X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Frename%2FRnNames.lhs;h=84568d97731546139feeff971f8545eda1991839;hp=d2add1f7be42a42f82f495e2a95489a01f8555ae;hb=e95ee1f718c6915c478005aad8af81705357d6ab;hpb=168b79b497c49f1a557aaeb173afd4d18528aeac diff --git a/compiler/rename/RnNames.lhs b/compiler/rename/RnNames.lhs index d2add1f..84568d9 100644 --- a/compiler/rename/RnNames.lhs +++ b/compiler/rename/RnNames.lhs @@ -6,7 +6,8 @@ \begin{code} module RnNames ( rnImports, getLocalNonValBinders, - rnExports, extendGlobalRdrEnvRn, + rnExports, extendGlobalRdrEnvRn, + gresFromAvails, reportUnusedNames, finishWarnings, ) where @@ -19,29 +20,29 @@ import RnEnv import RnHsDoc ( rnHsDoc ) import IfaceEnv ( ifaceExportNames ) import LoadIface ( loadSrcInterface, loadSysInterface ) -import TcRnMonad hiding (LIE) +import TcRnMonad +import HeaderInfo ( mkPrelImports ) import PrelNames import Module import Name import NameEnv import NameSet -import OccName import HscTypes import RdrName import Outputable import Maybes import SrcLoc -import FiniteMap import ErrUtils -import BasicTypes ( WarningTxt(..) ) -import DriverPhases ( isHsBoot ) import Util import FastString import ListSetOps -import Data.List ( partition, concatMap, (\\), delete ) -import IO ( openFile, IOMode(..) ) -import Monad ( when, mplus ) +import Data.List ( partition, (\\), delete ) +import qualified Data.Set as Set +import System.IO +import Control.Monad +import Data.Map (Map) +import qualified Data.Map as Map \end{code} @@ -62,7 +63,7 @@ rnImports imports -- warning for {- SOURCE -} ones that are unnecessary = do this_mod <- getModule implicit_prelude <- doptM Opt_ImplicitPrelude - let prel_imports = mkPrelImports this_mod implicit_prelude imports + let prel_imports = mkPrelImports (moduleName this_mod) implicit_prelude imports (source, ordinary) = partition is_source_import imports is_source_import (L _ (ImportDecl _ _ is_boot _ _ _)) = is_boot @@ -70,10 +71,11 @@ rnImports imports when (notNull prel_imports) $ addWarn (implicitPreludeWarn) ) - stuff1 <- mapM (rnImportDecl this_mod) (prel_imports ++ ordinary) - stuff2 <- mapM (rnImportDecl this_mod) source - let (decls, rdr_env, imp_avails,hpc_usage) = combine (stuff1 ++ stuff2) - return (decls, rdr_env, imp_avails,hpc_usage) + stuff1 <- mapM (rnImportDecl this_mod True) prel_imports + stuff2 <- mapM (rnImportDecl this_mod False) ordinary + stuff3 <- mapM (rnImportDecl this_mod False) source + let (decls, rdr_env, imp_avails, hpc_usage) = combine (stuff1 ++ stuff2 ++ stuff3) + return (decls, rdr_env, imp_avails, hpc_usage) where combine :: [(LImportDecl Name, GlobalRdrEnv, ImportAvails,AnyHpcUsage)] @@ -86,44 +88,13 @@ rnImports imports imp_avails1 `plusImportAvails` imp_avails2, hpc_usage1 || hpc_usage2) -mkPrelImports :: Module -> Bool -> [LImportDecl RdrName] -> [LImportDecl RdrName] --- Consruct the implicit declaration "import Prelude" (or not) --- --- NB: opt_NoImplicitPrelude is slightly different to import Prelude (); --- because the former doesn't even look at Prelude.hi for instance --- declarations, whereas the latter does. -mkPrelImports this_mod implicit_prelude import_decls - | this_mod == pRELUDE - || explicit_prelude_import - || not implicit_prelude - = [] - | otherwise = [preludeImportDecl] - where - explicit_prelude_import - = notNull [ () | L _ (ImportDecl mod Nothing _ _ _ _) <- import_decls, - unLoc mod == pRELUDE_NAME ] - - preludeImportDecl :: LImportDecl RdrName - preludeImportDecl - = L loc $ - ImportDecl (L loc pRELUDE_NAME) - Nothing {- no specific package -} - False {- Not a boot interface -} - False {- Not qualified -} - Nothing {- No "as" -} - Nothing {- No import list -} - - loc = mkGeneralSrcSpan (fsLit "Implicit import declaration") - - -rnImportDecl :: Module +rnImportDecl :: Module -> Bool -> LImportDecl RdrName -> RnM (LImportDecl Name, GlobalRdrEnv, ImportAvails,AnyHpcUsage) -rnImportDecl this_mod (L loc (ImportDecl loc_imp_mod_name mb_pkg want_boot +rnImportDecl this_mod implicit_prelude (L loc (ImportDecl loc_imp_mod_name mb_pkg want_boot qual_only as_mod imp_details)) - = - setSrcSpan loc $ do + = setSrcSpan loc $ do when (isJust mb_pkg) $ do pkg_imports <- doptM Opt_PackageImports @@ -135,6 +106,17 @@ rnImportDecl this_mod (L loc (ImportDecl loc_imp_mod_name mb_pkg want_boot imp_mod_name = unLoc