{- (c) The University of Glasgow 2006 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 -} {-# LANGUAGE CPP #-} {-# LANGUAGE DeriveDataTypeable #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE LambdaCase #-} {-# LANGUAGE PatternSynonyms #-} -- | -- #name_types# -- GHC uses several kinds of name internally: -- -- * 'GHC.Types.Name.Occurrence.OccName': see "GHC.Types.Name.Occurrence#name_types" -- -- * 'GHC.Types.Name.Reader.RdrName' is the type of names that come directly from the parser. They -- have not yet had their scoping and binding resolved by the renamer and can be -- thought of to a first approximation as an 'GHC.Types.Name.Occurrence.OccName' with an optional module -- qualifier -- -- * 'GHC.Types.Name.Name': see "GHC.Types.Name#name_types" -- -- * 'GHC.Types.Id.Id': see "GHC.Types.Id#name_types" -- -- * 'GHC.Types.Var.Var': see "GHC.Types.Var#name_types" module GHC.Types.Name.Reader ( -- * The main type RdrName(..), -- Constructors exported only to GHC.Iface.Binary -- ** Construction mkRdrUnqual, mkRdrQual, mkUnqual, mkVarUnqual, mkQual, mkOrig, nameRdrName, getRdrName, -- ** Destruction rdrNameOcc, rdrNameSpace, demoteRdrName, demoteRdrNameTv, promoteRdrName, isRdrDataCon, isRdrTyVar, isRdrTc, isQual, isQual_maybe, isUnqual, isOrig, isOrig_maybe, isExact, isExact_maybe, isSrcRdrName, -- * Local mapping of 'RdrName' to 'Name.Name' LocalRdrEnv, emptyLocalRdrEnv, extendLocalRdrEnv, extendLocalRdrEnvList, lookupLocalRdrEnv, lookupLocalRdrOcc, elemLocalRdrEnv, inLocalRdrEnvScope, localRdrEnvElts, minusLocalRdrEnv, minusLocalRdrEnvList, -- * Global mapping of 'RdrName' to 'GlobalRdrElt's GlobalRdrEnvX, GlobalRdrEnv, IfGlobalRdrEnv, emptyGlobalRdrEnv, mkGlobalRdrEnv, plusGlobalRdrEnv, extendGlobalRdrEnv, greOccName, pprGlobalRdrEnv, globalRdrEnvElts, -- ** Looking up 'GlobalRdrElt's FieldsOrSelectors(..), filterFieldGREs, allowGRE, LookupGRE(..), lookupGRE, WhichGREs(.., AllRelevantGREs, RelevantGREsFOS), greIsRelevant, LookupChild(..), lookupGRE_Name, lookupGRE_FieldLabel, getGRE_NameQualifier_maybes, transformGREs, pickGREs, pickGREsModExp, -- * GlobalRdrElts availFromGRE, greRdrNames, greSrcSpan, greQualModName, gresToAvailInfo, greDefinitionModule, greDefinitionSrcSpan, greFieldLabel_maybe, -- ** Global 'RdrName' mapping elements: 'GlobalRdrElt', 'Provenance', 'ImportSpec' GlobalRdrEltX(..), GlobalRdrElt, IfGlobalRdrElt, FieldGlobalRdrElt, greName, greNameSpace, greParent, greInfo, forceGlobalRdrEnv, hydrateGlobalRdrEnv, isLocalGRE, isImportedGRE, isRecFldGRE, fieldGREInfo, isDuplicateRecFldGRE, isNoFieldSelectorGRE, isFieldSelectorGRE, unQualOK, qualSpecOK, unQualSpecOK, pprNameProvenance, mkGRE, mkExactGRE, mkLocalGRE, mkLocalVanillaGRE, mkLocalTyConGRE, mkLocalConLikeGRE, mkLocalFieldGREs, gresToNameSet, -- ** Shadowing greClashesWith, shadowNames, -- ** Information attached to a 'GlobalRdrElt' ConLikeName(..), GREInfo(..), RecFieldInfo(..), plusGREInfo, recFieldConLike_maybe, recFieldInfo_maybe, fieldGRE_maybe, fieldGRELabel, -- ** Parent information Parent(..), greParent_maybe, mkParent, availParent, ImportSpec(..), ImpDeclSpec(..), ImpItemSpec(..), importSpecLoc, importSpecModule, isExplicitItem, bestImport, -- * Utils opIsAt ) where import GHC.Prelude import GHC.Data.Bag import GHC.Data.FastString import GHC.Data.Maybe import GHC.Types.Avail import GHC.Types.Basic import GHC.Types.GREInfo import GHC.Types.FieldLabel import GHC.Types.Name import GHC.Types.Name.Env ( NameEnv, nonDetNameEnvElts, emptyNameEnv, extendNameEnv_Acc ) import GHC.Types.Name.Set import GHC.Types.SrcLoc as SrcLoc import GHC.Types.Unique import GHC.Types.Unique.FM import GHC.Types.Unique.Set import GHC.Builtin.Uniques ( isFldNSUnique ) import GHC.Unit.Module import GHC.Utils.Misc as Utils import GHC.Utils.Outputable import GHC.Utils.Panic import Control.DeepSeq import Control.Monad ( guard ) import Data.Data import Data.List ( sort ) import qualified Data.List.NonEmpty as NE import qualified Data.Map.Strict as Map import qualified Data.Semigroup as S import System.IO.Unsafe ( unsafePerformIO ) {- ************************************************************************ * * \subsection{The main data type} * * ************************************************************************ -} -- | Reader Name -- -- Do not use the data constructors of RdrName directly: prefer the family -- of functions that creates them, such as 'mkRdrUnqual' -- -- - Note: A Located RdrName will only have API Annotations if it is a -- compound one, -- e.g. -- -- > `bar` -- > ( ~ ) -- -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnType', -- 'GHC.Parser.Annotation.AnnOpen' @'('@ or @'['@ or @'[:'@, -- 'GHC.Parser.Annotation.AnnClose' @')'@ or @']'@ or @':]'@,, -- 'GHC.Parser.Annotation.AnnBackquote' @'`'@, -- 'GHC.Parser.Annotation.AnnVal' -- 'GHC.Parser.Annotation.AnnTilde', -- For details on above see Note [exact print annotations] in "GHC.Parser.Annotation" data RdrName = Unqual OccName -- ^ Unqualified name -- -- Used for ordinary, unqualified occurrences, e.g. @x@, @y@ or @Foo@. -- Create such a 'RdrName' with 'mkRdrUnqual' | Qual ModuleName OccName -- ^ Qualified name -- -- A qualified name written by the user in -- /source/ code. The module isn't necessarily -- the module where the thing is defined; -- just the one from which it is imported. -- Examples are @Bar.x@, @Bar.y@ or @Bar.Foo@. -- Create such a 'RdrName' with 'mkRdrQual' | Orig Module OccName -- ^ Original name -- -- An original name; the module is the /defining/ module. -- This is used when GHC generates code that will be fed -- into the renamer (e.g. from deriving clauses), but where -- we want to say \"Use Prelude.map dammit\". One of these -- can be created with 'mkOrig' | Exact Name -- ^ Exact name -- -- We know exactly the 'Name'. This is used: -- -- (1) When the parser parses built-in syntax like @[]@ -- and @(,)@, but wants a 'RdrName' from it -- -- (2) By Template Haskell, when TH has generated a unique name -- -- Such a 'RdrName' can be created by using 'getRdrName' on a 'Name' deriving Data {- ************************************************************************ * * \subsection{Simple functions} * * ************************************************************************ -} instance HasOccName RdrName where occName = rdrNameOcc rdrNameOcc :: RdrName -> OccName rdrNameOcc (Qual _ occ) = occ rdrNameOcc (Unqual occ) = occ rdrNameOcc (Orig _ occ) = occ rdrNameOcc (Exact name) = nameOccName name rdrNameSpace :: RdrName -> NameSpace rdrNameSpace = occNameSpace . rdrNameOcc -- demoteRdrName lowers the NameSpace of RdrName. -- See Note [Demotion] in GHC.Rename.Env demoteRdrName :: RdrName -> Maybe RdrName demoteRdrName (Unqual occ) = fmap Unqual (demoteOccName occ) demoteRdrName (Qual m occ) = fmap (Qual m) (demoteOccName occ) demoteRdrName (Orig _ _) = Nothing demoteRdrName (Exact _) = Nothing demoteRdrNameTv :: RdrName -> Maybe RdrName demoteRdrNameTv (Unqual occ) = fmap Unqual (demoteOccTvName occ) demoteRdrNameTv (Qual m occ) = fmap (Qual m) (demoteOccTvName occ) demoteRdrNameTv (Orig _ _) = Nothing demoteRdrNameTv (Exact _) = Nothing -- promoteRdrName promotes the NameSpace of RdrName. -- See Note [Promotion] in GHC.Rename.Env. promoteRdrName :: RdrName -> Maybe RdrName promoteRdrName (Unqual occ) = fmap Unqual (promoteOccName occ) promoteRdrName (Qual m occ) = fmap (Qual m) (promoteOccName occ) promoteRdrName (Orig _ _) = Nothing promoteRdrName (Exact _) = Nothing -- These two are the basic constructors mkRdrUnqual :: OccName -> RdrName mkRdrUnqual occ = Unqual occ mkRdrQual :: ModuleName -> OccName -> RdrName mkRdrQual mod occ = Qual mod occ mkOrig :: Module -> OccName -> RdrName mkOrig mod occ = Orig mod occ --------------- -- These two are used when parsing source files -- They do encode the module and occurrence names mkUnqual :: NameSpace -> FastString -> RdrName mkUnqual sp n = Unqual (mkOccNameFS sp n) mkVarUnqual :: FastString -> RdrName mkVarUnqual n = Unqual (mkVarOccFS n) -- | Make a qualified 'RdrName' in the given namespace and where the 'ModuleName' and -- the 'OccName' are taken from the first and second elements of the tuple respectively mkQual :: NameSpace -> (FastString, FastString) -> RdrName mkQual sp (m, n) = Qual (mkModuleNameFS m) (mkOccNameFS sp n) getRdrName :: NamedThing thing => thing -> RdrName getRdrName name = nameRdrName (getName name) nameRdrName :: Name -> RdrName nameRdrName name = Exact name -- Keep the Name even for Internal names, so that the -- unique is still there for debug printing, particularly -- of Types (which are converted to IfaceTypes before printing) nukeExact :: Name -> RdrName nukeExact n | isExternalName n = Orig (nameModule n) (nameOccName n) | otherwise = Unqual (nameOccName n) isRdrDataCon :: RdrName -> Bool isRdrTyVar :: RdrName -> Bool isRdrTc :: RdrName -> Bool isRdrDataCon rn = isDataOcc (rdrNameOcc rn) isRdrTyVar rn = isTvOcc (rdrNameOcc rn) isRdrTc rn = isTcOcc (rdrNameOcc rn) isSrcRdrName :: RdrName -> Bool isSrcRdrName (Unqual _) = True isSrcRdrName (Qual _ _) = True isSrcRdrName _ = False isUnqual :: RdrName -> Bool isUnqual (Unqual _) = True isUnqual _ = False isQual :: RdrName -> Bool isQual (Qual _ _) = True isQual _ = False isQual_maybe :: RdrName -> Maybe (ModuleName, OccName) isQual_maybe (Qual m n) = Just (m,n) isQual_maybe _ = Nothing isOrig :: RdrName -> Bool isOrig (Orig _ _) = True isOrig _ = False isOrig_maybe :: RdrName -> Maybe (Module, OccName) isOrig_maybe (Orig m n) = Just (m,n) isOrig_maybe _ = Nothing isExact :: RdrName -> Bool isExact (Exact _) = True isExact _ = False isExact_maybe :: RdrName -> Maybe Name isExact_maybe (Exact n) = Just n isExact_maybe _ = Nothing {- ************************************************************************ * * \subsection{Instances} * * ************************************************************************ -} instance Outputable RdrName where ppr (Exact name) = ppr name ppr (Unqual occ) = ppr occ ppr (Qual mod occ) = ppr mod <> dot <> ppr occ ppr (Orig mod occ) = getPprStyle (\sty -> pprModulePrefix sty mod occ <> ppr occ) instance OutputableBndr RdrName where pprBndr _ n | isTvOcc (rdrNameOcc n) = char '@' <> ppr n | otherwise = ppr n pprInfixOcc rdr = pprInfixVar (isSymOcc (rdrNameOcc rdr)) (ppr rdr) pprPrefixOcc rdr | Just name <- isExact_maybe rdr = pprPrefixName name -- pprPrefixName has some special cases, so -- we delegate to them rather than reproduce them | otherwise = pprPrefixVar (isSymOcc (rdrNameOcc rdr)) (ppr rdr) instance Eq RdrName where (Exact n1) == (Exact n2) = n1==n2 -- Convert exact to orig (Exact n1) == r2@(Orig _ _) = nukeExact n1 == r2 r1@(Orig _ _) == (Exact n2) = r1 == nukeExact n2 (Orig m1 o1) == (Orig m2 o2) = m1==m2 && o1==o2 (Qual m1 o1) == (Qual m2 o2) = m1==m2 && o1==o2 (Unqual o1) == (Unqual o2) = o1==o2 _ == _ = False instance Ord RdrName where a <= b = case (a `compare` b) of { LT -> True; EQ -> True; GT -> False } a < b = case (a `compare` b) of { LT -> True; EQ -> False; GT -> False } a >= b = case (a `compare` b) of { LT -> False; EQ -> True; GT -> True } a > b = case (a `compare` b) of { LT -> False; EQ -> False; GT -> True } -- Exact < Unqual < Qual < Orig -- [Note: Apr 2004] We used to use nukeExact to convert Exact to Orig -- before comparing so that Prelude.map == the exact Prelude.map, but -- that meant that we reported duplicates when renaming bindings -- generated by Template Haskell; e.g -- do { n1 <- newName "foo"; n2 <- newName "foo"; -- } -- I think we can do without this conversion compare (Exact n1) (Exact n2) = n1 `compare` n2 compare (Exact _) _ = LT compare (Unqual _) (Exact _) = GT compare (Unqual o1) (Unqual o2) = o1 `compare` o2 compare (Unqual _) _ = LT compare (Qual _ _) (Exact _) = GT compare (Qual _ _) (Unqual _) = GT compare (Qual m1 o1) (Qual m2 o2) = compare o1 o2 S.<> compare m1 m2 compare (Qual _ _) (Orig _ _) = LT compare (Orig m1 o1) (Orig m2 o2) = compare o1 o2 S.<> compare m1 m2 compare (Orig _ _) _ = GT {- ************************************************************************ * * LocalRdrEnv * * ************************************************************************ -} {- Note [LocalRdrEnv] ~~~~~~~~~~~~~~~~~~~~~ The LocalRdrEnv is used to store local bindings (let, where, lambda, case). * It is keyed by OccName, because we never use it for qualified names. * It maps the OccName to a Name. That Name is almost always an Internal Name, but (hackily) it can be External too for top-level pattern bindings. See Note [bindLocalNames for an External name] in GHC.Rename.Pat * We keep the current mapping (lre_env), *and* the set of all Names in scope (lre_in_scope). Reason: see Note [Splicing Exact names] in GHC.Rename.Env. -} -- | Local Reader Environment -- See Note [LocalRdrEnv] data LocalRdrEnv = LRE { lre_env :: OccEnv Name , lre_in_scope :: NameSet } instance Outputable LocalRdrEnv where ppr (LRE {lre_env = env, lre_in_scope = ns}) = hang (text "LocalRdrEnv {") 2 (vcat [ text "env =" <+> pprOccEnv ppr_elt env , text "in_scope =" <+> pprUFM (getUniqSet ns) (braces . pprWithCommas ppr) ] <+> char '}') where ppr_elt name = parens (ppr (nameOccName name)) <+> ppr name -- So we can see if the keys line up correctly emptyLocalRdrEnv :: LocalRdrEnv emptyLocalRdrEnv = LRE { lre_env = emptyOccEnv , lre_in_scope = emptyNameSet } extendLocalRdrEnv :: LocalRdrEnv -> Name -> LocalRdrEnv -- See Note [LocalRdrEnv] extendLocalRdrEnv lre@(LRE { lre_env = env, lre_in_scope = ns }) name = lre { lre_env = extendOccEnv env (nameOccName name) name , lre_in_scope = extendNameSet ns name } extendLocalRdrEnvList :: LocalRdrEnv -> [Name] -> LocalRdrEnv -- See Note [LocalRdrEnv] extendLocalRdrEnvList lre@(LRE { lre_env = env, lre_in_scope = ns }) names = lre { lre_env = extendOccEnvList env [(nameOccName n, n) | n <- names] , lre_in_scope = extendNameSetList ns names } lookupLocalRdrEnv :: LocalRdrEnv -> RdrName -> Maybe Name lookupLocalRdrEnv (LRE { lre_env = env, lre_in_scope = ns }) rdr | Unqual occ <- rdr = lookupOccEnv env occ -- See Note [Local bindings with Exact Names] | Exact name <- rdr , name `elemNameSet` ns = Just name | otherwise = Nothing lookupLocalRdrOcc :: LocalRdrEnv -> OccName -> Maybe Name lookupLocalRdrOcc (LRE { lre_env = env }) occ = lookupOccEnv env occ elemLocalRdrEnv :: RdrName -> LocalRdrEnv -> Bool elemLocalRdrEnv rdr_name (LRE { lre_env = env, lre_in_scope = ns }) = case rdr_name of Unqual occ -> occ `elemOccEnv` env Exact name -> name `elemNameSet` ns -- See Note [Local bindings with Exact Names] Qual {} -> False Orig {} -> False localRdrEnvElts :: LocalRdrEnv -> [Name] localRdrEnvElts (LRE { lre_env = env }) = nonDetOccEnvElts env inLocalRdrEnvScope :: Name -> LocalRdrEnv -> Bool -- This is the point of the NameSet inLocalRdrEnvScope name (LRE { lre_in_scope = ns }) = name `elemNameSet` ns minusLocalRdrEnv :: LocalRdrEnv -> OccEnv a -> LocalRdrEnv minusLocalRdrEnv lre@(LRE { lre_env = env }) occs = lre { lre_env = minusOccEnv env occs } minusLocalRdrEnvList :: LocalRdrEnv -> [OccName] -> LocalRdrEnv minusLocalRdrEnvList lre@(LRE { lre_env = env }) occs = lre { lre_env = delListFromOccEnv env occs } {- Note [Local bindings with Exact Names] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ With Template Haskell we can make local bindings that have Exact Names. Computing shadowing etc may use elemLocalRdrEnv (at least it certainly does so in GHC.Rename.HsType.bindHsQTyVars), so for an Exact Name we must consult the in-scope-name-set. ************************************************************************ * * GlobalRdrEnv * * ************************************************************************ -} -- | Global Reader Environment type GlobalRdrEnv = GlobalRdrEnvX GREInfo -- ^ Keyed by 'OccName'; when looking up a qualified name -- we look up the 'OccName' part, and then check the 'Provenance' -- to see if the appropriate qualification is valid. This -- saves routinely doubling the size of the env by adding both -- qualified and unqualified names to the domain. -- -- The list in the codomain is required because there may be name clashes -- These only get reported on lookup, not on construction -- -- INVARIANT 1: All the members of the list have distinct -- 'gre_name' fields; that is, no duplicate Names -- -- INVARIANT 2: Imported provenance => Name is an ExternalName -- However LocalDefs can have an InternalName. This -- happens only when type-checking a [d| ... |] Template -- Haskell quotation; see this note in GHC.Rename.Names -- Note [Top-level Names in Template Haskell decl quotes] -- -- INVARIANT 3: If the GlobalRdrEnv maps [occ -> gre], then -- greOccName gre = occ -- | A 'GlobalRdrEnv' in which the 'GlobalRdrElt's don't have any 'GREInfo' -- attached to them. This is useful to avoid space leaks, see Note [IfGlobalRdrEnv]. type IfGlobalRdrEnv = GlobalRdrEnvX () -- | Parametrises 'GlobalRdrEnv' over the presence or absence of 'GREInfo'. -- -- See Note [IfGlobalRdrEnv]. type GlobalRdrEnvX info = OccEnv [GlobalRdrEltX info] -- | Global Reader Element -- -- Something in scope in the renamer; usually a member of the 'GlobalRdrEnv'. -- See Note [GlobalRdrElt provenance]. type GlobalRdrElt = GlobalRdrEltX GREInfo -- | A 'GlobalRdrElt' in which we stripped out the 'GREInfo' field, -- in order to avoid space leaks. -- -- See Note [IfGlobalRdrEnv]. type IfGlobalRdrElt = GlobalRdrEltX () -- | Global Reader Element -- -- Something in scope in the renamer; usually a member of the 'GlobalRdrEnv'. -- See Note [GlobalRdrElt provenance]. -- -- Why do we parametrise over the 'gre_info' field? See Note [IfGlobalRdrEnv]. data GlobalRdrEltX info = GRE { gre_name :: !Name , gre_par :: !Parent -- ^ See Note [Parents] , gre_lcl :: !Bool -- ^ True <=> the thing was defined locally , gre_imp :: !