-- -- (c) The University of Glasgow 2002-2006 -- -- Functions over HsSyn specialised to RdrName. {-# LANGUAGE CPP #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE MagicHash #-} {-# LANGUAGE ViewPatterns #-} {-# LANGUAGE GADTs #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE LambdaCase #-} {-# LANGUAGE TypeApplications #-} {-# LANGUAGE GeneralizedNewtypeDeriving #-} module RdrHsSyn ( mkHsOpApp, mkHsIntegral, mkHsFractional, mkHsIsString, mkHsDo, mkSpliceDecl, mkRoleAnnotDecl, mkClassDecl, mkTyData, mkDataFamInst, mkTySynonym, mkTyFamInstEqn, mkStandaloneKindSig, mkTyFamInst, mkFamDecl, mkLHsSigType, mkInlinePragma, mkPatSynMatchGroup, mkRecConstrOrUpdate, -- HsExp -> [HsFieldUpdate] -> P HsExp mkTyClD, mkInstD, mkRdrRecordCon, mkRdrRecordUpd, setRdrNameSpace, filterCTuple, cvBindGroup, cvBindsAndSigs, cvTopDecls, placeHolderPunRhs, -- Stuff to do with Foreign declarations mkImport, parseCImport, mkExport, mkExtName, -- RdrName -> CLabelString mkGadtDecl, -- [Located RdrName] -> LHsType RdrName -> ConDecl RdrName mkConDeclH98, -- Bunch of functions in the parser monad for -- checking and constructing values checkImportDecl, checkExpBlockArguments, checkPrecP, -- Int -> P Int checkContext, -- HsType -> P HsContext checkPattern, -- HsExp -> P HsPat checkPattern_msg, isBangRdr, isTildeRdr, checkMonadComp, -- P (HsStmtContext RdrName) checkValDef, -- (SrcLoc, HsExp, HsRhs, [HsDecl]) -> P HsDecl checkValSigLhs, LRuleTyTmVar, RuleTyTmVar(..), mkRuleBndrs, mkRuleTyVarBndrs, checkRuleTyVarBndrNames, checkRecordSyntax, checkEmptyGADTs, addFatalError, hintBangPat, TyEl(..), mergeOps, mergeDataCon, -- Help with processing exports ImpExpSubSpec(..), ImpExpQcSpec(..), mkModuleImpExp, mkTypeImpExp, mkImpExpSubSpec, checkImportSpec, -- Token symbols forallSym, starSym, -- Warnings and errors warnStarIsType, warnPrepositiveQualifiedModule, failOpFewArgs, failOpNotEnabledImportQualifiedPost, failOpImportQualifiedTwice, SumOrTuple (..), -- Expression/command/pattern ambiguity resolution PV, runPV, ECP(ECP, runECP_PV), runECP_P, DisambInfixOp(..), DisambECP(..), ecpFromExp, ecpFromCmd, PatBuilder, patBuilderBang, ) where import GhcPrelude import GHC.Hs -- Lots of it import TyCon ( TyCon, isTupleTyCon, tyConSingleDataCon_maybe ) import DataCon ( DataCon, dataConTyCon ) import ConLike ( ConLike(..) ) import CoAxiom ( Role, fsFromRole ) import RdrName import Name import BasicTypes import TcEvidence ( idHsWrapper ) import Lexer import Lexeme ( isLexCon ) import Type ( TyThing(..), funTyCon ) import TysWiredIn ( cTupleTyConName, tupleTyCon, tupleDataCon, nilDataConName, nilDataConKey, listTyConName, listTyConKey, eqTyCon_RDR, tupleTyConName, cTupleTyConNameArity_maybe ) import ForeignCall import PrelNames ( allNameStrings ) import SrcLoc import Unique ( hasKey ) import OrdList ( OrdList, fromOL ) import Bag ( emptyBag, consBag ) import Outputable import FastString import Maybes import Util import ApiAnnotation import Data.List import DynFlags ( WarningFlag(..), DynFlags ) import ErrUtils ( Messages ) import Control.Monad import Text.ParserCombinators.ReadP as ReadP import Data.Char import qualified Data.Monoid as Monoid import Data.Data ( dataTypeOf, fromConstr, dataTypeConstrs ) #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 (dL->L loc d) = cL loc (TyClD noExtField d) mkInstD :: LInstDecl (GhcPass p) -> LHsDecl (GhcPass p) mkInstD (dL->L loc d) = cL loc (InstD noExtField d) mkClassDecl :: SrcSpan -> Located (Maybe (LHsContext GhcPs), LHsType GhcPs) -> Located (a,[LHsFunDep GhcPs]) -> OrdList (LHsDecl GhcPs) -> P (LTyClDecl GhcPs) mkClassDecl loc (dL->L _ (mcxt, tycl_hdr)) fds where_cls = do { (binds, sigs, ats, at_defs, _, docs) <- cvBindsAndSigs where_cls ; let cxt = fromMaybe (noLoc []) mcxt ; (cls, tparams, fixity, ann) <- checkTyClHdr True tycl_hdr ; addAnnsAt loc ann -- Add any API Annotations to the top SrcSpan ; (tyvars,annst) <- checkTyVars (text "class") whereDots cls tparams ; addAnnsAt loc annst -- Add any API Annotations to the top SrcSpan ; return (cL loc (ClassDecl { tcdCExt = noExtField, tcdCtxt = cxt , 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 (Located CType) -> Located (Maybe (LHsContext GhcPs), LHsType GhcPs) -> Maybe (LHsKind GhcPs) -> [LConDecl GhcPs] -> HsDeriving GhcPs -> P (LTyClDecl