{- (c) The GRASP/AQUA Project, Glasgow University, 1992-2006 GHC.Rename.Env contains functions which convert RdrNames into Names. -} {-# LANGUAGE CPP, MultiWayIf, NamedFieldPuns #-} module GHC.Rename.Env ( newTopSrcBinder, lookupLocatedTopBndrRn, lookupTopBndrRn, lookupLocatedOccRn, lookupOccRn, lookupOccRn_maybe, lookupLocalOccRn_maybe, lookupInfoOccRn, lookupLocalOccThLvl_maybe, lookupLocalOccRn, lookupTypeOccRn, lookupGlobalOccRn, lookupGlobalOccRn_maybe, lookupOccRn_overloaded, lookupGlobalOccRn_overloaded, ChildLookupResult(..), lookupSubBndrOcc_helper, combineChildLookupResult, -- Called by lookupChildrenExport HsSigCtxt(..), lookupLocalTcNames, lookupSigOccRn, lookupSigCtxtOccRn, lookupInstDeclBndr, lookupRecFieldOcc, lookupFamInstName, lookupConstructorFields, lookupGreAvailRn, -- Rebindable Syntax lookupSyntax, lookupSyntaxExpr, lookupSyntaxName, lookupSyntaxNames, lookupIfThenElse, lookupReboundIf, -- QualifiedDo lookupQualifiedDoExpr, lookupQualifiedDo, lookupQualifiedDoName, lookupNameWithQualifier, -- Constructing usage information addUsedGRE, addUsedGREs, addUsedDataCons, dataTcOccs, --TODO: Move this somewhere, into utils? ) where #include "HsVersions.h" import GHC.Prelude import GHC.Iface.Load ( loadInterfaceForName, loadSrcInterface_maybe ) import GHC.Iface.Env import GHC.Hs import GHC.Types.Name.Reader import GHC.Driver.Types import GHC.Tc.Utils.Env import GHC.Tc.Utils.Monad import GHC.Parser.PostProcess ( filterCTuple, setRdrNameSpace ) import GHC.Builtin.RebindableNames import GHC.Builtin.Types import GHC.Types.Name import GHC.Types.Name.Set import GHC.Types.Name.Env import GHC.Types.Avail import GHC.Unit.Module import GHC.Core.ConLike import GHC.Core.DataCon import GHC.Core.TyCon import GHC.Utils.Error ( MsgDoc ) import GHC.Builtin.Names( rOOT_MAIN ) import GHC.Types.Basic ( pprWarningTxtForMsg, TopLevelFlag(..), TupleSort(..) ) import GHC.Types.SrcLoc as SrcLoc import GHC.Utils.Outputable as Outputable import GHC.Types.Unique.Set ( uniqSetAny ) import GHC.Utils.Misc import GHC.Data.Maybe import GHC.Driver.Session import GHC.Data.FastString import Control.Monad import GHC.Data.List.SetOps ( minusList ) import qualified GHC.LanguageExtensions as LangExt import GHC.Rename.Unbound import GHC.Rename.Utils import qualified Data.Semigroup as Semi import Data.Either ( partitionEithers ) import Data.List ( find, sortBy ) import Control.Arrow ( first ) import Data.Function {- ********************************************************* * * Source-code binders * * ********************************************************* Note [Signature lazy interface loading] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ GHC's lazy interface loading can be a bit confusing, so this Note is an empirical description of what happens in one interesting case. When compiling a signature module against an its implementation, we do NOT load interface files associated with its names until after the type checking phase. For example: module ASig where data T f :: T -> T Suppose we compile this with -sig-of "A is ASig": module B where data T = T f T = T module A(module B) where import B During type checking, we'll load A.hi because we need to know what the RdrEnv for the module is, but we DO NOT load the interface for B.hi! It's wholly unnecessary: our local definition 'data T' in ASig is all the information we need to finish type checking. This is contrast to type checking of ordinary Haskell files, in which we would not have the local definition "data T" and would need to consult B.hi immediately. (Also, this situation never occurs for hs-boot files, since you're not allowed to reexport from another module.) After type checking, we then check that the types we provided are consistent with the backing implementation (in checkHiBootOrHsigIface). At this point, B.hi is loaded, because we need something to compare against. I discovered this behavior when trying to figure out why type class instances for Data.Map weren't in the EPS when I was type checking a test very much like ASig (sigof02dm): the associated interface hadn't been loaded yet! (The larger issue is a moot point, since an instance declared in a signature can never be a duplicate.) This behavior might change in the future. Consider this alternate module B: module B where {-# DEPRECATED T, f "Don't use" #-} data T = T f T = T One might conceivably want to report deprecation warnings when compiling ASig with -sig-of B, in which case we need to look at B.hi to find the deprecation warnings during renaming. At the moment, you don't get any warning until you use the identifier further downstream. This would require adjusting addUsedGRE so that during signature compilation, we do not report deprecation warnings for LocalDef. See also Note [Handling of deprecations] -} newTopSrcBinder :: Located RdrName -> RnM Name newTopSrcBinder (L loc rdr_name) | Just name <- isExact_maybe rdr_name = -- This is here to catch -- (a) Exact-name binders created by Template Haskell -- (b) The PrelBase defn of (say) [] and similar, for which -- the parser reads the special syntax and returns an Exact RdrName -- We are at a binding site for the name, so check first that it -- the current module is the correct one; otherwise GHC can get -- very confused indeed. This test rejects code like -- data T = (,) Int Int -- unless we are in GHC.Tup if isExternalName name then do { this_mod <- getModule ; unless (this_mod == nameModule name) (addErrAt loc (badOrigBinding rdr_name)) ; return name } else -- See Note [Binders in Template Haskell] in "GHC.ThToHs" do { this_mod <- getModule ; externaliseName this_mod name } | Just (rdr_mod, rdr_occ) <- isOrig_maybe rdr_name = do { this_mod <- getModule ; unless (rdr_mod == this_mod || rdr_mod == rOOT_MAIN) (addErrAt loc (badOrigBinding rdr_name)) -- When reading External Core we get Orig names as binders, -- but they should agree with the module gotten from the monad -- -- We can get built-in syntax showing up here too, sadly. If you type -- data T = (,,,) -- the constructor is parsed as a type, and then GHC.Parser.PostProcess.tyConToDataCon -- uses setRdrNameSpace to make it into a data constructors. At that point -- the nice Exact name for the TyCon gets swizzled to an Orig name. -- Hence the badOrigBinding error message. -- -- Except for the ":Main.main = ..." definition inserted into -- the Main module; ugh! -- Because of this latter case, we call newGlobalBinder with a module from -- the RdrName, not from the environment. In principle, it'd be fine to -- have an arbitrary mixture of external core definitions in a single module, -- (apart from module-initialisation issues, perhaps). ; newGlobalBinder rdr_mod rdr_occ loc } | otherwise = do { when (isQual rdr_name) (addErrAt loc (badQualBndrErr rdr_name)) -- Binders should not be qualified; if they are, and with a different -- module name, we get a confusing "M.T is not in scope" error later ; stage <- getStage ; if isBrackStage stage then -- We are inside a TH bracket, so make an *Internal* name -- See Note [Top-level Names in Template Haskell decl quotes] in GHC.Rename.Names do { uniq <- newUnique ; return (mkInternalName uniq (rdrNameOcc rdr_name) loc) } else do { this_mod <- getModule ; traceRn "newTopSrcBinder" (ppr this_mod $$ ppr rdr_name $$ ppr loc) ; newGlobalBinder this_mod (rdrNameOcc rdr_name) loc } } {- ********************************************************* * * Source code occurrences * * ********************************************************* Looking up a name in the GHC.Rename.Env. Note [Type and class operator definitions] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We want to reject all of these unless we have -XTypeOperators (#3265) data a :*: b = ... class a :*: b where ... data (:*:) a b = .... class (:*:) a b where ... The latter two mean that we are not just looking for a *syntactically-infix* declaration, but one that uses an operator OccName. We use OccName.isSymOcc to detect that case, which isn't terribly efficient, but there seems to be no better way. -} -- Can be made to not be exposed -- Only used unwrapped