loc_imp_mod_name doc = ppr imp_mod_name <+> ptext (sLit "is directly imported") + let isExplicit lie = case unLoc lie of + IEThingAll _ -> False + _ -> True + case imp_details of + Just (False, lies) + | all isExplicit lies -> + return () + _ -> + unless implicit_prelude $ + ifOptM Opt_WarnMissingImportList (addWarn (missingImportListWarn imp_mod_name)) + iface <- loadSrcInterface doc imp_mod_name want_boot mb_pkg -- Compiler sanity check: if the import didn't say @@ -143,8 +125,14 @@ rnImportDecl this_mod (L loc (ImportDecl loc_imp_mod_name mb_pkg want_boot -- Issue a user warning for a redundant {- SOURCE -} import -- NB that we arrange to read all the ordinary imports before - -- any of the {- SOURCE -} imports - warnIf (want_boot && not (mi_boot iface)) + -- any of the {- SOURCE -} imports. + -- + -- in --make and GHCi, the compilation manager checks for this, + -- and indeed we shouldn't do it here because the existence of + -- the non-boot module depends on the compilation order, which + -- is not deterministic. The hs-boot test can show this up. + dflags <- getDOpts + warnIf (want_boot && not (mi_boot iface) && isOneShot (ghcMode dflags)) (warnRedundantSourceImport imp_mod_name) let @@ -286,23 +274,34 @@ top level binders specially in two ways 2. We make them *shadow* the outer bindings. If we don't do that, we'll get a complaint when extending the GlobalRdrEnv, saying that - there are two bindings for 'f'. - - This shadowing applies even if the binding for 'f' is in a - where-clause, and hence is in the *local* RdrEnv not the *global* - RdrEnv. - -We find out whether we are inside a [d| ... |] by testing the TH -stage. This is a slight hack, because the stage field was really meant for -the type checker, and here we are not interested in the fields of Brack, -hence the error thunks in thRnBrack. + there are two bindings for 'f'. There are several tricky points: + + * This shadowing applies even if the binding for 'f' is in a + where-clause, and hence is in the *local* RdrEnv not the *global* + RdrEnv. + + * The *qualified* name M.f from the enclosing module must certainly + still be available. So we don't nuke it entirely; we just make + it seem like qualified import. + + * We only shadow *External* names (which come from the main module) + Do not shadow *Inernal* names because in the bracket + [d| class C a where f :: a + f = 4 |] + rnSrcDecls will first call extendGlobalRdrEnvRn with C[f] from the + class decl, and *separately* extend the envt with the value binding. + +3. We find out whether we are inside a [d| ... |] by testing the TH + stage. This is a slight hack, because the stage field was really + meant for the type checker, and here we are not interested in the + fields of Brack, hence the error thunks in thRnBrack. \begin{code} extendGlobalRdrEnvRn :: [AvailInfo] -> MiniFixityEnv -> RnM (TcGblEnv, TcLclEnv) -- Updates both the GlobalRdrEnv and the FixityEnv - -- We return a new TcLclEnv only becuase we might have to + -- We return a new TcLclEnv only because we might have to -- delete some bindings from it; -- see Note [Top-level Names in Template Haskell decl quotes] @@ -318,7 +317,7 @@ extendGlobalRdrEnvRn avails new_fixities -- See Note [Top-level Names in Template Haskell decl quotes] shadowP = isBrackStage stage new_occs = map (nameOccName . gre_name) gres - rdr_env1 = hideSomeUnquals rdr_env new_occs + rdr_env1 = transformGREs qual_gre new_occs rdr_env lcl_env1 = lcl_env { tcl_rdr = delListFromOccEnv (tcl_rdr lcl_env) new_occs } (rdr_env2, lcl_env2) | shadowP = (rdr_env1, lcl_env1) | otherwise = (rdr_env, lcl_env) @@ -345,6 +344,35 @@ extendGlobalRdrEnvRn avails new_fixities where name = gre_name gre occ = nameOccName name + + qual_gre :: GlobalRdrElt -> GlobalRdrElt + -- Transform top-level GREs from the module being compiled + -- so that they are out of the way of new definitions in a Template + -- Haskell bracket + -- See Note [Top-level Names in Template Haskell decl quotes] + -- Seems like 5 times as much work as it deserves! + -- + -- For a LocalDef we make a (fake) qualified imported GRE for a + -- local GRE so that the original *qualified* name is still in scope + -- but the *unqualified* one no longer is. What a hack! + + qual_gre gre@(GRE { gre_prov = LocalDef, gre_name = name }) + | isExternalName name = gre { gre_prov = Imported [imp_spec] } + | otherwise = gre + -- Do not shadow Internal (ie Template Haskell) Names + -- See Note [Top-level Names in Template Haskell decl quotes] + where + mod = ASSERT2( isExternalName name, ppr name) moduleName (nameModule name) + imp_spec = ImpSpec { is_item = ImpAll, is_decl = decl_spec } + decl_spec = ImpDeclSpec { is_mod = mod, is_as = mod, + is_qual = True, -- Qualified only! + is_dloc = srcLocSpan (nameSrcLoc name) } + + qual_gre gre@(GRE { gre_prov = Imported specs }) + = gre { gre_prov = Imported (map qual_spec specs) } + + qual_spec spec@(ImpSpec { is_decl = decl_spec }) + = spec { is_decl = decl_spec { is_qual = True } } \end{code} @getLocalDeclBinders@ returns the names for an @HsDecl@. It's @@ -354,22 +382,56 @@ used for source code. Instances of type families ~~~~~~~~~~~~~~~~~~~~~~~~~~ -Indexed data/newtype instances contain data constructors that we need to -collect, too. Moreover, we need to descend into the data/newtypes instances -of associated families. +Family instances contain data constructors that we need to collect and we also +need to descend into the type instances of associated families in class +instances. The type constructor of a family instance is a usage occurence. +Hence, we don't return it as a subname in 'AvailInfo'; otherwise, we would get +a duplicate declaration error. + +Note [Looking up family names in family instances] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Consider + + module M where + type family T a :: * + type instance M.T Int = Bool + +We might think that we can simply use 'lookupOccRn' when processing the type +instance to look up 'M.T'. Alas, we can't! The type family declaration is in +the *same* HsGroup as the type instance declaration. Hence, as we are +currently collecting the binders declared in that HsGroup, these binders will +not have been added to the global environment yet. + +In the case of type classes, this problem does not arise, as a class instance +does not define any binders of it's own. So, we simply don't attempt to look +up the class names of class instances in 'get_local_binders' below. + +If we don't look up class instances, can't we get away without looking up type +instances, too? No, we can't. Data type instances define data constructors +and we need to -We need to be careful with the handling of the type constructor of each type -instance as the family constructor is already defined, and we want to avoid -raising a duplicate declaration error. So, we make a new name for it, but -don't return it in the 'AvailInfo'. + (1) collect those in 'get_local_binders' and + (2) we need to get their parent name in 'get_local_binders', too, to + produce an appropriate 'AvailTC'. + +This parent name is exactly the family name of the type instance that is so +difficult to look up. + +We solve this problem as follows: + + (a) We process all type declarations other than type instances first. + (b) Then, we compute a 'GlobalRdrEnv' from the result of the first step. + (c) Finally, we process all type instances (both those on the toplevel and + those nested in class instances) and check for the family names in the + 'GlobalRdrEnv' produced in the previous step before using 'lookupOccRn'. \begin{code} getLocalNonValBinders :: HsGroup RdrName -> RnM [AvailInfo] -- Get all the top-level binders bound the group *except* -- for value bindings, which are treated separately -- Specificaly we return AvailInfo for --- type decls --- class decls +-- type decls (incl constructors and record selectors) +-- class decls (including class ops) -- associated types -- foreign imports -- (in hs-boot files) value signatures @@ -383,12 +445,25 @@ get_local_binders gbl_env (HsGroup {hs_valds = ValBindsIn _ val_sigs, hs_tyclds = tycl_decls, hs_instds = inst_decls, hs_fords = foreign_decls }) - = do { tc_names_s <- mapM new_tc tycl_decls - ; at_names_s <- mapM inst_ats inst_decls - ; val_names <- mapM new_simple val_bndrs - ; return (val_names ++ tc_names_s ++ concat at_names_s) } + = do { -- separate out the family instance declarations + let (tyinst_decls1, tycl_decls_noinsts) + = partition (isFamInstDecl . unLoc) tycl_decls + tyinst_decls = tyinst_decls1 ++ instDeclATs inst_decls + + -- process all type/class decls except family instances + ; tc_names <- mapM new_tc