GhcPs) mkTyData loc new_or_data cType (dL->L _ (mcxt, tycl_hdr)) ksig data_cons maybe_deriv = do { (tc, tparams, fixity, ann) <- checkTyClHdr False tycl_hdr ; addAnnsAt loc ann -- Add any API Annotations to the top SrcSpan ; (tyvars, anns) <- checkTyVars (ppr new_or_data) equalsDots tc tparams ; addAnnsAt loc anns -- Add any API Annotations to the top SrcSpan ; defn <- mkDataDefn new_or_data cType mcxt ksig data_cons maybe_deriv ; return (cL loc (DataDecl { tcdDExt = noExtField, tcdLName = tc, tcdTyVars = tyvars, tcdFixity = fixity, tcdDataDefn = defn })) } mkDataDefn :: NewOrData -> Maybe (Located 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 ; let cxt = fromMaybe (noLoc []) mcxt ; return (HsDataDefn { dd_ext = noExtField , dd_ND = new_or_data, dd_cType = cType , dd_ctxt = cxt , dd_cons = data_cons , dd_kindSig = ksig , dd_derivs = maybe_deriv }) } mkTySynonym :: SrcSpan -> LHsType GhcPs -- LHS -> LHsType GhcPs -- RHS -> P (LTyClDecl GhcPs) mkTySynonym loc lhs rhs = do { (tc, tparams, fixity, ann) <- checkTyClHdr False lhs ; addAnnsAt loc ann -- Add any API Annotations to the top SrcSpan ; (tyvars, anns) <- checkTyVars (text "type") equalsDots tc tparams ; addAnnsAt loc anns -- Add any API Annotations to the top SrcSpan ; return (cL loc (SynDecl { tcdSExt = noExtField , tcdLName = tc, tcdTyVars = tyvars , tcdFixity = fixity , tcdRhs = rhs })) } mkStandaloneKindSig :: SrcSpan -> Located [Located RdrName] -- LHS -> LHsKind GhcPs -- RHS -> P (LStandaloneKindSig GhcPs) mkStandaloneKindSig loc lhs rhs = do { vs <- mapM check_lhs_name (unLoc lhs) ; v <- check_singular_lhs (reverse vs) ; return $ cL loc $ StandaloneKindSig noExtField v (mkLHsSigType rhs) } where check_lhs_name v@(unLoc->name) = if isUnqual name && isTcOcc (rdrNameOcc name) then return v else addFatalError (getLoc v) $ hang (text "Expected an unqualified type constructor:") 2 (ppr v) check_singular_lhs vs = case vs of [] -> panic "mkStandaloneKindSig: empty left-hand side" [v] -> return v _ -> addFatalError (getLoc lhs) $ vcat [ hang (text "Standalone kind signatures do not support multiple names at the moment:") 2 (pprWithCommas ppr vs) , text "See https://gitlab.haskell.org/ghc/ghc/issues/16754 for details." ] mkTyFamInstEqn :: Maybe [LHsTyVarBndr GhcPs] -> LHsType GhcPs -> LHsType GhcPs -> P (TyFamInstEqn GhcPs,[AddAnn]) mkTyFamInstEqn bndrs lhs rhs = do { (tc, tparams, fixity, ann) <- checkTyClHdr False lhs ; return (mkHsImplicitBndrs (FamEqn { feqn_ext = noExtField , feqn_tycon = tc , feqn_bndrs = bndrs , feqn_pats = tparams , feqn_fixity = fixity , feqn_rhs = rhs }), ann) } mkDataFamInst :: SrcSpan -> NewOrData -> Maybe (Located CType) -> (Maybe ( LHsContext GhcPs), Maybe [LHsTyVarBndr GhcPs] , LHsType GhcPs) -> Maybe (LHsKind GhcPs) -> [LConDecl GhcPs] -> HsDeriving GhcPs -> P (LInstDecl GhcPs) mkDataFamInst loc new_or_data cType (mcxt, bndrs, tycl_hdr) ksig data_cons maybe_deriv = do { (tc, tparams, fixity, ann) <- checkTyClHdr False tycl_hdr ; addAnnsAt loc ann -- Add any API Annotations to the top SrcSpan ; defn <- mkDataDefn new_or_data cType mcxt ksig data_cons maybe_deriv ; return (cL loc (DataFamInstD noExtField (DataFamInstDecl (mkHsImplicitBndrs (FamEqn { feqn_ext = noExtField , feqn_tycon = tc , feqn_bndrs = bndrs , feqn_pats = tparams , feqn_fixity = fixity , feqn_rhs = defn }))))) } mkTyFamInst :: SrcSpan -> TyFamInstEqn GhcPs -> P (LInstDecl GhcPs) mkTyFamInst loc eqn = return (cL loc (TyFamInstD noExtField (TyFamInstDecl eqn))) mkFamDecl :: SrcSpan -> FamilyInfo GhcPs -> LHsType GhcPs -- LHS -> Located (FamilyResultSig GhcPs) -- Optional result signature -> Maybe (LInjectivityAnn GhcPs) -- Injectivity annotation -> P (LTyClDecl GhcPs) mkFamDecl loc info lhs ksig injAnn = do { (tc, tparams, fixity, ann) <- checkTyClHdr False lhs ; addAnnsAt loc ann -- Add any API Annotations to the top SrcSpan ; (tyvars, anns) <- checkTyVars (ppr info) equals_or_where tc tparams ; addAnnsAt loc anns -- Add any API Annotations to the top SrcSpan ; return (cL loc (FamDecl noExtField (FamilyDecl { fdExt = noExtField , 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 -> HsDecl GhcPs -- If the user wrote -- [pads| ... ] then return a QuasiQuoteD -- $(e) then return a SpliceD -- but if she wrote, say, -- f x then behave as if