in rnAnnProvenance lookupTopBndrRn :: RdrName -> RnM Name -- Look up a top-level source-code binder. We may be looking up an unqualified 'f', -- and there may be several imported 'f's too, which must not confuse us. -- For example, this is OK: -- import Foo( f ) -- infix 9 f -- The 'f' here does not need to be qualified -- f x = x -- Nor here, of course -- So we have to filter out the non-local ones. -- -- A separate function (importsFromLocalDecls) reports duplicate top level -- decls, so here it's safe just to choose an arbitrary one. lookupTopBndrRn rdr_name = lookupExactOrOrig rdr_name id $ do { -- Check for operators in type or class declarations -- See Note [Type and class operator definitions] let occ = rdrNameOcc rdr_name ; when (isTcOcc occ && isSymOcc occ) (do { op_ok <- xoptM LangExt.TypeOperators ; unless op_ok (addErr (opDeclErr rdr_name)) }) ; env <- getGlobalRdrEnv ; case filter isLocalGRE (lookupGRE_RdrName rdr_name env) of [gre] -> return (gre_name gre) _ -> do -- Ambiguous (can't happen) or unbound traceRn "lookupTopBndrRN fail" (ppr rdr_name) unboundName WL_LocalTop rdr_name } lookupLocatedTopBndrRn :: Located RdrName -> RnM (Located Name) lookupLocatedTopBndrRn = wrapLocM lookupTopBndrRn -- | Lookup an @Exact@ @RdrName@. See Note [Looking up Exact RdrNames]. -- This never adds an error, but it may return one, see -- Note [Errors in lookup functions] lookupExactOcc_either :: Name -> RnM (Either MsgDoc Name) lookupExactOcc_either name | Just thing <- wiredInNameTyThing_maybe name , Just tycon <- case thing of ATyCon tc -> Just tc AConLike (RealDataCon dc) -> Just (dataConTyCon dc) _ -> Nothing , Just tupleSort <- tyConTuple_maybe tycon = do { let tupArity = case tupleSort of -- Unboxed tuples have twice as many arguments because of the -- 'RuntimeRep's (#17837) UnboxedTuple -> tyConArity tycon `div` 2 _ -> tyConArity tycon ; checkTupSize tupArity ; return (Right name) } | isExternalName name = return (Right name) | otherwise = do { env <- getGlobalRdrEnv ; let -- See Note [Splicing Exact names] main_occ = nameOccName name demoted_occs = case demoteOccName main_occ of Just occ -> [occ] Nothing -> [] gres = [ gre | occ <- main_occ : demoted_occs , gre <- lookupGlobalRdrEnv env occ , gre_name gre == name ] ; case gres of [gre] -> return (Right (gre_name gre)) [] -> -- See Note [Splicing Exact names] do { lcl_env <- getLocalRdrEnv ; if name `inLocalRdrEnvScope` lcl_env then return (Right name) else do { th_topnames_var <- fmap tcg_th_topnames getGblEnv ; th_topnames <- readTcRef th_topnames_var ; if name `elemNameSet` th_topnames then return (Right name) else return (Left (exactNameErr name)) } } gres -> return (Left (sameNameErr gres)) -- Ugh! See Note [Template Haskell ambiguity] } sameNameErr :: [GlobalRdrElt] -> MsgDoc sameNameErr [] = panic "addSameNameErr: empty list" sameNameErr gres@(_ : _) = hang (text "Same exact name in multiple name-spaces:") 2 (vcat (map pp_one sorted_names) $$ th_hint) where sorted_names = sortBy (SrcLoc.leftmost_smallest `on` nameSrcSpan) (map gre_name gres) pp_one name = hang (pprNameSpace (occNameSpace (getOccName name)) <+> quotes (ppr name) <> comma) 2 (text "declared at:" <+> ppr (nameSrcLoc name)) th_hint = vcat [ text "Probable cause: you bound a unique Template Haskell name (NameU)," , text "perhaps via newName, in different name-spaces." , text "If that's it, then -ddump-splices might be useful" ] ----------------------------------------------- lookupInstDeclBndr :: Name -> SDoc -> RdrName -> RnM Name -- This is called on the method name on the left-hand side of an -- instance declaration binding. eg. instance Functor T where -- fmap = ... -- ^^^^ called on this -- Regardless of how many unqualified fmaps are in scope, we want -- the one that comes from the Functor class. -- -- Furthermore, note that we take no account of whether the -- name is only in scope qualified. I.e. even if method op is -- in scope as M.op, we still allow plain 'op' on the LHS of -- an instance decl -- -- The "what" parameter says "method" or "associated type", -- depending on what we are looking up lookupInstDeclBndr cls what rdr = do { when (isQual rdr) (addErr (badQualBndrErr rdr)) -- In an instance decl you aren't allowed -- to use a qualified name for the method -- (Although it'd make perfect sense.) ; mb_name <- lookupSubBndrOcc False -- False => we don't give deprecated -- warnings when a deprecated class -- method is defined. We only warn -- when it's used cls doc rdr ; case mb_name of Left err -> do { addErr err; return (mkUnboundNameRdr rdr) } Right nm -> return nm } where doc = what <+> text "of class" <+> quotes (ppr cls) ----------------------------------------------- lookupFamInstName :: Maybe Name -> Located RdrName -> RnM (Located Name) -- Used for TyData and TySynonym family instances only, -- See Note [Family instance binders] lookupFamInstName (Just cls) tc_rdr -- Associated type; c.f GHC.Rename.Bind.rnMethodBind = wrapLocM (lookupInstDeclBndr cls (text "associated type")) tc_rdr lookupFamInstName Nothing tc_rdr -- Family instance; tc_rdr is an *occurrence* = lookupLocatedOccRn tc_rdr ----------------------------------------------- lookupConstructorFields :: Name -> RnM [FieldLabel] -- Look up the fields of a given constructor -- * For constructors from this module, use the record field env, -- which is itself gathered from the (as yet un-typechecked) -- data type decls -- -- * For constructors from imported modules, use the *type* environment -- since imported modules are already compiled, the info is conveniently -- right there lookupConstructorFields con_name = do { this_mod <- getModule ; if nameIsLocalOrFrom this_mod con_name then do { field_env <- getRecFieldEnv ; traceTc "lookupCF" (ppr con_name $$ ppr (lookupNameEnv field_env con_name) $$ ppr field_env) ; return (lookupNameEnv field_env con_name `orElse` []) } else do { con <- tcLookupConLike con_name ; traceTc "lookupCF 2" (ppr con) ; return (conLikeFieldLabels con) } } -- In CPS style as `RnM r` is monadic -- Reports an error if the name is an Exact or Orig and it can't find the name -- Otherwise if it is not an Exact or Orig, returns k lookupExactOrOrig :: RdrName -> (Name -> r) -> RnM r -> RnM r lookupExactOrOrig rdr_name res k = do { men <- lookupExactOrOrig_base rdr_name ; case men of FoundExactOrOrig n -> return (res n) ExactOrOrigError e -> do { addErr e ; return (res (mkUnboundNameRdr rdr_name)) } NotExactOrOrig -> k } -- Variant of 'lookupExactOrOrig' that does not report an error -- See Note [Errors in lookup functions] -- Calls k if the name is neither an Exact nor Orig lookupExactOrOrig_maybe :: RdrName -> (Maybe Name -> r) -> RnM r -> RnM r lookupExactOrOrig_maybe rdr_name res k = do { men <- lookupExactOrOrig_base rdr_name ; case men of FoundExactOrOrig n -> return (res (Just n)) ExactOrOrigError _ -> return (res Nothing) NotExactOrOrig -> k } data ExactOrOrigResult = FoundExactOrOrig Name -- ^ Found an Exact Or Orig Name | ExactOrOrigError MsgDoc -- ^ The RdrName was an Exact -- or Orig, but there was an -- error looking up the Name | NotExactOrOrig -- ^ The RdrName is neither an Exact nor -- Orig -- Does the actual looking up an Exact or Orig name, see 'ExactOrOrigResult' lookupExactOrOrig_base :: RdrName -> RnM ExactOrOrigResult lookupExactOrOrig_base rdr_name | Just n <- isExact_maybe rdr_name -- This happens in derived code = cvtEither <$> lookupExactOcc_either n | Just (rdr_mod, rdr_occ) <- isOrig_maybe rdr_name = FoundExactOrOrig <$> lookupOrig rdr_mod rdr_occ | otherwise = return NotExactOrOrig where cvtEither (Left e) = ExactOrOrigError e cvtEither (Right n) = FoundExactOrOrig n {- Note [Errors in lookup functions] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Many of these lookup functions will attach an error if it can't find the Name it is trying to lookup. However there are also _maybe and _either variants for many of these functions. These variants should *not* attach any errors, as there are places where we want to attempt looking up a name, but it's not the end of the world if we don't find it. For example, see