{-# LANGUAGE CPP #-} {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE ViewPatterns #-} {-# LANGUAGE LambdaCase #-} {-# OPTIONS_GHC -Wno-incomplete-record-updates #-} -- -- (c) The University of Glasgow 2002-2006 -- -- Functions over HsSyn specialised to RdrName. module GHC.Parser.PostProcess ( mkRdrGetField, mkRdrProjection, Fbind, -- RecordDot mkHsOpApp, mkHsIntegral, mkHsFractional, mkHsIsString, mkHsDo, mkSpliceDecl, mkRoleAnnotDecl, mkClassDecl, mkTyData, mkDataFamInst, mkTySynonym, mkTyFamInstEqn, mkStandaloneKindSig, mkTyFamInst, mkFamDecl, mkInlinePragma, mkPatSynMatchGroup, mkRecConstrOrUpdate, mkTyClD, mkInstD, mkRdrRecordCon, mkRdrRecordUpd, setRdrNameSpace, fromSpecTyVarBndr, fromSpecTyVarBndrs, annBinds, cvBindGroup, cvBindsAndSigs, cvTopDecls, placeHolderPunRhs, -- Stuff to do with Foreign declarations mkImport, parseCImport, mkExport, mkExtName, -- RdrName -> CLabelString mkGadtDecl, -- [LocatedA RdrName] -> LHsType RdrName -> ConDecl RdrName mkConDeclH98, -- Bunch of functions in the parser monad for -- checking and constructing values checkImportDecl, checkExpBlockArguments, checkCmdBlockArguments, checkPrecP, -- Int -> P Int checkContext, -- HsType -> P HsContext checkPattern, -- HsExp -> P HsPat checkPattern_hints, checkMonadComp, -- P (HsStmtContext GhcPs) checkValDef, -- (SrcLoc, HsExp, HsRhs, [HsDecl]) -> P HsDecl checkValSigLhs, LRuleTyTmVar, RuleTyTmVar(..), mkRuleBndrs, mkRuleTyVarBndrs, checkRuleTyVarBndrNames, checkRecordSyntax, checkEmptyGADTs, addFatalError, hintBangPat, mkBangTy, UnpackednessPragma(..), mkMultTy, -- Help with processing exports ImpExpSubSpec(..), ImpExpQcSpec(..), mkModuleImpExp, mkTypeImpExp, mkImpExpSubSpec, checkImportSpec, -- Token symbols starSym, -- Warnings and errors warnStarIsType, warnPrepositiveQualifiedModule, failOpFewArgs, failOpNotEnabledImportQualifiedPost, failOpImportQualifiedTwice, SumOrTuple (..), -- Expression/command/pattern ambiguity resolution PV, runPV, ECP(ECP, unECP), DisambInfixOp(..), DisambECP(..), ecpFromExp, ecpFromCmd, PatBuilder, -- Type/datacon ambiguity resolution DisambTD(..), addUnpackednessP, dataConBuilderCon, dataConBuilderDetails, ) where import GHC.Prelude import GHC.Hs -- Lots of it import GHC.Core.TyCon ( TyCon, isTupleTyCon, tyConSingleDataCon_maybe ) import GHC.Core.DataCon ( DataCon, dataConTyCon ) import GHC.Core.ConLike ( ConLike(..) ) import GHC.Core.Coercion.Axiom ( Role, fsFromRole ) import GHC.Types.Name.Reader import GHC.Types.Name import GHC.Unit.Module (ModuleName) import GHC.Types.Basic import GHC.Types.Fixity import GHC.Types.SourceText import GHC.Parser.Types import GHC.Parser.Lexer import GHC.Parser.Errors import GHC.Utils.Lexeme ( isLexCon ) import GHC.Types.TyThing import GHC.Core.Type ( unrestrictedFunTyCon, Specificity(..) ) import GHC.Builtin.Types( cTupleTyConName, tupleTyCon, tupleDataCon, nilDataConName, nilDataConKey, listTyConName, listTyConKey, eqTyCon_RDR ) import GHC.Types.ForeignCall import GHC.Types.SrcLoc import GHC.Types.Unique ( hasKey ) import GHC.Data.OrdList import GHC.Utils.Outputable as Outputable import GHC.Data.FastString import GHC.Data.Maybe import GHC.Data.Bag import GHC.Utils.Misc import Data.Either import Data.List import Data.Foldable import GHC.Driver.Flags ( WarningFlag(..) ) import qualified Data.Semigroup as Semi import GHC.Utils.Panic import Control.Monad import Text.ParserCombinators.ReadP as ReadP import Data.Char import Data.Data ( dataTypeOf, fromConstr, dataTypeConstrs ) import Data.Kind ( Type ) import Data.List.NonEmpty (NonEmpty) #include "HsVersions.h" {- ********************************************************************** Construction functions for Rdr stuff ********************************************************************* -} -- | mkClassDecl builds a RdrClassDecl, filling in the names for tycon and -- datacon by deriving them from the name of the class. We fill in the names -- for the tycon and datacon corresponding to the class, by deriving them -- from the name of the class itself. This saves recording the names in the -- interface file (which would be equally good). -- Similarly for mkConDecl, mkClassOpSig and default-method names. -- *** See Note [The Naming story] in GHC.Hs.Decls **** mkTyClD :: LTyClDecl (GhcPass p) -> LHsDecl (GhcPass p) mkTyClD (L loc d) = L loc (TyClD noExtField d) mkInstD :: LInstDecl (GhcPass p) -> LHsDecl (GhcPass p) mkInstD (L loc d) = L loc (InstD noExtField d) mkClassDecl :: SrcSpan -> Located (Maybe (LHsContext GhcPs), LHsType GhcPs) -> Located (a,[LHsFunDep GhcPs]) -> OrdList (LHsDecl GhcPs) -> LayoutInfo -> [AddEpAnn] -> P (LTyClDecl GhcPs) mkClassDecl loc' (L _ (mcxt, tycl_hdr)) fds where_cls layoutInfo annsIn = do { let loc = noAnnSrcSpan loc' ; (binds, sigs, ats, at_defs, _, docs) <- cvBindsAndSigs where_cls ; (cls, tparams, fixity, ann) <- checkTyClHdr True tycl_hdr ; tyvars <- checkTyVars (text "class") whereDots cls tparams ; cs <- getCommentsFor (locA loc) -- Get any remaining comments ; let anns' = addAnns (EpAnn (spanAsAnchor $ locA loc) annsIn emptyComments) ann cs ; return (L loc (ClassDecl { tcdCExt = (anns', NoAnnSortKey, layoutInfo) , tcdCtxt = mcxt , tcdLName = cls, tcdTyVars = tyvars , tcdFixity = fixity , tcdFDs = snd (unLoc fds) , tcdSigs = mkClassOpSigs sigs , tcdMeths = binds , tcdATs = ats, tcdATDefs = at_defs , tcdDocs = docs })) } mkTyData :: SrcSpan -> NewOrData -> Maybe (LocatedP CType) -> Located (Maybe (LHsContext GhcPs), LHsType GhcPs) -> Maybe (LHsKind GhcPs) -> [LConDecl GhcPs] -> Located (HsDeriving GhcPs) -> [AddEpAnn] -> P (LTyClDecl GhcPs) mkTyData loc' new_or_data cType (L _ (mcxt, tycl_hdr)) ksig data_cons (L _ maybe_deriv) annsIn = do { let loc = noAnnSrcSpan loc' ; (tc, tparams, fixity, ann) <- checkTyClHdr False tycl_hdr ; tyvars <- checkTyVars (ppr new_or_data) equalsDots tc tparams ; cs <- getCommentsFor (locA loc) -- Get any remaining comments ; let anns' = addAnns (EpAnn (spanAsAnchor $ locA loc) annsIn emptyComments) ann cs ; defn <- mkDataDefn new_or_data cType mcxt ksig data_cons maybe_deriv ; return (L loc (DataDecl { tcdDExt = anns', tcdLName = tc, tcdTyVars = tyvars, tcdFixity = fixity, tcdDataDefn = defn })) } mkDataDefn :: NewOrData -> Maybe (LocatedP CType) -> Maybe (LHsContext GhcPs) -> Maybe (LHsKind GhcPs) -> [LConDecl GhcPs] -> HsDeriving GhcPs -> P (HsDataDefn GhcPs) mkDataDefn new_or_data cType mcxt ksig data_cons maybe_deriv = do { checkDatatypeContext mcxt ; return (HsDataDefn { dd_ext = noExtField , dd_ND = new_or_data, dd_cType = cType , dd_ctxt = mcxt , dd_cons = data_cons , dd_kindSig = ksig , dd_derivs = maybe_deriv }) } mkTySynonym :: SrcSpan -> LHsType GhcPs -- LHS -> LHsType GhcPs -- RHS -> [AddEpAnn] -> P (LTyClDecl GhcPs) mkTySynonym loc lhs rhs annsIn = do { (tc, tparams, fixity, ann) <- checkTyClHdr False lhs ; cs1 <- getCommentsFor loc -- Add any API Annotations to the top SrcSpan [temp] ; tyvars <- checkTyVars (text "type") equalsDots tc tparams ; cs2 <- getCommentsFor loc -- Add any API Annotations to the top SrcSpan [temp] ; let anns' = addAnns (EpAnn (spanAsAnchor loc) annsIn emptyComments) ann (cs1 Semi.<> cs2) ; return (L (noAnnSrcSpan loc) (SynDecl { tcdSExt = anns' , tcdLName = tc, tcdTyVars = tyvars , tcdFixity = fixity , tcdRhs = rhs })) } mkStandaloneKindSig :: SrcSpan -> Located [LocatedN RdrName] -- LHS -> LHsSigType GhcPs -- RHS -> [AddEpAnn] -> P (LStandaloneKindSig GhcPs) mkStandaloneKindSig loc lhs rhs anns = do { vs <- mapM check_lhs_name (unLoc lhs) ; v <- check_singular_lhs (reverse vs) ; cs <- getCommentsFor loc ; return $ L (noAnnSrcSpan loc) $ StandaloneKindSig (EpAnn (spanAsAnchor loc) anns cs) v rhs } where check_lhs_name v@(unLoc->name) = if isUnqual name && isTcOcc (rdrNameOcc name) then return v else addFatalError $ PsError (PsErrUnexpectedQualifiedConstructor (unLoc v)) [] (getLocA v) check_singular_lhs vs = case vs of [] -> panic "mkStandaloneKindSig: empty left-hand side" [v] -> return v _ -> addFatalError $ PsError (PsErrMultipleNamesInStandaloneKindSignature vs) [] (getLoc lhs) mkTyFamInstEqn :: SrcSpan -> HsOuterFamEqnTyVarBndrs GhcPs -> LHsType GhcPs -> LHsType GhcPs -> [AddEpAnn] -> P (LTyFamInstEqn GhcPs) mkTyFamInstEqn loc bndrs lhs rhs anns = do { (tc, tparams, fixity, ann) <- checkTyClHdr False lhs ; cs <- getCommentsFor loc ; return (L (noAnnSrcSpan loc) $ FamEqn { feqn_ext = EpAnn (spanAsAnchor loc) (anns `mappend` ann) cs , feqn_tycon = tc , feqn_bndrs = bndrs , feqn_pats = tparams , feqn_fixity = fixity , feqn_rhs = rhs })} mkDataFamInst :: SrcSpan -> NewOrData -> Maybe (LocatedP CType) -> (Maybe ( LHsContext GhcPs), HsOuterFamEqnTyVarBndrs GhcPs , LHsType GhcPs) -> Maybe (LHsKind GhcPs) -> [LConDecl GhcPs] -> Located (HsDeriving GhcPs) -> [AddEpAnn] -> P (LInstDecl GhcPs) mkDataFamInst loc new_or_data cType (mcxt, bndrs, tycl_hdr) ksig data_cons (L _ maybe_deriv) anns = do { (tc, tparams, fixity, ann) <- checkTyClHdr False tycl_hdr ; cs <- getCommentsFor loc -- Add any API Annotations to the top SrcSpan ; let anns' = addAnns (EpAnn (spanAsAnchor loc) ann cs) anns emptyComments ; defn <- mkDataDefn new_or_data cType mcxt ksig data_cons maybe_deriv ; return (L (noAnnSrcSpan loc) (DataFamInstD anns' (DataFamInstDecl (FamEqn { feqn_ext = anns' , feqn_tycon = tc , feqn_bndrs = bndrs , feqn_pats = tparams , feqn_fixity = fixity , feqn_rhs = defn })))) } mkTyFamInst :: SrcSpan -> TyFamInstEqn GhcPs -> [AddEpAnn] -> P (LInstDecl GhcPs) mkTyFamInst loc eqn anns = do cs <- getCommentsFor loc return (L (noAnnSrcSpan loc) (TyFamInstD noExtField (TyFamInstDecl (EpAnn (spanAsAnchor loc) anns cs) eqn))) mkFamDecl :: SrcSpan -> FamilyInfo GhcPs -> TopLevelFlag -> LHsType GhcPs -- LHS -> Located (FamilyResultSig GhcPs) -- Optional result signature -> Maybe (LInjectivityAnn GhcPs) -- Injectivity annotation -> [AddEpAnn] -> P (LTyClDecl GhcPs) mkFamDecl loc info topLevel lhs ksig injAnn annsIn = do { (tc, tparams, fixity, ann) <- checkTyClHdr False lhs ; cs1 <- getCommentsFor loc -- Add any API Annotations to the top SrcSpan [temp] ; tyvars <- checkTyVars (ppr info) equals_or_where tc tparams ; cs2 <- getCommentsFor loc -- Add any API Annotations to the top SrcSpan [temp] ; let anns' = addAnns (EpAnn (spanAsAnchor loc) annsIn emptyComments) ann (cs1 Semi.<> cs2) ; return (L (noAnnSrcSpan loc) (FamDecl noExtField (FamilyDecl { fdExt = anns' , fdTopLevel = topLevel , fdInfo = info, fdLName = tc , fdTyVars = tyvars , fdFixity = fixity , fdResultSig = ksig , fdInjectivityAnn = injAnn }))) } where equals_or_where = case info of DataFamily -> empty OpenTypeFamily -> empty ClosedTypeFamily {} -> whereDots mkSpliceDecl :: LHsExpr GhcPs -> P (LHsDecl GhcPs) -- If the user wrote -- [pads| ... ] then return a QuasiQuoteD -- $(e) then return a SpliceD -- but if they wrote, say, -- f x then behave as if they'd written $(f x) -- ie a SpliceD -- -- Typed splices are not allowed at the top level, thus we do not represent them -- as spliced declaration. See #10945 mkSpliceDecl lexpr@(L loc expr) | HsSpliceE _ splice@(HsUntypedSplice {}) <- expr = do cs <- getCommentsFor (locA loc) return $ L (addCommentsToSrcAnn loc cs) $ SpliceD noExtField (SpliceDecl noExtField (L loc splice) ExplicitSplice) | HsSpliceE _ splice@(HsQuasiQuote {}) <- expr = do cs <- getCommentsFor (locA loc) return $ L (addCommentsToSrcAnn loc cs) $ SpliceD noExtField (SpliceDecl noExtField (L loc splice) ExplicitSplice) | otherwise = do cs <- getCommentsFor (locA loc) return $ L (addCommentsToSrcAnn loc cs) $ SpliceD noExtField (SpliceDecl noExtField (L loc (mkUntypedSplice noAnn BareSplice lexpr)) ImplicitSplice) mkRoleAnnotDecl :: SrcSpan -> LocatedN RdrName -- type being annotated -> [Located (Maybe FastString)] -- roles -> [AddEpAnn] -> P (LRoleAnnotDecl GhcPs) mkRoleAnnotDecl loc tycon roles anns = do { roles' <- mapM parse_role roles ; cs <- getCommentsFor loc ; return $ L (noAnnSrcSpan loc) $ RoleAnnotDecl (EpAnn (spanAsAnchor loc) anns cs) tycon roles' } where role_data_type = dataTypeOf (undefined :: Role) all_roles = map fromConstr $ dataTypeConstrs role_data_type possible_roles = [(fsFromRole role, role) | role <- all_roles] parse_role (L loc_role Nothing) = return $ L loc_role Nothing parse_role (L loc_role (Just role)) = case lookup role possible_roles of Just found_role -> return $ L loc_role $ Just found_role Nothing -> let nearby = fuzzyLookup (unpackFS role) (mapFst unpackFS possible_roles) in addFatalError $ PsError (PsErrIllegalRoleName role nearby) [] loc_role -- | Converts a list of 'LHsTyVarBndr's annotated with their 'Specificity' to -- binders without annotations. Only accepts specified variables, and errors if -- any of the provided binders has an 'InferredSpec' annotation. fromSpecTyVarBndrs :: [LHsTyVarBndr Specificity GhcPs] -> P [LHsTyVarBndr () GhcPs] fromSpecTyVarBndrs = mapM fromSpecTyVarBndr -- | Converts 'LHsTyVarBndr' annotated with its 'Specificity' to one without -- annotations. Only accepts specified variables, and errors if the provided -- binder has an 'InferredSpec' annotation. fromSpecTyVarBndr :: LHsTyVarBndr Specificity GhcPs -> P (LHsTyVarBndr () GhcPs) fromSpecTyVarBndr bndr = case bndr of (L loc (UserTyVar xtv flag idp)) -> (check_spec flag loc) >> return (L loc $ UserTyVar xtv () idp) (L loc (KindedTyVar xtv flag idp k)) -> (check_spec flag loc) >> return (L loc $ KindedTyVar xtv () idp k) where check_spec :: Specificity -> SrcSpanAnnA -> P () check_spec SpecifiedSpec _ = return () check_spec InferredSpec loc = addFatalError $ PsError PsErrInferredTypeVarNotAllowed [] (locA loc) -- | Add the annotation for a 'where' keyword to existing @HsLocalBinds@ annBinds :: AddEpAnn -> EpAnnComments -> HsLocalBinds GhcPs -> (HsLocalBinds GhcPs, Maybe EpAnnComments) annBinds a cs (HsValBinds an bs) = (HsValBinds (add_where a an cs) bs, Nothing) annBinds a cs (HsIPBinds an bs) = (HsIPBinds (add_where a an cs) bs, Nothing) annBinds _ cs (EmptyLocalBinds x) = (EmptyLocalBinds x, Just cs) add_where :: AddEpAnn -> EpAnn AnnList -> EpAnnComments -> EpAnn AnnList add_where an@(AddEpAnn _ (EpaSpan rs)) (EpAnn a (AnnList anc o c r t) cs) cs2 | valid_anchor (anchor a) = EpAnn (widenAnchor a [an]) (AnnList anc o c (an:r) t) (cs Semi.