she'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@(dL->L loc expr) | HsSpliceE _ splice@(HsUntypedSplice {}) <- expr = SpliceD noExtField (SpliceDecl noExtField (cL loc splice) ExplicitSplice) | HsSpliceE _ splice@(HsQuasiQuote {}) <- expr = SpliceD noExtField (SpliceDecl noExtField (cL loc splice) ExplicitSplice) | otherwise = SpliceD noExtField (SpliceDecl noExtField (cL loc (mkUntypedSplice NoParens lexpr)) ImplicitSplice) mkRoleAnnotDecl :: SrcSpan -> Located RdrName -- type being annotated -> [Located (Maybe FastString)] -- roles -> P (LRoleAnnotDecl GhcPs) mkRoleAnnotDecl loc tycon roles = do { roles' <- mapM parse_role roles ; return $ cL loc $ RoleAnnotDecl noExtField 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 (dL->L loc_role Nothing) = return $ cL loc_role Nothing parse_role (dL->L loc_role (Just role)) = case lookup role possible_roles of Just found_role -> return $ cL loc_role $ Just found_role Nothing -> let nearby = fuzzyLookup (unpackFS role) (mapFst unpackFS possible_roles) in addFatalError loc_role (text "Illegal role name" <+> quotes (ppr role) $$ suggestions nearby) parse_role _ = panic "parse_role: Impossible Match" -- due to #15884 suggestions [] = empty suggestions [r] = text "Perhaps you meant" <+> quotes (ppr r) -- will this last case ever happen?? suggestions list = hang (text "Perhaps you meant one of these:") 2 (pprWithCommas (quotes . ppr) list) {- ********************************************************************** #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 = go (fromOL decls) where go :: [LHsDecl GhcPs] -> [LHsDecl GhcPs] go [] = [] go ((dL->L l (ValD x b)) : ds) = cL l' (ValD x b') : go ds' where (dL->L l' b', ds') = getMonoBind (cL l b) ds go (d : ds) = d : go ds -- 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 noExtField mbs sigs } cvBindsAndSigs :: OrdList (LHsDecl GhcPs) -> P (LHsBinds GhcPs, [LSig GhcPs], [LFamilyDecl GhcPs] , [LTyFamInstDecl GhcPs], [LDataFamInstDecl GhcPs], [LDocDecl]) -- 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 = go (fromOL fb) where go [] = return (emptyBag, [], [], [], [], []) go ((dL->L l (ValD _ b)) : ds) = do { (bs, ss, ts, tfis, dfis, docs) <- go ds' ; return (b' `consBag` bs, ss, ts, tfis, dfis, docs) } where (b', ds') = getMonoBind (cL l b) ds go ((dL->L l decl) : ds) = do { (bs, ss, ts, tfis, dfis, docs) <- go ds ; case decl of SigD _ s -> return (bs, cL l s : ss, ts, tfis, dfis, docs) TyClD _ (FamDecl _ t) -> return (bs, ss, cL l t : ts, tfis, dfis, docs) InstD _ (TyFamInstD { tfid_inst = tfi }) -> return (bs, ss, ts, cL l tfi : tfis, dfis, docs) InstD _ (DataFamInstD { dfid_inst = dfi }) -> return (bs, ss, ts, tfis, cL l dfi : dfis, docs) DocD _ d -> return (bs, ss, ts, tfis, dfis, cL l d : docs) SpliceD _ d -> addFatalError l $ hang (text "Declaration splices are allowed only" <+> text "at the top level:") 2 (ppr d) _ -> pprPanic "cvBindsAndSigs" (ppr decl) } ----------------------------------------------------------------------------- -- 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 (dL->L loc1 (FunBind { fun_id = fun_id1@(dL->L _ f1) , fun_matches = MG { mg_alts = (dL->L _ mtchs1) } })) binds | has_args mtchs1 = go mtchs1 loc1 binds [] where go mtchs loc ((dL->L loc2 (ValD _ (FunBind { fun_id = (dL->L _ f2) , fun_matches = MG { mg_alts = (dL->L _ mtchs2) } }))) : binds) _ | f1 == f2 = go (mtchs2 ++ mtchs) (combineSrcSpans loc loc2) binds [] go mtchs loc (doc_decl@(dL->L loc2 (DocD {})) : binds) doc_decls = let doc_decls' = doc_decl : doc_decls in go mtchs (combineSrcSpans loc loc2) binds doc_decls' go mtchs loc binds doc_decls = ( cL loc (makeFunBind fun_id1 (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) has_args :: [LMatch GhcPs (LHsExpr GhcPs)] -> Bool has_args [] = panic "RdrHsSyn:has_args" has_args ((dL->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). has_args ((dL->L _ (XMatch nec)) : _) = noExtCon nec has_args (_ : _) = panic "has_args:Impossible Match" -- due to #15884 {- ********************************************************************** #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. To further complicate matters, the interpretation of (!) and (~) is different in constructors and types: (b1) type T = C ! D (b2) data T = C ! D (b3) data T = C ! D => E In (b1) and (b3), (!) is a type operator with two arguments: 'C' and 'D'. At the same time, in (b2) it is a strictness annotation: 'C' is a data constructor with a single strict argument 'D'. For the programmer, these cases are usually easy to tell apart due to whitespace conventions: (b2) data T = C !D -- no space after the bang hints that -- it is a strictness annotation For the parser, on the other hand, this whitespace does not matter. We cannot tell apart (b2) from (b3) until we encounter (=>), so it requires unlimited lookahead. The solution that accounts for all of these issues is to initially parse data declarations and types as a reversed list of TyEl: data TyEl = TyElOpr RdrName | TyElOpd (HsType GhcPs) | TyElBang | TyElTilde | ... For example, both occurences of (C ! D) in the following example are parsed into equal lists of TyEl: data T = C ! D => C ! D results in [ TyElOpd (HsTyVar "D") , TyElBang , TyElOpd (HsTyVar "C") ] Note that elements are in reverse order. Also, 'C' is parsed as a type constructor (HsTyVar) even when it is a data constructor. We fix this in `tyConToDataCon`. By the time the list of TyEl is assembled, we have looked ahead enough to decide whether to reduce using `mergeOps` (for types) or `mergeDataCon` (for data constructors). These functions are where the actual job of parsing is done. -} -- | Reinterpret a type constructor, including type operators, as a data -- constructor. -- See Note [Parsing data constructors is hard] tyConToDataCon :: SrcSpan -> RdrName -> Either (SrcSpan, SDoc) (Located RdrName) tyConToDataCon loc tc | isTcOcc occ || isDataOcc occ , isLexCon (occNameFS occ) = return (cL loc (setRdrNameSpace tc srcDataName)) | otherwise = Left (loc, msg) where occ = rdrNameOcc tc msg = text "Not a data constructor:" <+> quotes (ppr tc) mkPatSynMatchGroup :: Located RdrName -> Located (OrdList (LHsDecl GhcPs)) -> P (MatchGroup GhcPs (LHsExpr GhcPs)) mkPatSynMatchGroup (dL->L loc patsyn_name) (dL->L _ decls) = do { matches <- mapM fromDecl (fromOL decls) ; when (null matches) (wrongNumberErr loc) ; return $ mkMatchGroup FromSource matches } where fromDecl (dL->L loc decl@(ValD _ (PatBind _ pat@(dL->L _ (ConPatIn ln@(dL->L _ name) details)) rhs _))) = do { unless (name == patsyn_name) $ wrongNameBindingErr loc decl ; match <- case details of PrefixCon pats -> return $ Match { m_ext = noExtField , 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 = noExtField , m_ctxt = ctxt , m_pats = [p1, p2] , m_grhss = rhs } where ctxt = FunRhs { mc_fun = ln , mc_fixity = Infix , mc_strictness = NoSrcStrict } RecCon{} -> recordPatSynErr loc pat ; return $ cL loc match } fromDecl (dL->L loc decl) = extraDeclErr loc decl extraDeclErr loc decl = addFatalError loc $ text "pattern synonym 'where' clause must contain a single binding:" $$ ppr decl wrongNameBindingErr loc decl = addFatalError loc $ text "pattern synonym 'where' clause must bind the pattern synonym's name" <+> quotes (ppr patsyn_name) $$ ppr decl wrongNumberErr loc = addFatalError loc $ text "pattern synonym 'where' clause cannot be empty" $$ text "In the pattern synonym declaration for: " <+> ppr (patsyn_name) recordPatSynErr :: SrcSpan -> LPat GhcPs -> P a recordPatSynErr loc pat = addFatalError loc $ text "record syntax not supported for pattern synonym declarations:" $$ ppr pat mkConDeclH98 :: Located RdrName -> Maybe [LHsTyVarBndr GhcPs] -> Maybe (LHsContext GhcPs) -> HsConDeclDetails GhcPs -> ConDecl GhcPs mkConDeclH98 name mb_forall mb_cxt args = ConDeclH98 { con_ext = noExtField , con_name = name , con_forall = noLoc $ isJust mb_forall , con_ex_tvs = mb_forall `orElse` [] , con_mb_cxt = mb_cxt , con_args = args , con_doc = Nothing } mkGadtDecl :: [Located RdrName] -> LHsType GhcPs -- Always a HsForAllTy -> (ConDecl GhcPs, [AddAnn]) mkGadtDecl names ty = (ConDeclGADT { con_g_ext = noExtField , con_names = names , con_forall = cL l $ isLHsForAllTy ty' , con_qvars = mkHsQTvs tvs , con_mb_cxt = mcxt , con_args = args , con_res_ty = res_ty , con_doc = Nothing } , anns1 ++ anns2) where (ty'@(dL->L l _),anns1) = peel_parens ty [] (tvs, rho) = splitLHsForAllTyInvis ty' (mcxt, tau, anns2) = split_rho rho [] split_rho (dL->L _ (HsQualTy { hst_ctxt = cxt, hst_body = tau })) ann = (Just cxt, tau, ann) split_rho (dL->L l (HsParTy _ ty)) ann = split_rho