lookupThName_maybe: It calls lookupGlobalOccRn_maybe multiple times for varying names in different namespaces. lookupGlobalOccRn_maybe should therefore never attach an error, instead just return a Nothing. For these _maybe/_either variant functions then, avoid calling further lookup functions that can attach errors and instead call their _maybe/_either counterparts. -} ----------------------------------------------- -- | Look up an occurrence of a field in record construction or pattern -- matching (but not update). When the -XDisambiguateRecordFields -- flag is on, take account of the data constructor name to -- disambiguate which field to use. -- -- See Note [DisambiguateRecordFields]. lookupRecFieldOcc :: Maybe Name -- Nothing => just look it up as usual -- Just con => use data con to disambiguate -> RdrName -> RnM Name lookupRecFieldOcc mb_con rdr_name | Just con <- mb_con , isUnboundName con -- Avoid error cascade = return (mkUnboundNameRdr rdr_name) | Just con <- mb_con = do { flds <- lookupConstructorFields con ; env <- getGlobalRdrEnv ; let lbl = occNameFS (rdrNameOcc rdr_name) mb_field = do fl <- find ((== lbl) . flLabel) flds -- We have the label, now check it is in -- scope (with the correct qualifier if -- there is one, hence calling pickGREs). gre <- lookupGRE_FieldLabel env fl guard (not (isQual rdr_name && null (pickGREs rdr_name [gre]))) return (fl, gre) ; case mb_field of Just (fl, gre) -> do { addUsedGRE True gre ; return (flSelector fl) } Nothing -> lookupGlobalOccRn rdr_name } -- See Note [Fall back on lookupGlobalOccRn in lookupRecFieldOcc] | otherwise -- This use of Global is right as we are looking up a selector which -- can only be defined at the top level. = lookupGlobalOccRn rdr_name {- Note [DisambiguateRecordFields] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ When we are looking up record fields in record construction or pattern matching, we can take advantage of the data constructor name to resolve fields that would otherwise be ambiguous (provided the -XDisambiguateRecordFields flag is on). For example, consider: data S = MkS { x :: Int } data T = MkT { x :: Int } e = MkS { x = 3 } When we are renaming the occurrence of `x` in `e`, instead of looking `x` up directly (and finding both fields), lookupRecFieldOcc will search the fields of `MkS` to find the only possible `x` the user can mean. Of course, we still have to check the field is in scope, using lookupGRE_FieldLabel. The handling of qualified imports is slightly subtle: the occurrence may be unqualified even if the field is imported only qualified (but if the occurrence is qualified, the qualifier must be correct). For example: module A where data S = MkS { x :: Int } data T = MkT { x :: Int } module B where import qualified A (S(..)) import A (T(MkT)) e1 = MkT { x = 3 } -- x not in scope, so fail e2 = A.MkS { B.x = 3 } -- module qualifier is wrong, so fail e3 = A.MkS { x = 3 } -- x in scope (lack of module qualifier permitted) In case `e1`, lookupGRE_FieldLabel will return Nothing. In case `e2`, lookupGRE_FieldLabel will return the GRE for `A.x`, but then the guard will fail because the field RdrName `B.x` is qualified and pickGREs rejects the GRE. In case `e3`, lookupGRE_FieldLabel will return the GRE for `A.x` and the guard will succeed because the field RdrName `x` is unqualified. Note [Fall back on lookupGlobalOccRn in lookupRecFieldOcc] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Whenever we fail to find the field or it is not in scope, mb_field will be False, and we fall back on looking it up normally using lookupGlobalOccRn. We don't report an error immediately because the actual problem might be located elsewhere. For example (#9975): data Test = Test { x :: Int } pattern Test wat = Test { x = wat } Here there are multiple declarations of Test (as a data constructor and as a pattern synonym), which will be reported as an error. We shouldn't also report an error about the occurrence of `x` in the pattern synonym RHS. However, if the pattern synonym gets added to the environment first, we will try and fail to find `x` amongst the (nonexistent) fields of the pattern synonym. Alternatively, the scope check can fail due to Template Haskell. Consider (#12130): module Foo where import M b = $(funny) module M(funny) where data T = MkT { x :: Int } funny :: Q Exp funny = [| MkT { x = 3 } |] When we splice, `MkT` is not lexically in scope, so lookupGRE_FieldLabel will fail. But there is no need for disambiguation anyway, because `x` is an original name, and lookupGlobalOccRn will find it. -} -- | Used in export lists to lookup the children. lookupSubBndrOcc_helper :: Bool -> Bool -> Name -> RdrName -> RnM ChildLookupResult lookupSubBndrOcc_helper must_have_parent warn_if_deprec parent rdr_name | isUnboundName parent -- Avoid an error cascade = return (FoundName NoParent (mkUnboundNameRdr rdr_name)) | otherwise = do gre_env <- getGlobalRdrEnv let original_gres = lookupGlobalRdrEnv gre_env (rdrNameOcc rdr_name) -- Disambiguate the lookup based on the parent information. -- The remaining GREs are things that we *could* export here, note that -- this includes things which have `NoParent`. Those are sorted in -- `checkPatSynParent`. traceRn "parent" (ppr parent) traceRn "lookupExportChild original_gres:" (ppr original_gres) traceRn "lookupExportChild picked_gres:" (ppr $ picked_gres original_gres) case picked_gres original_gres of NoOccurrence -> noMatchingParentErr original_gres UniqueOccurrence g -> if must_have_parent then noMatchingParentErr original_gres else checkFld g DisambiguatedOccurrence g -> checkFld g AmbiguousOccurrence gres -> mkNameClashErr gres where -- Convert into FieldLabel if necessary checkFld :: GlobalRdrElt -> RnM ChildLookupResult checkFld g@GRE{gre_name, gre_par} = do addUsedGRE warn_if_deprec g return $ case gre_par of FldParent _ mfs -> FoundFL (fldParentToFieldLabel gre_name mfs) _ -> FoundName gre_par gre_name fldParentToFieldLabel :: Name -> Maybe FastString -> FieldLabel fldParentToFieldLabel name mfs = case mfs of Nothing -> let fs = occNameFS (nameOccName name) in FieldLabel fs False name Just fs -> FieldLabel fs True name -- Called when we find no matching GREs after disambiguation but -- there are three situations where this happens. -- 1. There were none to begin with. -- 2. None of the matching ones were the parent but -- a. They were from an overloaded record field so we can report -- a better error -- b. The original lookup was actually ambiguous. -- For example, the case where overloading is off and two -- record fields are in scope from different record -- constructors, neither of which is the parent. noMatchingParentErr :: [GlobalRdrElt] -> RnM ChildLookupResult noMatchingParentErr original_gres = do overload_ok <- xoptM LangExt.DuplicateRecordFields case original_gres of [] -> return NameNotFound [g] -> return $ IncorrectParent parent (gre_name g) (ppr $ gre_name g) [p | Just p <- [getParent g]] gss@(g:_:_) -> if all isRecFldGRE gss && overload_ok then return $ IncorrectParent parent (gre_name g) (ppr $ expectJust "noMatchingParentErr" (greLabel g)) [p | x <- gss, Just p <- [getParent x]] else mkNameClashErr gss mkNameClashErr :: [GlobalRdrElt] -> RnM ChildLookupResult mkNameClashErr gres = do addNameClashErrRn rdr_name gres return (FoundName (gre_par (head gres)) (gre_name (head gres))) getParent :: GlobalRdrElt -> Maybe Name getParent (GRE { gre_par = p } ) = case p of ParentIs cur_parent -> Just cur_parent FldParent { par_is = cur_parent } -> Just cur_parent NoParent -> Nothing picked_gres :: [GlobalRdrElt] -> DisambigInfo -- For Unqual, find GREs that are in scope qualified or unqualified -- For Qual, find GREs that are in scope with that qualification picked_gres gres | isUnqual rdr_name = mconcat (map right_parent gres) | otherwise = mconcat (map right_parent (pickGREs rdr_name gres)) right_parent :: GlobalRdrElt -> DisambigInfo right_parent p = case getParent p of Just cur_parent | parent == cur_parent -> DisambiguatedOccurrence p | otherwise -> NoOccurrence Nothing -> UniqueOccurrence p -- This domain