(Bag ImportSpec) -- ^ In scope through these imports -- See Note [GlobalRdrElt provenance] for the relation between gre_lcl and gre_imp. , gre_info :: info -- ^ Information the renamer knows about this particular 'Name'. -- -- Careful about forcing this field! Forcing it can trigger -- the loading of interface files. -- -- Note [Retrieving the GREInfo from interfaces] in GHC.Types.GREInfo. } deriving (Data) {- Note [IfGlobalRdrEnv] ~~~~~~~~~~~~~~~~~~~~~~~~ Information pertinent to the renamer about a 'Name' is stored in the fields of 'GlobalRdrElt'. The 'gre_info' field, described in Note [GREInfo] in GHC.Types.GREInfo, is a bit special: as Note [Retrieving the GREInfo from interfaces] in GHC.Types.GREInfo describes, for imported 'Name's it is usually obtained by a look up in a type environment, and forcing can cause the interface file for the module defining the 'Name' to be loaded. As described in Note [Forcing GREInfo] in GHC.Types.GREInfo, keeping it a thunk can cause space leaks, while forcing it can cause extra work to be done. So it's best to discard it when we don't need it, for example when we are about to store it in a 'ModIface'. We thus parametrise 'GlobalRdrElt' (and 'GlobalRdrEnv') over the presence or absence of the 'GREInfo' field. - When we are about to stash the 'GlobalRdrElt' in a long-lived data structure, e.g. a 'ModIface', we force it by setting all the 'GREInfo' fields to '()'. See 'forceGlobalRdrEnv'. - To go back the other way, we use 'hydrateGlobalRdrEnv', which sets the 'gre_info' fields back to lazy lookups. This parametrisation also helps ensure that we don't accidentally force the GREInfo field (which can cause unnecessary loading of interface files). In particular, the 'lookupGRE' function is statically guaranteed to not consult the 'GREInfo' field when using 'SameNameSpace', which is important as we sometimes need to use this function with an 'IfaceGlobalRdrEnv' in which the 'GREInfo' fields have been stripped. -} -- | A 'FieldGlobalRdrElt' is a 'GlobalRdrElt' -- in which the 'gre_info' field is 'IAmRecField'. type FieldGlobalRdrElt = GlobalRdrElt greName :: GlobalRdrEltX info -> Name greName = gre_name greNameSpace :: GlobalRdrEltX info -> NameSpace greNameSpace = nameNameSpace . greName greParent :: GlobalRdrEltX info -> Parent greParent = gre_par greInfo :: GlobalRdrElt -> GREInfo greInfo = gre_info instance NFData IfGlobalRdrElt where rnf !_ = () -- | See Note [Parents] data Parent = NoParent | ParentIs { par_is :: Name } deriving (Eq, Data) instance Outputable Parent where ppr NoParent = empty ppr (ParentIs n) = text "parent:" <> ppr n plusParent :: Parent -> Parent -> Parent -- See Note [Combining parents] plusParent p1@(ParentIs _) p2 = hasParent p1 p2 plusParent p1 p2@(ParentIs _) = hasParent p2 p1 plusParent NoParent NoParent = NoParent hasParent :: Parent -> Parent -> Parent #if defined(DEBUG) hasParent p NoParent = p hasParent p p' | p /= p' = pprPanic "hasParent" (ppr p <+> ppr p') -- Parents should agree #endif hasParent p _ = p {- Note [GlobalRdrElt provenance] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The gre_lcl and gre_imp fields of a GlobalRdrElt describe its "provenance", i.e. how the Name came to be in scope. It can be in scope in one of the following three ways: A. The Name was locally bound, in the current module. gre_lcl = True The renamer adds this Name to the GlobalRdrEnv after renaming the binding. See the calls to "extendGlobalRdrEnvRn" in GHC.Rename.Module.rnSrcDecls. B. The Name was imported gre_imp = Just imps <=> brought into scope by the imports "imps" The renamer adds this Name to the GlobalRdrEnv after processing the imports. See GHC.Rename.Names.filterImports and GHC.Tc.Module.tcRnImports. C. We followed an exact reference (i.e. an Exact or Orig RdrName) gre_lcl = False, gre_imp = Nothing In this case, we directly fetch a Name and its GREInfo from direct reference. We don't add it to the GlobalRdrEnv. See "GHC.Rename.Env.lookupExactOrOrig". It is just about possible to have *both* gre_lcl = True and gre_imp = Just imps. This can happen with module loops: a Name is defined locally in A, and also brought into scope by importing a module that SOURCE-imported A. Example (#7672): A.hs-boot module A where data T B.hs module B(Decl.T) where import {-# SOURCE #-} qualified A as Decl A.hs module A where import qualified B data T = Z | S B.T In A.hs, 'T' is locally bound, *and* imported as B.T. Note [Parents] ~~~~~~~~~~~~~~~~~ The children of a Name are the things that are abbreviated by the ".." notation in export lists. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Parent Children ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ data T Data constructors Record-field ids data family T Data constructors and record-field ids of all visible data instances of T class C Class operations Associated type constructors ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Constructor Meaning ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NoParent Not bundled with a type constructor. ParentIs n Bundled with the type constructor corresponding to n. Pattern synonym constructors (and their record fields, if any) are unusual: their gre_par is NoParent in the module in which they are defined. However, a pattern synonym can be bundled with a type constructor on export, in which case whenever the pattern synonym is imported the gre_par will be ParentIs. Thus the gre_name and gre_par fields are independent, because a normal datatype introduces FieldGlobalRdrElts using ParentIs, but a record pattern synonym can introduce FieldGlobalRdrElts that use NoParent. (In the past we represented fields using an additional constructor of the Parent type, which could not adequately represent this situation.) See also Note [Representing pattern synonym fields in AvailInfo] in GHC.Types.Avail. Note [Combining parents] ~~~~~~~~~~~~~~~~~~~~~~~~ With an associated type we might have module M where class C a where data T a op :: T a -> a instance C Int where data T Int = TInt instance C Bool where data T Bool = TBool Then: C is the parent of T T is the parent of TInt and TBool So: in an export list C(..) is short for C( op, T ) T(..) is short for T( TInt, TBool ) Module M exports everything, so its exports will be AvailTC C [C,T,op] AvailTC T [T,TInt,TBool] On import we convert to GlobalRdrElt and then combine those. For T that will mean we have one GRE with Parent C one GRE with NoParent That's why plusParent picks the "best" case. -} mkGRE :: (Name -> Maybe ImportSpec) -> GREInfo -> Parent -> Name -> GlobalRdrElt mkGRE prov_fn info par n = case prov_fn n of -- Nothing => bound locally -- Just is => imported from 'is' Nothing -> GRE { gre_name = n, gre_par = par , gre_lcl = True, gre_imp = emptyBag , gre_info = info } Just is -> GRE { gre_name = n, gre_par = par , gre_lcl = False, gre_imp = unitBag is , gre_info = info } mkExactGRE :: Name -> GREInfo -> GlobalRdrElt mkExactGRE nm info = GRE { gre_name = nm, gre_par = NoParent , gre_lcl = False, gre_imp = emptyBag , gre_info = info } mkLocalGRE :: GREInfo -> Parent -> Name -> GlobalRdrElt mkLocalGRE = mkGRE (const Nothing) mkLocalVanillaGRE :: Parent -> Name -> GlobalRdrElt mkLocalVanillaGRE = mkLocalGRE Vanilla -- | Create a local 'GlobalRdrElt' for a 'TyCon'. mkLocalTyConGRE :: TyConFlavour Name -> Name -> GlobalRdrElt mkLocalTyConGRE flav nm = mkLocalGRE (IAmTyCon flav) par nm where par = case tyConFlavourAssoc_maybe flav of Nothing -> NoParent Just p -> ParentIs p mkLocalConLikeGRE :: Parent -> (ConLikeName, ConInfo) -> GlobalRdrElt mkLocalConLikeGRE p (con_nm, con_info) = mkLocalGRE (IAmConLike con_info) p (conLikeName_Name con_nm ) mkLocalFieldGREs :: Parent -> [(ConLikeName, ConInfo)] -> [GlobalRdrElt] mkLocalFieldGREs p cons = [ mkLocalGRE (IAmRecField fld_info) p fld_nm | (S.Arg fld_nm fl, fl_cons) <- flds , let fld_info = RecFieldInfo { recFieldLabel = fl , recFieldCons = fl_cons } ] where -- We are given a map taking a constructor to its fields, but we want -- a map taking a field to the contructors which have it. -- We thus need to convert [(Con, [Field])] into [(Field, [Con])]. flds = Map.toList $ Map.fromListWith unionUniqSets [ (S.Arg (flSelector fl) fl, unitUniqSet con) | (con, con_info) <- cons , ConHasRecordFields fls <- [con_info] , fl <- NE.toList fls ] instance HasOccName (GlobalRdrEltX info) where occName = greOccName greOccName :: GlobalRdrEltX info -> OccName greOccName ( GRE { gre_name = nm } ) = nameOccName nm -- | The SrcSpan of the name pointed to by the GRE. greDefinitionSrcSpan :: GlobalRdrEltX info -> SrcSpan greDefinitionSrcSpan = nameSrcSpan . greName -- | The module in which the name pointed to by the GRE is defined. greDefinitionModule :: GlobalRdrEltX info -> Maybe Module greDefinitionModule = nameModule_maybe . greName greQualModName :: Outputable info => GlobalRdrEltX info -> ModuleName -- Get a suitable module qualifier for the GRE -- (used in mkPrintUnqualified) -- Precondition: the gre_name is always External greQualModName gre@(GRE { gre_lcl = lcl, gre_imp = iss }) | lcl, Just mod <- greDefinitionModule gre = moduleName mod | Just is <- headMaybe iss = is_as (is_decl is) | otherwise = pprPanic "greQualModName" (ppr gre) greRdrNames :: GlobalRdrEltX info -> [RdrName] greRdrNames gre@GRE{ gre_lcl = lcl, gre_imp = iss } = bagToList $ (if lcl then unitBag unqual else emptyBag) `unionBags` concatMapBag do_spec (mapBag is_decl iss) where occ = greOccName gre unqual = Unqual occ do_spec decl_spec | is_qual decl_spec = unitBag qual | otherwise = listToBag [unqual,qual] where qual = Qual (is_as decl_spec) occ -- the SrcSpan that pprNameProvenance prints out depends on whether -- the Name is defined locally or not: for a local definition the -- definition site is used, otherwise the location of the import -- declaration. We want to sort the export locations in -- exportClashErr by this SrcSpan, we need to extract it: greSrcSpan :: Outputable info => GlobalRdrEltX info -> SrcSpan greSrcSpan gre@(GRE { gre_lcl = lcl, gre_imp = iss } ) | lcl = greDefinitionSrcSpan gre | Just is <- headMaybe iss = is_dloc (is_decl is) | otherwise = pprPanic "greSrcSpan" (ppr gre) mkParent :: Name -> AvailInfo -> Parent mkParent _ (Avail _) = NoParent mkParent n (AvailTC m _) | n == m = NoParent | otherwise = ParentIs m availParent :: AvailInfo -> Parent availParent (AvailTC m _) = ParentIs m availParent (Avail {}) = NoParent greParent_maybe :: GlobalRdrEltX info -> Maybe Name greParent_maybe gre = case gre_par gre of NoParent -> Nothing ParentIs n -> Just n gresToNameSet :: [GlobalRdrEltX info] -> NameSet gresToNameSet gres = foldr add emptyNameSet gres where add gre set = extendNameSet set (greName gre) -- | Takes a list of distinct GREs and folds them -- into AvailInfos. This is more efficient than mapping each individual -- GRE to an AvailInfo and then folding using `plusAvail`, but needs the -- uniqueness assumption. gresToAvailInfo :: forall info. [GlobalRdrEltX info] -> [AvailInfo] gresToAvailInfo gres = nonDetNameEnvElts avail_env where avail_env :: NameEnv AvailInfo -- Keyed by the parent (avail_env, _) = foldl' add (emptyNameEnv, emptyNameSet) gres add :: (NameEnv AvailInfo, NameSet) -> GlobalRdrEltX info -> (NameEnv AvailInfo, NameSet) add (env, done) gre | name `elemNameSet` done = (env, done) -- Don't insert twice into the AvailInfo | otherwise = ( extendNameEnv_Acc comb availFromGRE env key gre , done `extendNameSet` name ) where name = greName gre key = case greParent_maybe gre of Just parent -> parent Nothing -> greName gre -- We want to insert the child `k` into a list of children but -- need to maintain the invariant that the parent is first. -- -- We also use the invariant that `k` is not already in `ns`. insertChildIntoChildren :: Name -> [Name] -> Name -> [Name] insertChildIntoChildren _ [] k = [k] insertChildIntoChildren p (n:ns) k | p == k = k:n:ns | otherwise = n:k:ns comb :: GlobalRdrEltX info -> AvailInfo -> AvailInfo comb _ (Avail n) = Avail n -- Duplicated name, should not happen comb gre (AvailTC m ns) = case gre_par gre of NoParent -> AvailTC m (greName gre:ns) -- Not sure this ever happens ParentIs {} -> AvailTC m (insertChildIntoChildren m ns (greName gre)) availFromGRE :: GlobalRdrEltX info -> AvailInfo availFromGRE (GRE { gre_name = child, gre_par = parent }) = case parent of ParentIs p -> AvailTC p [child] NoParent | isTyConName child -- NB: don't force the GREInfo field unnecessarily. -> AvailTC child [child] | otherwise -> Avail child emptyGlobalRdrEnv :: GlobalRdrEnvX info emptyGlobalRdrEnv = emptyOccEnv globalRdrEnvElts :: GlobalRdrEnvX info -> [GlobalRdrEltX info] globalRdrEnvElts env = nonDetFoldOccEnv (++) [] env -- | Drop all 'GREInfo' fields in a 'GlobalRdrEnv' in order to -- avoid space leaks. -- -- See Note [Forcing GREInfo] in GHC.Types.GREInfo. forceGlobalRdrEnv :: GlobalRdrEnvX info -> IfGlobalRdrEnv forceGlobalRdrEnv rdrs = strictMapOccEnv (strictMap (\ gre -> gre { gre_info = () })) rdrs -- | Hydrate a previously dehydrated 'GlobalRdrEnv', -- by (lazily!) looking up the 'GREInfo' using the provided function. -- -- See Note [Forcing GREInfo] in GHC.Types.GREInfo. hydrateGlobalRdrEnv :: forall info noInfo . (Name -> IO info) -> GlobalRdrEnvX noInfo -> GlobalRdrEnvX info hydrateGlobalRdrEnv f = mapOccEnv (fmap g) where g gre = gre { gre_info = unsafePerformIO $ f (greName gre) } -- NB: use unsafePerformIO to delay the lookup until it is forced. -- See also 'GHC.Rename.Env.lookupGREInfo'. instance Outputable info => Outputable (GlobalRdrEltX info) where ppr gre = hang (ppr (greName gre) <+> ppr (gre_par gre) <+> ppr (gre_info gre)) 2 (pprNameProvenance gre) pprGlobalRdrEnv :: Bool -> GlobalRdrEnv -> SDoc pprGlobalRdrEnv locals_only env = vcat [ text "GlobalRdrEnv" <+> ppWhen locals_only (text "(locals only)") <+> lbrace , nest 2 (vcat [ pp (remove_locals gre_list) | gre_list <- nonDetOccEnvElts env ] <+> rbrace) ] where remove_locals gres | locals_only = filter isLocalGRE gres | otherwise = gres pp [] = empty pp gres@(gre:_) = hang (ppr occ <> colon) 2 (vcat (map ppr gres)) where occ = nameOccName (greName gre) {- Note [NoFieldSelectors] ~~~~~~~~~~~~~~~~~~~~~~~ The NoFieldSelectors extension allows record fields to be defined without bringing the corresponding selector functions into scope. However, such fields may still be used in contexts such as record construction, pattern matching or update. This requires us to distinguish contexts in which selectors are required from those in which any field may be used. For example: {-# LANGUAGE NoFieldSelectors #-} module M (T(foo), foo) where -- T(foo) refers to the field, -- unadorned foo to the value binding data T = MkT { foo :: Int } foo = () bar = foo -- refers to the value binding, field ignored module N where import M (T(..)) baz = MkT { foo = 3 } -- refers to the field oops = foo -- an error: the field is in scope but the value binding is not Each 'FieldLabel' indicates (in the 'flHasFieldSelector' field) whether the FieldSelectors extension was enabled in the defining module. This allows them to be filtered out by 'filterFieldGREs'. Even when NoFieldSelectors is in use, we still generate selector functions internally. For example, the expression getField @"foo" t or (with dot-notation) t.foo extracts the `foo` field of t::T, and hence needs the selector function (see Note [HasField instances] in GHC.Tc.Instance.Class). In many of the name lookup functions in this module we pass a FieldsOrSelectors value, indicating what we are looking for: * WantNormal: fields are in scope only if they have an accompanying selector function, e.g. we are looking up a variable in an expression (lookupExprOccRn). * WantBoth: any name or field will do, regardless of whether the selector function is available, e.g. record updates (lookupRecUpdFields) with NoDisambiguateRecordFields. * WantField: any field will do, regardless of whether the selector function is available, but ignoring any non-field names, e.g. record updates (lookupRecUpdFields with DisambiguateRecordFields. ----------------------------------------------------------------------------------- Context FieldsOrSelectors ----------------------------------------------------------------------------------- Record construction/pattern match WantField, but unless DisambiguateRecordFields e.g. MkT { foo = 3 } is in effect, also look up using WantBoth Record update, e.g. e { foo = 3 } to report when a non-field clashes with a field. :info in GHCi WantBoth Variable occurrence in expression WantNormal Type variable, data constructor Pretty much everything else ----------------------------------------------------------------------------------- -} fieldGRE_maybe :: GlobalRdrElt -> Maybe FieldGlobalRdrElt fieldGRE_maybe gre = do guard (isRecFldGRE gre) return gre fieldGRELabel :: HasDebugCallStack => FieldGlobalRdrElt -> FieldLabel fieldGRELabel = recFieldLabel . fieldGREInfo fieldGREInfo :: HasDebugCallStack => FieldGlobalRdrElt -> RecFieldInfo fieldGREInfo gre = assertPpr (isRecFldGRE gre) (ppr gre) $ case greInfo gre of IAmRecField info -> info info -> pprPanic "fieldGREInfo" $ vcat [ text "gre_name:" <+> ppr (greName gre) , text "info:" <+> ppr info ] recFieldConLike_maybe :: HasDebugCallStack => GlobalRdrElt -> Maybe ConInfo recFieldConLike_maybe gre = case greInfo gre of IAmConLike info -> Just info _ -> Nothing recFieldInfo_maybe :: HasDebugCallStack => GlobalRdrElt -> Maybe RecFieldInfo recFieldInfo_maybe gre = case greInfo gre of IAmRecField info -> assertPpr (isRecFldGRE gre) (ppr