tycl_decls_noinsts + + -- create a temporary rdr env of the type binders + ; let tc_gres = gresFromAvails LocalDef tc_names + tc_name_env = foldl extendGlobalRdrEnv emptyGlobalRdrEnv tc_gres + + -- process all family instances + ; ti_names <- mapM (new_ti tc_name_env) tyinst_decls + + -- finish off with value binder in case of a hs-boot file + ; val_names <- mapM new_simple val_bndrs + ; return (val_names ++ tc_names ++ ti_names) } where - mod = tcg_mod gbl_env is_hs_boot = isHsBoot (tcg_src gbl_env) ; for_hs_bndrs :: [Located RdrName] @@ -402,24 +477,23 @@ get_local_binders gbl_env (HsGroup {hs_valds = ValBindsIn _ val_sigs, new_simple :: Located RdrName -> RnM (GenAvailInfo Name) new_simple rdr_name = do - nm <- newTopSrcBinder mod rdr_name + nm <- newTopSrcBinder rdr_name return (Avail nm) - new_tc tc_decl - | isFamInstDecl (unLoc tc_decl) - = do { main_name <- lookupFamInstDeclBndr mod main_rdr - ; sub_names <- mapM (newTopSrcBinder mod) sub_rdrs - ; return (AvailTC main_name sub_names) } - -- main_name is not bound here! - | otherwise - = do { main_name <- newTopSrcBinder mod main_rdr - ; sub_names <- mapM (newTopSrcBinder mod) sub_rdrs + new_tc tc_decl -- NOT for type/data instances + = do { main_name <- newTopSrcBinder main_rdr + ; sub_names <- mapM newTopSrcBinder sub_rdrs ; return (AvailTC main_name (main_name : sub_names)) } where - (main_rdr : sub_rdrs) = tyClDeclNames (unLoc tc_decl) + (main_rdr : sub_rdrs) = hsTyClDeclBinders tc_decl - inst_ats inst_decl - = mapM new_tc (instDeclATs (unLoc inst_decl)) + new_ti tc_name_env ti_decl -- ONLY for type/data instances + = do { main_name <- lookupFamInstDeclBndr tc_name_env main_rdr + ; sub_names <- mapM newTopSrcBinder sub_rdrs + ; return (AvailTC main_name sub_names) } + -- main_name is not bound here! + where + (main_rdr : sub_rdrs) = hsTyClDeclBinders ti_decl get_local_binders _ g = pprPanic "get_local_binders" (ppr g) \end{code} @@ -527,12 +601,13 @@ filterImports iface decl_spec (Just (want_hiding, import_items)) all_avails -- different parents). See the discussion at occ_env. lookup_ie :: Bool -> IE RdrName -> MaybeErr Message [(IE Name,AvailInfo)] lookup_ie opt_typeFamilies ie - = let bad_ie = Failed (badImportItemErr iface decl_spec ie) + = let bad_ie :: MaybeErr Message a + bad_ie = Failed (badImportItemErr iface decl_spec ie) - lookup_name rdrName = - case lookupOccEnv occ_env (rdrNameOcc rdrName) of - Nothing -> bad_ie - Just n -> return n + lookup_name rdr + | isQual rdr = Failed (qualImportItemErr rdr) + | Just nm <- lookupOccEnv occ_env (rdrNameOcc rdr) = return nm + | otherwise = bad_ie in case ie of IEVar n -> do @@ -671,7 +746,7 @@ gresFromIE decl_spec (L loc ie, avail) mkChildEnv :: [GlobalRdrElt] -> NameEnv [Name] mkChildEnv gres = foldr add emptyNameEnv gres where - add (GRE { gre_name = n, gre_par = ParentIs p }) env = extendNameEnv_C (++) env p [n] + add (GRE { gre_name = n, gre_par = ParentIs p }) env = extendNameEnv_Acc (:) singleton env p n add _ env = env findChildren :: NameEnv [Name] -> Name -> [Name] @@ -691,6 +766,7 @@ type AvailEnv = NameEnv AvailInfo -- Maps a Name to the AvailInfo that contains emptyAvailEnv :: AvailEnv emptyAvailEnv = emptyNameEnv +{- Dead code unitAvailEnv :: AvailInfo -> AvailEnv unitAvailEnv a = unitNameEnv (availName a) a @@ -699,6 +775,7 @@ plusAvailEnv = plusNameEnv_C plusAvail availEnvElts :: AvailEnv -> [AvailInfo] availEnvElts = nameEnvElts +-} addAvail :: AvailEnv -> AvailInfo -> AvailEnv addAvail avails avail = extendNameEnv_C plusAvail avails (availName avail) avail @@ -798,7 +875,6 @@ rnExports explicit_mod exports tcg_dus = tcg_dus tcg_env `plusDU` usesOnly (availsToNameSet final_avails) }) } - exports_from_avail :: Maybe [LIE RdrName] -- Nothing => no explicit export list -> GlobalRdrEnv @@ -841,16 +917,23 @@ exports_from_avail (Just rdr_items) rdr_env imports this_mod | otherwise = do { implicit_prelude <- doptM Opt_ImplicitPrelude - ; let { exportValid = (mod `elem` imported_modules) + ; warnDodgyExports <- doptM Opt_WarnDodgyExports + ; let { exportValid = (mod `elem` imported_modules) || (moduleName this_mod == mod) - ; gres = filter (isModuleExported implicit_prelude mod) - (globalRdrEnvElts rdr_env) - } + ; gres = filter (isModuleExported implicit_prelude mod) + (globalRdrEnvElts rdr_env) + ; names = map gre_name gres + } - ; checkErr exportValid (moduleNotImported mod) - ; warnIf (exportValid && null gres) (nullModuleExport mod) + ; checkErr exportValid (moduleNotImported mod) + ; warnIf (warnDodgyExports && exportValid && null gres) (nullModuleExport mod) - ; occs' <- check_occs ie occs (map gre_name gres) + ; addUsedRdrNames (concat [ [mkRdrQual mod occ, mkRdrUnqual occ] + | occ <- map nameOccName names ]) + -- The qualified and unqualified version of all of + -- these names are, in effect, used by this export + + ; occs' <- check_occs ie occs names -- This check_occs not only finds conflicts -- between this item and others, but also -- internally within this item. That is, if @@ -893,12 +976,18 @@ exports_from_avail (Just rdr_items) rdr_env imports this_mod lookup_ie ie@(IEThingAll rdr) = do name <- lookupGlobalOccRn rdr let kids = findChildren kids_env name - when (null kids) - (if (isTyConName name) then addWarn (dodgyExportWarn name) - -- This occurs when you export T(..), but - -- only import T abstractly, or T is a synonym. - else addErr (exportItemErr ie)) - + mkKidRdrName = case isQual_maybe rdr of + Nothing -> mkRdrUnqual + Just (modName, _) -> mkRdrQual modName + addUsedRdrNames $ map (mkKidRdrName . nameOccName) kids + warnDodgyExports <- doptM Opt_WarnDodgyExports + when (null kids) $ + if isTyConName name + then when warnDodgyExports $ addWarn (dodgyExportWarn name) + else -- This occurs when you export T(..), but + -- only import T abstractly, or T is a synonym. + addErr (exportItemErr ie) + return (IEThingAll name, AvailTC name (name:kids)) lookup_ie ie@(IEThingWith rdr sub_rdrs) @@ -1083,13 +1172,10 @@ this is, after all, wired-in stuff. \begin{code} reportUnusedNames :: Maybe [LIE RdrName] -- Export list -> TcGblEnv -> RnM () -reportUnusedNames export_decls gbl_env +reportUnusedNames _export_decls gbl_env = do { traceRn ((text "RUN") <+> (ppr (tcg_dus gbl_env))) - ; warnUnusedTopBinds unused_locals - ; warnUnusedModules unused_imp_mods - ; warnUnusedImports unused_imports - ; warnDuplicateImports defined_and_used - ; printMinimalImports minimal_imports } + ; warnUnusedImportDecls gbl_env + ; warnUnusedTopBinds unused_locals } where used_names :: NameSet used_names = findUses (tcg_dus gbl_env) emptyNameSet @@ -1103,8 +1189,8 @@ reportUnusedNames export_decls gbl_env -- Note that defined_and_used, defined_but_not_used -- are both [GRE]; that's why we need defined_and_used -- rather than just used_names - defined_and_used, defined_but_not_used :: [GlobalRdrElt] - (defined_and_used, defined_but_not_used) + _defined_and_used, defined_but_not_used :: [GlobalRdrElt] + (_defined_and_used, defined_but_not_used) = partition (gre_is_used used_names) defined_names kids_env = mkChildEnv defined_names @@ -1125,220 +1211,174 @@ reportUnusedNames export_decls gbl_env unused_locals = filter is_unused_local defined_but_not_used is_unused_local :: GlobalRdrElt -> Bool is_unused_local gre = isLocalGRE gre && isExternalName (gre_name gre) - - unused_imports :: [GlobalRdrElt] - unused_imports = mapCatMaybes unused_imp defined_but_not_used - unused_imp :: GlobalRdrElt -> Maybe GlobalRdrElt -- Result has trimmed Imported provenances - unused_imp (GRE {gre_prov = LocalDef}) = Nothing - unused_imp gre@(GRE {gre_prov = Imported imp_specs}) - | null trimmed_specs = Nothing - | otherwise = Just (gre {gre_prov = Imported trimmed_specs}) - where - trimmed_specs = filter report_if_unused imp_specs - - -- 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 ModuleName AvailEnv - 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 - -- even if we import nothing explicitly. - -- It's not necessarily redundant to import such modules. Consider - -- module This - -- import M () - -- - -- The import M() is not *necessarily* redundant, even if - -- we suck in no instance decls from M (e.g. it contains - -- no instance decls, or This contains no code). It may be - -- that we import M solely to ensure that M's orphan instance - -- decls (or those in its imports) are visible to people who - -- import This. Sigh. - -- There's really no good way to detect this, so the error message - -- in RnEnv.warnUnusedModules is weakened instead - - -- We've carefully preserved the provenance so that we can - -- construct minimal imports that import the name by (one of) - -- the same route(s) as