specific datatype is used to record why we decided it was -- possible that a GRE could be exported with a parent. data DisambigInfo = NoOccurrence -- The GRE could never be exported. It has the wrong parent. | UniqueOccurrence GlobalRdrElt -- The GRE has no parent. It could be a pattern synonym. | DisambiguatedOccurrence GlobalRdrElt -- The parent of the GRE is the correct parent | AmbiguousOccurrence [GlobalRdrElt] -- For example, two normal identifiers with the same name are in -- scope. They will both be resolved to "UniqueOccurrence" and the -- monoid will combine them to this failing case. instance Outputable DisambigInfo where ppr NoOccurrence = text "NoOccurence" ppr (UniqueOccurrence gre) = text "UniqueOccurrence:" <+> ppr gre ppr (DisambiguatedOccurrence gre) = text "DiambiguatedOccurrence:" <+> ppr gre ppr (AmbiguousOccurrence gres) = text "Ambiguous:" <+> ppr gres instance Semi.Semigroup DisambigInfo where -- This is the key line: We prefer disambiguated occurrences to other -- names. _ <> DisambiguatedOccurrence g' = DisambiguatedOccurrence g' DisambiguatedOccurrence g' <> _ = DisambiguatedOccurrence g' NoOccurrence <> m = m m <> NoOccurrence = m UniqueOccurrence g <> UniqueOccurrence g' = AmbiguousOccurrence [g, g'] UniqueOccurrence g <> AmbiguousOccurrence gs = AmbiguousOccurrence (g:gs) AmbiguousOccurrence gs <> UniqueOccurrence g' = AmbiguousOccurrence (g':gs) AmbiguousOccurrence gs <> AmbiguousOccurrence gs' = AmbiguousOccurrence (gs ++ gs') instance Monoid DisambigInfo where mempty = NoOccurrence mappend = (Semi.<>) -- Lookup SubBndrOcc can never be ambiguous -- -- Records the result of looking up a child. data ChildLookupResult = NameNotFound -- We couldn't find a suitable name | IncorrectParent Name -- Parent Name -- Name of thing we were looking for SDoc -- How to print the name [Name] -- List of possible parents | FoundName Parent Name -- We resolved to a normal name | FoundFL FieldLabel -- We resolved to a FL -- | Specialised version of msum for RnM ChildLookupResult combineChildLookupResult :: [RnM ChildLookupResult] -> RnM ChildLookupResult combineChildLookupResult [] = return NameNotFound combineChildLookupResult (x:xs) = do res <- x case res of NameNotFound -> combineChildLookupResult xs _ -> return res instance Outputable ChildLookupResult where ppr NameNotFound = text "NameNotFound" ppr (FoundName p n) = text "Found:" <+> ppr p <+> ppr n ppr (FoundFL fls) = text "FoundFL:" <+> ppr fls ppr (IncorrectParent p n td ns) = text "IncorrectParent" <+> hsep [ppr p, ppr n, td, ppr ns] lookupSubBndrOcc :: Bool -> Name -- Parent -> SDoc -> RdrName -> RnM (Either MsgDoc Name) -- Find all the things the rdr-name maps to -- and pick the one with the right parent namep lookupSubBndrOcc warn_if_deprec the_parent doc rdr_name = do res <- lookupExactOrOrig rdr_name (FoundName NoParent) $ -- This happens for built-in classes, see mod052 for example lookupSubBndrOcc_helper True warn_if_deprec the_parent rdr_name case res of NameNotFound -> return (Left (unknownSubordinateErr doc rdr_name)) FoundName _p n -> return (Right n) FoundFL fl -> return (Right (flSelector fl)) IncorrectParent {} -- See [Mismatched class methods and associated type families] -- in TcInstDecls. -> return $ Left (unknownSubordinateErr doc rdr_name) {- Note [Family instance binders] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Consider data family F a data instance F T = X1 | X2 The 'data instance' decl has an *occurrence* of F (and T), and *binds* X1 and X2. (This is unlike a normal data type declaration which would bind F too.) So we want an AvailTC F [X1,X2]. Now consider a similar pair: class C a where data G a instance C S where data G S = Y1 | Y2 The 'data G S' *binds* Y1 and Y2, and has an *occurrence* of G. But there is a small complication: in an instance decl, we don't use qualified names on the LHS; instead we use the class to disambiguate. Thus: module M where import Blib( G ) class C a where data G a instance C S where data G S = Y1 | Y2 Even though there are two G's in scope (M.G and Blib.G), the occurrence of 'G' in the 'instance C S' decl is unambiguous, because C has only one associated type called G. This is exactly what happens for methods, and it is only consistent to do the same thing for types. That's the role of the function lookupTcdName; the (Maybe Name) give the class of the encloseing instance decl, if any. Note [Looking up Exact RdrNames] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Exact RdrNames are generated by: * Template Haskell (See Note [Binders in Template Haskell] in GHC.ThToHs) * Derived instances (See Note [Auxiliary binders] in GHC.Tc.Deriv.Generate) For data types and classes have Exact system Names in the binding positions for constructors, TyCons etc. For example [d| data T = MkT Int |] when we splice in and convert to HsSyn RdrName, we'll get data (Exact (system Name "T")) = (Exact (system Name "MkT")) ... These System names are generated by GHC.ThToHs.thRdrName But, constructors and the like need External Names, not System Names! So we do the following * In GHC.Rename.Env.newTopSrcBinder we spot Exact RdrNames that wrap a non-External Name, and make an External name for it. This is the name that goes in the GlobalRdrEnv * When looking up an occurrence of an Exact name, done in GHC.Rename.Env.lookupExactOcc, we find the Name with the right unique in the GlobalRdrEnv, and use the one from the envt -- it will be an External Name in the case of the data type/constructor above. * Exact names are also use for purely local binders generated by TH, such as \x_33. x_33 Both binder and occurrence are Exact RdrNames. The occurrence gets looked up in the LocalRdrEnv by GHC.Rename.Env.lookupOccRn, and misses, because lookupLocalRdrEnv always returns Nothing for an Exact Name. Now we fall through to lookupExactOcc, which will find the Name is not in the GlobalRdrEnv, so we just use the Exact supplied Name. Note [Splicing Exact names] ~~~~~~~~~~~~~~~~~~~~~~~~~~~ Consider the splice $(do { x <- newName "x"; return (VarE x) }) This will generate a (HsExpr RdrName) term that mentions the Exact RdrName "x_56" (or whatever), but does not bind it. So when looking such Exact names we want to check that it's in scope, otherwise the type checker will get confused. To do this we need to keep track of all the Names in scope, and the LocalRdrEnv does just that; we consult it with RdrName.inLocalRdrEnvScope. There is another wrinkle. With TH and -XDataKinds, consider $( [d| data Nat = Zero data T = MkT (Proxy 'Zero) |] ) After splicing, but before renaming we get this: data Nat_77{tc} = Zero_78{d} data T_79{tc} = MkT_80{d} (Proxy 'Zero_78{tc}) |] ) The occurrence of 'Zero in the data type for T has the right unique, but it has a TcClsName name-space in its OccName. (This is set by the ctxt_ns argument of Convert.thRdrName.) When we check that is in scope in the GlobalRdrEnv, we need to look up the DataName namespace too. (An alternative would be to make the GlobalRdrEnv also have a Name -> GRE mapping.) Note [Template Haskell ambiguity] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The GlobalRdrEnv invariant says that if occ -> [gre1, ..., gren] then the gres have distinct Names (INVARIANT 1 of GlobalRdrEnv). This is guaranteed by extendGlobalRdrEnvRn (the dups check in add_gre). So how can we get multiple gres in lookupExactOcc_maybe? Because in TH we might use the same TH NameU in two different name spaces. eg (#7241): $(newName "Foo" >>= \o -> return [DataD [] o [] [RecC o []] [''Show]]) Here we generate a type constructor and data constructor with the same unique, but different name spaces. It'd be nicer to rule this out in extendGlobalRdrEnvRn, but that would mean looking up the OccName in every name-space, just in case, and that seems a bit brutal. So it's just done here on lookup. But we might need to revisit that choice. Note [Usage for sub-bndrs] ~~~~~~~~~~~~~~~~~~~~~~~~~~ If you have this import qualified M( C( f ) ) instance M.C T where f x = x then is the qualified import M.f used? Obviously yes. But the RdrName used in