<> cs2) | otherwise = EpAnn (patch_anchor rs a) (AnnList (fmap (patch_anchor rs) anc) o c (an:r) t) (cs Semi.<> cs2) add_where an@(AddEpAnn _ (EpaSpan rs)) EpAnnNotUsed cs = EpAnn (Anchor rs UnchangedAnchor) (AnnList (Just $ Anchor rs UnchangedAnchor) Nothing Nothing [an] []) cs add_where (AddEpAnn _ (EpaDelta _ _)) _ _ = panic "add_where" -- EpaDelta should only be used for transformations valid_anchor :: RealSrcSpan -> Bool valid_anchor r = srcSpanStartLine r >= 0 -- If the decl list for where binds is empty, the anchor ends up -- invalid. In this case, use the parent one patch_anchor :: RealSrcSpan -> Anchor -> Anchor patch_anchor r1 (Anchor r0 op) = Anchor r op where r = if srcSpanStartLine r0 < 0 then r1 else r0 {- ********************************************************************** #cvBinds-etc# Converting to @HsBinds@, etc. ********************************************************************* -} -- | Function definitions are restructured here. Each is assumed to be recursive -- initially, and non recursive definitions are discovered by the dependency -- analyser. -- | Groups together bindings for a single function cvTopDecls :: OrdList (LHsDecl GhcPs) -> [LHsDecl GhcPs] cvTopDecls decls = getMonoBindAll (fromOL decls) -- Declaration list may only contain value bindings and signatures. cvBindGroup :: OrdList (LHsDecl GhcPs) -> P (HsValBinds GhcPs) cvBindGroup binding = do { (mbs, sigs, fam_ds, tfam_insts , dfam_insts, _) <- cvBindsAndSigs binding ; ASSERT( null fam_ds && null tfam_insts && null dfam_insts) return $ ValBinds NoAnnSortKey mbs sigs } cvBindsAndSigs :: OrdList (LHsDecl GhcPs) -> P (LHsBinds GhcPs, [LSig GhcPs], [LFamilyDecl GhcPs] , [LTyFamInstDecl GhcPs], [LDataFamInstDecl GhcPs], [LDocDecl GhcPs]) -- Input decls contain just value bindings and signatures -- and in case of class or instance declarations also -- associated type declarations. They might also contain Haddock comments. cvBindsAndSigs fb = do fb' <- drop_bad_decls (fromOL fb) return (partitionBindsAndSigs (getMonoBindAll fb')) where -- cvBindsAndSigs is called in several places in the parser, -- and its items can be produced by various productions: -- -- * decl (when parsing a where clause or a let-expression) -- * decl_inst (when parsing an instance declaration) -- * decl_cls (when parsing a class declaration) -- -- partitionBindsAndSigs can handle almost all declaration forms produced -- by the aforementioned productions, except for SpliceD, which we filter -- out here (in drop_bad_decls). -- -- We're not concerned with every declaration form possible, such as those -- produced by the topdecl parser production, because cvBindsAndSigs is not -- called on top-level declarations. drop_bad_decls [] = return [] drop_bad_decls (L l (SpliceD _ d) : ds) = do addError $ PsError (PsErrDeclSpliceNotAtTopLevel d) [] (locA l) drop_bad_decls ds drop_bad_decls (d:ds) = (d:) <$> drop_bad_decls ds ----------------------------------------------------------------------------- -- Group function bindings into equation groups getMonoBind :: LHsBind GhcPs -> [LHsDecl GhcPs] -> (LHsBind GhcPs, [LHsDecl GhcPs]) -- Suppose (b',ds') = getMonoBind b ds -- ds is a list of parsed bindings -- b is a MonoBinds that has just been read off the front -- Then b' is the result of grouping more equations from ds that -- belong with b into a single MonoBinds, and ds' is the depleted -- list of parsed bindings. -- -- All Haddock comments between equations inside the group are -- discarded. -- -- No AndMonoBinds or EmptyMonoBinds here; just single equations getMonoBind (L loc1 (FunBind { fun_id = fun_id1@(L _ f1) , fun_matches = MG { mg_alts = (L _ m1@[L _ mtchs1]) } })) binds | has_args m1 = go [L (removeCommentsA loc1) mtchs1] (commentsOnlyA loc1) binds [] where go :: [LMatch GhcPs (LHsExpr GhcPs)] -> SrcSpanAnnA -> [LHsDecl GhcPs] -> [LHsDecl GhcPs] -> (LHsBind GhcPs,[LHsDecl GhcPs]) -- AZ go mtchs loc ((L loc2 (ValD _ (FunBind { fun_id = (L _ f2) , fun_matches = MG { mg_alts = (L _ [L lm2 mtchs2]) } }))) : binds) _ | f1 == f2 = let (loc2', lm2') = transferAnnsA loc2 lm2 in go (L lm2' mtchs2 : mtchs) (combineSrcSpansA loc loc2') binds [] go mtchs loc (doc_decl@(L loc2 (DocD {})) : binds) doc_decls = let doc_decls' = doc_decl : doc_decls in go mtchs (combineSrcSpansA loc loc2) binds doc_decls' go mtchs loc binds doc_decls = ( L loc (makeFunBind fun_id1 (mkLocatedList $ reverse mtchs)) , (reverse doc_decls) ++ binds) -- Reverse the final matches, to get it back in the right order -- Do the same thing with the trailing doc comments getMonoBind bind binds = (bind, binds) -- Group together adjacent FunBinds for every function. getMonoBindAll :: [LHsDecl GhcPs] -> [LHsDecl GhcPs] getMonoBindAll [] = [] getMonoBindAll (L l (ValD _ b) : ds) = let (L l' b', ds') = getMonoBind (L l b) ds in L l' (ValD noExtField b') : getMonoBindAll ds' getMonoBindAll (d : ds) = d : getMonoBindAll ds has_args :: [LMatch GhcPs (LHsExpr GhcPs)] -> Bool has_args [] = panic "GHC.Parser.PostProcess.has_args" has_args (L _ (Match { m_pats = args }) : _) = not (null args) -- Don't group together FunBinds if they have -- no arguments. This is necessary now that variable bindings -- with no arguments are now treated as FunBinds rather -- than pattern bindings (tests/rename/should_fail/rnfail002). {- ********************************************************************** #PrefixToHS-utils# Utilities for conversion ********************************************************************* -} {- Note [Parsing data constructors is hard] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The problem with parsing data constructors is that they look a lot like types. Compare: (s1) data T = C t1 t2 (s2) type T = C t1 t2 Syntactically, there's little difference between these declarations, except in (s1) 'C' is a data constructor, but in (s2) 'C' is a type constructor. This similarity would pose no problem if we knew ahead of time if we are parsing a type or a constructor declaration. Looking at (s1) and (s2), a simple (but wrong!) rule comes to mind: in 'data' declarations assume we are parsing data constructors, and in other contexts (e.g. 'type' declarations) assume we are parsing type constructors. This simple rule does not work because of two problematic cases: (p1) data T = C t1 t2 :+ t3 (p2) data T = C t1 t2 => t3 In (p1) we encounter (:+) and it turns out we are parsing an infix data declaration, so (C t1 t2) is a type and 'C' is a type constructor. In (p2) we encounter (=>) and it turns out we are parsing an existential context, so (C t1 t2) is a constraint and 'C' is a type constructor. As the result, in order to determine whether (C t1 t2) declares a data constructor, a type, or a context, we would need unlimited lookahead which 'happy' is not so happy with. -} -- | Reinterpret a type constructor, including type operators, as a data -- constructor. -- See Note [Parsing data constructors is hard] tyConToDataCon :: LocatedN RdrName -> Either PsError (LocatedN RdrName) tyConToDataCon (L loc tc) | isTcOcc occ || isDataOcc occ , isLexCon (occNameFS occ) = return (L loc (setRdrNameSpace tc srcDataName)) | otherwise = Left $ PsError (PsErrNotADataCon tc) [] (locA loc) where occ = rdrNameOcc tc mkPatSynMatchGroup :: LocatedN RdrName -> LocatedL (OrdList (LHsDecl GhcPs)) -> P (MatchGroup GhcPs (LHsExpr GhcPs)) mkPatSynMatchGroup (L loc patsyn_name) (L ld decls) = do { matches <- mapM fromDecl (fromOL decls) ; when (null matches) (wrongNumberErr (locA loc)) ; return $ mkMatchGroup FromSource (L ld matches) } where fromDecl (L loc decl@(ValD _ (PatBind _ -- AZ: where should these anns come from? pat@(L _ (ConPat noAnn ln@(L _ name) details)) rhs _))) = do { unless (name == patsyn_name) $ wrongNameBindingErr (locA loc) decl ; match <- case details of PrefixCon _ pats -> return $ Match { m_ext = noAnn , m_ctxt = ctxt, m_pats = pats , m_grhss = rhs } where ctxt = FunRhs { mc_fun = ln , mc_fixity = Prefix , mc_strictness = NoSrcStrict } InfixCon p1 p2 -> return $ Match { m_ext = noAnn , m_ctxt = ctxt , m_pats = [p1, p2] , m_grhss = rhs } where ctxt = FunRhs { mc_fun = ln , mc_fixity = Infix , mc_strictness = NoSrcStrict } RecCon{} -> recordPatSynErr (locA loc) pat ; return $ L loc match } fromDecl (L loc decl) = extraDeclErr (locA loc) decl extraDeclErr loc decl = addFatalError $ PsError (PsErrNoSingleWhereBindInPatSynDecl patsyn_name decl) [] loc wrongNameBindingErr loc decl = addFatalError $ PsError (PsErrInvalidWhereBindInPatSynDecl patsyn_name decl) [] loc wrongNumberErr loc = addFatalError $ PsError (PsErrEmptyWhereInPatSynDecl patsyn_name) [] loc recordPatSynErr :: SrcSpan -> LPat GhcPs -> P a recordPatSynErr loc pat = addFatalError $ PsError (PsErrRecordSyntaxInPatSynDecl pat) [] loc mkConDeclH98 :: EpAnn [AddEpAnn] -> LocatedN RdrName -> Maybe [LHsTyVarBndr Specificity GhcPs] -> Maybe (LHsContext GhcPs) -> HsConDeclH98Details GhcPs -> ConDecl GhcPs mkConDeclH98 ann name mb_forall mb_cxt args = ConDeclH98 { con_ext = ann , con_name = name , con_forall = isJust mb_forall , con_ex_tvs = mb_forall `orElse` [] , con_mb_cxt = mb_cxt , con_args = args , con_doc = Nothing } -- | Construct a GADT-style data constructor from the constructor names and -- their type. Some interesting aspects of this function: -- -- * This splits up the constructor type into its quantified type variables (if -- provided), context (if provided), argument types, and result type, and -- records whether this is a prefix or record GADT constructor. See -- Note [GADT abstract syntax] in "GHC.Hs.Decls" for more details. mkGadtDecl :: SrcSpan -> [LocatedN RdrName] -> LHsSigType GhcPs -> [AddEpAnn] -> P (LConDecl GhcPs) mkGadtDecl loc names ty annsIn = do cs <- getCommentsFor loc let l = noAnnSrcSpan loc let (args, res_ty, annsa, csa) | L ll (HsFunTy af _w (L loc' (HsRecTy an rf)) res_ty) <- body_ty = let an' = addTrailingAnnToL (locA loc') (anns af) (comments af) an in ( RecConGADT (L (SrcSpanAnn an' (locA loc')) rf), res_ty , [], epAnnComments (ann ll)) | otherwise = let (anns, cs, arg_types, res_type) = splitHsFunType body_ty in (PrefixConGADT arg_types, res_type, anns, cs) an = case outer_bndrs of _ -> EpAnn (spanAsAnchor loc) (annsIn ++ annsa) (cs Semi.<> csa) pure $ L l ConDeclGADT { con_g_ext = an , con_names = names , con_bndrs = L (getLoc ty) outer_bndrs , con_mb_cxt = mcxt , con_g_args = args , con_res_ty = res_ty , con_doc = Nothing } where (outer_bndrs, mcxt, body_ty) = splitLHsGadtTy ty setRdrNameSpace :: RdrName -> NameSpace -> RdrName -- ^ This rather gruesome function is used mainly by the parser. -- When parsing: -- -- > data T a = T | T1 Int -- -- we parse the data constructors as /types/ because of parser ambiguities, -- so then we need to change the /type constr/ to a /data constr/ -- -- The exact-name case /can/ occur when parsing: -- -- > data [] a = [] | a : [a] -- -- For the exact-name case we return an original name. setRdrNameSpace (Unqual occ) ns = Unqual (setOccNameSpace ns occ) setRdrNameSpace (Qual m occ) ns = Qual m (setOccNameSpace ns occ) setRdrNameSpace (Orig m occ) ns = Orig m (setOccNameSpace ns occ) setRdrNameSpace (Exact n) ns | Just thing <- wiredInNameTyThing_maybe n = setWiredInNameSpace thing ns -- Preserve Exact Names for wired-in things, -- notably tuples and lists | isExternalName n = Orig (nameModule n) occ | otherwise -- This can happen when quoting and then -- splicing a fixity declaration for a type = Exact (mkSystemNameAt (nameUnique n) occ (nameSrcSpan n)) where occ = setOccNameSpace ns (nameOccName n) setWiredInNameSpace :: TyThing -> NameSpace -> RdrName setWiredInNameSpace (ATyCon tc) ns | isDataConNameSpace ns = ty_con_data_con tc | isTcClsNameSpace ns = Exact (getName tc) -- No-op setWiredInNameSpace (AConLike (RealDataCon dc)) ns | isTcClsNameSpace ns = data_con_ty_con dc | isDataConNameSpace ns = Exact (getName dc) -- No-op setWiredInNameSpace thing ns = pprPanic "setWiredinNameSpace" (pprNameSpace ns <+> ppr thing) ty_con_data_con :: TyCon -> RdrName ty_con_data_con tc | isTupleTyCon tc , Just dc <- tyConSingleDataCon_maybe tc = Exact (getName dc) | tc `hasKey` listTyConKey = Exact nilDataConName | otherwise -- See Note [setRdrNameSpace for wired-in names] = Unqual (setOccNameSpace srcDataName (getOccName tc)) data_con_ty_con :: DataCon -> RdrName data_con_ty_con dc | let tc = dataConTyCon dc , isTupleTyCon tc = Exact (getName tc) | dc `hasKey` nilDataConKey = Exact listTyConName | otherwise -- See Note [setRdrNameSpace for wired-in names] = Unqual (setOccNameSpace tcClsName (getOccName dc)) {- Note [setRdrNameSpace for wired-in names] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In GHC.Types, which declares (:), we have infixr 5 : The ambiguity about which ":" is meant is resolved by parsing it as a data constructor, but then using dataTcOccs to try the type constructor too; and that in turn calls setRdrNameSpace to change the name-space of ":" to tcClsName. There isn't a corresponding ":" type constructor, but it's painful to make setRdrNameSpace partial, so we just make an Unqual name instead. It really doesn't matter! -} eitherToP :: MonadP m => Either PsError a -> m a -- Adapts the Either monad to the P monad eitherToP (Left err) = addFatalError err eitherToP (Right thing) = return thing checkTyVars :: SDoc -> SDoc -> LocatedN RdrName -> [LHsTypeArg GhcPs] -> P (LHsQTyVars GhcPs) -- the synthesized type variables -- ^ Check whether the given list of type parameters are all type variables -- (possibly with a kind signature). checkTyVars pp_what equals_or_where tc tparms = do { tvs <- mapM check tparms ; return (mkHsQTvs tvs) } where check (HsTypeArg _ ki@(L loc _)) = addFatalError $ PsError (PsErrUnexpectedTypeAppInDecl ki pp_what (unLoc tc)) [] (locA loc) check (HsValArg ty) = chkParens [] [] emptyComments ty check (HsArgPar sp) = addFatalError $ PsError (PsErrMalformedDecl pp_what (unLoc tc)) [] sp -- Keep around an action for adjusting the annotations of extra parens chkParens :: [AddEpAnn] -> [AddEpAnn] -> EpAnnComments -> LHsType GhcPs -> P (LHsTyVarBndr () GhcPs) chkParens ops cps cs (L l (HsParTy an ty)) = let (o,c) = mkParensEpAnn (realSrcSpan $ locA l) in chkParens (o:ops) (c:cps) (cs Semi.