flag) loc msg1 -- Nothing used; drop entire decl - | null unused = return () -- Everything imported is used; nop - | otherwise = addWarnAt (Reason flag) loc msg2 -- Some imports are unused + = return () + + -- Nothing used; drop entire declaration + | null used + = addWarnAt (Reason flag) loc msg1 + + -- Everything imported is used; nop + | null unused + = return () + + -- Some imports are unused + | otherwise + = addWarnAt (Reason flag) loc msg2 + where - msg1 = vcat [pp_herald <+> quotes pp_mod <+> pp_not_used, - nest 2 (text "except perhaps to import instances from" - <+> quotes pp_mod), - text "To import instances alone, use:" + msg1 = vcat [ pp_herald <+> quotes pp_mod <+> is_redundant + , nest 2 (text "except perhaps to import instances from" + <+> quotes pp_mod) + , text "To import instances alone, use:" <+> text "import" <+> pp_mod <> parens Outputable.empty ] - msg2 = sep [pp_herald <+> quotes sort_unused, - text "from module" <+> quotes pp_mod <+> pp_not_used] + msg2 = sep [ pp_herald <+> quotes sort_unused + , text "from module" <+> quotes pp_mod <+> is_redundant] pp_herald = text "The" <+> pp_qual <+> text "import of" pp_qual | ideclQualified decl = text "qualified" | otherwise = Outputable.empty - pp_mod = ppr (unLoc (ideclName decl)) - pp_not_used = text "is redundant" + pp_mod = ppr (unLoc (ideclName decl)) + is_redundant = text "is redundant" -- In warning message, pretty-print identifiers unqualified unconditionally -- to improve the consistent for ambiguous/unambiguous identifiers. @@ -1446,8 +1465,9 @@ warnUnusedImport flag fld_env (L loc decl, used, unused) Nothing -> pprNameUnqualified n -- Print unused names in a deterministic (lexicographic) order + sort_unused :: SDoc sort_unused = pprWithCommas ppr_possible_field $ - sortBy (comparing nameOccName) unused + sortBy (comparing nameOccName) unused {- Note [Do not warn about Prelude hiding] @@ -1475,7 +1495,7 @@ decls, and simply trim their import lists. NB that getMinimalImports :: [ImportDeclUsage] -> RnM [LImportDecl GhcRn] getMinimalImports = mapM mk_minimal where - mk_minimal (L l decl, used, unused) + mk_minimal (L l decl, used_gres, unused) | null unused , Just (False, _) <- ideclHiding decl = return (L l decl) @@ -1484,7 +1504,8 @@ getMinimalImports = mapM mk_minimal , ideclSource = is_boot , ideclPkgQual = mb_pkg } = decl ; iface <- loadSrcInterface doc mod_name is_boot (fmap sl_fs mb_pkg) - ; let lies = map (L l) (concatMap (to_ie iface) used) + ; let used_avails = gresToAvailInfo used_gres + lies = map (L l) (concatMap (to_ie iface) used_avails) ; return (L l (decl { ideclHiding = Just (False, L l lies) })) } where doc = text "Compute minimal imports for" <+> ppr decl |