gre) $ Just info _ -> Nothing -- | When looking up GREs, we may or may not want to include fields that were -- defined in modules with @NoFieldSelectors@ enabled. See Note -- [NoFieldSelectors]. data FieldsOrSelectors = WantNormal -- ^ Include normal names, and fields with selectors, but -- ignore fields without selectors. | WantBoth -- ^ Include normal names and all fields (regardless of whether -- they have selectors). | WantField -- ^ Include only fields, with or without selectors, ignoring -- any non-fields in scope. deriving (Eq, Show) filterFieldGREs :: FieldsOrSelectors -> [GlobalRdrElt] -> [GlobalRdrElt] filterFieldGREs WantBoth = id filterFieldGREs fos = filter (allowGRE fos) allowGRE :: FieldsOrSelectors -> GlobalRdrElt -> Bool allowGRE WantBoth _ = True allowGRE WantNormal gre -- NB: we only need to consult the GREInfo for record field GREs, -- to check whether they define field selectors. -- By checking 'isRecFldGRE' first, which only consults the NameSpace, -- we avoid forcing the GREInfo for things that aren't record fields. | isRecFldGRE gre = flHasFieldSelector (fieldGRELabel gre) == FieldSelectors | otherwise = True allowGRE WantField gre = isRecFldGRE gre -- | What should we look up in a 'GlobalRdrEnv'? Should we only look up -- names with the exact same 'OccName', or do we allow different 'NameSpace's? -- -- Depending on the answer, we might need more or less information from the -- 'GlobalRdrEnv', e.g. if we want to include matching record fields we need -- to know if the corresponding record fields define field selectors, for which -- we need to consult the 'GREInfo'. This is why this datatype is a GADT. -- -- See Note [IfGlobalRdrEnv]. data LookupGRE info where -- | Look for this specific 'OccName', with the exact same 'NameSpace', -- in the 'GlobalRdrEnv'. LookupOccName :: OccName -- ^ the 'OccName' to look up -> WhichGREs info -- ^ information about other relevant 'NameSpace's -> LookupGRE info -- | Look up the 'OccName' of this 'RdrName' in the 'GlobalRdrEnv', -- filtering out those whose qualification matches that of the 'RdrName'. -- -- Lookup returns an empty result for 'Exact' or 'Orig' 'RdrName's. LookupRdrName :: RdrName -- ^ the 'RdrName' to look up -> WhichGREs info -- ^ information about other relevant 'NameSpace's -> LookupGRE info -- | Look for 'GRE's with the same unique as the given 'Name' -- in the 'GlobalRdrEnv'. LookupExactName :: { lookupExactName :: Name -- ^ the 'Name' to look up , lookInAllNameSpaces :: Bool -- ^ whether to look in *all* 'NameSpace's, or just -- in the 'NameSpace' of the 'Name' -- See Note [Template Haskell ambiguity] } -> LookupGRE info -- | Look up children 'GlobalRdrElt's with a given 'Parent'. LookupChildren :: OccName -- ^ the 'OccName' to look up -> LookupChild -- ^ information to decide which 'GlobalRdrElt's -- are valid children after looking up -> LookupGRE info -- | How should we look up in a 'GlobalRdrEnv'? -- Which 'NameSpace's are considered relevant for a given lookup? data WhichGREs info where -- | Only consider 'GlobalRdrElt's with the exact 'NameSpace' we look up. SameNameSpace :: WhichGREs info -- | Allow 'GlobalRdrElt's with different 'NameSpace's, e.g. allow looking up -- record fields from the variable 'NameSpace', or looking up a 'TyCon' from -- the data constructor 'NameSpace'. RelevantGREs :: { includeFieldSelectors :: !FieldsOrSelectors -- ^ how should we handle looking up variables? -- -- - should we include record fields defined with @-XNoFieldSelectors@? -- - should we include non-fields? -- -- See Note [NoFieldSelectors]. , lookupVariablesForFields :: !Bool -- ^ when looking up a record field, should we also look up plain variables? , lookupTyConsAsWell :: !Bool -- ^ when looking up a variable, field or data constructor, should we -- also try the type constructor 'NameSpace'? } -> WhichGREs GREInfo -- | Look up as many possibly relevant 'GlobalRdrElt's as possible. pattern AllRelevantGREs :: WhichGREs GREInfo pattern AllRelevantGREs = RelevantGREs { includeFieldSelectors = WantBoth , lookupVariablesForFields = True , lookupTyConsAsWell = True } -- | Look up relevant GREs, taking into account the interaction between the -- variable and field 'NameSpace's as determined by the 'FieldsOrSelector' -- argument. pattern RelevantGREsFOS :: FieldsOrSelectors -> WhichGREs GREInfo pattern RelevantGREsFOS fos <- RelevantGREs { includeFieldSelectors = fos } where RelevantGREsFOS fos = RelevantGREs { includeFieldSelectors = fos , lookupVariablesForFields = fos == WantBoth , lookupTyConsAsWell = False } data LookupChild = LookupChild { wantedParent :: Name -- ^ the parent we are looking up children of , lookupDataConFirst :: Bool -- ^ for type constructors, should we look in the data constructor -- namespace first? , prioritiseParent :: Bool -- ^ should we prioritise getting the right 'Parent'? -- -- - @True@: prioritise getting the right 'Parent' -- - @False@: prioritise getting the right 'NameSpace' -- -- See Note [childGREPriority]. } -- | After looking up something with the given 'NameSpace', is the resulting -- 'GlobalRdrElt' we have obtained relevant, according to the 'RelevantGREs' -- specification of which 'NameSpace's are relevant? greIsRelevant :: WhichGREs GREInfo -- ^ specification of which 'GlobalRdrElt's to consider relevant -> NameSpace -- ^ the 'NameSpace' of the thing we are looking up -> GlobalRdrElt -- ^ the 'GlobalRdrElt' we have looked up, in a -- potentially different 'NameSpace' than we wanted -> Bool greIsRelevant which_gres ns gre | ns == other_ns = True | otherwise = case which_gres of SameNameSpace -> False RelevantGREs { includeFieldSelectors = fos , lookupVariablesForFields = vars_for_flds , lookupTyConsAsWell = tycons_too } | ns == varName -> (isFieldNameSpace other_ns && allowGRE fos gre) || tc_too | isFieldNameSpace ns -> vars_for_flds && ( other_ns == varName || (isFieldNameSpace other_ns && allowGRE fos gre) || tc_too ) | isDataConNameSpace ns -> tc_too | otherwise -> False where tc_too = tycons_too && isTcClsNameSpace other_ns where other_ns = greNameSpace gre {- Note [childGREPriority] ~~~~~~~~~~~~~~~~~~~~~~~~~~ There are currently two places in the compiler where we look up GlobalRdrElts which have a given Parent. These are the two calls to lookupSubBndrOcc_helper: A. Looking up children in an export item, e.g. module M ( T(MkT, D) ) where { data T = MkT; data D = D } B. Looking up binders in a class or instance declaration, e.g. the operator +++ in the fixity declaration: class C a where { type (+++) :: a -> a ->; infixl 6 +++ } (+++) :: Int -> Int -> Int; (+++) = (+) In these two situations, there are two competing metrics for finding the "best" 'GlobalRdrElt' that a particular 'OccName' resolves to: - does the resolved 'GlobalRdrElt' have the correct parent? - does the resolved 'GlobalRdrElt' have the same 'NameSpace' as the 'OccName'? (A) and (B) have competing requirements. For the example of (A) above, we know that the child 'D' of 'T' must live in the data namespace, so we look up the OccName 'OccName DataName "D"' and prioritise the lookup results based on the 'NameSpace'. This means we get an error message of the form: The type constructor 'T' is not the parent of the data constructor 'D'. as opposed to the rather unhelpful and confusing: The type constructor 'T' is not the parent of the type constructor 'D'. See test case T11970. For the example of (B) above, the fixity declaration for +++ lies inside the class, so we should prioritise looking up 'GlobalRdrElt's whose parent is 'C'. Not doing so led to #23664. -} -- | Scoring priority function for looking up children 'GlobalRdrElt'. -- -- We score by 'Parent' and 'NameSpace', with higher priorities having lower -- numbers. Which lexicographic order we use ('Parent' or 'NameSpace' first) -- is determined by the first argument; see Note [childGREPriority]. childGREPriority :: LookupChild -- ^ what kind of child do we want, -- e.g. what should its parent be? -> NameSpace -- ^ what 'NameSpace' are we originally looking in? -> GlobalRdrEltX info -- ^ the result of looking up; it might be in a different -- 'NameSpace', which is used to determine the score -- (in the first component) -> Maybe (Int, Int) childGREPriority (LookupChild { wantedParent = wanted_parent , lookupDataConFirst = try_dc_first , prioritiseParent = par_first }) ns gre = case child_ns_prio $ greNameSpace gre of Nothing -> Nothing Just ns_prio -> let par_prio = parent_prio $ greParent gre in Just $ if par_first then (par_prio, ns_prio) else (ns_prio, par_prio) -- See Note [childGREPriority]. where -- Pick out the possible 'NameSpace's in order of priority. child_ns_prio :: (NameSpace -> Maybe Int) child_ns_prio other_ns | other_ns == ns = Just 0 | isTermVarOrFieldNameSpace ns , isTermVarOrFieldNameSpace other_ns = Just 0 | isValNameSpace