the programmer originally did. - add_name gre@(GRE {gre_prov = Imported (imp_spec:_)}) acc - = addToFM_C plusAvailEnv acc - (importSpecModule imp_spec) (unitAvailEnv (greAvail gre)) - add_name _ acc = acc -- Local - - -- 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 +\end{code} + +%********************************************************* +%* * + Unused imports +%* * +%********************************************************* + +This code finds which import declarations are unused. The +specification and implementation notes are here: + http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/UnusedImports + +\begin{code} +type ImportDeclUsage + = ( LImportDecl Name -- The import declaration + , [AvailInfo] -- What *is* used (normalised) + , [Name] ) -- What is imported but *not* used +\end{code} + +\begin{code} +warnUnusedImportDecls :: TcGblEnv -> RnM () +warnUnusedImportDecls gbl_env + = do { uses <- readMutVar (tcg_used_rdrnames gbl_env) + ; let imports = filter explicit_import (tcg_rn_imports gbl_env) + rdr_env = tcg_rdr_env gbl_env + + ; let usage :: [ImportDeclUsage] + usage = findImportUsage imports rdr_env (Set.elems uses) + + ; ifOptM Opt_WarnUnusedImports $ + mapM_ warnUnusedImport usage + + ; ifOptM Opt_D_dump_minimal_imports $ + printMinimalImports usage } + where + explicit_import (L loc _) = isGoodSrcSpan loc + -- Filter out the implicit Prelude import + -- which we do not want to bleat about +\end{code} - add_inst_mod (mod, _) acc - | mod_name `elemFM` acc = acc -- We import something already - | otherwise = addToFM acc mod_name emptyAvailEnv +\begin{code} +findImportUsage :: [LImportDecl Name] + -> GlobalRdrEnv + -> [RdrName] + -> [ImportDeclUsage] + +type ImportMap = Map SrcLoc [AvailInfo] + -- The intermediate data struture 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 start + -- of a particular 'import' declaration + -- + -- The AvailInfos are the things imported from that decl + -- (just a list, not normalised) + +findImportUsage imports rdr_env rdrs + = map unused_decl imports + where + import_usage :: ImportMap + import_usage = foldr add_rdr Map.empty rdrs + + unused_decl decl@(L loc (ImportDecl { ideclHiding = imps })) + = (decl, nubAvails used_avails, unused_imps) where - mod_name = moduleName mod - -- Add an empty collection of imports for a module - -- from which we have sucked only instance decls - - imports = tcg_imports gbl_env - - direct_import_mods :: [(Module, [(ModuleName, Bool, SrcSpan)])] - -- See the type of the imp_mods for this triple - direct_import_mods = fmToList (imp_mods imports) - - -- unused_imp_mods are the directly-imported modules - -- 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: this code is generally buggy - unused_imp_mods :: [(ModuleName, SrcSpan)] - unused_imp_mods = [(mod_name,loc) - | (mod, xs) <- direct_import_mods, - (_, no_imp, loc) <- xs, - let mod_name = moduleName mod, - not (mod_name `elemFM` minimal_imports1), - moduleName mod /= pRELUDE_NAME, - -- XXX not really correct, but we don't want - -- to generate warnings when compiling against - -- a compat version of base. - not no_imp] - -- The not no_imp part is not to complain about - -- import M (), which is an idiom for importing - -- instance declarations - - module_unused :: ModuleName -> Bool - module_unused mod = any (((==) mod) . fst) unused_imp_mods - - report_if_unused :: ImportSpec -> Bool - -- Do we want to report this as an unused import? - report_if_unused (ImpSpec {is_decl = d, is_item = i}) - = not (module_unused (is_mod d)) -- Not if we've already said entire import is unused - && isExplicitItem i -- Only if the import was explicit + used_avails = Map.lookup (srcSpanStart loc) import_usage `orElse` [] + used_names = availsToNameSet used_avails + + unused_imps = case imps of + Just (False, imp_ies) -> nameSetToList unused_imps + where + imp_names = mkNameSet (concatMap (ieNames . unLoc) imp_ies) + unused_imps = imp_names `minusNameSet` used_names + + _other -> [] -- No explicit import list => no unused-name list ---------------------- -warnDuplicateImports :: [GlobalRdrElt] -> RnM () --- Given the GREs for names that are used, figure out which imports --- could be omitted without changing the top-level environment. --- --- NB: Given import Foo( T ) --- import qualified Foo --- we do not report