the instance decl is unqualified. In effect, we fill in the qualification by looking for f's whose class is M.C But when adding to the UsedRdrNames we must make that qualification explicit (saying "used M.f"), otherwise we get "Redundant import of M.f". So we make up a suitable (fake) RdrName. But be careful import qualified M import M( C(f) ) instance C T where f x = x Here we want to record a use of 'f', not of 'M.f', otherwise we'll miss the fact that the qualified import is redundant. -------------------------------------------------- -- Occurrences -------------------------------------------------- -} lookupLocatedOccRn :: Located RdrName -> RnM (Located Name) lookupLocatedOccRn = wrapLocM lookupOccRn lookupLocalOccRn_maybe :: RdrName -> RnM (Maybe Name) -- Just look in the local environment lookupLocalOccRn_maybe rdr_name = do { local_env <- getLocalRdrEnv ; return (lookupLocalRdrEnv local_env rdr_name) } lookupLocalOccThLvl_maybe :: Name -> RnM (Maybe (TopLevelFlag, ThLevel)) -- Just look in the local environment lookupLocalOccThLvl_maybe name = do { lcl_env <- getLclEnv ; return (lookupNameEnv (tcl_th_bndrs lcl_env) name) } -- lookupOccRn looks up an occurrence of a RdrName lookupOccRn :: RdrName -> RnM Name lookupOccRn rdr_name = do { mb_name <- lookupOccRn_maybe rdr_name ; case mb_name of Just name -> return name Nothing -> reportUnboundName rdr_name } -- Only used in one place, to rename pattern synonym binders. -- See Note [Renaming pattern synonym variables] in GHC.Rename.Bind lookupLocalOccRn :: RdrName -> RnM Name lookupLocalOccRn rdr_name = do { mb_name <- lookupLocalOccRn_maybe rdr_name ; case mb_name of Just name -> return name Nothing -> unboundName WL_LocalOnly rdr_name } -- lookupTypeOccRn looks up an optionally promoted RdrName. lookupTypeOccRn :: RdrName -> RnM Name -- see Note [Demotion] lookupTypeOccRn rdr_name | isVarOcc (rdrNameOcc rdr_name) -- See Note [Promoted variables in types] = badVarInType rdr_name | otherwise = do { mb_name <- lookupOccRn_maybe rdr_name ; case mb_name of Just name -> return name Nothing -> lookup_demoted rdr_name } lookup_demoted :: RdrName -> RnM Name lookup_demoted rdr_name | Just demoted_rdr <- demoteRdrName rdr_name -- Maybe it's the name of a *data* constructor = do { data_kinds <- xoptM LangExt.DataKinds ; star_is_type <- xoptM LangExt.StarIsType ; let star_info = starInfo star_is_type rdr_name ; if data_kinds then do { mb_demoted_name <- lookupOccRn_maybe demoted_rdr ; case mb_demoted_name of Nothing -> unboundNameX WL_Any rdr_name star_info Just demoted_name -> do { whenWOptM Opt_WarnUntickedPromotedConstructors $ addWarn (Reason Opt_WarnUntickedPromotedConstructors) (untickedPromConstrWarn demoted_name) ; return demoted_name } } else do { -- We need to check if a data constructor of this name is -- in scope to give good error messages. However, we do -- not want to give an additional error if the data -- constructor happens to be out of scope! See #13947. mb_demoted_name <- discardErrs $ lookupOccRn_maybe demoted_rdr ; let suggestion | isJust mb_demoted_name = suggest_dk | otherwise = star_info ; unboundNameX WL_Any rdr_name suggestion } } | otherwise = reportUnboundName rdr_name where suggest_dk = text "A data constructor of that name is in scope; did you mean DataKinds?" untickedPromConstrWarn name = text "Unticked promoted constructor" <> colon <+> quotes (ppr name) <> dot $$ hsep [ text "Use" , quotes (char '\'' <> ppr name) , text "instead of" , quotes (ppr name) <> dot ] badVarInType :: RdrName -> RnM Name badVarInType rdr_name = do { addErr (text "Illegal promoted term variable in a type:" <+> ppr rdr_name) ; return (mkUnboundNameRdr rdr_name) } {- Note [Promoted variables in types] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Consider this (#12686): x = True data Bad = Bad 'x The parser treats the quote in 'x as saying "use the term namespace", so we'll get (Bad x{v}), with 'x' in the VarName namespace. If we don't test for this, the renamer will happily rename it to the x bound at top level, and then the typecheck falls over because it doesn't have 'x' in scope when kind-checking. Note [Demotion] ~~~~~~~~~~~~~~~ When the user writes: data Nat = Zero | Succ Nat foo :: f Zero -> Int 'Zero' in the type signature of 'foo' is parsed as: HsTyVar ("Zero", TcClsName) When the renamer hits this occurrence of 'Zero' it's going to realise that it's not in scope. But because it is renaming a type, it knows that 'Zero' might be a promoted data constructor, so it will demote its namespace to DataName and do a second lookup. The final result (after the renamer) will be: HsTyVar ("Zero", DataName) -} lookupOccRnX_maybe :: (RdrName -> RnM (Maybe r)) -> (Name -> r) -> RdrName -> RnM (Maybe r) lookupOccRnX_maybe globalLookup wrapper rdr_name = runMaybeT . msum . map MaybeT $ [ fmap wrapper <$> lookupLocalOccRn_maybe rdr_name , globalLookup rdr_name ] lookupOccRn_maybe :: RdrName -> RnM (Maybe Name) lookupOccRn_maybe = lookupOccRnX_maybe lookupGlobalOccRn_maybe id lookupOccRn_overloaded :: Bool -> RdrName -> RnM (Maybe (Either Name [Name])) lookupOccRn_overloaded overload_ok = lookupOccRnX_maybe global_lookup Left where global_lookup :: RdrName -> RnM (Maybe (Either Name [Name])) global_lookup n = runMaybeT . msum . map MaybeT $ [ lookupGlobalOccRn_overloaded overload_ok n , fmap Left . listToMaybe <$> lookupQualifiedNameGHCi n ] lookupGlobalOccRn_maybe :: RdrName -> RnM (Maybe Name) -- Looks up a RdrName occurrence in the top-level -- environment, including using lookupQualifiedNameGHCi -- for the GHCi case, but first tries to find an Exact or Orig name. -- No filter function; does not report an error on failure -- See Note [Errors in lookup functions] -- Uses addUsedRdrName to record use and deprecations lookupGlobalOccRn_maybe rdr_name = lookupExactOrOrig_maybe rdr_name id (lookupGlobalOccRn_base rdr_name) lookupGlobalOccRn :: RdrName -> RnM Name -- lookupGlobalOccRn is like lookupOccRn, except that it looks in the global -- environment. Adds an error message if the RdrName is not in scope. -- You usually want to use "lookupOccRn" which also looks in the local -- environment. lookupGlobalOccRn rdr_name = lookupExactOrOrig rdr_name id $ do mn <- lookupGlobalOccRn_base rdr_name case mn of Just n -> return n Nothing -> do { traceRn "lookupGlobalOccRn" (ppr rdr_name) ; unboundName WL_Global rdr_name } -- Looks up a RdrName occurence in the GlobalRdrEnv and with -- lookupQualifiedNameGHCi. Does not try to find an Exact or Orig name first. -- lookupQualifiedNameGHCi here is used when we're in GHCi and a name like -- 'Data.Map.elems' is typed, even if you didn't import Data.Map lookupGlobalOccRn_base :: RdrName -> RnM (Maybe Name) lookupGlobalOccRn_base rdr_name = runMaybeT . msum . map MaybeT $ [ fmap gre_name <$> lookupGreRn_maybe rdr_name , listToMaybe <$> lookupQualifiedNameGHCi rdr_name ] -- This test is not expensive, -- and only happens for failed lookups lookupInfoOccRn :: RdrName -> RnM [Name] -- lookupInfoOccRn is intended for use in GHCi's ":info" command -- It finds all the GREs that RdrName could mean, not complaining -- about ambiguity, but rather returning them all -- C.f. #9881 -- lookupInfoOccRn is also used in situations where we check for -- at least one definition of the RdrName, not complaining about -- multiple definitions. (See #17832) lookupInfoOccRn rdr_name = lookupExactOrOrig rdr_name (:[]) $ do { rdr_env <- getGlobalRdrEnv ; let ns = map gre_name (lookupGRE_RdrName rdr_name rdr_env) ; qual_ns <- lookupQualifiedNameGHCi rdr_name ; return (ns ++ (qual_ns `minusList` ns)) } -- | Like 'lookupOccRn_maybe', but with a more informative result if -- the 'RdrName' happens to be a record selector: -- -- * Nothing -> name not in scope (no error reported) -- * Just (Left x) -> name uniquely refers to x, -- or there is a name clash (reported) -- * Just (Right xs) -> name refers to one or more record selectors; -- if overload_ok was False, this list will be -- a singleton. lookupGlobalOccRn_overloaded :: Bool -> RdrName -> RnM (Maybe (Either Name [Name])) lookupGlobalOccRn_overloaded