<> epAnnComments an) ty chkParens ops cps cs ty = chk ops cps cs ty -- Check that the name space is correct! chk :: [AddEpAnn] -> [AddEpAnn] -> EpAnnComments -> LHsType GhcPs -> P (LHsTyVarBndr () GhcPs) chk ops cps cs (L l (HsKindSig annk (L annt (HsTyVar ann _ (L lv tv))) k)) | isRdrTyVar tv = let an = (reverse ops) ++ cps in return (L (widenLocatedAn (l Semi.<> annt) an) (KindedTyVar (addAnns (annk Semi.<> ann) an cs) () (L lv tv) k)) chk ops cps cs (L l (HsTyVar ann _ (L ltv tv))) | isRdrTyVar tv = let an = (reverse ops) ++ cps in return (L (widenLocatedAn l an) (UserTyVar (addAnns ann an cs) () (L ltv tv))) chk _ _ _ t@(L loc _) = addFatalError $ PsError (PsErrUnexpectedTypeInDecl t pp_what (unLoc tc) tparms equals_or_where) [] (locA loc) whereDots, equalsDots :: SDoc -- Second argument to checkTyVars whereDots = text "where ..." equalsDots = text "= ..." checkDatatypeContext :: Maybe (LHsContext GhcPs) -> P () checkDatatypeContext Nothing = return () checkDatatypeContext (Just c) = do allowed <- getBit DatatypeContextsBit unless allowed $ addError $ PsError (PsErrIllegalDataTypeContext c) [] (getLocA c) type LRuleTyTmVar = Located RuleTyTmVar data RuleTyTmVar = RuleTyTmVar (EpAnn [AddEpAnn]) (LocatedN RdrName) (Maybe (LHsType GhcPs)) -- ^ Essentially a wrapper for a @RuleBndr GhcPs@ -- turns RuleTyTmVars into RuleBnrs - this is straightforward mkRuleBndrs :: [LRuleTyTmVar] -> [LRuleBndr GhcPs] mkRuleBndrs = fmap (fmap cvt_one) where cvt_one (RuleTyTmVar ann v Nothing) = RuleBndr ann v cvt_one (RuleTyTmVar ann v (Just sig)) = RuleBndrSig ann v (mkHsPatSigType noAnn sig) -- turns RuleTyTmVars into HsTyVarBndrs - this is more interesting mkRuleTyVarBndrs :: [LRuleTyTmVar] -> [LHsTyVarBndr () GhcPs] mkRuleTyVarBndrs = fmap cvt_one where cvt_one (L l (RuleTyTmVar ann v Nothing)) = L (noAnnSrcSpan l) (UserTyVar ann () (fmap tm_to_ty v)) cvt_one (L l (RuleTyTmVar ann v (Just sig))) = L (noAnnSrcSpan l) (KindedTyVar ann () (fmap tm_to_ty v) sig) -- takes something in namespace 'varName' to something in namespace 'tvName' tm_to_ty (Unqual occ) = Unqual (setOccNameSpace tvName occ) tm_to_ty _ = panic "mkRuleTyVarBndrs" -- See note [Parsing explicit foralls in Rules] in Parser.y checkRuleTyVarBndrNames :: [LHsTyVarBndr flag GhcPs] -> P () checkRuleTyVarBndrNames = mapM_ (check . fmap hsTyVarName) where check (L loc (Unqual occ)) = -- TODO: don't use string here, OccName has a Unique/FastString when ((occNameString occ ==) `any` ["forall","family","role"]) (addFatalError $ PsError (PsErrParseErrorOnInput occ) [] (locA loc)) check _ = panic "checkRuleTyVarBndrNames" checkRecordSyntax :: (MonadP m, Outputable a) => LocatedA a -> m (LocatedA a) checkRecordSyntax lr@(L loc r) = do allowed <- getBit TraditionalRecordSyntaxBit unless allowed $ addError $ PsError (PsErrIllegalTraditionalRecordSyntax (ppr r)) [] (locA loc) return lr -- | Check if the gadt_constrlist is empty. Only raise parse error for -- `data T where` to avoid affecting existing error message, see #8258. checkEmptyGADTs :: Located ([AddEpAnn], [LConDecl GhcPs]) -> P (Located ([AddEpAnn], [LConDecl GhcPs])) checkEmptyGADTs gadts@(L span (_, [])) -- Empty GADT declaration. = do gadtSyntax <- getBit GadtSyntaxBit -- GADTs implies GADTSyntax unless gadtSyntax $ addError $ PsError PsErrIllegalWhereInDataDecl [] span return gadts checkEmptyGADTs gadts = return gadts -- Ordinary GADT declaration. checkTyClHdr :: Bool -- True <=> class header -- False <=> type header -> LHsType GhcPs -> P (LocatedN RdrName, -- the head symbol (type or class name) [LHsTypeArg GhcPs], -- parameters of head symbol LexicalFixity, -- the declaration is in infix format [AddEpAnn]) -- API Annotation for HsParTy -- when stripping parens -- Well-formedness check and decomposition of type and class heads. -- Decomposes T ty1 .. tyn into (T, [ty1, ..., tyn]) -- Int :*: Bool into (:*:, [Int, Bool]) -- returning the pieces checkTyClHdr is_cls ty = goL ty [] [] [] Prefix where goL (L l ty) acc ops cps fix = go (locA l) ty acc ops cps fix -- workaround to define '*' despite StarIsType go _ (HsParTy an (L l (HsStarTy _ isUni))) acc ops' cps' fix = do { addWarning Opt_WarnStarBinder (PsWarnStarBinder (locA l)) ; let name = mkOccName tcClsName (starSym isUni) ; let a' = newAnns l an ; return (L a' (Unqual name), acc, fix , (reverse ops') ++ cps') } go _ (HsTyVar _ _ ltc@(L _ tc)) acc ops cps fix | isRdrTc tc = return (ltc, acc, fix, (reverse ops) ++ cps) go _ (HsOpTy _ t1 ltc@(L _ tc) t2) acc ops cps _fix | isRdrTc tc = return (ltc, HsValArg t1:HsValArg t2:acc, Infix, (reverse ops) ++ cps) go l (HsParTy _ ty) acc ops cps fix = goL ty acc (o:ops) (c:cps) fix where (o,c) = mkParensEpAnn (realSrcSpan l) go _ (HsAppTy _ t1 t2) acc ops cps fix = goL t1 (HsValArg t2:acc) ops cps fix go _ (HsAppKindTy l ty ki) acc ops cps fix = goL ty (HsTypeArg l ki:acc) ops cps fix go l (HsTupleTy _ HsBoxedOrConstraintTuple ts) [] ops cps fix = return (L (noAnnSrcSpan l) (nameRdrName tup_name) , map HsValArg ts, fix, (reverse ops)++cps) where arity = length ts tup_name | is_cls = cTupleTyConName arity | otherwise = getName (tupleTyCon Boxed arity) -- See Note [Unit tuples] in GHC.Hs.Type (TODO: is this still relevant?) go l _ _ _ _ _ = addFatalError $ PsError (PsErrMalformedTyOrClDecl ty) [] l -- Combine the annotations from the HsParTy and HsStarTy into a -- new one for the LocatedN RdrName newAnns :: SrcSpanAnnA -> EpAnn AnnParen -> SrcSpanAnnN newAnns (SrcSpanAnn EpAnnNotUsed l) (EpAnn as (AnnParen _ o c) cs) = let lr = combineRealSrcSpans (realSrcSpan l) (anchor as) -- lr = widenAnchorR as (realSrcSpan l) an = (EpAnn (Anchor lr UnchangedAnchor) (NameAnn NameParens o (EpaSpan $ realSrcSpan l) c []) cs) in SrcSpanAnn an (RealSrcSpan lr Nothing) newAnns _ EpAnnNotUsed = panic "missing AnnParen" newAnns (SrcSpanAnn (EpAnn ap (AnnListItem ta) csp) l) (EpAnn as (AnnParen _ o c) cs) = let lr = combineRealSrcSpans (anchor ap) (anchor as) an = (EpAnn (Anchor lr UnchangedAnchor) (NameAnn NameParens o (EpaSpan $ realSrcSpan l) c ta) (csp Semi.<> cs)) in SrcSpanAnn an (RealSrcSpan lr Nothing) -- | Yield a parse error if we have a function applied directly to a do block -- etc. and BlockArguments is not enabled. checkExpBlockArguments :: LHsExpr GhcPs -> PV () checkCmdBlockArguments :: LHsCmd GhcPs -> PV () (checkExpBlockArguments, checkCmdBlockArguments) = (checkExpr, checkCmd) where checkExpr :: LHsExpr GhcPs -> PV () checkExpr expr = case unLoc expr of HsDo _ (DoExpr m) _ -> check (PsErrDoInFunAppExpr m) expr HsDo _ (MDoExpr m) _ -> check (PsErrMDoInFunAppExpr m) expr HsLam {} -> check PsErrLambdaInFunAppExpr expr HsCase {} -> check PsErrCaseInFunAppExpr expr HsLamCase {} -> check PsErrLambdaCaseInFunAppExpr expr HsLet {} -> check PsErrLetInFunAppExpr expr HsIf {} -> check PsErrIfInFunAppExpr expr HsProc {} -> check PsErrProcInFunAppExpr expr _ -> return () checkCmd :: LHsCmd GhcPs -> PV () checkCmd cmd = case unLoc cmd of HsCmdLam {} -> check PsErrLambdaCmdInFunAppCmd cmd HsCmdCase {} -> check PsErrCaseCmdInFunAppCmd cmd HsCmdIf {} -> check PsErrIfCmdInFunAppCmd cmd HsCmdLet {} -> check PsErrLetCmdInFunAppCmd cmd HsCmdDo {} -> check PsErrDoCmdInFunAppCmd cmd _ -> return () check err a = do blockArguments <- getBit BlockArgumentsBit unless blockArguments $ addError $ PsError (err a) [] (getLocA a) -- | Validate the context constraints and break up a context into a list -- of predicates. -- -- @ -- (Eq a, Ord b) --> [Eq a, Ord b] -- Eq a --> [Eq a] -- (Eq a) --> [Eq a] -- (((Eq a))) --> [Eq a] -- @ checkContext :: LHsType GhcPs -> P (LHsContext GhcPs) checkContext orig_t@(L (SrcSpanAnn _ l) _orig_t) = check ([],[],emptyComments) orig_t where check :: ([EpaLocation],[EpaLocation],EpAnnComments) -> LHsType GhcPs -> P (LHsContext GhcPs) check (oparens,cparens,cs) (L _l (HsTupleTy ann' HsBoxedOrConstraintTuple ts)) -- (Eq a, Ord b) shows up as a tuple type. Only boxed tuples can -- be used as context constraints. -- Ditto () = do let (op,cp,cs') = case ann' of EpAnnNotUsed -> ([],[],emptyComments) EpAnn _ (AnnParen _ o c) cs -> ([o],[c],cs) return (L (SrcSpanAnn (EpAnn (spanAsAnchor l) -- Append parens so that the original order in the source is maintained (AnnContext Nothing (oparens ++ op) (cp ++ cparens)) (cs Semi.<> cs')) l) ts) check (opi,cpi,csi) (L _lp1 (HsParTy ann' ty)) -- to be sure HsParTy doesn't get into the way = do let (op,cp,cs') = case ann' of EpAnnNotUsed -> ([],[],emptyComments) EpAnn _ (AnnParen _ open close ) cs -> ([open],[close],cs) check (op++opi,cp++cpi,cs' Semi.<> csi) ty -- No need for anns, returning original check (_opi,_cpi,_csi) _t = return (L (SrcSpanAnn (EpAnn (spanAsAnchor l) (AnnContext Nothing [] []) emptyComments) l) [orig_t]) checkImportDecl :: Maybe EpaLocation -> Maybe EpaLocation -> P () checkImportDecl mPre mPost = do let whenJust mg f = maybe (pure ()) f mg importQualifiedPostEnabled <- getBit ImportQualifiedPostBit -- Error if 'qualified' found in postpositive position and -- 'ImportQualifiedPost' is not in effect. whenJust mPost $ \post -> when (not importQualifiedPostEnabled) $ failOpNotEnabledImportQualifiedPost (RealSrcSpan (epaLocationRealSrcSpan post) Nothing) -- Error if 'qualified' occurs in both pre and postpositive -- positions. whenJust mPost $ \post -> when (isJust mPre) $ failOpImportQualifiedTwice (RealSrcSpan (epaLocationRealSrcSpan post) Nothing) -- Warn if 'qualified' found in prepositive position and -- 'Opt_WarnPrepositiveQualifiedModule' is enabled. whenJust mPre $ \pre -> warnPrepositiveQualifiedModule (RealSrcSpan (epaLocationRealSrcSpan pre) Nothing) -- ------------------------------------------------------------------------- -- Checking Patterns. -- We parse patterns as expressions and check for valid patterns below, -- converting the expression into a pattern at the same time. checkPattern :: LocatedA (PatBuilder GhcPs) -> P (LPat GhcPs) checkPattern = runPV . checkLPat checkPattern_hints :: [Hint] -> PV (LocatedA (PatBuilder GhcPs)) -> P (LPat GhcPs) checkPattern_hints hints pp = runPV_hints hints (pp >>= checkLPat) checkLPat :: LocatedA (PatBuilder GhcPs) -> PV (LPat GhcPs) checkLPat e@(L l _) = checkPat l e [] [] checkPat :: SrcSpanAnnA -> LocatedA (PatBuilder GhcPs) -> [HsPatSigType GhcPs] -> [LPat GhcPs] -> PV (LPat GhcPs) checkPat loc (L l e@(PatBuilderVar (L ln c))) tyargs args | isRdrDataCon c = return . L loc $ ConPat { pat_con_ext = noAnn -- AZ: where should this come from? , pat_con = L ln c , pat_args = PrefixCon tyargs args } | not (null tyargs) = add_hint TypeApplicationsInPatternsOnlyDataCons $ patFail (locA l) (ppr e <+> hsep [text "@" <> ppr t | t <- tyargs]) | not (null args) && patIsRec c = add_hint SuggestRecursiveDo $ patFail (locA l) (ppr e) checkPat loc (L _ (PatBuilderAppType f t)) tyargs args = checkPat loc f (t : tyargs) args checkPat loc (L _ (PatBuilderApp f e)) [] args = do p <- checkLPat e checkPat loc f [] (p : args) checkPat loc (L l e) [] [] = do p <- checkAPat loc e return (L l p) checkPat loc e _ _ = patFail (locA loc) (ppr e) checkAPat :: SrcSpanAnnA -> PatBuilder GhcPs -> PV (Pat GhcPs) checkAPat loc e0 = do nPlusKPatterns <- getBit NPlusKPatternsBit case e0 of PatBuilderPat p -> return p PatBuilderVar x -> return (VarPat noExtField x) -- Overloaded numeric patterns (e.g. f 0 x = x) -- Negation is recorded separately, so that the literal is zero or +ve -- NB. Negative *primitive* literals are already handled by the lexer PatBuilderOverLit pos_lit -> return (mkNPat (L (locA loc) pos_lit) Nothing noAnn) -- n+k patterns PatBuilderOpApp (L _ (PatBuilderVar (L nloc n))) (L l plus) (L lloc (PatBuilderOverLit lit@(OverLit {ol_val = HsIntegral {}}))) (EpAnn anc _ cs) | nPlusKPatterns && (plus == plus_RDR) -> return (mkNPlusKPat (L nloc n) (L (locA lloc) lit) (EpAnn anc (epaLocationFromSrcAnn l) cs)) -- Improve error messages for the @-operator when the user meant an @-pattern PatBuilderOpApp _ op _ _ | opIsAt (unLoc op) -> do addError $ PsError PsErrAtInPatPos [] (getLocA op) return (WildPat noExtField) PatBuilderOpApp l (L cl c) r anns | isRdrDataCon c -> do l <- checkLPat l r <- checkLPat r return $ ConPat { pat_con_ext = anns , pat_con = L cl c , pat_args = InfixCon l r } PatBuilderPar e an@(AnnParen pt o c) -> do (L l p) <- checkLPat e let aa = [AddEpAnn ai o, AddEpAnn ac c] (ai,ac) = parenTypeKws pt return (ParPat (EpAnn (spanAsAnchor $ (widenSpan (locA l) aa)) an emptyComments) (L l p)) _ -> patFail (locA loc) (ppr e0) placeHolderPunRhs :: DisambECP b => PV (LocatedA b) -- The RHS of a punned record field will be filled in by the renamer -- It's better not to make it an error, in case we want to print it when -- debugging placeHolderPunRhs = mkHsVarPV (noLocA pun_RDR) plus_RDR, pun_RDR :: RdrName plus_RDR = mkUnqual varName (fsLit "+") -- Hack pun_RDR = mkUnqual varName (fsLit "pun-right-hand-side") checkPatField :: LHsRecField GhcPs (LocatedA (PatBuilder GhcPs)) -> PV (LHsRecField GhcPs (LPat GhcPs)) checkPatField (L l fld) = do p <- checkLPat (hsRecFieldArg fld) return (L l (fld { hsRecFieldArg = p })) patFail :: SrcSpan -> SDoc -> PV a patFail loc e = addFatalError $ PsError (PsErrParseErrorInPat e) [] loc patIsRec :: RdrName -> Bool patIsRec e = e == mkUnqual varName (fsLit "rec") --------------------------------------------------------------------------- -- Check Equation Syntax checkValDef :: SrcSpan -> LocatedA (PatBuilder GhcPs) -> Maybe (AddEpAnn, LHsType GhcPs) -> Located (GRHSs GhcPs (LHsExpr GhcPs)) -> P (HsBind GhcPs) checkValDef loc lhs (Just (sigAnn, sig)) grhss -- x :: ty = rhs parses as a *pattern* binding = do lhs' <- runPV $ mkHsTySigPV (combineLocsA lhs sig) lhs sig [sigAnn] >>= checkLPat checkPatBind loc [] lhs' grhss checkValDef loc lhs Nothing g = do { mb_fun <- isFunLhs lhs ; case mb_fun of Just (fun, is_infix, pats, ann) -> checkFunBind NoSrcStrict loc ann fun is_infix pats g Nothing -> do lhs' <- checkPattern lhs checkPatBind loc [] lhs' g } checkFunBind :: SrcStrictness -> SrcSpan -> [AddEpAnn] -> LocatedN RdrName -> LexicalFixity -> [LocatedA (PatBuilder GhcPs)] -> Located (GRHSs GhcPs (LHsExpr GhcPs)) -> P (HsBind GhcPs) checkFunBind strictness locF ann fun is_infix pats (L _ grhss) = do ps <- runPV_hints param_hints (mapM checkLPat pats) let match_span = noAnnSrcSpan $ locF cs <- getCommentsFor locF return (makeFunBind fun (L (noAnnSrcSpan $ locA match_span) [L match_span (Match { m_ext = EpAnn (spanAsAnchor locF) ann cs , m_ctxt = FunRhs { mc_fun = fun , mc_fixity = is_infix , mc_strictness = strictness } , m_pats = ps , m_grhss = grhss })])) -- The span of the match covers the entire equation. -- That isn't quite right, but it'll do for now. where param_hints | Infix <- is_infix = [SuggestInfixBindMaybeAtPat (unLoc fun)] | otherwise = [] makeFunBind :: LocatedN RdrName -> LocatedL [LMatch GhcPs (LHsExpr GhcPs)] -> HsBind GhcPs -- Like GHC.Hs.Utils.mkFunBind, but we need to be able to set the fixity too makeFunBind fn ms = FunBind { fun_ext = noExtField, fun_id = fn, fun_matches = mkMatchGroup FromSource ms, fun_tick = [] } -- See Note [FunBind vs PatBind] checkPatBind :: SrcSpan -> [AddEpAnn] -> LPat GhcPs -> Located (GRHSs GhcPs (LHsExpr GhcPs)) -> P (HsBind GhcPs) checkPatBind loc annsIn (L _ (BangPat (EpAnn _ ans cs) (L _ (VarPat _ v)))) (L _match_span grhss) = return (makeFunBind v (L (noAnnSrcSpan loc) [L (noAnnSrcSpan loc) (m (EpAnn (spanAsAnchor loc) (ans++annsIn) cs) v)])) where m a v = Match { m_ext = a , m_ctxt = FunRhs { mc_fun = v , mc_fixity = Prefix , mc_strictness = SrcStrict } , m_pats = [] , m_grhss = grhss } checkPatBind loc annsIn lhs (L _ grhss) = do cs <- getCommentsFor loc return (PatBind (EpAnn (spanAsAnchor loc) annsIn cs) lhs grhss ([],[])) checkValSigLhs :: LHsExpr GhcPs -> P (LocatedN RdrName) checkValSigLhs (L _ (HsVar _ lrdr@(L _ v))) | isUnqual v , not (isDataOcc (rdrNameOcc v)) = return lrdr checkValSigLhs lhs@(L l _) = addFatalError $ PsError (PsErrInvalidTypeSignature lhs) [] (locA l) checkDoAndIfThenElse :: (Outputable a, Outputable b, Outputable c) => (a -> Bool -> b -> Bool -> c -> PsErrorDesc) -> LocatedA a -> Bool -> LocatedA b -> Bool -> LocatedA c -> PV () checkDoAndIfThenElse err guardExpr semiThen thenExpr semiElse elseExpr | semiThen || semiElse = do doAndIfThenElse <- getBit DoAndIfThenElseBit let e = err (unLoc guardExpr) semiThen (unLoc thenExpr) semiElse (unLoc elseExpr) loc = combineLocs (reLoc guardExpr) (reLoc elseExpr) unless doAndIfThenElse $ addError (PsError e [] loc) | otherwise = return () isFunLhs :: LocatedA (PatBuilder GhcPs) -> P (Maybe (LocatedN RdrName, LexicalFixity, [LocatedA (PatBuilder GhcPs)],[AddEpAnn])) -- A variable binding is parsed as a FunBind. -- Just (fun, is_infix, arg_pats) if e is a function LHS isFunLhs e = go e [] [] [] where go (L _ (PatBuilderVar (L loc f))) es ops cps | not (isRdrDataCon f) = return (Just (L loc f, Prefix, es, (reverse ops) ++ cps)) go (L _ (PatBuilderApp f e)) es ops cps = go f (e:es) ops cps go (L l (PatBuilderPar e _)) es@(_:_) ops cps = let (o,c) = mkParensEpAnn (realSrcSpan $ locA l) in go e es (o:ops) (c:cps) go (L loc (PatBuilderOpApp l (L loc' op) r (EpAnn loca anns cs))) es ops cps | not (isRdrDataCon op) -- We have found the function! = return (Just (L loc' op, Infix, (l:r:es), (anns ++ reverse ops ++ cps))) | otherwise -- Infix data con; keep going = do { mb_l <- go l es ops cps ; case mb_l of Just (op', Infix, j : k : es', anns') -> return (Just (op', Infix, j : op_app : es', anns')) where op_app = L loc (PatBuilderOpApp k (L loc' op) r (EpAnn loca (reverse ops++cps) cs)) _ -> return Nothing } go _ _ _ _ = return Nothing mkBangTy :: EpAnn [AddEpAnn] -> SrcStrictness -> LHsType GhcPs -> HsType GhcPs mkBangTy anns strictness = HsBangTy anns (HsSrcBang NoSourceText NoSrcUnpack strictness) -- | Result of parsing @{-\# UNPACK \#-}@ or @{-\# NOUNPACK \#-}@. data UnpackednessPragma = UnpackednessPragma [AddEpAnn] SourceText SrcUnpackedness -- | Annotate a type with either an @{-\# UNPACK \#-}@ or a @{-\# NOUNPACK \#-}@ pragma. addUnpackednessP :: MonadP m => Located UnpackednessPragma -> LHsType GhcPs -> m (LHsType GhcPs) addUnpackednessP (L lprag (UnpackednessPragma anns prag unpk)) ty = do let l' = combineSrcSpans lprag (getLocA ty) cs <- getCommentsFor l' let an = EpAnn (spanAsAnchor l') anns cs t' = addUnpackedness an ty return (L (noAnnSrcSpan l') t') where -- If we have a HsBangTy that only has a strictness annotation, -- such as ~T or !T, then add the pragma to the existing HsBangTy. -- -- Otherwise, wrap the type in a new HsBangTy constructor. addUnpackedness an (L _ (HsBangTy x bang t)) | HsSrcBang NoSourceText NoSrcUnpack strictness <- bang = HsBangTy (addAnns an (epAnnAnns x) (epAnnComments x)) (HsSrcBang prag unpk strictness) t addUnpackedness an t = HsBangTy an (HsSrcBang prag unpk NoSrcStrict) t --------------------------------------------------------------------------- -- | Check for monad comprehensions -- -- If the flag MonadComprehensions is set, return a 'MonadComp' context, -- otherwise use the usual 'ListComp' context checkMonadComp :: PV (HsStmtContext GhcRn) checkMonadComp = do monadComprehensions <- getBit MonadComprehensionsBit return $ if monadComprehensions then MonadComp else ListComp -- ------------------------------------------------------------------------- -- Expression/command/pattern ambiguity. -- See Note [Ambiguous syntactic categories] -- -- See Note [Ambiguous syntactic categories] -- -- This newtype is required to avoid impredicative types in monadic -- productions. That is, in a production that looks like -- -- | ... {% return (ECP ...) } -- -- we are dealing with -- P ECP -- whereas without a newtype we would be dealing with -- P (forall b. DisambECP b => PV (Located b)) -- newtype ECP = ECP { unECP :: forall b. DisambECP b => PV (LocatedA b) } ecpFromExp :: LHsExpr GhcPs -> ECP ecpFromExp a = ECP (ecpFromExp' a) ecpFromCmd :: LHsCmd GhcPs -> ECP ecpFromCmd a = ECP (ecpFromCmd' a) -- The 'fbinds' parser rule produces values of this type. See Note -- [RecordDotSyntax field updates]. type Fbind b = Either (LHsRecField GhcPs (LocatedA b)) (LHsRecProj GhcPs (LocatedA b)) -- | Disambiguate infix operators. -- See Note [Ambiguous syntactic categories] class DisambInfixOp b where mkHsVarOpPV :: LocatedN RdrName -> PV (LocatedN b) mkHsConOpPV :: LocatedN RdrName -> PV (LocatedN b) mkHsInfixHolePV :: SrcSpan -> (EpAnnComments -> EpAnn EpAnnUnboundVar) -> PV (Located b) instance DisambInfixOp (HsExpr GhcPs) where mkHsVarOpPV v = return $ L (getLoc v) (HsVar noExtField v) mkHsConOpPV v = return $ L (getLoc v) (HsVar noExtField v) mkHsInfixHolePV l ann = do cs <- getCommentsFor l return $ L l (hsHoleExpr (ann cs)) instance DisambInfixOp RdrName where mkHsConOpPV (L l v) = return $ L l v mkHsVarOpPV (L l v) = return $ L l v mkHsInfixHolePV l _ = addFatalError $ PsError PsErrInvalidInfixHole [] l type AnnoBody b = ( Anno (GRHS GhcPs (LocatedA (Body b GhcPs))) ~ SrcSpan , Anno [LocatedA (Match GhcPs (LocatedA (Body b GhcPs)))] ~ SrcSpanAnnL , Anno (Match GhcPs (LocatedA (Body b GhcPs))) ~ SrcSpanAnnA , Anno (StmtLR GhcPs GhcPs (LocatedA (Body (Body b GhcPs) GhcPs))) ~ SrcSpanAnnA , Anno [LocatedA (StmtLR GhcPs GhcPs (LocatedA (Body (Body (Body b GhcPs) GhcPs) GhcPs)))] ~ SrcSpanAnnL ) -- | Disambiguate constructs that may appear when we do not know ahead of time whether we are -- parsing an expression, a command, or a pattern. -- See Note [Ambiguous syntactic categories] class (b ~ (Body b) GhcPs, AnnoBody b) => DisambECP b where -- | See Note [Body in DisambECP] type Body b :: Type -> Type -- | Return a command without ambiguity, or fail in a non-command context. ecpFromCmd' :: LHsCmd GhcPs -> PV (LocatedA b) -- | Return an expression without ambiguity, or fail in a non-expression context. ecpFromExp' :: LHsExpr GhcPs -> PV (LocatedA b) mkHsProjUpdatePV :: SrcSpan -> Located [Located (HsFieldLabel GhcPs)] -> LocatedA b -> Bool -> [AddEpAnn] -> PV (LHsRecProj GhcPs (LocatedA b)) -- | Disambiguate "\... -> ..." (lambda) mkHsLamPV :: SrcSpan -> (EpAnnComments -> MatchGroup GhcPs (LocatedA b)) -> PV (LocatedA b) -- | Disambiguate "let ... in ..." mkHsLetPV :: SrcSpan -> HsLocalBinds GhcPs -> LocatedA b -> AnnsLet -> PV (LocatedA b) -- | Infix operator representation type InfixOp b -- | Bring superclass constraints on InfixOp into scope. -- See Note [UndecidableSuperClasses for associated types] superInfixOp :: (DisambInfixOp (InfixOp b) => PV (LocatedA b )) -> PV (LocatedA b) -- | Disambiguate "f # x" (infix operator) mkHsOpAppPV :: SrcSpan -> LocatedA b -> LocatedN (InfixOp b) -> LocatedA b -> PV (LocatedA b) -- | Disambiguate "case ... of ..." mkHsCasePV :: SrcSpan -> LHsExpr GhcPs -> (LocatedL [LMatch GhcPs (LocatedA b)]) -> EpAnnHsCase -> PV (LocatedA b) mkHsLamCasePV :: SrcSpan -> (LocatedL [LMatch GhcPs (LocatedA b)]) -> [AddEpAnn] -> PV (LocatedA b) -- | Function argument representation type FunArg b -- | Bring superclass constraints on FunArg into scope. -- See Note [UndecidableSuperClasses for associated types] superFunArg :: (DisambECP (FunArg b) => PV (LocatedA b)) -> PV (LocatedA b) -- | Disambiguate "f x" (function application) mkHsAppPV :: SrcSpanAnnA -> LocatedA b -> LocatedA (FunArg b) -> PV (LocatedA b) -- | Disambiguate "f @t" (visible type application) mkHsAppTypePV :: SrcSpanAnnA -> LocatedA b -> SrcSpan -> LHsType GhcPs -> PV (LocatedA b) -- | Disambiguate "if ... then ... else ..." mkHsIfPV :: SrcSpan -> LHsExpr GhcPs -> Bool -- semicolon? -> LocatedA b -> Bool -- semicolon? -> LocatedA b -> AnnsIf -> PV (LocatedA b) -- | Disambiguate "do { ... }" (do notation) mkHsDoPV :: SrcSpan -> Maybe ModuleName -> LocatedL [LStmt GhcPs (LocatedA b)] -> AnnList -> PV (LocatedA b) -- | Disambiguate "( ... )" (parentheses) mkHsParPV :: SrcSpan -> LocatedA b -> AnnParen -> PV (LocatedA b) -- | Disambiguate a variable "f" or a data constructor "MkF". mkHsVarPV :: LocatedN RdrName -> PV (LocatedA b) -- | Disambiguate a monomorphic literal mkHsLitPV :: Located (HsLit GhcPs) -> PV (Located b) -- | Disambiguate an overloaded literal mkHsOverLitPV :: Located (HsOverLit GhcPs) -> PV (Located b) -- | Disambiguate a wildcard mkHsWildCardPV :: SrcSpan -> PV (Located b) -- | Disambiguate "a :: t" (type annotation) mkHsTySigPV :: SrcSpanAnnA -> LocatedA b -> LHsType GhcPs -> [AddEpAnn] -> PV (LocatedA b) -- | Disambiguate "[a,b,c]" (list syntax) mkHsExplicitListPV :: SrcSpan -> [LocatedA b] -> AnnList -> PV (LocatedA b) -- | Disambiguate "$(...)" and "[quasi|...