ty (ann++mkParensApiAnn l) split_rho tau ann = (Nothing, tau, ann) (args, res_ty) = split_tau tau -- See Note [GADT abstract syntax] in GHC.Hs.Decls split_tau (dL->L _ (HsFunTy _ (dL->L loc (HsRecTy _ rf)) res_ty)) = (RecCon (cL loc rf), res_ty) split_tau tau = (PrefixCon [], tau) peel_parens (dL->L l (HsParTy _ ty)) ann = peel_parens ty (ann++mkParensApiAnn l) peel_parens ty ann = (ty, ann) 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)) -- | Replaces constraint tuple names with corresponding boxed ones. filterCTuple :: RdrName -> RdrName filterCTuple (Exact n) | Just arity <- cTupleTyConNameArity_maybe n = Exact $ tupleTyConName BoxedTuple arity filterCTuple rdr = rdr {- 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 :: Either (SrcSpan, SDoc) a -> P a -- Adapts the Either monad to the P monad eitherToP (Left (loc, doc)) = addFatalError loc doc eitherToP (Right thing) = return thing checkTyVars :: SDoc -> SDoc -> Located RdrName -> [LHsTypeArg GhcPs] -> P ( LHsQTyVars GhcPs -- the synthesized type variables , [AddAnn] ) -- action which adds annotations -- ^ 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, anns) <- fmap unzip $ mapM check tparms ; return (mkHsQTvs tvs, concat anns) } where check (HsTypeArg _ ki@(L loc _)) = addFatalError loc $ vcat [ text "Unexpected type application" <+> text "@" <> ppr ki , text "In the" <+> pp_what <+> ptext (sLit "declaration for") <+> quotes (ppr tc)] check (HsValArg ty) = chkParens [] ty check (HsArgPar sp) = addFatalError sp $ vcat [text "Malformed" <+> pp_what <+> text "declaration for" <+> quotes (ppr tc)] -- Keep around an action for adjusting the annotations of extra parens chkParens :: [AddAnn] -> LHsType GhcPs -> P (LHsTyVarBndr GhcPs, [AddAnn]) chkParens acc (dL->L l (HsParTy _ ty)) = chkParens (mkParensApiAnn l ++ acc) ty chkParens acc ty = do tv <- chk ty return (tv, reverse acc) -- Check that the name space is correct! chk :: LHsType GhcPs -> P (LHsTyVarBndr GhcPs) chk (dL->L l (HsKindSig _ (dL->L lv (HsTyVar _ _ (dL->L _ tv))) k)) | isRdrTyVar tv = return (cL l (KindedTyVar noExtField (cL lv tv) k)) chk (dL->L l (HsTyVar _ _ (dL->L ltv tv))) | isRdrTyVar tv = return (cL l (UserTyVar noExtField (cL ltv tv))) chk t@(dL->L loc _) = addFatalError loc $ vcat [ text "Unexpected type" <+> quotes (ppr t) , text "In the" <+> pp_what <+> ptext (sLit "declaration for") <+> quotes tc' , vcat[ (text "A" <+> pp_what <+> ptext (sLit "declaration should have form")) , nest 2 (pp_what <+> tc' <+> hsep (map text (takeList tparms allNameStrings)) <+> equals_or_where) ] ] -- Avoid printing a constraint tuple in the error message. Print -- a plain old tuple instead (since that's what the user probably -- wrote). See #14907 tc' = ppr $ fmap filterCTuple tc 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 (getLoc c) (text "Illegal datatype context (use DatatypeContexts):" <+> pprLHsContext c) type LRuleTyTmVar = Located RuleTyTmVar data RuleTyTmVar = RuleTyTmVar (Located 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 v Nothing) = RuleBndr noExtField v cvt_one (RuleTyTmVar v (Just sig)) = RuleBndrSig noExtField v (mkLHsSigWcType sig) -- turns RuleTyTmVars into HsTyVarBndrs - this is more interesting mkRuleTyVarBndrs :: [LRuleTyTmVar] -> [LHsTyVarBndr GhcPs] mkRuleTyVarBndrs = fmap (fmap cvt_one) where cvt_one (RuleTyTmVar v Nothing) = UserTyVar noExtField (fmap tm_to_ty v) cvt_one (RuleTyTmVar v (Just sig)) = KindedTyVar noExtField (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 GhcPs] -> P () checkRuleTyVarBndrNames = mapM_ (check . fmap hsTyVarName) where check (dL->L loc (Unqual occ)) = do when ((occNameString occ ==) `any` ["forall","family","role"]) (addFatalError loc (text $ "parse error on input " ++ occNameString occ)) check _ = panic "checkRuleTyVarBndrNames" checkRecordSyntax :: (MonadP m, Outputable a) => Located a -> m (Located a) checkRecordSyntax lr@(dL->L loc r) = do allowed <- getBit TraditionalRecordSyntaxBit unless allowed $ addError loc $ text "Illegal record syntax (use TraditionalRecordSyntax):" <+> ppr r 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 ([AddAnn], [LConDecl GhcPs]) -> P (Located ([AddAnn], [LConDecl GhcPs])) checkEmptyGADTs gadts@(dL->L span (_, [])) -- Empty GADT declaration. = do gadtSyntax <- getBit