overload_ok rdr_name = lookupExactOrOrig_maybe rdr_name (fmap Left) $ do { res <- lookupGreRn_helper rdr_name ; case res of GreNotFound -> return Nothing OneNameMatch gre -> do let wrapper = if isRecFldGRE gre then Right . (:[]) else Left return $ Just (wrapper (gre_name gre)) MultipleNames gres | all isRecFldGRE gres && overload_ok -> -- Don't record usage for ambiguous selectors -- until we know which is meant return $ Just (Right (map gre_name gres)) MultipleNames gres -> do addNameClashErrRn rdr_name gres return (Just (Left (gre_name (head gres)))) } -------------------------------------------------- -- Lookup in the Global RdrEnv of the module -------------------------------------------------- data GreLookupResult = GreNotFound | OneNameMatch GlobalRdrElt | MultipleNames [GlobalRdrElt] lookupGreRn_maybe :: RdrName -> RnM (Maybe GlobalRdrElt) -- Look up the RdrName in the GlobalRdrEnv -- Exactly one binding: records it as "used", return (Just gre) -- No bindings: return Nothing -- Many bindings: report "ambiguous", return an arbitrary (Just gre) -- Uses addUsedRdrName to record use and deprecations lookupGreRn_maybe rdr_name = do res <- lookupGreRn_helper rdr_name case res of OneNameMatch gre -> return $ Just gre MultipleNames gres -> do traceRn "lookupGreRn_maybe:NameClash" (ppr gres) addNameClashErrRn rdr_name gres return $ Just (head gres) GreNotFound -> return Nothing {- Note [ Unbound vs Ambiguous Names ] lookupGreRn_maybe deals with failures in two different ways. If a name is unbound then we return a `Nothing` but if the name is ambiguous then we raise an error and return a dummy name. The reason for this is that when we call `lookupGreRn_maybe` we are speculatively looking for whatever we are looking up. If we don't find it, then we might have been looking for the wrong thing and can keep trying. On the other hand, if we find a clash then there is no way to recover as we found the thing we were looking for but can no longer resolve which the correct one is. One example of this is in `lookupTypeOccRn` which first looks in the type constructor namespace before looking in the data constructor namespace to deal with `DataKinds`. There is however, as always, one exception to this scheme. If we find an ambiguous occurrence of a record selector and DuplicateRecordFields is enabled then we defer the selection until the typechecker. -} -- Internal Function lookupGreRn_helper :: RdrName -> RnM GreLookupResult lookupGreRn_helper rdr_name = do { env <- getGlobalRdrEnv ; case lookupGRE_RdrName rdr_name env of [] -> return GreNotFound [gre] -> do { addUsedGRE True gre ; return (OneNameMatch gre) } gres -> return (MultipleNames gres) } lookupGreAvailRn :: RdrName -> RnM (Name, AvailInfo) -- Used in export lists -- If not found or ambiguous, add error message, and fake with UnboundName -- Uses addUsedRdrName to record use and deprecations lookupGreAvailRn rdr_name = do mb_gre <- lookupGreRn_helper rdr_name case mb_gre of GreNotFound -> do traceRn "lookupGreAvailRn" (ppr rdr_name) name <- unboundName WL_Global rdr_name return (name, avail name) MultipleNames gres -> do addNameClashErrRn rdr_name gres let unbound_name = mkUnboundNameRdr rdr_name return (unbound_name, avail unbound_name) -- Returning an unbound name here prevents an error -- cascade OneNameMatch gre -> return (gre_name gre, availFromGRE gre) {- ********************************************************* * * Deprecations * * ********************************************************* Note [Handling of deprecations] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ * We report deprecations at each *occurrence* of the deprecated thing (see #5867) * We do not report deprecations for locally-defined names. For a start, we may be exporting a deprecated thing. Also we may use a deprecated thing in the defn of another deprecated things. We may even use a deprecated thing in the defn of a non-deprecated thing, when changing a module's interface. * addUsedGREs: we do not report deprecations for sub-binders: - the ".." completion for records - the ".." in an export item 'T(..)' - the things exported by a module export 'module M' -} addUsedDataCons :: GlobalRdrEnv -> TyCon -> RnM () -- Remember use of in-scope data constructors (#7969) addUsedDataCons rdr_env tycon = addUsedGREs [ gre | dc <- tyConDataCons tycon , Just gre <- [lookupGRE_Name rdr_env (dataConName dc)] ] addUsedGRE :: Bool -> GlobalRdrElt -> RnM () -- Called for both local and imported things -- Add usage *and* warn if deprecated addUsedGRE warn_if_deprec gre = do { when warn_if_deprec (warnIfDeprecated gre) ; unless (isLocalGRE gre) $ do { env <- getGblEnv ; traceRn "addUsedGRE" (ppr gre) ; updMutVar (tcg_used_gres env) (gre :) } } addUsedGREs :: [GlobalRdrElt] -> RnM () -- Record uses of any *imported* GREs -- Used for recording used sub-bndrs -- NB: no call to warnIfDeprecated; see Note [Handling of deprecations] addUsedGREs gres | null imp_gres = return () | otherwise = do { env <- getGblEnv ; traceRn "addUsedGREs" (ppr imp_gres) ; updMutVar (tcg_used_gres env) (imp_gres ++) } where imp_gres = filterOut isLocalGRE gres warnIfDeprecated :: GlobalRdrElt -> RnM () warnIfDeprecated gre@(GRE { gre_name = name, gre_imp = iss }) | (imp_spec : _) <- iss = do { dflags <- getDynFlags ; this_mod <- getModule ; when (wopt Opt_WarnWarningsDeprecations dflags && not (nameIsLocalOrFrom this_mod name)) $ -- See Note [Handling of deprecations] do { iface <- loadInterfaceForName doc name ; case lookupImpDeprec iface gre of Just txt -> addWarn (Reason Opt_WarnWarningsDeprecations) (mk_msg imp_spec txt) Nothing -> return () } } | otherwise = return () where occ = greOccName gre name_mod = ASSERT2( isExternalName name, ppr name ) nameModule name doc = text "The name" <+> quotes (ppr occ) <+> ptext (sLit "is mentioned explicitly") mk_msg imp_spec txt = sep [ sep [ text "In the use of" <+> pprNonVarNameSpace (occNameSpace occ) <+> quotes (ppr occ) , parens imp_msg <> colon ] , pprWarningTxtForMsg txt ] where imp_mod = importSpecModule imp_spec imp_msg = text "imported from" <+> ppr imp_mod <> extra extra | imp_mod == moduleName name_mod = Outputable.empty | otherwise = text ", but defined in" <+> ppr name_mod lookupImpDeprec :: ModIface -> GlobalRdrElt -> Maybe WarningTxt lookupImpDeprec iface gre = mi_warn_fn (mi_final_exts iface) (greOccName gre) `mplus` -- Bleat if the thing, case gre_par gre of -- or its parent, is warn'd ParentIs p -> mi_warn_fn (mi_final_exts iface) (nameOccName p) FldParent { par_is = p } -> mi_warn_fn (mi_final_exts iface) (nameOccName p) NoParent -> Nothing {- Note [Used names with interface not loaded] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ It's (just) possible to find a used Name whose interface hasn't been loaded: a) It might be a WiredInName; in that case we may not load its interface (although we could). b) It might be GHC.Real.fromRational, or GHC.Num.fromInteger These are seen as "used" by the renamer (if -XRebindableSyntax) is on), but the typechecker may discard their uses if in fact the in-scope fromRational is GHC.Read.fromRational, (see tcPat.tcOverloadedLit), and the typechecker sees that the type is fixed, say, to GHC.Base.Float (see Inst.lookupSimpleInst). In that obscure case it won't force the interface in. In both cases we simply don't permit deprecations; this is, after all, wired-in stuff. ********************************************************* * * GHCi support * * ********************************************************* A qualified name on the command line can refer to any module at all: we try to load the interface if we don't already have it, just as if there was an "import qualified M" declaration for every module. For example, writing `Data.List.sort` will load the interface file for `Data.List` as if the user had written `import qualified Data.List`. If we fail we just return Nothing, rather than bleating about "attempting to use module ‘D’ (./D.hs) which is not loaded" which is what loadSrcInterface does. It is enabled by default and disabled by the flag `-fno-implicit-import-qualified`. Note [Safe Haskell and GHCi] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We DON'T do this Safe Haskell as we need to check imports. We can and should instead check the qualified import but at the moment this requires some refactoring so leave as a TODO -} lookupQualifiedNameGHCi :: RdrName -> RnM [Name] lookupQualifiedNameGHCi rdr_name = -- We want to behave as we would for a source file import here, -- and respect hiddenness of modules/packages, hence loadSrcInterface. do { dflags <- getDynFlags ; is_ghci <- getIsGHCi ; go_for_it dflags is_ghci } where go_for_it dflags is_ghci | Just (mod,occ) <- isQual_maybe rdr_name , is_ghci , gopt Opt_ImplicitImportQualified dflags -- Enables this GHCi behaviour , not (safeDirectImpsReq dflags) -- See Note [Safe Haskell and GHCi] = do { res <- loadSrcInterface_maybe doc mod NotBoot Nothing ; case res of Succeeded iface -> return [ name | avail <- mi_exports iface , name <- availNames avail , nameOccName name == occ ] _ -> -- Either we couldn't load the interface, or -- we could but we didn't find the name in it do { traceRn "lookupQualifiedNameGHCi" (ppr rdr_name) ; return [] } } | otherwise = do { traceRn "lookupQualifiedNameGHCi: off" (ppr rdr_name) ; return [] } doc = text "Need to find" <+> ppr rdr_name {- Note [Looking up signature names] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ lookupSigOccRn is used for type signatures and pragmas Is this valid? module A import M( f ) f :: Int -> Int f x = x It's clear that the 'f' in the signature must refer to A.f The Haskell98 report does not stipulate this, but it will! So we must treat the 'f' in the signature in the same way as the binding occurrence of 'f', using lookupBndrRn However, consider this case: import M( f ) f :: Int -> Int g x = x We don't want to say 'f' is out of scope; instead, we want to return the imported 'f', so that later on the renamer will correctly report "misplaced type sig". Note [Signatures for top level things] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ data HsSigCtxt = ... | TopSigCtxt NameSet | .... * The NameSet says what is bound in this group of bindings. We can't use isLocalGRE from the GlobalRdrEnv, because of this: f x = x $( ...some TH splice... ) f :: Int -> Int When we encounter the signature for 'f', the binding for 'f' will be in the GlobalRdrEnv, and will be a LocalDef. Yet the signature is mis-placed * For type signatures the NameSet should be the names bound by the value bindings; for fixity declarations, the NameSet should also include class sigs and record selectors infix 3 `f` -- Yes, ok f :: C a => a -> a -- No, not ok class C a where f :: a -> a -} data HsSigCtxt = TopSigCtxt NameSet -- At top level, binding these names -- See Note [Signatures for top level things] | LocalBindCtxt NameSet -- In a local binding, binding these names | ClsDeclCtxt Name -- Class decl for this class | InstDeclCtxt NameSet -- Instance decl whose user-written method -- bindings are for these methods | HsBootCtxt NameSet -- Top level of a hs-boot file, binding these names | RoleAnnotCtxt NameSet -- A role annotation, with the names of all types -- in the group instance Outputable HsSigCtxt where ppr (TopSigCtxt ns) = text "TopSigCtxt" <+> ppr ns ppr (LocalBindCtxt ns) = text "LocalBindCtxt" <+> ppr ns ppr (ClsDeclCtxt n) = text "ClsDeclCtxt" <+> ppr n ppr (InstDeclCtxt ns) = text "InstDeclCtxt" <+> ppr ns ppr (HsBootCtxt ns) = text "HsBootCtxt" <+> ppr ns ppr (RoleAnnotCtxt ns) = text "RoleAnnotCtxt" <+> ppr ns lookupSigOccRn :: HsSigCtxt -> Sig GhcPs -> Located RdrName -> RnM (Located Name) lookupSigOccRn ctxt sig = lookupSigCtxtOccRn ctxt (hsSigDoc sig) -- | Lookup a name in relation to the names in a 'HsSigCtxt' lookupSigCtxtOccRn :: HsSigCtxt -> SDoc -- ^ description of thing we're looking up, -- like "type family" -> Located RdrName -> RnM (Located Name) lookupSigCtxtOccRn ctxt what = wrapLocM $ \ rdr_name -> do { mb_name <- lookupBindGroupOcc ctxt what rdr_name ; case mb_name of Left err -> do { addErr err; return (mkUnboundNameRdr rdr_name) } Right name -> return name } lookupBindGroupOcc :: HsSigCtxt -> SDoc -> RdrName -> RnM (Either MsgDoc Name) -- Looks up the RdrName, expecting it to resolve to one of the -- bound names passed in. If not, return an appropriate error message -- -- See Note [Looking up signature names] lookupBindGroupOcc ctxt what rdr_name | Just n <- isExact_maybe rdr_name = lookupExactOcc_either n -- allow for the possibility of missing Exacts; -- see Note [dataTcOccs and Exact Names] -- Maybe we should check the side conditions -- but it's a pain, and Exact things only show -- up when you know what you are doing | Just (rdr_mod, rdr_occ) <- isOrig_maybe rdr_name = do { n' <- lookupOrig rdr_mod rdr_occ ; return (Right n') } | otherwise = case ctxt of HsBootCtxt ns -> lookup_top (`elemNameSet` ns) TopSigCtxt ns -> lookup_top (`elemNameSet` ns) RoleAnnotCtxt ns -> lookup_top (`elemNameSet` ns) LocalBindCtxt ns -> lookup_group ns ClsDeclCtxt cls -> lookup_cls_op cls InstDeclCtxt ns -> if uniqSetAny isUnboundName ns -- #16610 then return (Right $ mkUnboundNameRdr rdr_name) else lookup_top (`elemNameSet` ns) where lookup_cls_op cls = lookupSubBndrOcc True cls doc rdr_name where doc = text "method of class" <+> quotes (ppr cls) lookup_top keep_me = do { env <- getGlobalRdrEnv ; let all_gres = lookupGlobalRdrEnv env (rdrNameOcc rdr_name) names_in_scope = -- If rdr_name lacks a binding, only -- recommend alternatives from related -- namespaces. See #17593. filter (\n -> nameSpacesRelated (rdrNameSpace rdr_name) (nameNameSpace n)) $ map gre_name $ filter isLocalGRE $ globalRdrEnvElts env candidates_msg = candidates names_in_scope ; case filter (keep_me . gre_name) all_gres of [] | null all_gres -> bale_out_with candidates_msg | otherwise -> bale_out_with local_msg (gre:_) -> return (Right (gre_name gre)) } lookup_group bound_names -- Look in the local envt (not top level) = do { mname <- lookupLocalOccRn_maybe rdr_name ; env <- getLocalRdrEnv ; let candidates_msg = candidates $ localRdrEnvElts env ; case mname of Just n | n `elemNameSet` bound_names -> return (Right n) | otherwise -> bale_out_with local_msg Nothing -> bale_out_with candidates_msg } bale_out_with msg = return (Left (sep [ text "The" <+> what <+> text "for" <+> quotes (ppr rdr_name) , nest 2 $ text "lacks an accompanying binding"] $$ nest 2 msg)) local_msg = parens $ text "The" <+> what <+> ptext (sLit "must be given where") <+> quotes (ppr rdr_name) <+> text "is declared" -- Identify all similar names and produce a message listing them candidates :: [Name] -> MsgDoc candidates names_in_scope = case similar_names of [] -> Outputable.empty [n] -> text "Perhaps you meant" <+> pp_item n _ -> sep [ text "Perhaps you meant one of these:" , nest 2 (pprWithCommas pp_item similar_names) ] where similar_names = fuzzyLookup (unpackFS $ occNameFS $ rdrNameOcc rdr_name) $ map (\x -> ((unpackFS $ occNameFS $ nameOccName x), x)) names_in_scope pp_item x = quotes (ppr x) <+> parens (pprDefinedAt x) --------------- lookupLocalTcNames :: HsSigCtxt -> SDoc -> RdrName -> RnM [(RdrName, Name)] -- GHC extension: look up both the tycon and data con or variable. -- Used for top-level fixity signatures and deprecations. -- Complain if neither is in scope. -- See Note [Fixity signature lookup] lookupLocalTcNames ctxt what rdr_name = do { mb_gres <- mapM lookup (dataTcOccs rdr_name) ; let (errs, names) = partitionEithers mb_gres ; when (null names) $ addErr (head errs) -- Bleat about one only ; return names } where lookup rdr = do { this_mod <- getModule ; nameEither <- lookupBindGroupOcc ctxt what rdr ; return (guard_builtin_syntax this_mod rdr nameEither) } -- Guard against the built-in syntax (ex: `infixl 6 :`), see #15233 guard_builtin_syntax this_mod rdr (Right name) | Just _ <- isBuiltInOcc_maybe (occName rdr) , this_mod /= nameModule name = Left (hsep [text "Illegal", what, text "of built-in syntax:", ppr rdr]) | otherwise = Right (rdr, name) guard_builtin_syntax _ _ (Left err) = Left err dataTcOccs :: RdrName -> [RdrName] -- Return both the given name and