a duplicate import, even though Foo.T is brought --- into scope by both, because there's nothing you can *omit* without --- changing the top-level environment. So we complain only if it's --- explicitly named in both imports or neither. --- --- Furthermore, we complain about Foo.T only if --- there is no complaint about (unqualified) T - -warnDuplicateImports gres - = ifOptM Opt_WarnUnusedImports $ - sequence_ [ warn name pr - | GRE { gre_name = name, gre_prov = Imported imps } <- gres - , pr <- redundants imps ] + add_rdr :: RdrName -> ImportMap -> ImportMap + add_rdr rdr iu + = case lookupGRE_RdrName rdr rdr_env of + [gre] | Imported imps <- gre_prov gre + -> add_imp gre (bestImport imps) iu + _other -> iu + + add_imp :: GlobalRdrElt -> ImportSpec -> ImportMap -> ImportMap + add_imp gre (ImpSpec { is_decl = imp_decl_spec }) iu + = Map.insertWith add decl_loc [avail] iu + where + add _ avails = avail : avails -- add is really just a specialised (++) + decl_loc = srcSpanStart (is_dloc imp_decl_spec) + name = gre_name gre + avail = case gre_par gre of + ParentIs p -> AvailTC p [p,name] + NoParent | isTyConName name -> AvailTC name [name] + | otherwise -> Avail name + -- If you use (+) from Num, then for this purpose we want + -- to say that Num is used as well. That is why in the + -- ParentIs case we have [p,name] in the ParentIs case + +bestImport :: [ImportSpec] -> ImportSpec +bestImport iss + = case partition isImpAll iss of + ([], imp_somes) -> textuallyFirst imp_somes + (imp_alls, _) -> textuallyFirst imp_alls + +textuallyFirst :: [ImportSpec] -> ImportSpec +textuallyFirst iss = case sortWith (is_dloc . is_decl) iss of + [] -> pprPanic "textuallyFirst" (ppr iss) + (is:_) -> is + +isImpAll :: ImportSpec -> Bool +isImpAll (ImpSpec { is_item = ImpAll }) = True +isImpAll _other = False +\end{code} + +\begin{code} +warnUnusedImport :: ImportDeclUsage -> RnM () +warnUnusedImport (L loc decl, used, unused) + | Just (False,[]) <- ideclHiding decl + = return () -- Do not warn for 'import M()' + | null used = addWarnAt loc msg1 -- Nothing used; drop entire decl + | null unused = return () -- Everything imported is used; nop + | otherwise = addWarnAt loc msg2 -- Some imports are unused where - warn name (red_imp, cov_imp) - = addWarnAt (importSpecLoc red_imp) - (vcat [ptext (sLit "Redundant import of:") <+> quotes pp_name, - ptext (sLit "It is also") <+> ppr cov_imp]) - where - pp_name | is_qual red_decl = ppr (is_as red_decl) <> dot <> ppr occ - | otherwise = ppr occ - occ = nameOccName name - red_decl = is_decl red_imp - - redundants :: [ImportSpec] -> [(ImportSpec,ImportSpec)] - -- The returned pair is (redundant-import, covering-import) - redundants imps - = [ (red_imp, cov_imp) - | red_imp <- imps - , isExplicitItem (is_item red_imp) - -- Complain only about redundant imports - -- mentioned explicitly by the user - , cov_imp <- take 1 (filter (covers red_imp) imps) ] - -- The 'take 1' picks the first offending group - -- for this particular name - - -- "red_imp" is a putative redundant import - -- "cov_imp" potentially covers it - -- This test decides whether red_imp could be dropped - -- - -- NOTE: currently the test does not warn about - -- import M( x ) - -- import N( x ) - -- even if the same underlying 'x' is involved, because dropping - -- either import would change the qualified names in scope (M.x, N.x) - -- But if the qualified names aren't used, the import is indeed redundant - -- Sadly we don't know that. Oh well. - covers red_imp@(ImpSpec { is_decl = red_decl }) - cov_imp@(ImpSpec { is_decl = cov_decl, is_item = cov_item }) - | red_loc == cov_loc - = False -- Ignore diagonal elements - | not (is_as red_decl == is_as cov_decl) - = False -- They bring into scope different qualified names - | not (is_qual red_decl) && is_qual cov_decl - = False -- Covering one doesn't bring unqualified name into scope - | otherwise - = not (isExplicitItem cov_item) -- Redundant one is selective and covering one isn't - || red_later -- or both are explicit; tie-break using red_later -{- - | red_selective - = not cov_selective -- Redundant one is selective and covering one isn't - || red_later -- Both are explicit; tie-break using red_later - | otherwise - = not cov_selective -- Neither import is selective - && (is_mod red_decl == is_mod cov_decl) -- They