|]" (TH splices) mkHsSplicePV :: Located (HsSplice GhcPs) -> PV (Located b) -- | Disambiguate "f { a = b, ... }" syntax (record construction and record updates) mkHsRecordPV :: Bool -> -- Is OverloadedRecordUpdate in effect? SrcSpan -> SrcSpan -> LocatedA b -> ([Fbind b], Maybe SrcSpan) -> [AddEpAnn] -> PV (LocatedA b) -- | Disambiguate "-a" (negation) mkHsNegAppPV :: SrcSpan -> LocatedA b -> [AddEpAnn] -> PV (LocatedA b) -- | Disambiguate "(# a)" (right operator section) mkHsSectionR_PV :: SrcSpan -> LocatedA (InfixOp b) -> LocatedA b -> PV (Located b) -- | Disambiguate "(a -> b)" (view pattern) mkHsViewPatPV :: SrcSpan -> LHsExpr GhcPs -> LocatedA b -> [AddEpAnn] -> PV (LocatedA b) -- | Disambiguate "a@b" (as-pattern) mkHsAsPatPV :: SrcSpan -> LocatedN RdrName -> LocatedA b -> [AddEpAnn] -> PV (LocatedA b) -- | Disambiguate "~a" (lazy pattern) mkHsLazyPatPV :: SrcSpan -> LocatedA b -> [AddEpAnn] -> PV (LocatedA b) -- | Disambiguate "!a" (bang pattern) mkHsBangPatPV :: SrcSpan -> LocatedA b -> [AddEpAnn] -> PV (LocatedA b) -- | Disambiguate tuple sections and unboxed sums mkSumOrTuplePV :: SrcSpanAnnA -> Boxity -> SumOrTuple b -> [AddEpAnn] -> PV (LocatedA b) -- | Validate infixexp LHS to reject unwanted {-# SCC ... #-} pragmas rejectPragmaPV :: LocatedA b -> PV () {- Note [UndecidableSuperClasses for associated types] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ (This Note is about the code in GHC, not about the user code that we are parsing) Assume we have a class C with an associated type T: class C a where type T a ... If we want to add 'C (T a)' as a superclass, we need -XUndecidableSuperClasses: {-# LANGUAGE UndecidableSuperClasses #-} class C (T a) => C a where type T a ... Unfortunately, -XUndecidableSuperClasses don't work all that well, sometimes making GHC loop. The workaround is to bring this constraint into scope manually with a helper method: class C a where type T a superT :: (C (T a) => r) -> r In order to avoid ambiguous types, 'r' must mention 'a'. For consistency, we use this approach for all constraints on associated types, even when -XUndecidableSuperClasses are not required. -} {- Note [Body in DisambECP] ~~~~~~~~~~~~~~~~~~~~~~~~~~~ There are helper functions (mkBodyStmt, mkBindStmt, unguardedRHS, etc) that require their argument to take a form of (body GhcPs) for some (body :: Type -> *). To satisfy this requirement, we say that (b ~ Body b GhcPs) in the superclass constraints of DisambECP. The alternative is to change mkBodyStmt, mkBindStmt, unguardedRHS, etc, to drop this requirement. It is possible and would allow removing the type index of PatBuilder, but leads to worse type inference, breaking some code in the typechecker. -} instance DisambECP (HsCmd GhcPs) where type Body (HsCmd GhcPs) = HsCmd ecpFromCmd' = return ecpFromExp' (L l e) = cmdFail (locA l) (ppr e) mkHsProjUpdatePV l _ _ _ _ = addFatalError $ PsError PsErrOverloadedRecordDotInvalid [] l mkHsLamPV l mg = do cs <- getCommentsFor l return $ L (noAnnSrcSpan l) (HsCmdLam NoExtField (mg cs)) mkHsLetPV l bs e anns = do cs <- getCommentsFor l return $ L (noAnnSrcSpan l) (HsCmdLet (EpAnn (spanAsAnchor l) anns cs) bs e) type InfixOp (HsCmd GhcPs) = HsExpr GhcPs superInfixOp m = m mkHsOpAppPV l c1 op c2 = do let cmdArg c = L (getLocA c) $ HsCmdTop noExtField c cs <- getCommentsFor l return $ L (noAnnSrcSpan l) $ HsCmdArrForm (EpAnn (spanAsAnchor l) (AnnList Nothing Nothing Nothing [] []) cs) (reLocL op) Infix Nothing [cmdArg c1, cmdArg c2] mkHsCasePV l c (L lm m) anns = do cs <- getCommentsFor l let mg = mkMatchGroup FromSource (L lm m) return $ L (noAnnSrcSpan l) (HsCmdCase (EpAnn (spanAsAnchor l) anns cs) c mg) mkHsLamCasePV l (L lm m) anns = do cs <- getCommentsFor l let mg = mkMatchGroup FromSource (L lm m) return $ L (noAnnSrcSpan l) (HsCmdLamCase (EpAnn (spanAsAnchor l) anns cs) mg) type FunArg (HsCmd GhcPs) = HsExpr GhcPs superFunArg m = m mkHsAppPV l c e = do cs <- getCommentsFor (locA l) checkCmdBlockArguments c checkExpBlockArguments e return $ L l (HsCmdApp (comment (realSrcSpan $ locA l) cs) c e) mkHsAppTypePV l c _ t = cmdFail (locA l) (ppr c <+> text "@" <> ppr t) mkHsIfPV l c semi1 a semi2 b anns = do checkDoAndIfThenElse PsErrSemiColonsInCondCmd c semi1 a semi2 b cs <- getCommentsFor l return $ L (noAnnSrcSpan l) (mkHsCmdIf c a b (EpAnn (spanAsAnchor l) anns cs)) mkHsDoPV l Nothing stmts anns = do cs <- getCommentsFor l return $ L (noAnnSrcSpan l) (HsCmdDo (EpAnn (spanAsAnchor l) anns cs) stmts) mkHsDoPV l (Just m) _ _ = addFatalError $ PsError (PsErrQualifiedDoInCmd m) [] l mkHsParPV l c ann = do cs <- getCommentsFor l return $ L (noAnnSrcSpan l) (HsCmdPar (EpAnn (spanAsAnchor l) ann cs) c) mkHsVarPV (L l v) = cmdFail (locA l) (ppr v) mkHsLitPV (L l a) = cmdFail l (ppr a) mkHsOverLitPV (L l a) = cmdFail l (ppr a) mkHsWildCardPV l = cmdFail l (text "_") mkHsTySigPV l a sig _ = cmdFail (locA l) (ppr a <+> text "::" <+> ppr sig) mkHsExplicitListPV l xs _ = cmdFail l $ brackets (fsep (punctuate comma (map ppr xs))) mkHsSplicePV (L l sp) = cmdFail l (ppr sp) mkHsRecordPV _ l _ a (fbinds, ddLoc) _ = do let (fs, ps) = partitionEithers fbinds if not (null ps) then addFatalError $ PsError PsErrOverloadedRecordDotInvalid [] l else cmdFail l $ ppr a <+> ppr (mk_rec_fields fs ddLoc) mkHsNegAppPV l a _ = cmdFail l (text "-" <> ppr a) mkHsSectionR_PV l op c = cmdFail l $ let pp_op = fromMaybe (panic "cannot print infix operator") (ppr_infix_expr (unLoc op)) in pp_op <> ppr c mkHsViewPatPV l a b _ = cmdFail l $ ppr a <+> text "->" <+> ppr b mkHsAsPatPV l v c _ = cmdFail l $ pprPrefixOcc (unLoc v) <> text "@" <> ppr c mkHsLazyPatPV l c _ = cmdFail l $ text "~" <> ppr c mkHsBangPatPV l c _ = cmdFail l $ text "!" <> ppr c mkSumOrTuplePV l boxity a _ = cmdFail (locA l) (pprSumOrTuple boxity a) rejectPragmaPV _ = return () cmdFail :: SrcSpan -> SDoc -> PV a cmdFail loc e = addFatalError $ PsError (PsErrParseErrorInCmd e) [] loc instance DisambECP (HsExpr GhcPs) where type Body (HsExpr GhcPs) = HsExpr ecpFromCmd' (L l c) = do addError $ PsError (PsErrArrowCmdInExpr c) [] (locA l) return (L l (hsHoleExpr noAnn)) ecpFromExp' = return mkHsProjUpdatePV l fields arg isPun anns = do cs <- getCommentsFor l return $ mkRdrProjUpdate (noAnnSrcSpan l) fields arg isPun (EpAnn (spanAsAnchor l) anns cs) mkHsLamPV l mg = do cs <- getCommentsFor l return $ L (noAnnSrcSpan l) (HsLam NoExtField (mg cs)) mkHsLetPV l bs c anns = do cs <- getCommentsFor l return $ L (noAnnSrcSpan l) (HsLet (EpAnn (spanAsAnchor l) anns cs) bs c) type InfixOp (HsExpr GhcPs) = HsExpr GhcPs superInfixOp m = m mkHsOpAppPV l e1 op e2 = do cs <- getCommentsFor l return $ L (noAnnSrcSpan l) $ OpApp (EpAnn (spanAsAnchor l) [] cs) e1 (reLocL op) e2 mkHsCasePV l e (L lm m) anns = do cs <- getCommentsFor l let mg = mkMatchGroup FromSource (L lm m) return $ L (noAnnSrcSpan l) (HsCase (EpAnn (spanAsAnchor l) anns cs) e mg) mkHsLamCasePV l (L lm m) anns = do cs <- getCommentsFor l let mg = mkMatchGroup FromSource (L lm m) return $ L (noAnnSrcSpan l) (HsLamCase (EpAnn (spanAsAnchor l) anns cs) mg) type FunArg (HsExpr GhcPs) = HsExpr GhcPs superFunArg m = m mkHsAppPV l e1 e2 = do cs <- getCommentsFor (locA l) checkExpBlockArguments e1 checkExpBlockArguments e2 return $ L l (HsApp (comment (realSrcSpan $ locA l) cs) e1 e2) mkHsAppTypePV l e la t = do checkExpBlockArguments e return $ L l (HsAppType la e (mkHsWildCardBndrs t)) mkHsIfPV l c semi1 a semi2 b anns = do checkDoAndIfThenElse PsErrSemiColonsInCondExpr c semi1 a semi2 b cs <- getCommentsFor l return $ L (noAnnSrcSpan l) (mkHsIf c a b (EpAnn (spanAsAnchor l) anns cs)) mkHsDoPV l mod stmts anns = do cs <- getCommentsFor l return $ L (noAnnSrcSpan l) (HsDo (EpAnn (spanAsAnchor l) anns cs) (DoExpr mod) stmts) mkHsParPV l e ann = do cs <- getCommentsFor l return $ L (noAnnSrcSpan l) (HsPar (EpAnn (spanAsAnchor l) ann cs) e) mkHsVarPV v@(L l _) = return $ L (na2la l) (HsVar noExtField v) mkHsLitPV (L l a) = do cs <- getCommentsFor l return $ L l (HsLit (comment (realSrcSpan l) cs) a) mkHsOverLitPV (L l a) = do cs <- getCommentsFor l return $ L l (HsOverLit (comment (realSrcSpan l) cs) a) mkHsWildCardPV l = return $ L l (hsHoleExpr noAnn) mkHsTySigPV l a sig anns = do cs <- getCommentsFor (locA l) return $ L l (ExprWithTySig (EpAnn (spanAsAnchor $ locA l) anns cs) a (hsTypeToHsSigWcType sig)) mkHsExplicitListPV l xs anns = do cs <- getCommentsFor l return $ L (noAnnSrcSpan l) (ExplicitList (EpAnn (spanAsAnchor l) anns cs) xs) mkHsSplicePV sp@(L l _) = do cs <- getCommentsFor l return $ mapLoc (HsSpliceE (EpAnn (spanAsAnchor l) NoEpAnns cs)) sp mkHsRecordPV opts l lrec a (fbinds, ddLoc) anns = do cs <- getCommentsFor l r <- mkRecConstrOrUpdate opts a lrec (fbinds, ddLoc) (EpAnn (spanAsAnchor l) anns cs) checkRecordSyntax (L (noAnnSrcSpan l) r) mkHsNegAppPV l a anns = do cs <- getCommentsFor l return $ L (noAnnSrcSpan l) (NegApp (EpAnn (spanAsAnchor l) anns cs) a noSyntaxExpr) mkHsSectionR_PV l op e = do cs <- getCommentsFor l return $ L l (SectionR (comment (realSrcSpan l) cs) op e) mkHsViewPatPV l a b _ = addError (PsError (PsErrViewPatInExpr a b) [] l) >> return (L (noAnnSrcSpan l) (hsHoleExpr noAnn)) mkHsAsPatPV l v e _ = addError (PsError (PsErrTypeAppWithoutSpace (unLoc v) e) [] l) >> return (L (noAnnSrcSpan l) (hsHoleExpr noAnn)) mkHsLazyPatPV l e _ = addError (PsError (PsErrLazyPatWithoutSpace e) [] l) >> return (L (noAnnSrcSpan l) (hsHoleExpr noAnn)) mkHsBangPatPV l e _ = addError (PsError (PsErrBangPatWithoutSpace e) [] l) >> return (L (noAnnSrcSpan l) (hsHoleExpr noAnn)) mkSumOrTuplePV = mkSumOrTupleExpr rejectPragmaPV (L _ (OpApp _ _ _ e)) = -- assuming left-associative parsing of operators rejectPragmaPV e rejectPragmaPV (L l (HsPragE _ prag _)) = addError $ PsError (PsErrUnallowedPragma prag) [] (locA l) rejectPragmaPV _ = return () hsHoleExpr :: EpAnn EpAnnUnboundVar -> HsExpr GhcPs hsHoleExpr anns = HsUnboundVar anns (mkVarOcc "_") type instance Anno (GRHS GhcPs (LocatedA (PatBuilder GhcPs))) = SrcSpan type instance Anno [LocatedA (Match GhcPs (LocatedA (PatBuilder GhcPs)))] = SrcSpanAnnL type instance Anno (Match GhcPs (LocatedA (PatBuilder GhcPs))) = SrcSpanAnnA type instance Anno (StmtLR GhcPs GhcPs (LocatedA (PatBuilder GhcPs))) = SrcSpanAnnA instance DisambECP (PatBuilder GhcPs) where type Body (PatBuilder GhcPs) = PatBuilder ecpFromCmd' (L l c) = addFatalError $ PsError (PsErrArrowCmdInPat c) [] (locA l) ecpFromExp' (L l e) = addFatalError $ PsError (PsErrArrowExprInPat e) [] (locA l) mkHsLamPV l _ = addFatalError $ PsError PsErrLambdaInPat [] l mkHsLetPV l _ _ _ = addFatalError $ PsError PsErrLetInPat [] l mkHsProjUpdatePV l _ _ _ _ = addFatalError $ PsError PsErrOverloadedRecordDotInvalid [] l type InfixOp (PatBuilder GhcPs) = RdrName superInfixOp m = m mkHsOpAppPV l p1 op p2 = do cs <- getCommentsFor l let anns = EpAnn (spanAsAnchor l) [] cs return $ L (noAnnSrcSpan l) $ PatBuilderOpApp p1 op p2 anns mkHsCasePV l _ _ _ = addFatalError $ PsError PsErrCaseInPat [] l mkHsLamCasePV l _ _ = addFatalError $ PsError PsErrLambdaCaseInPat [] l type FunArg (PatBuilder GhcPs) = PatBuilder GhcPs superFunArg m = m mkHsAppPV l p1 p2 = return $ L l (PatBuilderApp p1 p2) mkHsAppTypePV l p la t = do cs <- getCommentsFor (locA l) let anns = EpAnn (spanAsAnchor (combineSrcSpans la (getLocA t))) (EpaSpan (realSrcSpan la)) cs return $ L l (PatBuilderAppType p (mkHsPatSigType anns t)) mkHsIfPV l _ _ _ _ _ _ = addFatalError $ PsError PsErrIfTheElseInPat [] l mkHsDoPV l _ _ _ = addFatalError $ PsError PsErrDoNotationInPat [] l mkHsParPV l p an = return $ L (noAnnSrcSpan l) (PatBuilderPar p an) mkHsVarPV v@(getLoc -> l) = return $ L (na2la l) (PatBuilderVar v) mkHsLitPV lit@(L l a) = do checkUnboxedStringLitPat lit return $ L l (PatBuilderPat (LitPat noExtField a)) mkHsOverLitPV (L l a) = return $ L l (PatBuilderOverLit a) mkHsWildCardPV l = return $ L l (PatBuilderPat (WildPat noExtField)) mkHsTySigPV l b sig anns = do p <- checkLPat b cs <- getCommentsFor (locA l) return $ L l (PatBuilderPat (SigPat (EpAnn (spanAsAnchor $ locA l) anns cs) p (mkHsPatSigType noAnn sig))) mkHsExplicitListPV l xs anns = do ps <- traverse checkLPat xs cs <- getCommentsFor l return (L (noAnnSrcSpan l) (PatBuilderPat (ListPat (EpAnn (spanAsAnchor l) anns cs) ps))) mkHsSplicePV (L l sp) = return $ L l (PatBuilderPat (SplicePat noExtField sp)) mkHsRecordPV _ l _ a (fbinds, ddLoc) anns = do let (fs, ps) = partitionEithers fbinds if not (null ps) then addFatalError $ PsError PsErrOverloadedRecordDotInvalid [] l else do cs <- getCommentsFor l r <- mkPatRec a (mk_rec_fields fs ddLoc) (EpAnn (spanAsAnchor l) anns cs) checkRecordSyntax (L (noAnnSrcSpan l) r) mkHsNegAppPV l (L lp p) anns = do lit <- case p of PatBuilderOverLit pos_lit -> return (L (locA lp) pos_lit) _ -> patFail l (text "-" <> ppr p) cs <- getCommentsFor l let an = EpAnn (spanAsAnchor l) anns cs return $ L (noAnnSrcSpan l) (PatBuilderPat (mkNPat lit (Just noSyntaxExpr) an)) mkHsSectionR_PV l op p = patFail l (pprInfixOcc (unLoc op) <> ppr p) mkHsViewPatPV l a b anns = do p <- checkLPat b cs <- getCommentsFor l return $ L (noAnnSrcSpan l) (PatBuilderPat (ViewPat (EpAnn (spanAsAnchor l) anns cs) a p)) mkHsAsPatPV l v e a = do p <- checkLPat e cs <- getCommentsFor l return $ L (noAnnSrcSpan l) (PatBuilderPat (AsPat (EpAnn (spanAsAnchor l) a cs) v p)) mkHsLazyPatPV l e a = do p <- checkLPat e cs <- getCommentsFor l return $ L (noAnnSrcSpan l) (PatBuilderPat (LazyPat (EpAnn (spanAsAnchor l) a cs) p)) mkHsBangPatPV l e an = do p <- checkLPat e cs <- getCommentsFor l let pb = BangPat (EpAnn (spanAsAnchor l) an cs) p hintBangPat l pb return $ L (noAnnSrcSpan l) (PatBuilderPat pb) mkSumOrTuplePV = mkSumOrTuplePat rejectPragmaPV _ = return () checkUnboxedStringLitPat :: Located (HsLit GhcPs) -> PV () checkUnboxedStringLitPat (L loc lit) = case lit of HsStringPrim _ _ -- Trac #13260 -> addFatalError $ PsError (PsErrIllegalUnboxedStringInPat lit) [] loc _ -> return () mkPatRec :: LocatedA (PatBuilder GhcPs) -> HsRecFields GhcPs (LocatedA (PatBuilder GhcPs)) -> EpAnn [AddEpAnn] -> PV (PatBuilder GhcPs) mkPatRec (unLoc -> PatBuilderVar c) (HsRecFields fs dd) anns | isRdrDataCon (unLoc c) = do fs <- mapM checkPatField fs return $ PatBuilderPat $ ConPat { pat_con_ext = anns , pat_con = c , pat_args = RecCon (HsRecFields fs dd) } mkPatRec p _ _ = addFatalError $ PsError (PsErrInvalidRecordCon (unLoc p)) [] (getLocA p) -- | Disambiguate constructs that may appear when we do not know -- ahead of time whether we are parsing a type or a newtype/data constructor. -- -- See Note [Ambiguous syntactic categories] for the general idea. -- -- See Note [Parsing data constructors is