varName , other_ns == tcName -- When looking up children, we sometimes want a value name -- to resolve to a type constructor. -- For example, for an infix declaration "infixr 3 +!" or "infix 2 `Fun`" -- inside a class declaration, we want to account for the possibility -- that the identifier refers to an associated type (type constructor -- NameSpace), when otherwise "+!" would be in the term-level variable -- NameSpace, and "Fun" would be in the term-level data constructor -- NameSpace. See tests T10816, T23664, T24037. = Just 1 | ns == tcName , other_ns == dataName , try_dc_first -- try data namespace before type/class namespace? = Just (-1) | otherwise = Nothing parent_prio :: Parent -> Int parent_prio (ParentIs other_parent) | other_parent == wanted_parent = 0 | otherwise = 1 parent_prio NoParent = 0 -- | Look something up in the Global Reader Environment. -- -- The 'LookupGRE' argument specifies what to look up, and in particular -- whether there should there be any lee-way if the 'NameSpace's don't -- exactly match. lookupGRE :: GlobalRdrEnvX info -> LookupGRE info -> [GlobalRdrEltX info] lookupGRE env = \case LookupOccName occ which_gres -> case which_gres of SameNameSpace -> concat $ lookupOccEnv env occ rel@(RelevantGREs{}) -> filter (greIsRelevant rel (occNameSpace occ)) $ concat $ lookupOccEnv_AllNameSpaces env occ LookupRdrName rdr rel -> pickGREs rdr $ lookupGRE env (LookupOccName (rdrNameOcc rdr) rel) LookupExactName { lookupExactName = nm , lookInAllNameSpaces = all_ns } -> [ gre | gre <- lkup, greName gre == nm ] where occ = nameOccName nm lkup | all_ns = concat $ lookupOccEnv_AllNameSpaces env occ | otherwise = fromMaybe [] $ lookupOccEnv env occ LookupChildren occ which_child -> let ns = occNameSpace occ all_gres = concat $ lookupOccEnv_AllNameSpaces env occ in highestPriorityGREs (childGREPriority which_child ns) all_gres -- | Collect the 'GlobalRdrElt's with the highest priority according -- to the given function (lower value <=> higher priority). -- -- This allows us to first look in e.g. the data 'NameSpace', and then fall back -- to the type/class 'NameSpace'. highestPriorityGREs :: forall gre prio . Ord prio => (gre -> Maybe prio) -- ^ priority function -- lower value <=> higher priority -> [gre] -> [gre] highestPriorityGREs priority gres = take_highest_prio $ NE.group $ sort [ S.Arg prio gre | gre <- gres , prio <- maybeToList $ priority gre ] where take_highest_prio :: [NE.NonEmpty (S.Arg prio gre)] -> [gre] take_highest_prio [] = [] take_highest_prio (fs:_) = map (\ (S.Arg _ gre) -> gre) $ NE.toList fs {-# INLINEABLE highestPriorityGREs #-} -- | Look for precisely this 'Name' in the environment, -- in the __same 'NameSpace'__ as the 'Name'. -- -- This tests whether it is in scope, ignoring anything -- else that might be in scope which doesn't have the same 'Unique'. lookupGRE_Name :: Outputable info => GlobalRdrEnvX info -> Name -> Maybe (GlobalRdrEltX info) lookupGRE_Name env name = case lookupGRE env (LookupExactName { lookupExactName = name , lookInAllNameSpaces = False }) of [] -> Nothing [gre] -> Just gre gres -> pprPanic "lookupGRE_Name" (ppr name $$ ppr (nameOccName name) $$ ppr gres) -- See INVARIANT 1 on GlobalRdrEnv -- | Look for a particular record field selector in the environment. lookupGRE_FieldLabel :: GlobalRdrEnv -> FieldLabel -> Maybe FieldGlobalRdrElt lookupGRE_FieldLabel env fl = case lookupGRE_Name env (flSelector fl) of Nothing -> Nothing Just gre -> assertPpr (isRecFldGRE gre) (vcat [ text "lookupGre_FieldLabel:" <+> ppr fl ]) $ Just gre getGRE_NameQualifier_maybes :: GlobalRdrEnv -> Name -> [Maybe [ModuleName]] -- Returns all the qualifiers by which 'x' is in scope -- Nothing means "the unqualified version is in scope" -- [] means the thing is not in scope at all getGRE_NameQualifier_maybes env name = case lookupGRE_Name env name of Just gre -> [qualifier_maybe gre] Nothing -> [] where qualifier_maybe (GRE { gre_lcl = lcl, gre_imp = iss }) | lcl = Nothing | otherwise = Just $ map (is_as . is_decl) (bagToList iss) -- | Is this 'GlobalRdrElt' defined locally? isLocalGRE :: GlobalRdrEltX info -> Bool isLocalGRE (GRE { gre_lcl = lcl }) = lcl -- | Is this 'GlobalRdrElt' imported? -- -- Not just the negation of 'isLocalGRE', because it might be an Exact or -- Orig name reference. See Note [GlobalRdrElt provenance]. isImportedGRE :: GlobalRdrEltX info -> Bool isImportedGRE (GRE { gre_imp = imps }) = not $ isEmptyBag imps -- | Is this a record field GRE? -- -- Important: does /not/ consult the 'GreInfo' field. isRecFldGRE :: GlobalRdrEltX info -> Bool isRecFldGRE (GRE { gre_name = nm }) = isFieldName nm isDuplicateRecFldGRE :: GlobalRdrElt -> Bool -- ^ Is this a record field defined with DuplicateRecordFields? isDuplicateRecFldGRE = maybe False ((DuplicateRecordFields ==) . flHasDuplicateRecordFields) . greFieldLabel_maybe isNoFieldSelectorGRE :: GlobalRdrElt -> Bool -- ^ Is this a record field defined with NoFieldSelectors? -- (See Note [NoFieldSelectors] in GHC.Rename.Env) isNoFieldSelectorGRE = maybe False ((NoFieldSelectors ==) . flHasFieldSelector) . greFieldLabel_maybe isFieldSelectorGRE :: GlobalRdrElt -> Bool -- ^ Is this a record field defined with FieldSelectors? -- (See Note [NoFieldSelectors] in GHC.Rename.Env) isFieldSelectorGRE = maybe False ((FieldSelectors ==) . flHasFieldSelector) . greFieldLabel_maybe greFieldLabel_maybe :: GlobalRdrElt -> Maybe FieldLabel -- ^ Returns the field label of this GRE, if it has one greFieldLabel_maybe = fmap fieldGRELabel . fieldGRE_maybe unQualOK :: GlobalRdrEltX info -> Bool -- ^ Test if an unqualified version of this thing would be in scope unQualOK (GRE {gre_lcl = lcl, gre_imp = iss }) | lcl = True | otherwise = any unQualSpecOK iss {- Note [GRE filtering] ~~~~~~~~~~~~~~~~~~~~~~~ (pickGREs rdr gres) takes a list of GREs which have the same OccName as 'rdr', say "x". It does two things: (a) filters the GREs to a subset that are in scope * Qualified, as 'M.x' if want_qual is Qual M _ * Unqualified, as 'x' if want_unqual is Unqual _ (b) for that subset, filter the provenance field (gre_lcl and gre_imp) to ones that brought it into scope qualified or unqualified resp. Example: module A ( f ) where import qualified Foo( f ) import Baz( f ) f = undefined Let's suppose that Foo.f and Baz.f are the same entity really, but the local 'f' is different, so there will be two GREs matching "f": gre1: gre_lcl = True, gre_imp = [] gre2: gre_lcl = False, gre_imp = [ imported from Foo, imported from Bar ] The use of "f" in the export list is ambiguous because it's in scope from the local def and the import Baz(f); but *not* the import qualified Foo. pickGREs returns two GRE gre1: gre_lcl = True, gre_imp = [] gre2: gre_lcl = False, gre_imp = [ imported from Bar ] Now the "ambiguous occurrence" message can correctly report how the ambiguity arises. -} pickGREs :: RdrName -> [GlobalRdrEltX info] -> [GlobalRdrEltX info] -- ^ Takes a list of GREs which have the right OccName 'x' -- Pick those GREs that are in scope -- * Qualified, as 'M.x' if want_qual is Qual M _ -- * Unqualified, as 'x' if want_unqual is Unqual _ -- -- Return each such GRE, with its ImportSpecs filtered, to reflect -- how it is in scope qualified or unqualified respectively. -- See Note [GRE filtering] pickGREs (Unqual {}) gres = mapMaybe pickUnqualGRE gres pickGREs (Qual mod _) gres = mapMaybe (pickQualGRE mod) gres pickGREs _ _ = [] -- I don't think this actually happens pickUnqualGRE :: GlobalRdrEltX info -> Maybe (GlobalRdrEltX info) pickUnqualGRE gre@(GRE { gre_lcl = lcl, gre_imp = iss }) | not lcl, null iss' = Nothing | otherwise = Just (gre { gre_imp = iss' }) where iss' = filterBag unQualSpecOK iss pickQualGRE :: ModuleName -> GlobalRdrEltX info -> Maybe (GlobalRdrEltX info) pickQualGRE mod gre@(GRE { gre_lcl = lcl, gre_imp = iss }) | not lcl', null iss' = Nothing | otherwise = Just (gre { gre_lcl = lcl', gre_imp = iss' }) where iss' = filterBag (qualSpecOK mod) iss lcl' = lcl && name_is_from mod name_is_from :: ModuleName -> Bool name_is_from mod = case greDefinitionModule gre of Just n_mod -> moduleName n_mod == mod Nothing -> False pickGREsModExp :: ModuleName -> [GlobalRdrEltX info] -> [(GlobalRdrEltX info,GlobalRdrEltX info)] -- ^ Pick GREs that are in scope *both* qualified *and* unqualified -- Return each GRE that is, as a pair -- (qual_gre, unqual_gre) -- These two GREs are the original GRE with imports filtered to express how -- it is in scope qualified an unqualified respectively -- -- Used only for the 'module M' item in export list; -- see 'GHC.Tc.Gen.Export.exports_from_avail' pickGREsModExp mod gres = mapMaybe (pickBothGRE mod) gres -- | isBuiltInSyntax filter out names for built-in syntax They -- just clutter up the environment (esp tuples), and the -- parser will generate Exact RdrNames for