the same name promoted to the TcClsName -- namespace. This is useful when we aren't sure which we are looking at. -- See also Note [dataTcOccs and Exact Names] dataTcOccs rdr_name | isDataOcc occ || isVarOcc occ = [rdr_name, rdr_name_tc] | otherwise = [rdr_name] where occ = rdrNameOcc rdr_name rdr_name_tc = case rdr_name of -- The (~) type operator is always in scope, so we need a special case -- for it here, or else :info (~) fails in GHCi. -- See Note [eqTyCon (~) is built-in syntax] Unqual occ | occNameFS occ == fsLit "~" -> eqTyCon_RDR _ -> setRdrNameSpace rdr_name tcName {- Note [dataTcOccs and Exact Names] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Exact RdrNames can occur in code generated by Template Haskell, and generally those references are, well, exact. However, the TH `Name` type isn't expressive enough to always track the correct namespace information, so we sometimes get the right Unique but wrong namespace. Thus, we still have to do the double-lookup for Exact RdrNames. There is also an awkward situation for built-in syntax. Example in GHCi :info [] This parses as the Exact RdrName for nilDataCon, but we also want the list type constructor. Note that setRdrNameSpace on an Exact name requires the Name to be External, which it always is for built in syntax. -} {- ************************************************************************ * * Rebindable names Dealing with rebindable syntax is driven by the Opt_RebindableSyntax dynamic flag. In "deriving" code we don't want to use rebindable syntax so we switch off the flag locally * * ************************************************************************ Haskell 98 says that when you say "3" you get the "fromInteger" from the Standard Prelude, regardless of what is in scope. However, to experiment with having a language that is less coupled to the standard prelude, we're trying a non-standard extension that instead gives you whatever "Prelude.fromInteger" happens to be in scope. Then you can import Prelude () import MyPrelude as Prelude to get the desired effect. At the moment this just happens for * fromInteger, fromRational on literals (in expressions and patterns) * negate (in expressions) * minus (arising from n+k patterns) * "do" notation We store the relevant Name in the HsSyn tree, in * HsIntegral/HsFractional/HsIsString * NegApp * NPlusKPat * HsDo respectively. Initially, we just store the "standard" name (GHC.Builtin.Names.fromIntegralName, fromRationalName etc), but the renamer changes this to the appropriate user name if Opt_NoImplicitPrelude is on. That is what lookupSyntax does. We treat the original (standard) names as free-vars too, because the type checker checks the type of the user thing against the type of the standard thing. -} lookupIfThenElse :: Bool -- False <=> don't use rebindable syntax under any conditions -> RnM (SyntaxExpr GhcRn, FreeVars) -- Different to lookupSyntax because in the non-rebindable -- case we desugar directly rather than calling an existing function -- Hence the (Maybe (SyntaxExpr GhcRn)) return type lookupIfThenElse maybe_use_rs = do { rebindable_on <- xoptM LangExt.RebindableSyntax ; if not (rebindable_on && maybe_use_rs) then return (NoSyntaxExprRn, emptyFVs) else do { ite <- lookupOccRn (mkVarUnqual (fsLit "ifThenElse")) ; return ( mkRnSyntaxExpr ite , unitFV ite ) } } lookupSyntaxName :: Name -- ^ The standard name -> RnM (Name, FreeVars) -- ^ Possibly a non-standard name lookupSyntaxName std_name = do { rebindable_on <- xoptM LangExt.RebindableSyntax ; if not rebindable_on then return (std_name, emptyFVs) else -- Get the similarly named thing from the local environment do { usr_name <- lookupOccRn (mkRdrUnqual (nameOccName std_name)) ; return (usr_name, unitFV usr_name) } } lookupSyntaxExpr :: Name -- ^ The standard name -> RnM (HsExpr GhcRn, FreeVars) -- ^ Possibly a non-standard name lookupSyntaxExpr std_name = fmap (first nl_HsVar) $ lookupSyntaxName std_name lookupSyntax :: Name -- The standard name -> RnM (SyntaxExpr GhcRn, FreeVars) -- Possibly a non-standard -- name lookupSyntax std_name = fmap (first mkSyntaxExpr) $ lookupSyntaxExpr std_name lookupSyntaxNames :: [Name] -- Standard names -> RnM ([HsExpr GhcRn], FreeVars) -- See comments with HsExpr.ReboundNames -- this works with CmdTop, which wants HsExprs, not SyntaxExprs lookupSyntaxNames std_names = do { rebindable_on <- xoptM LangExt.RebindableSyntax ; if not rebindable_on then return (map (HsVar noExtField . noLoc) std_names, emptyFVs) else do { usr_names <- mapM (lookupOccRn . mkRdrUnqual . nameOccName) std_names ; return (map (HsVar noExtField . noLoc) usr_names, mkFVs usr_names) } } {- Note [QualifiedDo] ~~~~~~~~~~~~~~~~~~ QualifiedDo is implemented using the same placeholders for operation names in the AST that were devised for RebindableSyntax. Whenever the renamer checks which names to use for do syntax, it first checks if the do block is qualified (e.g. M.do { stmts }), in which case it searches for qualified names. If the qualified names are not in scope, an error is produced. If the do block is not qualified, the renamer does the usual search of the names which considers whether RebindableSyntax is enabled or not. Dealing with QualifiedDo is driven by the Opt_QualifiedDo dynamic flag. -} -- Lookup operations for a qualified do. If the context is not a qualified -- do, then use lookupSyntaxExpr. See Note [QualifiedDo]. lookupQualifiedDoExpr :: HsStmtContext p -> Name -> RnM (HsExpr GhcRn, FreeVars) lookupQualifiedDoExpr ctxt std_name = first nl_HsVar <$> lookupQualifiedDoName ctxt std_name -- Like lookupQualifiedDoExpr but for producing SyntaxExpr. -- See Note [QualifiedDo]. lookupQualifiedDo :: HsStmtContext p -> Name -> RnM (SyntaxExpr GhcRn, FreeVars) lookupQualifiedDo ctxt std_name = first mkSyntaxExpr <$> lookupQualifiedDoExpr ctxt std_name lookupNameWithQualifier :: Name -> ModuleName -> RnM (Name, FreeVars) lookupNameWithQualifier std_name modName = do { qname <- lookupOccRn (mkRdrQual modName (nameOccName std_name)) ; return (qname, unitFV qname) } -- See Note [QualifiedDo]. lookupQualifiedDoName :: HsStmtContext p -> Name -> RnM (Name, FreeVars) lookupQualifiedDoName ctxt std_name = case qualifiedDoModuleName_maybe ctxt of Nothing -> lookupSyntaxName std_name Just modName -> lookupNameWithQualifier std_name modName -- Lookup a locally-rebound name for Rebindable Syntax (RS). -- -- - When RS is off, 'lookupRebound' just returns 'Nothing', whatever -- name it is given. -- -- - When RS is on, we always try to return a 'Just', and GHC errors out -- if no suitable name is found in the environment. -- -- 'Nothing' really is "reserved" and means that rebindable syntax is off. lookupRebound :: FastString -> RnM (Maybe (Located Name)) lookupRebound nameStr = do rebind <- xoptM LangExt.RebindableSyntax if rebind -- If repetitive lookups ever become a problem perormance-wise, -- we could lookup all the names we will ever care about just once -- at the beginning and stick them in the environment, possibly -- populating that "cache" lazily too. then (\nm -> Just (L (nameSrcSpan nm) nm)) <$> lookupOccRn (mkVarUnqual nameStr) else pure Nothing -- | Lookup an @ifThenElse@ binding (see 'lookupRebound'). lookupReboundIf :: RnM (Maybe (Located Name)) lookupReboundIf = lookupRebound reboundIfSymbol -- Error messages opDeclErr :: RdrName -> SDoc opDeclErr n = hang (text "Illegal declaration of a type or class operator" <+> quotes (ppr n)) 2 (text "Use TypeOperators to declare operators in type and declarations") badOrigBinding :: RdrName -> SDoc badOrigBinding name | Just _ <- isBuiltInOcc_maybe occ = text "Illegal binding of built-in syntax:" <+> ppr occ -- Use an OccName here because we don't want to print Prelude.(,) | otherwise = text "Cannot redefine a Name retrieved by a Template Haskell quote:" <+> ppr name -- This can happen when one tries to use a Template Haskell splice to -- define a top-level identifier with an already existing name, e.g., -- -- $(pure [ValD (VarP 'succ) (NormalB (ConE 'True)) []]) -- -- (See #13968.) where occ = rdrNameOcc $ filterCTuple name