hard] for the specific issue this -- particular class is solving. -- class DisambTD b where -- | Process the head of a type-level function/constructor application, -- i.e. the @H@ in @H a b c@. mkHsAppTyHeadPV :: LHsType GhcPs -> PV (LocatedA b) -- | Disambiguate @f x@ (function application or prefix data constructor). mkHsAppTyPV :: LocatedA b -> LHsType GhcPs -> PV (LocatedA b) -- | Disambiguate @f \@t@ (visible kind application) mkHsAppKindTyPV :: LocatedA b -> SrcSpan -> LHsType GhcPs -> PV (LocatedA b) -- | Disambiguate @f \# x@ (infix operator) mkHsOpTyPV :: LHsType GhcPs -> LocatedN RdrName -> LHsType GhcPs -> PV (LocatedA b) -- | Disambiguate @{-\# UNPACK \#-} t@ (unpack/nounpack pragma) mkUnpackednessPV :: Located UnpackednessPragma -> LocatedA b -> PV (LocatedA b) instance DisambTD (HsType GhcPs) where mkHsAppTyHeadPV = return mkHsAppTyPV t1 t2 = return (mkHsAppTy t1 t2) mkHsAppKindTyPV t l_at ki = return (mkHsAppKindTy l_at t ki) mkHsOpTyPV t1 op t2 = return (mkLHsOpTy t1 op t2) mkUnpackednessPV = addUnpackednessP dataConBuilderCon :: DataConBuilder -> LocatedN RdrName dataConBuilderCon (PrefixDataConBuilder _ dc) = dc dataConBuilderCon (InfixDataConBuilder _ dc _) = dc dataConBuilderDetails :: DataConBuilder -> HsConDeclH98Details GhcPs -- Detect when the record syntax is used: -- data T = MkT { ... } dataConBuilderDetails (PrefixDataConBuilder flds _) | [L l_t (HsRecTy an fields)] <- toList flds = RecCon (L (SrcSpanAnn an (locA l_t)) fields) -- Normal prefix constructor, e.g. data T = MkT A B C dataConBuilderDetails (PrefixDataConBuilder flds _) = PrefixCon noTypeArgs (map hsLinear (toList flds)) -- Infix constructor, e.g. data T = Int :! Bool dataConBuilderDetails (InfixDataConBuilder lhs _ rhs) = InfixCon (hsLinear lhs) (hsLinear rhs) instance DisambTD DataConBuilder where mkHsAppTyHeadPV = tyToDataConBuilder mkHsAppTyPV (L l (PrefixDataConBuilder flds fn)) t = return $ L (noAnnSrcSpan $ combineSrcSpans (locA l) (getLocA t)) (PrefixDataConBuilder (flds `snocOL` t) fn) mkHsAppTyPV (L _ InfixDataConBuilder{}) _ = -- This case is impossible because of the way -- the grammar in Parser.y is written (see infixtype/ftype). panic "mkHsAppTyPV: InfixDataConBuilder" mkHsAppKindTyPV lhs l_at ki = addFatalError $ PsError (PsErrUnexpectedKindAppInDataCon (unLoc lhs) (unLoc ki)) [] l_at mkHsOpTyPV lhs tc rhs = do check_no_ops (unLoc rhs) -- check the RHS because parsing type operators is right-associative data_con <- eitherToP $ tyConToDataCon tc return $ L l (InfixDataConBuilder lhs data_con rhs) where l = combineLocsA lhs rhs check_no_ops (HsBangTy _ _ t) = check_no_ops (unLoc t) check_no_ops (HsOpTy{}) = addError $ PsError (PsErrInvalidInfixDataCon (unLoc lhs) (unLoc tc) (unLoc rhs)) [] (locA l) check_no_ops _ = return () mkUnpackednessPV unpk constr_stuff | L _ (InfixDataConBuilder lhs data_con rhs) <- constr_stuff = -- When the user writes data T = {-# UNPACK #-} Int :+ Bool -- we apply {-# UNPACK #-} to the LHS do lhs' <- addUnpackednessP unpk lhs let l = combineLocsA (reLocA unpk) constr_stuff return $ L l (InfixDataConBuilder lhs' data_con rhs) | otherwise = do addError $ PsError PsErrUnpackDataCon [] (getLoc unpk) return constr_stuff tyToDataConBuilder :: LHsType GhcPs -> PV (LocatedA DataConBuilder) tyToDataConBuilder (L l (HsTyVar _ NotPromoted v)) = do data_con <- eitherToP $ tyConToDataCon v return $ L l (PrefixDataConBuilder nilOL data_con) tyToDataConBuilder (L l (HsTupleTy _ HsBoxedOrConstraintTuple ts)) = do let data_con = L (l2l l) (getRdrName (tupleDataCon Boxed (length ts))) return $ L l (PrefixDataConBuilder (toOL ts) data_con) tyToDataConBuilder t = addFatalError $ PsError (PsErrInvalidDataCon (unLoc t)) [] (getLocA t) {- Note [Ambiguous syntactic categories] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ There are places in the grammar where we do not know whether we are parsing an expression or a pattern without unlimited lookahead (which we do not have in 'happy'): View patterns: f (Con a b ) = ... -- 'Con a b' is a pattern f (Con a b -> x) = ... -- 'Con a b' is an expression do-notation: do { Con a b <- x } -- 'Con a b' is a pattern do { Con a b } -- 'Con a b' is an expression Guards: x | True <- p && q = ... -- 'True' is a pattern x | True = ... -- 'True' is an expression Top-level value/function declarations (FunBind/PatBind): f ! a -- TH splice f ! a = ... -- function declaration Until we encounter the = sign, we don't know if it's a top-level TemplateHaskell splice where ! is used, or if it's a function declaration where ! is bound. There are also places in the grammar where we do not know whether we are parsing an expression or a command: proc x -> do { (stuff) -< x } -- 'stuff' is an expression proc x -> do { (stuff) } -- 'stuff' is a command Until we encounter arrow syntax (-<) we don't know whether to parse 'stuff' as an expression or a command. In fact, do-notation is subject to both ambiguities: proc x -> do { (stuff) -< x } -- 'stuff' is an expression proc x -> do { (stuff) <- f -< x } -- 'stuff' is a pattern proc x -> do { (stuff) } -- 'stuff' is a command There are many possible solutions to this problem. For an overview of the ones we decided against, see Note [Resolving parsing ambiguities: non-taken alternatives] The solution that keeps basic definitions (such as HsExpr) clean, keeps the concerns local to the parser, and does not require duplication of hsSyn types, or an extra pass over the entire AST, is to parse into an overloaded parser-validator (a so-called tagless final encoding): class DisambECP b where ... instance DisambECP (HsCmd GhcPs) where ... instance DisambECP (HsExp GhcPs) where ... instance DisambECP (PatBuilder GhcPs) where ... The 'DisambECP' class contains functions to build and validate 'b'. For example, to add parentheses we have: mkHsParPV :: DisambECP b => SrcSpan -> Located b -> PV (Located b) 'mkHsParPV' will wrap the inner value in HsCmdPar for commands, HsPar for expressions, and 'PatBuilderPar' for patterns (later transformed into ParPat, see Note [PatBuilder]). Consider the 'alts' production used to parse case-of alternatives: alts :: { Located ([AddEpAnn],[LMatch GhcPs (LHsExpr GhcPs)]) } : alts1 { sL1 $1 (fst $ unLoc $1,snd $ unLoc $1) } | ';' alts { sLL $1 $> ((mj AnnSemi $1:(fst $ unLoc $2)),snd $ unLoc $2) } We abstract over LHsExpr GhcPs, and it becomes: alts :: { forall b. DisambECP b => PV (Located ([AddEpAnn],[LMatch GhcPs (Located b)])) } : alts1 { $1 >>= \ $1 -> return $ sL1 $1 (fst $ unLoc $1,snd $ unLoc $1) } | ';' alts { $2 >>= \ $2 -> return $ sLL $1 $> ((mj AnnSemi $1:(fst $ unLoc $2)),snd $ unLoc $2) } Compared to the initial definition, the added bits are: forall b. DisambECP b => PV ( ... ) -- in the type signature $1 >>= \ $1 -> return $ -- in one reduction rule $2 >>= \ $2 -> return $ -- in another reduction rule The overhead is constant relative to the size of the rest of the reduction rule, so this approach scales well to large parser productions. Note that we write ($1 >>= \ $1 -> ...), so the second $1 is in a binding position and shadows the previous $1. We can do this because internally 'happy' desugars $n to happy_var_n, and the rationale behind this idiom is to be able to write (sLL $1 $>) later on. The alternative would be to write this as ($1 >>= \ fresh_name -> ...), but then we couldn't refer to the last fresh name as $>. Finally, we instantiate the polymorphic type to a concrete one, and run the parser-validator, for example: stmt :: { forall b. DisambECP b => PV (LStmt GhcPs (Located b)) } e_stmt :: { LStmt GhcPs (LHsExpr GhcPs) } : stmt {% runPV $1 } In e_stmt, three things happen: 1. we instantiate: b ~ HsExpr GhcPs 2. we embed the PV computation into P by using runPV 3. we run validation by using a monadic production, {% ... } At this point the ambiguity is resolved. -} {- Note [Resolving parsing ambiguities: non-taken alternatives] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Alternative I, extra constructors in GHC.Hs.Expr ------------------------------------------------ We could add extra constructors to HsExpr to represent command-specific and pattern-specific syntactic constructs. Under this scheme, we parse patterns and commands as expressions and rejig later. This is what GHC used to do, and it polluted 'HsExpr' with irrelevant constructors: * for commands: 'HsArrForm', 'HsArrApp' * for patterns: 'EWildPat', 'EAsPat', 'EViewPat', 'ELazyPat' (As of now, we still do that for patterns, but we plan to fix it). There are several issues with this: * The implementation details of parsing are leaking into hsSyn definitions. * Code that uses HsExpr has to panic on these impossible-after-parsing cases. * HsExpr is arbitrarily selected as the extension basis. Why not extend HsCmd or HsPat with extra constructors instead? Alternative II, extra constructors in GHC.Hs.Expr for GhcPs ----------------------------------------------------------- We could address some of the problems with Alternative I by using Trees That Grow and extending HsExpr only in the GhcPs pass. However, GhcPs corresponds to the output of parsing, not to its intermediate results, so we wouldn't want them there either. Alternative III, extra constructors in GHC.Hs.Expr for GhcPrePs --------------------------------------------------------------- We could introduce a new pass, GhcPrePs, to keep GhcPs pristine. Unfortunately, creating a new pass would significantly bloat conversion code and slow down the compiler by adding another linear-time pass over the entire AST. For example, in order to build HsExpr GhcPrePs, we would need to build HsLocalBinds GhcPrePs (as part of HsLet), and we never want HsLocalBinds GhcPrePs. Alternative IV, sum type and bottom-up data flow ------------------------------------------------ Expressions and commands are disjoint. There are no user inputs that could be interpreted as either an expression or a command depending on outer context: 5 -- definitely an expression x -< y -- definitely a command Even though we have both 'HsLam' and 'HsCmdLam', we can look at the body to disambiguate: \p -> 5 -- definitely an expression \p -> x -< y -- definitely a command This means we could use a bottom-up flow of information to determine whether we are parsing an expression or a command, using a sum type for intermediate results: Either (LHsExpr GhcPs) (LHsCmd GhcPs) There are two problems with this: * We cannot handle the ambiguity between expressions and patterns, which are not disjoint. * Bottom-up flow of information leads to poor error messages. Consider if ... then 5 else (x -< y) Do we report that '5' is not a valid command or that (x -< y) is not a valid expression? It depends on whether we want the entire node to be 'HsIf' or 'HsCmdIf', and this information flows top-down, from the surrounding parsing context (are we in 'proc'?) Alternative V, backtracking with parser combinators --------------------------------------------------- One might think we could sidestep the issue entirely by using a backtracking parser and doing something along the lines of (try pExpr <|> pPat). Turns out, this wouldn't work very well, as there can be patterns inside expressions (e.g. via 'case', 'let', 'do') and expressions inside patterns (e.g. view patterns). To handle this, we would need to backtrack while backtracking, and unbound levels of backtracking lead to very fragile performance. Alternative VI, an intermediate data type ----------------------------------------- There are common syntactic elements of expressions, commands, and patterns (e.g. all of them must have balanced parentheses), and we can capture this common structure in an intermediate data type, Frame: data Frame = FrameVar RdrName -- ^ Identifier: Just, map, BS.length | FrameTuple [LTupArgFrame] Boxity -- ^ Tuple (section): (a,b) (a,b,c) (a,,) (,a,) | FrameTySig LFrame (LHsSigWcType GhcPs) -- ^ Type signature: x :: ty | FramePar (SrcSpan, SrcSpan) LFrame -- ^ Parentheses | FrameIf LFrame LFrame LFrame -- ^ If-expression: if p then x else y | FrameCase LFrame [LFrameMatch] -- ^ Case-expression: case x of { p1 -> e1; p2 -> e2 } | FrameDo (HsStmtContext GhcRn) [LFrameStmt] -- ^ Do-expression: do { s1; a <- s2; s3 } ... | FrameExpr (HsExpr GhcPs) -- unambiguously an expression | FramePat (HsPat GhcPs) -- unambiguously a pattern | FrameCommand (HsCmd GhcPs) -- unambiguously a command To determine which constructors 'Frame' needs to have, we take the union of intersections between HsExpr, HsCmd, and HsPat. The intersection between HsPat and HsExpr: HsPat = VarPat | TuplePat | SigPat | ParPat | ... HsExpr = HsVar | ExplicitTuple | ExprWithTySig | HsPar | ... ------------------------------------------------------------------- Frame = FrameVar | FrameTuple | FrameTySig | FramePar | ... The intersection between HsCmd and HsExpr: HsCmd = HsCmdIf | HsCmdCase | HsCmdDo | HsCmdPar HsExpr = HsIf | HsCase | HsDo | HsPar ------------------------------------------------ Frame = FrameIf | FrameCase | FrameDo | FramePar The intersection between HsCmd and HsPat: HsPat = ParPat | ... HsCmd = HsCmdPar | ... ----------------------- Frame = FramePar | ... Take the union of each intersection and this yields the final 'Frame' data type. The problem with this approach is that we end up duplicating a good portion of hsSyn: Frame for HsExpr, HsPat, HsCmd TupArgFrame for HsTupArg FrameMatch for Match FrameStmt for StmtLR FrameGRHS for GRHS FrameGRHSs for GRHSs ... Alternative VII, a product type ------------------------------- We