them, so the -- cluttered envt is no use. Really, it's only useful for -- GHC.Base and GHC.Tuple. pickBothGRE :: ModuleName -> GlobalRdrEltX info -> Maybe (GlobalRdrEltX info, GlobalRdrEltX info) pickBothGRE mod gre | isBuiltInSyntax (greName gre) = Nothing | Just gre1 <- pickQualGRE mod gre , Just gre2 <- pickUnqualGRE gre = Just (gre1, gre2) | otherwise = Nothing -- Building GlobalRdrEnvs plusGlobalRdrEnv :: GlobalRdrEnv -> GlobalRdrEnv -> GlobalRdrEnv plusGlobalRdrEnv env1 env2 = plusOccEnv_C (foldr insertGRE) env1 env2 mkGlobalRdrEnv :: [GlobalRdrElt] -> GlobalRdrEnv mkGlobalRdrEnv gres = foldr add emptyGlobalRdrEnv gres where add gre env = extendOccEnv_Acc insertGRE Utils.singleton env (greOccName gre) gre insertGRE :: GlobalRdrElt -> [GlobalRdrElt] -> [GlobalRdrElt] insertGRE new_g [] = [new_g] insertGRE new_g (old_g : old_gs) | greName new_g == greName old_g = new_g `plusGRE` old_g : old_gs | otherwise = old_g : insertGRE new_g old_gs plusGRE :: GlobalRdrElt -> GlobalRdrElt -> GlobalRdrElt -- Used when the gre_name fields match plusGRE g1 g2 = GRE { gre_name = gre_name g1 , gre_lcl = gre_lcl g1 || gre_lcl g2 , gre_imp = gre_imp g1 `unionBags` gre_imp g2 , gre_par = gre_par g1 `plusParent` gre_par g2 , gre_info = gre_info g1 `plusGREInfo` gre_info g2 } transformGREs :: (GlobalRdrElt -> GlobalRdrElt) -> [OccName] -> GlobalRdrEnv -> GlobalRdrEnv -- ^ Apply a transformation function to the GREs for these OccNames transformGREs trans_gre occs rdr_env = foldr trans rdr_env occs where trans occ env = case lookupOccEnv env occ of Just gres -> extendOccEnv env occ (map trans_gre gres) Nothing -> env extendGlobalRdrEnv :: GlobalRdrEnv -> GlobalRdrElt -> GlobalRdrEnv extendGlobalRdrEnv env gre = extendOccEnv_Acc insertGRE Utils.singleton env (greOccName gre) gre {- Note [GlobalRdrEnv shadowing] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Before adding new names to the GlobalRdrEnv we nuke some existing entries; this is "shadowing". The actual work is done by GHC.Types.Name.Reader.shadowNames. Suppose env' = shadowNames env { f } `extendGlobalRdrEnv` { M.f } Then: * Looking up (Unqual f) in env' should succeed, returning M.f, even if env contains existing unqualified bindings for f. They are shadowed * Looking up (Qual M.f) in env' should succeed, returning M.f * Looking up (Qual X.f) in env', where X /= M, should be the same as looking up (Qual X.f) in env. That is, shadowNames does /not/ delete earlier qualified bindings There are two reasons for shadowing: * The GHCi REPL - Ids bought into scope on the command line (eg let x = True) have External Names, like Ghci4.x. We want a new binding for 'x' (say) to override the existing binding for 'x'. Example: ghci> :load M -- Brings `x` and `M.x` into scope ghci> x ghci> "Hello" ghci> M.x ghci> "hello" ghci> let x = True -- Shadows `x` ghci> x -- The locally bound `x` -- NOT an ambiguous reference ghci> True ghci> M.x -- M.x is still in scope! ghci> "Hello" So when we add `x = True` we must not delete the `M.x` from the `GlobalRdrEnv`; rather we just want to make it "qualified only"; hence the `set_qual` in `shadowNames`. See also Note [Interactively-bound Ids in GHCi] in GHC.Runtime.Context - Data types also have External Names, like Ghci4.T; but we still want 'T' to mean the newly-declared 'T', not an old one. * Nested Template Haskell declaration brackets See Note [Top-level Names in Template Haskell decl quotes] in GHC.Rename.Names Consider a TH decl quote: module M where f x = h [d| f = ...f...M.f... |] We must shadow the outer unqualified binding of 'f', else we'll get a complaint when extending the GlobalRdrEnv, saying that 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. This is done in lcl_env_TH in extendGlobalRdrEnvRn. - The External 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), or from earlier GHCi commands. Do not shadow *Internal* 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. At that stage, the class op 'f' will have an Internal name. Wrinkle [Shadowing namespaces] In the following GHCi session: > data A = MkA { foo :: Int } > foo = False > bar = foo We expect the variable 'foo' to shadow the record field 'foo', even though they are in separate namespaces, so that the occurrence of 'foo' in the body of 'bar' is not ambiguous. -} shadowNames :: Bool -- ^ discard names that are only available qualified? -> GlobalRdrEnv -> GlobalRdrEnv -> GlobalRdrEnv -- Remove certain old GREs that share the same OccName as this new Name. -- See Note [GlobalRdrEnv shadowing] for details shadowNames drop_only_qualified env new_gres = minusOccEnv_C_Ns do_shadowing env new_gres where do_shadowing :: UniqFM NameSpace [GlobalRdrElt] -> UniqFM NameSpace [GlobalRdrElt] -> UniqFM NameSpace [GlobalRdrElt] do_shadowing olds news = -- Start off by accumulating all 'NameSpace's shadowed -- by the entire collection of new GREs. let shadowed_gres :: ShadowedGREs shadowed_gres = nonDetFoldUFM (\ gres shads -> foldMap greShadowedNameSpaces gres S.<> shads) mempty news -- Then shadow the old 'GlobalRdrElt's, now that we know which 'NameSpace's -- should be shadowed. shadow_list :: Unique -> [GlobalRdrElt] -> Maybe [GlobalRdrElt] shadow_list old_ns old_gres = case namespace_is_shadowed old_ns shadowed_gres of IsNotShadowed -> Just old_gres IsShadowed -> guard_nonEmpty $ mapMaybe shadow old_gres IsShadowedIfFieldSelector -> guard_nonEmpty $ mapMaybe (\ old_gre -> if isFieldSelectorGRE old_gre then shadow old_gre else Just old_gre) old_gres -- Now do all of the shadowing in a single go. This avoids traversing -- the old GlobalRdrEnv multiple times over. in mapMaybeWithKeyUFM shadow_list olds guard_nonEmpty :: [a] -> Maybe [a] guard_nonEmpty xs | null xs = Nothing | otherwise = Just xs -- Shadow a single GRE, by either qualifying it or removing it entirely. shadow :: GlobalRdrElt-> Maybe GlobalRdrElt shadow old_gre@(GRE { gre_lcl = lcl, gre_imp = iss }) = case greDefinitionModule old_gre of Nothing -> Just old_gre -- Old name is Internal; do not shadow Just old_mod | null iss' -- Nothing remains || drop_only_qualified -> Nothing | otherwise -> Just (old_gre { gre_lcl = False, gre_imp = iss' }) where iss' = lcl_imp `unionBags` mapBag set_qual iss lcl_imp | lcl = unitBag $ mk_fake_imp_spec old_gre old_mod | otherwise = emptyBag mk_fake_imp_spec old_gre old_mod -- Urgh! = ImpSpec id_spec ImpAll where old_mod_name = moduleName old_mod id_spec = ImpDeclSpec { is_mod = old_mod , is_as = old_mod_name , is_qual = True , is_dloc = greDefinitionSrcSpan old_gre } set_qual :: ImportSpec -> ImportSpec set_qual is = is { is_decl = (is_decl is) { is_qual = True } } -- | @greClashesWith new_gre old_gre@ computes whether @new_gre@ clashes -- with @old_gre@ (assuming they both have the same underlying 'occNameFS'). greClashesWith :: GlobalRdrElt -> (GlobalRdrElt -> Bool) greClashesWith new_gre old_gre = old_gre `greIsShadowed` greShadowedNameSpaces new_gre -- | Is the given 'GlobalRdrElt' shadowed, as specified by the 'ShadowedNameSpace's? greIsShadowed :: GlobalRdrElt -> ShadowedGREs -> Bool greIsShadowed old_gre shadowed = case getUnique old_ns `namespace_is_shadowed` shadowed of IsShadowed -> True IsNotShadowed -> False IsShadowedIfFieldSelector -> isFieldSelectorGRE old_gre where old_ns = occNameSpace $ greOccName old_gre -- | Whether a 'GlobalRdrElt' is definitely shadowed, definitely not shadowed, -- or conditionally shadowed based on more information beyond the 'NameSpace'. data IsShadowed -- | The GRE is not shadowed. = IsNotShadowed -- | The GRE is shadowed. | IsShadowed -- | The GRE is shadowed iff it is a record field GRE -- which defines a field selector (i.e. FieldSelectors is enabled in its -- defining module). | IsShadowedIfFieldSelector -- | Internal function: is a 'GlobalRdrElt' with the 'NameSpace' with given -- 'Unique' shadowed by the specified 'ShadowedGREs'? namespace_is_shadowed :: Unique -> ShadowedGREs -> IsShadowed namespace_is_shadowed old_ns (ShadowedGREs shadowed_nonflds shadowed_flds) | isFldNSUnique old_ns = case shadowed_flds of ShadowAllFieldGREs -> IsShadowed ShadowFieldSelectorsAnd shadowed | old_ns `elemUniqSet_Directly` shadowed -> IsShadowed | otherwise -> IsShadowedIfFieldSelector ShadowFieldNameSpaces shadowed | old_ns `elemUniqSet_Directly` shadowed -> IsShadowed | otherwise -> IsNotShadowed | old_ns `elemUniqSet_Directly` shadowed_nonflds = IsShadowed | otherwise = IsNotShadowed -- | What are all the 'GlobalRdrElt's that are shadowed by this new 'GlobalRdrElt'? greShadowedNameSpaces :: GlobalRdrElt -> ShadowedGREs greShadowedNameSpaces gre = ShadowedGREs shadowed_nonflds shadowed_flds where ns = occNameSpace $ greOccName gre !shadowed_nonflds | isFieldNameSpace ns -- A new record field shadows variables if it defines a field selector. = if isFieldSelectorGRE gre then unitUniqSet varName else emptyUniqSet | otherwise = unitUniqSet ns !shadowed_flds | ns == varName -- A new variable shadows record fields with field selectors. = ShadowFieldSelectorsAnd emptyUniqSet | isFieldNameSpace ns -- A new record field shadows record fields unless it is a duplicate record field. = if isDuplicateRecFldGRE gre then ShadowFieldNameSpaces (unitUniqSet ns) -- NB: we must still shadow fields with the same constructor name. else ShadowAllFieldGREs | otherwise = ShadowFieldNameSpaces emptyUniqSet -- | A description of which 'GlobalRdrElt's are shadowed. data ShadowedGREs = ShadowedGREs { shadowedNonFieldNameSpaces :: !