import the same module - && red_later -- Tie-break --} - where - red_loc = importSpecLoc red_imp - cov_loc = importSpecLoc cov_imp - red_later = red_loc > cov_loc - --- ToDo: deal with original imports with 'qualified' and 'as M' clauses -printMinimalImports :: FiniteMap ModuleName AvailEnv -- Minimal imports - -> RnM () -printMinimalImports imps - = ifOptM Opt_D_dump_minimal_imports $ do { - - mod_ies <- initIfaceTcRn $ mapM to_ies (fmToList imps) ; - this_mod <- getModule ; - rdr_env <- getGlobalRdrEnv ; - dflags <- getDOpts ; - liftIO $ do h <- openFile (mkFilename this_mod) WriteMode - printForUser h (mkPrintUnqualified dflags rdr_env) - (vcat (map ppr_mod_ie mod_ies)) - } + msg1 = vcat [pp_herald <+> quotes pp_mod <+> pp_not_used, + nest 2 (ptext (sLit "except perhaps to import instances from") + <+> quotes pp_mod), + ptext (sLit "To import instances alone, use:") + <+> ptext (sLit "import") <+> pp_mod <> parens empty ] + msg2 = sep [pp_herald <+> quotes (pprWithCommas ppr unused), + text "from module" <+> quotes pp_mod <+> pp_not_used] + pp_herald = text "The import of" + pp_mod = ppr (unLoc (ideclName decl)) + pp_not_used = text "is redundant" +\end{code} + +To print the minimal imports we walk over the user-supplied import +decls, and simply trim their import lists. NB that + + * We do *not* change the 'qualified' or 'as' parts! + + * We do not disard a decl altogether; we might need instances + from it. Instead we just trim to an empty import list + +\begin{code} +printMinimalImports :: [ImportDeclUsage] -> RnM () +printMinimalImports imports_w_usage + = do { imports' <- mapM mk_minimal imports_w_usage + ; this_mod <- getModule + ; liftIO $ + do { h <- openFile (mkFilename this_mod) WriteMode + ; printForUser h neverQualify (vcat (map ppr imports')) } + -- The neverQualify is important. We are printing Names + -- but they are in the context of an 'import' decl, and + -- we never qualify things inside there + -- E.g. import Blag( f, b ) + -- not import Blag( Blag.f, Blag.g )! + } where mkFilename this_mod = moduleNameString (moduleName this_mod) ++ ".imports" - ppr_mod_ie (mod_name, ies) - | mod_name == moduleName pRELUDE - = empty - | null ies -- Nothing except instances comes from here - = ptext (sLit "import") <+> ppr mod_name <> ptext (sLit "() -- Instances only") - | otherwise - = ptext (sLit "import") <+> ppr mod_name <> - parens (fsep (punctuate comma (map ppr ies))) - to_ies (mod, avail_env) = do ies <- mapM to_ie (availEnvElts avail_env) - return (mod, ies) + mk_minimal (L l decl, used, unused) + | null unused + , Just (False, _) <- ideclHiding decl + = return (L l decl) + | otherwise + = do { ies <- initIfaceTcRn $ mapM to_ie used + ; return (L l (decl { ideclHiding = Just (False, map (L l) ies) })) } to_ie :: AvailInfo -> IfG (IE Name) -- The main trick here is that if we're importing all the constructors @@ -1363,7 +1403,6 @@ printMinimalImports imps n_mod = ASSERT( isExternalName n ) nameModule n \end{code} - %************************************************************************ %* * \subsection{Errors} @@ -1371,6 +1410,11 @@ printMinimalImports imps %************************************************************************ \begin{code} +qualImportItemErr :: RdrName -> SDoc +qualImportItemErr rdr + = hang (ptext (sLit "Illegal qualified name in import item:")) + 2 (ppr rdr) + badImportItemErr :: ModIface -> ImpDeclSpec -> IE RdrName -> SDoc badImportItemErr iface decl_spec ie = sep [ptext (sLit "Module"), quotes (ppr (is_mod decl_spec)), source_import, @@ -1457,14 +1501,18 @@ nullModuleExport :: ModuleName -> SDoc nullModuleExport mod = ptext (sLit "The export item `module") <+> ppr mod <> ptext (sLit "' exports nothing") +missingImportListWarn :: ModuleName -> SDoc +missingImportListWarn mod + = ptext (sLit "The module") <+> quotes (ppr mod) <+> ptext (sLit "does not have an explicit import list") + moduleWarn :: ModuleName -> WarningTxt -> SDoc moduleWarn mod (WarningTxt txt) = sep [ ptext (sLit "Module") <+> quotes (ppr mod) <> ptext (sLit ":"), - nest 4 (ppr txt) ] + nest 2 (vcat (map ppr txt)) ] moduleWarn mod (DeprecatedTxt txt) = sep [ ptext (sLit "Module") <+> quotes (ppr mod) <+> ptext (sLit "is deprecated:"), - nest 4 (ppr txt) ] + nest 2 (vcat (map ppr txt)) ] implicitPreludeWarn :: SDoc implicitPreludeWarn