GadtSyntaxBit -- GADTs implies GADTSyntax unless gadtSyntax $ addError span $ vcat [ text "Illegal keyword 'where' in data declaration" , text "Perhaps you intended to use GADTs or a similar language" , text "extension to enable syntax: data T where" ] return gadts checkEmptyGADTs gadts = return gadts -- Ordinary GADT declaration. checkTyClHdr :: Bool -- True <=> class header -- False <=> type header -> LHsType GhcPs -> P (Located RdrName, -- the head symbol (type or class name) [LHsTypeArg GhcPs], -- parameters of head symbol LexicalFixity, -- the declaration is in infix format [AddAnn]) -- 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 (dL->L l ty) acc ann fix = go l ty acc ann fix -- workaround to define '*' despite StarIsType go lp (HsParTy _ (dL->L l (HsStarTy _ isUni))) acc ann fix = do { warnStarBndr l ; let name = mkOccName tcClsName (starSym isUni) ; return (cL l (Unqual name), acc, fix, (ann ++ mkParensApiAnn lp)) } go _ (HsTyVar _ _ ltc@(dL->L _ tc)) acc ann fix | isRdrTc tc = return (ltc, acc, fix, ann) go _ (HsOpTy _ t1 ltc@(dL->L _ tc) t2) acc ann _fix | isRdrTc tc = return (ltc, HsValArg t1:HsValArg t2:acc, Infix, ann) go l (HsParTy _ ty) acc ann fix = goL ty acc (ann ++mkParensApiAnn l) fix go _ (HsAppTy _ t1 t2) acc ann fix = goL t1 (HsValArg t2:acc) ann fix go _ (HsAppKindTy l ty ki) acc ann fix = goL ty (HsTypeArg l ki:acc) ann fix go l (HsTupleTy _ HsBoxedOrConstraintTuple ts) [] ann fix = return (cL l (nameRdrName tup_name), map HsValArg ts, fix, ann) where arity = length ts tup_name | is_cls = cTupleTyConName arity | otherwise = getName (tupleTyCon Boxed arity) -- See Note [Unit tuples] in GHC.Hs.Types (TODO: is this still relevant?) go l _ _ _ _ = addFatalError l (text "Malformed head of type or class declaration:" <+> ppr ty) -- | 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 _ -> check "do block" expr HsDo _ MDoExpr _ -> check "mdo block" expr HsLam {} -> check "lambda expression" expr HsCase {} -> check "case expression" expr HsLamCase {} -> check "lambda-case expression" expr HsLet {} -> check "let expression" expr HsIf {} -> check "if expression" expr HsProc {} -> check "proc expression" expr _ -> return () checkCmd :: LHsCmd GhcPs -> PV () checkCmd cmd = case unLoc cmd of HsCmdLam {} -> check "lambda command" cmd HsCmdCase {} -> check "case command" cmd HsCmdIf {} -> check "if command" cmd HsCmdLet {} -> check "let command" cmd HsCmdDo {} -> check "do command" cmd _ -> return () check :: (HasSrcSpan a, Outputable a) => String -> a -> PV () check element a = do blockArguments <- getBit BlockArgumentsBit unless blockArguments $ addError (getLoc a) $ text "Unexpected " <> text element <> text " in function application:" $$ nest 4 (ppr a) $$ text "You could write it with parentheses" $$ text "Or perhaps you meant to enable BlockArguments?" -- | 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 ([AddAnn],LHsContext GhcPs) checkContext (dL->L l orig_t) = check [] (cL l orig_t) where check anns (dL->L lp (HsTupleTy _ HsBoxedOrConstraintTuple ts)) -- (Eq a, Ord b) shows up as a tuple type. Only boxed tuples can -- be used as context constraints. = return (anns ++ mkParensApiAnn lp,cL l ts) -- Ditto () check anns (dL->L lp1 (HsParTy _ ty)) -- to be sure HsParTy doesn't get into the way = check anns' ty where anns' = if l == lp1 then anns else (anns ++ mkParensApiAnn lp1) -- no need for anns, returning original check _anns t = checkNoDocs msg t *> return ([],cL l [cL l orig_t]) msg = text "data constructor context" -- | Check recursively if there are any 'HsDocTy's in the given type. -- This only works on a subset of types produced by 'btype_no_ops' checkNoDocs :: SDoc -> LHsType GhcPs -> P () checkNoDocs msg ty = go ty where go (dL->L _ (HsAppKindTy _ ty ki)) = go ty *> go ki go (dL->L _ (HsAppTy _ t1 t2)) = go t1 *> go t2 go (dL->L l (HsDocTy _ t ds)) = addError l $ hsep [ text "Unexpected haddock", quotes (ppr ds) , text "on", msg, quotes (ppr t) ] go _ = pure () checkImportDecl :: Maybe (Located Token) -> Maybe (Located Token) -> P () checkImportDecl mPre mPost = do let whenJust mg f = maybe (pure ()) f mg importQualifiedPostEnabled <- getBit ImportQualifiedPostBit -- Error if 'qualified' found in postpostive position and -- 'ImportQualifiedPost' is not in effect. whenJust