(UniqSet NameSpace) -- ^ These specific non-field 'NameSpace's are shadowed. , shadowedFieldGREs :: !ShadowedFieldGREs -- ^ These field 'GlobalRdrElt's are shadowed. } -- | A description of which record field 'GlobalRdrElt's are shadowed. data ShadowedFieldGREs -- | All field 'GlobalRdrElt's are shadowed. = ShadowAllFieldGREs -- | Record field GREs defining field selectors, as well as those -- with the explicitly specified field 'NameSpace's, are shadowed. | ShadowFieldSelectorsAnd { shadowedFieldNameSpaces :: !(UniqSet NameSpace) } -- | These specific field 'NameSpace's are shadowed. | ShadowFieldNameSpaces { shadowedFieldNameSpaces :: !(UniqSet NameSpace) } instance Monoid ShadowedFieldGREs where mempty = ShadowFieldNameSpaces { shadowedFieldNameSpaces = emptyUniqSet } instance Semigroup ShadowedFieldGREs where ShadowAllFieldGREs <> _ = ShadowAllFieldGREs _ <> ShadowAllFieldGREs = ShadowAllFieldGREs ShadowFieldSelectorsAnd ns1 <> ShadowFieldSelectorsAnd ns2 = ShadowFieldSelectorsAnd (ns1 S.<> ns2) ShadowFieldSelectorsAnd ns1 <> ShadowFieldNameSpaces ns2 = ShadowFieldSelectorsAnd (ns1 S.<> ns2) ShadowFieldNameSpaces ns1 <> ShadowFieldSelectorsAnd ns2 = ShadowFieldSelectorsAnd (ns1 S.<> ns2) ShadowFieldNameSpaces ns1 <> ShadowFieldNameSpaces ns2 = ShadowFieldNameSpaces (ns1 S.<> ns2) instance Monoid ShadowedGREs where mempty = ShadowedGREs { shadowedNonFieldNameSpaces = emptyUniqSet , shadowedFieldGREs = mempty } instance Semigroup ShadowedGREs where ShadowedGREs nonflds1 flds1 <> ShadowedGREs nonflds2 flds2 = ShadowedGREs (nonflds1 S.<> nonflds2) (flds1 S.<> flds2) {- ************************************************************************ * * ImportSpec * * ************************************************************************ -} -- | Import Specification -- -- The 'ImportSpec' of something says how it came to be imported -- It's quite elaborate so that we can give accurate unused-name warnings. data ImportSpec = ImpSpec { is_decl :: ImpDeclSpec, is_item :: ImpItemSpec } deriving( Eq, Data ) -- | Import Declaration Specification -- -- Describes a particular import declaration and is -- shared among all the 'Provenance's for that decl data ImpDeclSpec = ImpDeclSpec { is_mod :: Module, -- ^ Module imported, e.g. @import Muggle@ -- Note the @Muggle@ may well not be -- the defining module for this thing! -- TODO: either should be Module, or there -- should be a Maybe UnitId here too. is_as :: ModuleName, -- ^ Import alias, e.g. from @as M@ (or @Muggle@ if there is no @as@ clause) is_qual :: Bool, -- ^ Was this import qualified? is_dloc :: SrcSpan -- ^ The location of the entire import declaration } deriving (Eq, Data) -- | Import Item Specification -- -- Describes import info a particular Name data ImpItemSpec = ImpAll -- ^ The import had no import list, -- or had a hiding list | ImpSome { is_explicit :: Bool, is_iloc :: SrcSpan -- Location of the import item } -- ^ The import had an import list. -- The 'is_explicit' field is @True@ iff the thing was named -- /explicitly/ in the import specs rather -- than being imported as part of a "..." group. Consider: -- -- > import C( T(..) ) -- -- Here the constructors of @T@ are not named explicitly; -- only @T@ is named explicitly. deriving (Eq, Data) bestImport :: NE.NonEmpty ImportSpec -> ImportSpec -- See Note [Choosing the best import declaration] bestImport iss = NE.head $ NE.sortBy best iss where best :: ImportSpec -> ImportSpec -> Ordering -- Less means better -- Unqualified always wins over qualified; then -- import-all wins over import-some; then -- earlier declaration wins over later best (ImpSpec { is_item = item1, is_decl = d1 }) (ImpSpec { is_item = item2, is_decl = d2 }) = (is_qual d1 `compare` is_qual d2) S.<> best_item item1 item2 S.<> SrcLoc.leftmost_smallest (is_dloc d1) (is_dloc d2) best_item :: ImpItemSpec -> ImpItemSpec -> Ordering best_item ImpAll ImpAll = EQ best_item ImpAll (ImpSome {}) = LT best_item (ImpSome {}) ImpAll = GT best_item (ImpSome { is_explicit = e1 }) (ImpSome { is_explicit = e2 }) = e1 `compare` e2 -- False < True, so if e1 is explicit and e2 is not, we get GT {- Note [Choosing the best import declaration] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ When reporting unused import declarations we use the following rules. (see [wiki:commentary/compiler/unused-imports]) Say that an import-item is either * an entire import-all decl (eg import Foo), or * a particular item in an import list (eg import Foo( ..., x, ...)). The general idea is that for each /occurrence/ of an imported name, we will attribute that use to one import-item. Once we have processed all the occurrences, any import items with no uses attributed to them are unused, and are warned about. More precisely: 1. For every RdrName in the program text, find its GlobalRdrElt. 2. Then, from the [ImportSpec] (gre_imp) of that GRE, choose one the "chosen import-item", and mark it "used". This is done by 'bestImport' 3. After processing all the RdrNames, bleat about any import-items that are unused. This is done in GHC.Rename.Names.warnUnusedImportDecls. The function 'bestImport' returns the dominant import among the ImportSpecs it is given, implementing Step 2. We say import-item A dominates import-item B if we choose A over B. In general, we try to choose the import that is most likely to render other imports unnecessary. Here is the dominance relationship we choose: a) import Foo dominates import qualified Foo. b) import Foo dominates import Foo(x). c) Otherwise choose the textually first one. Rationale for (a). Consider import qualified M -- Import #1 import M( x ) -- Import #2 foo = M.x + x The unqualified 'x' can only come from import #2. The qualified 'M.x' could come from either, but bestImport picks import #2, because it is more likely to be useful in other imports, as indeed it is in this case (see #5211 for a concrete example). But the rules are not perfect; consider import qualified M -- Import #1 import M( x ) -- Import #2 foo = M.x + M.y The M.x will use import #2, but M.y can only use import #1. -} unQualSpecOK :: ImportSpec -> Bool -- ^ Is in scope unqualified? unQualSpecOK is = not (is_qual (is_decl is)) qualSpecOK :: ModuleName -> ImportSpec -> Bool -- ^ Is in scope qualified with the given module? qualSpecOK mod is = mod == is_as (is_decl is) importSpecLoc :: ImportSpec -> SrcSpan importSpecLoc (ImpSpec decl ImpAll) = is_dloc decl importSpecLoc (ImpSpec _ item) = is_iloc item importSpecModule :: ImportSpec -> ModuleName importSpecModule = moduleName . is_mod . is_decl isExplicitItem :: ImpItemSpec -> Bool isExplicitItem ImpAll = False isExplicitItem (ImpSome {is_explicit = exp}) = exp pprNameProvenance :: GlobalRdrEltX info -> SDoc -- ^ Print out one place where the name was define/imported -- (With -dppr-debug, print them all) pprNameProvenance (GRE { gre_name = name, gre_lcl = lcl, gre_imp = iss }) = ifPprDebug (vcat pp_provs) (head pp_provs) where pp_provs = pp_lcl ++ map pp_is (bagToList iss) pp_lcl = if lcl then [text "defined at" <+> ppr (nameSrcLoc name)] else [] pp_is is = sep [ppr is, ppr_defn_site is name] -- If we know the exact definition point (which we may do with GHCi) -- then show that too. But not if it's just "imported from X". ppr_defn_site :: ImportSpec -> Name -> SDoc ppr_defn_site imp_spec name | same_module && not (isGoodSrcSpan loc) = empty -- Nothing interesting to say | otherwise = parens $ hang (text "and originally defined" <+> pp_mod) 2 (pprLoc loc) where loc = nameSrcSpan name defining_mod = assertPpr (isExternalName name) (ppr name) $ nameModule name same_module = importSpecModule imp_spec == moduleName defining_mod pp_mod | same_module = empty | otherwise = text "in" <+> quotes (ppr defining_mod) instance Outputable ImportSpec where ppr imp_spec = text "imported" <+> qual <+> text "from" <+> quotes (ppr (importSpecModule imp_spec)) <+> pprLoc (importSpecLoc imp_spec) where qual | is_qual (is_decl imp_spec) = text "qualified" | otherwise = empty pprLoc :: SrcSpan -> SDoc pprLoc (RealSrcSpan s _) = text "at" <+> ppr s pprLoc (UnhelpfulSpan {}) = empty -- | Indicate if the given name is the "@" operator opIsAt :: RdrName -> Bool opIsAt e = e == mkUnqual varName (fsLit "@")