could avoid the intermediate representation of Alternative VI by parsing into a product of interpretations directly: type ExpCmdPat = ( PV (LHsExpr GhcPs) , PV (LHsCmd GhcPs) , PV (LHsPat GhcPs) ) This means that in positions where we do not know whether to produce expression, a pattern, or a command, we instead produce a parser-validator for each possible option. Then, as soon as we have parsed far enough to resolve the ambiguity, we pick the appropriate component of the product, discarding the rest: checkExpOf3 (e, _, _) = e -- interpret as an expression checkCmdOf3 (_, c, _) = c -- interpret as a command checkPatOf3 (_, _, p) = p -- interpret as a pattern We can easily define ambiguities between arbitrary subsets of interpretations. For example, when we know ahead of type that only an expression or a command is possible, but not a pattern, we can use a smaller type: type ExpCmd = (PV (LHsExpr GhcPs), PV (LHsCmd GhcPs)) checkExpOf2 (e, _) = e -- interpret as an expression checkCmdOf2 (_, c) = c -- interpret as a command However, there is a slight problem with this approach, namely code duplication in parser productions. Consider the 'alts' production used to parse case-of alternatives: alts :: { Located ([AddEpAnn],[LMatch GhcPs (LHsExpr GhcPs)]) } : alts1 { sL1 $1 (fst $ unLoc $1,snd $ unLoc $1) } | ';' alts { sLL $1 $> ((mj AnnSemi $1:(fst $ unLoc $2)),snd $ unLoc $2) } Under the new scheme, we have to completely duplicate its type signature and each reduction rule: alts :: { ( PV (Located ([AddEpAnn],[LMatch GhcPs (LHsExpr GhcPs)])) -- as an expression , PV (Located ([AddEpAnn],[LMatch GhcPs (LHsCmd GhcPs)])) -- as a command ) } : alts1 { ( checkExpOf2 $1 >>= \ $1 -> return $ sL1 $1 (fst $ unLoc $1,snd $ unLoc $1) , checkCmdOf2 $1 >>= \ $1 -> return $ sL1 $1 (fst $ unLoc $1,snd $ unLoc $1) ) } | ';' alts { ( checkExpOf2 $2 >>= \ $2 -> return $ sLL $1 $> ((mj AnnSemi $1:(fst $ unLoc $2)),snd $ unLoc $2) , checkCmdOf2 $2 >>= \ $2 -> return $ sLL $1 $> ((mj AnnSemi $1:(fst $ unLoc $2)),snd $ unLoc $2) ) } And the same goes for other productions: 'altslist', 'alts1', 'alt', 'alt_rhs', 'ralt', 'gdpats', 'gdpat', 'exp', ... and so on. That is a lot of code! Alternative VIII, a function from a GADT ---------------------------------------- We could avoid code duplication of the Alternative VII by representing the product as a function from a GADT: data ExpCmdG b where ExpG :: ExpCmdG HsExpr CmdG :: ExpCmdG HsCmd type ExpCmd = forall b. ExpCmdG b -> PV (Located (b GhcPs)) checkExp :: ExpCmd -> PV (LHsExpr GhcPs) checkCmd :: ExpCmd -> PV (LHsCmd GhcPs) checkExp f = f ExpG -- interpret as an expression checkCmd f = f CmdG -- interpret as a command Consider the 'alts' production used to parse case-of alternatives: alts :: { Located ([AddEpAnn],[LMatch GhcPs (LHsExpr GhcPs)]) } : alts1 { sL1 $1 (fst $ unLoc $1,snd $ unLoc $1) } | ';' alts { sLL $1 $> ((mj AnnSemi $1:(fst $ unLoc $2)),snd $ unLoc $2) } We abstract over LHsExpr, and it becomes: alts :: { forall b. ExpCmdG b -> PV (Located ([AddEpAnn],[LMatch GhcPs (Located (b GhcPs))])) } : alts1 { \tag -> $1 tag >>= \ $1 -> return $ sL1 $1 (fst $ unLoc $1,snd $ unLoc $1) } | ';' alts { \tag -> $2 tag >>= \ $2 -> return $ sLL $1 $> ((mj AnnSemi $1:(fst $ unLoc $2)),snd $ unLoc $2) } Note that 'ExpCmdG' is a singleton type, the value is completely determined by the type: when (b~HsExpr), tag = ExpG when (b~HsCmd), tag = CmdG This is a clear indication that we can use a class to pass this value behind the scenes: class ExpCmdI b where expCmdG :: ExpCmdG b instance ExpCmdI HsExpr where expCmdG = ExpG instance ExpCmdI HsCmd where expCmdG = CmdG And now the 'alts' production is simplified, as we no longer need to thread 'tag' explicitly: alts :: { forall b. ExpCmdI b => PV (Located ([AddEpAnn],[LMatch GhcPs (Located (b GhcPs))])) } : alts1 { $1 >>= \ $1 -> return $ sL1 $1 (fst $ unLoc $1,snd $ unLoc $1) } | ';' alts { $2 >>= \ $2 -> return $ sLL $1 $> ((mj AnnSemi $1:(fst $ unLoc $2)),snd $ unLoc $2) } This encoding works well enough, but introduces an extra GADT unlike the tagless final encoding, and there's no need for this complexity. -} {- Note [PatBuilder] ~~~~~~~~~~~~~~~~~~~~ Unlike HsExpr or HsCmd, the Pat type cannot accommodate all intermediate forms, so we introduce the notion of a PatBuilder. Consider a pattern like this: Con a b c We parse arguments to "Con" one at a time in the fexp aexp parser production, building the result with mkHsAppPV, so the intermediate forms are: 1. Con 2. Con a 3. Con a b 4. Con a b c In 'HsExpr', we have 'HsApp', so the intermediate forms are represented like this (pseudocode): 1. "Con" 2. HsApp "Con" "a" 3. HsApp (HsApp "Con" "a") "b" 3. HsApp (HsApp (HsApp "Con" "a") "b") "c" Similarly, in 'HsCmd' we have 'HsCmdApp'. In 'Pat', however, what we have instead is 'ConPatIn', which is very awkward to modify and thus unsuitable for the intermediate forms. We also need an intermediate representation to postpone disambiguation between FunBind and PatBind. Consider: a `Con` b = ... a `fun` b = ... How do we know that (a `Con` b) is a PatBind but (a `fun` b) is a FunBind? We learn this by inspecting an intermediate representation in 'isFunLhs' and seeing that 'Con' is a data constructor but 'f' is not. We need an intermediate representation capable of representing both a FunBind and a PatBind, so Pat is insufficient. PatBuilder is an extension of Pat that is capable of representing intermediate parsing results for patterns and function bindings: data PatBuilder p = PatBuilderPat (Pat p) | PatBuilderApp (LocatedA (PatBuilder p)) (LocatedA (PatBuilder p)) | PatBuilderOpApp (LocatedA (PatBuilder p)) (LocatedA RdrName) (LocatedA (PatBuilder p)) ... It can represent any pattern via 'PatBuilderPat', but it also has a variety of other constructors which were added by following a simple principle: we never pattern match on the pattern stored inside 'PatBuilderPat'. -} --------------------------------------------------------------------------- -- Miscellaneous utilities -- | Check if a fixity is valid. We support bypassing the usual bound checks -- for some special operators. checkPrecP :: Located (SourceText,Int) -- ^ precedence -> Located (OrdList (LocatedN RdrName)) -- ^ operators -> P () checkPrecP (L l (_,i)) (L _ ol) | 0 <= i, i <= maxPrecedence = pure () | all specialOp ol = pure () | otherwise = addFatalError $ PsError (PsErrPrecedenceOutOfRange i) [] l where -- If you change this, consider updating Note [Fixity of (->)] in GHC/Types.hs specialOp op = unLoc op `elem` [ eqTyCon_RDR , getRdrName unrestrictedFunTyCon ] mkRecConstrOrUpdate :: Bool -> LHsExpr GhcPs -> SrcSpan -> ([Fbind (HsExpr GhcPs)], Maybe SrcSpan) -> EpAnn [AddEpAnn] -> PV (HsExpr GhcPs) mkRecConstrOrUpdate _ (L _ (HsVar _ (L l c))) _lrec (fbinds,dd) anns | isRdrDataCon c = do let (fs, ps) = partitionEithers fbinds if not (null ps) then addFatalError $ PsError PsErrOverloadedRecordDotInvalid [] (getLocA (head ps)) else return (mkRdrRecordCon (L l c) (mk_rec_fields fs dd) anns) mkRecConstrOrUpdate overloaded_update exp _ (fs,dd) anns | Just dd_loc <- dd = addFatalError $ PsError PsErrDotsInRecordUpdate [] dd_loc | otherwise = mkRdrRecordUpd overloaded_update exp fs anns mkRdrRecordUpd :: Bool -> LHsExpr GhcPs -> [Fbind (HsExpr GhcPs)] -> EpAnn [AddEpAnn] -> PV (HsExpr GhcPs) mkRdrRecordUpd overloaded_on exp@(L loc _) fbinds anns = do -- We do not need to know if OverloadedRecordDot is in effect. We do -- however need to know if OverloadedRecordUpdate (passed in -- overloaded_on) is in effect because it affects the Left/Right nature -- of the RecordUpd value we calculate. let (fs, ps) = partitionEithers fbinds fs' = map (fmap mk_rec_upd_field) fs case overloaded_on of False | not $ null ps -> -- A '.' was found in an update and OverloadedRecordUpdate isn't on. addFatalError $ PsError PsErrOverloadedRecordUpdateNotEnabled [] (locA loc) False -> -- This is just a regular record update. return RecordUpd { rupd_ext = anns , rupd_expr = exp , rupd_flds = Left fs' } True -> do let qualifiedFields = [ L l lbl | L _ (HsRecField _ (L l lbl) _ _) <- fs' , isQual . rdrNameAmbiguousFieldOcc $ lbl ] if not $ null qualifiedFields then addFatalError $ PsError PsErrOverloadedRecordUpdateNoQualifiedFields [] (getLoc (head qualifiedFields)) else -- This is a RecordDotSyntax update. return RecordUpd { rupd_ext = anns , rupd_expr = exp , rupd_flds = Right (toProjUpdates fbinds) } where toProjUpdates :: [Fbind (HsExpr GhcPs)] -> [LHsRecUpdProj GhcPs] toProjUpdates = map (\case { Right p -> p; Left f -> recFieldToProjUpdate f }) -- Convert a top-level field update like {foo=2} or {bar} (punned) -- to a projection update. recFieldToProjUpdate :: LHsRecField GhcPs (LHsExpr GhcPs) -> LHsRecUpdProj GhcPs recFieldToProjUpdate (L l (HsRecField anns (L _ (FieldOcc _ (L loc rdr))) arg pun)) = -- The idea here is to convert the label to a singleton [FastString]. let f = occNameFS . rdrNameOcc $ rdr fl = HsFieldLabel noAnn (L lf f) -- AZ: what about the ann? lf = locA loc in mkRdrProjUpdate l (L lf [L lf fl]) (punnedVar f) pun anns where -- If punning, compute HsVar "f" otherwise just arg. This -- has the effect that sentinel HsVar "pun-rhs" is replaced -- by HsVar "f" here, before the update is written to a -- setField expressions. punnedVar :: FastString -> LHsExpr GhcPs punnedVar f = if not pun then arg else noLocA . HsVar noExtField . noLocA . mkRdrUnqual . mkVarOccFS $ f mkRdrRecordCon :: LocatedN RdrName -> HsRecordBinds GhcPs -> EpAnn [AddEpAnn] -> HsExpr GhcPs mkRdrRecordCon con flds anns = RecordCon { rcon_ext = anns, rcon_con = con, rcon_flds = flds } mk_rec_fields :: [LocatedA (HsRecField (GhcPass p) arg)] -> Maybe SrcSpan -> HsRecFields (GhcPass p) arg mk_rec_fields fs Nothing = HsRecFields { rec_flds = fs, rec_dotdot = Nothing } mk_rec_fields fs (Just s) = HsRecFields { rec_flds = fs , rec_dotdot = Just (L s (length fs)) } mk_rec_upd_field :: HsRecField GhcPs (LHsExpr GhcPs) -> HsRecUpdField GhcPs mk_rec_upd_field (HsRecField noAnn (L loc (FieldOcc _ rdr)) arg pun) = HsRecField noAnn (L loc (Unambiguous noExtField rdr)) arg pun mkInlinePragma :: SourceText -> (InlineSpec, RuleMatchInfo) -> Maybe Activation -> InlinePragma -- The (Maybe Activation) is because the user can omit -- the activation spec (and usually does) mkInlinePragma src (inl, match_info) mb_act = InlinePragma { inl_src = src -- Note [Pragma source text] in GHC.Types.SourceText , inl_inline = inl , inl_sat = Nothing , inl_act = act , inl_rule = match_info } where act = case mb_act of Just act -> act Nothing -> -- No phase specified case inl of NoInline -> NeverActive _other -> AlwaysActive ----------------------------------------------------------------------------- -- utilities for foreign declarations -- construct a foreign import declaration -- mkImport :: Located CCallConv -> Located Safety -> (Located StringLiteral, LocatedN RdrName, LHsSigType GhcPs) -> P (EpAnn [AddEpAnn] -> HsDecl GhcPs) mkImport cconv safety (L loc (StringLiteral esrc entity _), v, ty) = case unLoc cconv of CCallConv -> mkCImport CApiConv -> mkCImport StdCallConv -> mkCImport PrimCallConv -> mkOtherImport JavaScriptCallConv -> mkOtherImport where -- Parse a C-like entity string of the following form: -- "[static] [chname] [&] [cid]" | "dynamic" | "wrapper" -- If 'cid' is missing, the function name 'v' is used instead as symbol -- name (cf section 8.5.1 in Haskell 2010 report). mkCImport = do let e = unpackFS entity case parseCImport cconv safety (mkExtName (unLoc v)) e (L loc esrc) of Nothing -> addFatalError $ PsError PsErrMalformedEntityString [] loc Just importSpec -> returnSpec importSpec -- currently, all the other import conventions only support a symbol name in -- the entity string. If it is missing, we use the function name instead. mkOtherImport = returnSpec importSpec where entity' = if nullFS entity then mkExtName (unLoc v) else entity funcTarget = CFunction (StaticTarget esrc entity' Nothing True) importSpec = CImport cconv safety Nothing funcTarget (L loc esrc) returnSpec spec = return $ \ann -> ForD noExtField $ ForeignImport { fd_i_ext = ann , fd_name = v , fd_sig_ty = ty , fd_fi = spec } -- the string "foo" is ambiguous: either a header or a C identifier. The -- C identifier case comes first in the alternatives below, so we pick -- that one. parseCImport :: Located CCallConv -> Located Safety -> FastString -> String -> Located SourceText -> Maybe ForeignImport parseCImport cconv safety nm str sourceText = listToMaybe $ map fst $ filter (null.snd) $ readP_to_S parse str where parse = do skipSpaces r <- choice [ string "dynamic" >> return (mk Nothing (CFunction DynamicTarget)), string "wrapper" >> return (mk Nothing CWrapper), do optional (token "static" >> skipSpaces) ((mk Nothing <$> cimp nm) +++ (do h <- munch1 hdr_char skipSpaces mk (Just (Header (SourceText h) (mkFastString h))) <$> cimp nm)) ] skipSpaces return r token str = do _ <- string str toks <- look case toks of c : _ | id_char c -> pfail _ -> return () mk h n = CImport cconv safety h n sourceText hdr_char c = not (isSpace c) -- header files are filenames, which can contain -- pretty much any char (depending on the platform), -- so just accept any non-space character id_first_char c = isAlpha c || c == '_' id_char c = isAlphaNum c || c == '_' cimp nm = (ReadP.char '&' >> skipSpaces >> CLabel <$> cid) +++ (do isFun <- case unLoc cconv of CApiConv -> option True (do token "value" skipSpaces return False) _ -> return True cid' <- cid return (CFunction (StaticTarget NoSourceText cid' Nothing isFun))) where cid = return nm +++ (do c <- satisfy id_first_char cs <- many (satisfy id_char) return (mkFastString (c:cs))) -- construct a foreign export declaration -- mkExport :: Located CCallConv -> (Located StringLiteral, LocatedN RdrName, LHsSigType GhcPs) -> P (EpAnn [AddEpAnn] -> HsDecl GhcPs) mkExport (L lc cconv) (L le (StringLiteral esrc entity _), v, ty) = return $ \ann -> ForD noExtField $ ForeignExport { fd_e_ext = ann, fd_name = v, fd_sig_ty = ty , fd_fe = CExport (L lc (CExportStatic esrc entity' cconv)) (L le esrc) } where entity' | nullFS entity = mkExtName (unLoc v) | otherwise = entity -- Supplying the ext_name in a foreign decl is optional; if it -- isn't there, the Haskell name is assumed. Note that no transformation -- of the Haskell name is then performed, so if you foreign export (++), -- it's external name will be "++". Too bad; it's important because we don't -- want z-encoding (e.g. names with z's in them shouldn't be doubled) -- mkExtName :: RdrName -> CLabelString mkExtName rdrNm = mkFastString (occNameString (rdrNameOcc rdrNm)) -------------------------------------------------------------------------------- -- Help with module system imports/exports data ImpExpSubSpec = ImpExpAbs | ImpExpAll | ImpExpList [LocatedA ImpExpQcSpec] | ImpExpAllWith [LocatedA ImpExpQcSpec] data ImpExpQcSpec = ImpExpQcName (LocatedN RdrName) | ImpExpQcType EpaLocation (LocatedN RdrName) | ImpExpQcWildcard mkModuleImpExp :: [AddEpAnn] -> LocatedA ImpExpQcSpec -> ImpExpSubSpec -> P (IE GhcPs) mkModuleImpExp anns (L l specname) subs = do cs <- getCommentsFor (locA l) -- AZ: IEVar can discard comments let ann = EpAnn (spanAsAnchor $ locA l) anns cs case subs of ImpExpAbs | isVarNameSpace (rdrNameSpace name) -> return $ IEVar noExtField (L l (ieNameFromSpec specname)) | otherwise -> IEThingAbs ann . L l <$> nameT ImpExpAll -> IEThingAll ann . L l <$> nameT ImpExpList xs -> (\newName -> IEThingWith ann (L l newName) NoIEWildcard (wrapped xs)) <$> nameT ImpExpAllWith xs -> do allowed <- getBit PatternSynonymsBit if allowed then let withs = map unLoc xs pos = maybe NoIEWildcard IEWildcard (findIndex isImpExpQcWildcard withs) ies :: [LocatedA (IEWrappedName RdrName)] ies = wrapped $ filter (not . isImpExpQcWildcard . unLoc) xs in (\newName -> IEThingWith ann (L l newName) pos ies) <$> nameT else addFatalError $ PsError PsErrIllegalPatSynExport [] (locA l) where name = ieNameVal specname nameT = if isVarNameSpace (rdrNameSpace name) then addFatalError $ PsError (PsErrVarForTyCon name) [] (locA l) else return $ ieNameFromSpec specname ieNameVal (ImpExpQcName ln) = unLoc ln ieNameVal (ImpExpQcType _ ln) = unLoc ln ieNameVal (ImpExpQcWildcard) = panic "ieNameVal got wildcard" ieNameFromSpec (ImpExpQcName ln) = IEName ln ieNameFromSpec (ImpExpQcType r ln) = IEType r ln ieNameFromSpec (ImpExpQcWildcard) = panic "ieName got wildcard" wrapped = map (mapLoc ieNameFromSpec) mkTypeImpExp :: LocatedN RdrName -- TcCls or Var name space -> P (LocatedN RdrName) mkTypeImpExp name = do allowed <- getBit ExplicitNamespacesBit unless allowed $ addError $ PsError PsErrIllegalExplicitNamespace [] (getLocA name) return (fmap (`setRdrNameSpace` tcClsName) name) checkImportSpec :: LocatedL [LIE GhcPs] -> P (LocatedL [LIE GhcPs]) checkImportSpec ie@(L _ specs) = case [l | (L l (IEThingWith _ _ (IEWildcard _) _)) <- specs] of [] -> return ie (l:_) -> importSpecError (locA l) where importSpecError l = addFatalError $ PsError PsErrIllegalImportBundleForm [] l -- In the correct order mkImpExpSubSpec :: [LocatedA ImpExpQcSpec] -> P ([AddEpAnn], ImpExpSubSpec) mkImpExpSubSpec [] = return ([], ImpExpList []) mkImpExpSubSpec [L la ImpExpQcWildcard] = return ([AddEpAnn AnnDotdot (EpaSpan $ la2r la)], ImpExpAll) mkImpExpSubSpec xs = if (any (isImpExpQcWildcard . unLoc) xs) then return $ ([], ImpExpAllWith xs) else return $ ([], ImpExpList xs) isImpExpQcWildcard :: ImpExpQcSpec -> Bool isImpExpQcWildcard ImpExpQcWildcard = True isImpExpQcWildcard _ = False ----------------------------------------------------------------------------- -- Warnings and failures warnPrepositiveQualifiedModule :: SrcSpan -> P () warnPrepositiveQualifiedModule span = addWarning Opt_WarnPrepositiveQualifiedModule (PsWarnImportPreQualified span) failOpNotEnabledImportQualifiedPost :: SrcSpan -> P () failOpNotEnabledImportQualifiedPost loc = addError $ PsError PsErrImportPostQualified [] loc failOpImportQualifiedTwice :: SrcSpan -> P () failOpImportQualifiedTwice loc = addError $ PsError PsErrImportQualifiedTwice [] loc warnStarIsType :: SrcSpan -> P () warnStarIsType span = addWarning Opt_WarnStarIsType (PsWarnStarIsType span) failOpFewArgs :: MonadP m => LocatedN RdrName -> m a failOpFewArgs (L loc op) = do { star_is_type <- getBit StarIsTypeBit ; addFatalError $ PsError (PsErrOpFewArgs (StarIsType star_is_type) op) [] (locA loc) } ----------------------------------------------------------------------------- -- Misc utils data PV_Context = PV_Context { pv_options :: ParserOpts , pv_hints :: [Hint] -- See Note [Parser-Validator Hint] } data PV_Accum = PV_Accum { pv_warnings :: Bag PsWarning , pv_errors :: Bag PsError , pv_header_comments :: Maybe [LEpaComment] , pv_comment_q :: [LEpaComment] } data PV_Result a = PV_Ok PV_Accum a | PV_Failed PV_Accum -- During parsing, we make use of several monadic effects: reporting parse errors, -- accumulating warnings, adding API annotations, and checking for extensions. These -- effects are captured by the 'MonadP' type class. -- -- Sometimes we need to postpone some of these effects to a later stage due to -- ambiguities described in Note [Ambiguous syntactic categories]. -- We could use two layers of the P monad, one for each stage: -- -- abParser :: forall x. DisambAB x => P (P x) -- -- The outer layer of P consumes the input and builds the inner layer, which -- validates the input. But this type is not particularly helpful, as it obscures -- the fact that the inner layer of P never consumes any input. -- -- For clarity, we introduce the notion of a parser-validator: a parser that does -- not consume any input, but may fail or use other effects. Thus we have: -- -- abParser :: forall x. DisambAB x => P (PV x) -- newtype PV a = PV { unPV :: PV_Context -> PV_Accum -> PV_Result a } instance Functor PV where fmap = liftM instance Applicative PV where pure a = a `seq` PV (\_ acc -> PV_Ok acc a) (<*>) = ap instance Monad PV where m >>= f = PV $ \ctx acc -> case unPV m ctx acc of PV_Ok acc' a -> unPV (f a) ctx acc' PV_Failed acc' -> PV_Failed acc' runPV :: PV a -> P a runPV = runPV_hints [] runPV_hints :: [Hint] -> PV a -> P a runPV_hints hints m = P $ \s -> let pv_ctx = PV_Context { pv_options = options s , pv_hints = hints } pv_acc = PV_Accum { pv_warnings = warnings s , pv_errors = errors s , pv_header_comments = header_comments s , pv_comment_q = comment_q s } mkPState acc' = s { warnings = pv_warnings acc' , errors = pv_errors acc' , comment_q = pv_comment_q acc' } in case unPV m pv_ctx pv_acc of PV_Ok acc' a -> POk (mkPState acc') a PV_Failed acc' -> PFailed (mkPState acc') add_hint :: Hint -> PV a -> PV a add_hint hint m = let modifyHint ctx = ctx{pv_hints = pv_hints ctx ++ [hint]} in PV (\ctx acc -> unPV m (modifyHint ctx) acc) instance MonadP PV where addError err@(PsError e hints loc) = PV $ \ctx acc -> let err' | null (pv_hints ctx) = err | otherwise = PsError e (hints ++ pv_hints ctx) loc in PV_Ok acc{pv_errors = err' `consBag` pv_errors acc} () addWarning option w = PV $ \ctx acc -> if warnopt option (pv_options ctx) then PV_Ok acc{pv_warnings= w `consBag` pv_warnings acc} () else PV_Ok acc () addFatalError err = addError err >> PV (const PV_Failed) getBit ext = PV $ \ctx acc -> let b = ext `xtest` pExtsBitmap (pv_options ctx) in PV_Ok acc $! b allocateCommentsP ss = PV $ \_ s -> let (comment_q', newAnns) = allocateComments ss (pv_comment_q s) in PV_Ok s { pv_comment_q = comment_q' } (EpaComments newAnns) allocatePriorCommentsP ss = PV $ \_ s -> let (header_comments', comment_q', newAnns) = allocatePriorComments ss (pv_comment_q s) (pv_header_comments s) in PV_Ok s { pv_header_comments = header_comments', pv_comment_q = comment_q' } (EpaComments newAnns) allocateFinalCommentsP ss = PV $ \_ s -> let (header_comments', comment_q', newAnns) = allocateFinalComments ss (pv_comment_q s) (pv_header_comments s) in PV_Ok s { pv_header_comments = header_comments', pv_comment_q = comment_q' } (EpaCommentsBalanced (fromMaybe [] header_comments') (reverse newAnns)) {- Note [Parser-Validator Hint] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ A PV computation is parametrized by a hint for error messages, which can be set depending on validation context. We use this in checkPattern to fix #984. Consider this example, where the user has forgotten a 'do': f _ = do x <- computation case () of _ -> result <- computation case () of () -> undefined GHC parses it as follows: f _ = do x <- computation (case () of _ -> result) <- computation case () of () -> undefined Note that this fragment is parsed as a pattern: case () of _ -> result We attempt to detect such cases and add a hint to the error messages: T984.hs:6:9: Parse error in pattern: case () of { _ -> result } Possibly caused by a missing 'do'? The "Possibly caused by a missing 'do'?" suggestion is the hint that is passed as the 'pv_hints' field 'PV_Context'. When validating in a context other than 'bindpat' (a pattern to the left of <-), we set the hint to 'empty' and it has no effect on the error messages. -} -- | Hint about bang patterns, assuming @BangPatterns@ is off. hintBangPat :: SrcSpan -> Pat GhcPs -> PV () hintBangPat span e = do bang_on <- getBit BangPatBit unless bang_on $ addError $ PsError (PsErrIllegalBangPattern e) [] span mkSumOrTupleExpr :: SrcSpanAnnA -> Boxity -> SumOrTuple (HsExpr GhcPs) -> [AddEpAnn] -> PV (LHsExpr GhcPs) -- Tuple mkSumOrTupleExpr l boxity (Tuple es) anns = do cs <- getCommentsFor (locA l) return $ L l (ExplicitTuple (EpAnn (spanAsAnchor $ locA l) anns cs) (map toTupArg es) boxity) where toTupArg :: Either (EpAnn EpaLocation) (LHsExpr GhcPs) -> HsTupArg GhcPs toTupArg (Left ann) = missingTupArg ann toTupArg (Right a) = Present noAnn a -- Sum -- mkSumOrTupleExpr l Unboxed (Sum alt arity e) = -- return $ L l (ExplicitSum noExtField alt arity e) mkSumOrTupleExpr l Unboxed (Sum alt arity e barsp barsa) anns = do let an = case anns of [AddEpAnn AnnOpenPH o, AddEpAnn AnnClosePH c] -> AnnExplicitSum o barsp barsa c _ -> panic "mkSumOrTupleExpr" cs <- getCommentsFor (locA l) return $ L l (ExplicitSum (EpAnn (spanAsAnchor $ locA l) an cs) alt arity e) mkSumOrTupleExpr l Boxed a@Sum{} _ = addFatalError $ PsError (PsErrUnsupportedBoxedSumExpr a) [] (locA l) mkSumOrTuplePat :: SrcSpanAnnA -> Boxity -> SumOrTuple (PatBuilder GhcPs) -> [AddEpAnn] -> PV (LocatedA (PatBuilder GhcPs)) -- Tuple mkSumOrTuplePat l boxity (Tuple ps) anns = do ps' <- traverse toTupPat ps cs <- getCommentsFor (locA l) return $ L l (PatBuilderPat (TuplePat (EpAnn (spanAsAnchor $ locA l) anns cs) ps' boxity)) where toTupPat :: Either (EpAnn EpaLocation) (LocatedA (PatBuilder GhcPs)) -> PV (LPat GhcPs) -- Ignore the element location so that the error message refers to the -- entire tuple. See #19504 (and the discussion) for details. toTupPat p = case p of Left _ -> addFatalError $ PsError PsErrTupleSectionInPat [] (locA l) Right p' -> checkLPat p' -- Sum mkSumOrTuplePat l Unboxed (Sum alt arity p barsb barsa) anns = do p' <- checkLPat p cs <- getCommentsFor (locA l) let an = EpAnn (spanAsAnchor $ locA l) (EpAnnSumPat anns barsb barsa) cs return $ L l (PatBuilderPat (SumPat an p' alt arity)) mkSumOrTuplePat l Boxed a@Sum{} _ = addFatalError $ PsError (PsErrUnsupportedBoxedSumPat a) [] (locA l) mkLHsOpTy :: LHsType GhcPs -> LocatedN RdrName -> LHsType GhcPs -> LHsType GhcPs mkLHsOpTy x op y = let loc = getLoc x `combineSrcSpansA` (noAnnSrcSpan $ getLocA op) `combineSrcSpansA` getLoc y in L loc (mkHsOpTy x op y) mkMultTy :: IsUnicodeSyntax -> Located Token -> LHsType GhcPs -> HsArrow GhcPs mkMultTy u tok t@(L _ (HsTyLit _ (HsNumTy (SourceText "1") 1))) -- See #18888 for the use of (SourceText "1") above = HsLinearArrow u (Just $ AddEpAnn AnnPercentOne (EpaSpan $ realSrcSpan $ combineLocs tok (reLoc t))) mkMultTy u tok t = HsExplicitMult u (Just $ AddEpAnn AnnPercent (EpaSpan $ realSrcSpan $ getLoc tok)) t ----------------------------------------------------------------------------- -- Token symbols starSym :: Bool -> String starSym True = "★" starSym False = "*" ----------------------------------------- -- Bits and pieces for RecordDotSyntax. mkRdrGetField :: SrcSpanAnnA -> LHsExpr GhcPs -> Located (HsFieldLabel GhcPs) -> EpAnnCO -> LHsExpr GhcPs mkRdrGetField loc arg field anns = L loc HsGetField { gf_ext = anns , gf_expr = arg , gf_field = field } mkRdrProjection :: NonEmpty (Located (HsFieldLabel GhcPs)) -> EpAnn AnnProjection -> HsExpr GhcPs mkRdrProjection flds anns = HsProjection { proj_ext = anns , proj_flds = flds } mkRdrProjUpdate :: SrcSpanAnnA -> Located [Located (HsFieldLabel GhcPs)] -> LHsExpr GhcPs -> Bool -> EpAnn [AddEpAnn] -> LHsRecProj GhcPs (LHsExpr GhcPs) mkRdrProjUpdate _ (L _ []) _ _ _ = panic "mkRdrProjUpdate: The impossible has happened!" mkRdrProjUpdate loc (L l flds) arg isPun anns = L loc HsRecField { hsRecFieldAnn = anns , hsRecFieldLbl = L l (FieldLabelStrings flds) , hsRecFieldArg = arg , hsRecPun = isPun }