mPost $ \post -> when (not importQualifiedPostEnabled) $ failOpNotEnabledImportQualifiedPost (getLoc post) -- Error if 'qualified' occurs in both pre and postpositive -- positions. whenJust mPost $ \post -> when (isJust mPre) $ failOpImportQualifiedTwice (getLoc post) -- Warn if 'qualified' found in prepositive position and -- 'Opt_WarnPrepositiveQualifiedModule' is enabled. whenJust mPre $ \pre -> warnPrepositiveQualifiedModule (getLoc pre) -- ------------------------------------------------------------------------- -- Checking Patterns. -- We parse patterns as expressions and check for valid patterns below, -- converting the expression into a pattern at the same time. checkPattern :: Located (PatBuilder GhcPs) -> P (LPat GhcPs) checkPattern = runPV . checkLPat checkPattern_msg :: SDoc -> PV (Located (PatBuilder GhcPs)) -> P (LPat GhcPs) checkPattern_msg msg pp = runPV_msg msg (pp >>= checkLPat) checkLPat :: Located (PatBuilder GhcPs) -> PV (LPat GhcPs) checkLPat e@(dL->L l _) = checkPat l e [] checkPat :: SrcSpan -> Located (PatBuilder GhcPs) -> [LPat GhcPs] -> PV (LPat GhcPs) checkPat loc (dL->L l e@(PatBuilderVar (dL->L _ c))) args | isRdrDataCon c = return (cL loc (ConPatIn (cL l c) (PrefixCon args))) | not (null args) && patIsRec c = localPV_msg (\_ -> text "Perhaps you intended to use RecursiveDo") $ patFail l (ppr e) checkPat loc e args -- OK to let this happen even if bang-patterns -- are not enabled, because there is no valid -- non-bang-pattern parse of (C ! e) | Just (e', args') <- splitBang e = do { args'' <- mapM checkLPat args' ; checkPat loc e' (args'' ++ args) } checkPat loc (dL->L _ (PatBuilderApp f e)) args = do p <- checkLPat e checkPat loc f (p : args) checkPat loc (dL->L _ e) [] = do p <- checkAPat loc e return (cL loc p) checkPat loc e _ = patFail loc (ppr e) checkAPat :: SrcSpan -> 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 (cL loc pos_lit) Nothing) PatBuilderBang lb e -- (! x) -> do { hintBangPat loc e0 ; e' <- checkLPat e ; addAnnotation loc AnnBang lb ; return (BangPat noExtField e') } -- n+k patterns PatBuilderOpApp (dL->L nloc (PatBuilderVar (dL->L _ n))) (dL->L _ plus) (dL->L lloc (PatBuilderOverLit lit@(OverLit {ol_val = HsIntegral {}}))) | nPlusKPatterns && (plus == plus_RDR) -> return (mkNPlusKPat (cL nloc n) (cL lloc lit)) PatBuilderOpApp l (dL->L cl c) r | isRdrDataCon c -> do l <- checkLPat l r <- checkLPat r return (ConPatIn (cL cl c) (InfixCon l r)) PatBuilderPar e -> checkLPat e >>= (return . (ParPat noExtField)) _ -> patFail loc (ppr e0) placeHolderPunRhs :: DisambECP b => PV (Located 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 (noLoc pun_RDR) plus_RDR, pun_RDR :: RdrName plus_RDR = mkUnqual varName (fsLit "+") -- Hack pun_RDR = mkUnqual varName (fsLit "pun-right-hand-side") isBangRdr, isTildeRdr :: RdrName -> Bool isBangRdr (Unqual occ) = occNameFS occ == fsLit "!" isBangRdr _ = False isTildeRdr = (==eqTyCon_RDR) checkPatField :: LHsRecField GhcPs (Located (PatBuilder GhcPs)) -> PV (LHsRecField GhcPs (LPat GhcPs)) checkPatField (dL->L l fld) = do p <- checkLPat (hsRecFieldArg fld) return (cL l (fld { hsRecFieldArg = p })) patFail :: SrcSpan -> SDoc -> PV a patFail loc e = addFatalError loc $ text "Parse error in pattern:" <+> ppr e patIsRec :: RdrName -> Bool patIsRec e = e == mkUnqual varName (fsLit "rec") --------------------------------------------------------------------------- -- Check Equation Syntax checkValDef :: SrcStrictness -> Located (PatBuilder GhcPs) -> Maybe (LHsType GhcPs) -> Located (a,GRHSs GhcPs (LHsExpr GhcPs)) -> P ([AddAnn],HsBind GhcPs) checkValDef _strictness lhs (Just sig) grhss -- x :: ty = rhs parses as a *pattern* binding = do lhs' <- runPV $ mkHsTySigPV (combineLocs lhs sig) lhs sig >>= checkLPat checkPatBind lhs' grhss checkValDef strictness lhs Nothing g@(dL->L l (_,grhss)) = do { mb_fun <- isFunLhs lhs ; case mb_fun of Just (fun, is_infix, pats, ann) -> checkFunBind strictness ann (getLoc lhs) fun is_infix pats (cL l grhss) Nothing -> do lhs' <- checkPattern lhs checkPatBind lhs' g } checkFunBind :: SrcStrictness -> [AddAnn] -> SrcSpan -> Located RdrName -> LexicalFixity -> [Located (PatBuilder GhcPs)] -> Located (GRHSs GhcPs (LHsExpr GhcPs)) -> P ([AddAnn],HsBind GhcPs) checkFunBind strictness ann lhs_loc fun is_infix pats (dL->L rhs_span grhss) = do ps <- mapM checkPattern pats let match_span = combineSrcSpans lhs_loc rhs_span -- Add back the annotations stripped from any HsPar values in the lhs -- mapM_ (\a -> a match_span) ann return (ann, makeFunBind fun [cL match_span (Match { m_ext = noExtField , 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. makeFunBind :: Located RdrName -> [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_co_fn = idHsWrapper, fun_tick = [] } checkPatBind :: LPat GhcPs -> Located (a,GRHSs GhcPs (LHsExpr GhcPs)) -> P ([AddAnn],HsBind GhcPs) checkPatBind lhs (dL->L _ (_,grhss)) = return ([],PatBind noExtField lhs grhss ([],[])) checkValSigLhs :: LHsExpr GhcPs -> P (Located RdrName) checkValSigLhs (dL->L _ (HsVar _ lrdr@(dL->L _ v))) | isUnqual v , not (isDataOcc (rdrNameOcc v)) = return lrdr checkValSigLhs lhs@(dL->L l _) = addFatalError l ((text "Invalid type signature:" <+> ppr lhs <+> text ":: ...") $$ text hint) where hint | foreign_RDR `looks_like` lhs = "Perhaps you meant to use ForeignFunctionInterface?" | default_RDR `looks_like` lhs = "Perhaps you meant to use DefaultSignatures?" | pattern_RDR `looks_like` lhs = "Perhaps you meant to use PatternSynonyms?" | otherwise = "Should be of form :: " -- A common error is to forget the ForeignFunctionInterface flag -- so check for that, and suggest. cf #3805 -- Sadly 'foreign import' still barfs 'parse error' because -- 'import' is a keyword looks_like s (dL->L _ (HsVar _ (dL->L _ v))) = v == s looks_like s (dL->L _ (HsApp _ lhs _)) = looks_like s lhs looks_like _ _ = False foreign_RDR = mkUnqual varName (fsLit "foreign") default_RDR = mkUnqual varName (fsLit "default") pattern_RDR = mkUnqual varName (fsLit "pattern") checkDoAndIfThenElse :: (HasSrcSpan a, Outputable a, Outputable b, HasSrcSpan c, Outputable c) => a -> Bool -> b -> Bool -> c -> PV () checkDoAndIfThenElse guardExpr semiThen thenExpr semiElse elseExpr | semiThen || semiElse = do doAndIfThenElse <- getBit DoAndIfThenElseBit unless doAndIfThenElse $ do addError (combineLocs guardExpr elseExpr) (text "Unexpected semi-colons in conditional:" $$ nest 4 expr $$ text "Perhaps you meant to use DoAndIfThenElse?") | otherwise = return () where pprOptSemi True = semi pprOptSemi False = empty expr = text "if" <+> ppr guardExpr <> pprOptSemi semiThen <+> text "then" <+> ppr thenExpr <> pprOptSemi semiElse <+> text "else" <+> ppr elseExpr -- The parser left-associates, so there should -- not be any OpApps inside the e's splitBang :: Located (PatBuilder GhcPs) -> Maybe (Located (PatBuilder GhcPs), [Located (PatBuilder GhcPs)]) -- Splits (f ! g a b) into (f, [(! g), a, b]) splitBang (dL->L _ (PatBuilderOpApp l_arg op r_arg)) | isBangRdr (unLoc op) = Just (l_arg, cL l' (PatBuilderBang (getLoc op) arg1) : argns) where l' = combineLocs op arg1 (arg1,argns) = split_bang r_arg [] split_bang (dL->L _ (PatBuilderApp f e)) es = split_bang f (e:es) split_bang e es = (e,es) splitBang _ = Nothing -- See Note [isFunLhs vs mergeDataCon] isFunLhs :: Located (PatBuilder GhcPs) -> P (Maybe (Located RdrName, LexicalFixity, [Located (PatBuilder GhcPs)],[AddAnn])) -- A variable binding is parsed as a FunBind. -- Just (fun, is_infix, arg_pats) if e is a function LHS -- -- The whole LHS is parsed as a single expression. -- Any infix operators on the LHS will parse left-associatively -- E.g. f !x y !z -- will parse (rather strangely) as -- (f ! x y) ! z -- It's up to isFunLhs to sort out the mess -- -- a .!. !b isFunLhs e = go e [] [] where go (dL->L loc (PatBuilderVar (dL->L _ f))) es ann | not (isRdrDataCon f) = return (Just (cL loc f, Prefix, es, ann)) go (dL->L _ (PatBuilderApp f e)) es ann = go f (e:es) ann go (dL->L l (PatBuilderPar e)) es@(_:_) ann = go e es (ann ++ mkParensApiAnn l) -- Things of the form `!x` are also FunBinds -- See Note [FunBind vs PatBind] go (dL->L _ (PatBuilderBang _ (L _ (PatBuilderVar (dL -> L l var))))) [] ann | not (isRdrDataCon var) = return (Just (cL l var, Prefix, [], ann)) -- For infix function defns, there should be only one infix *function* -- (though there may be infix *datacons* involved too). So we don't -- need fixity info to figure out which function is being defined. -- a `K1` b `op` c `K2` d -- must parse as -- (a `K1` b) `op` (c `K2` d) -- The renamer checks later that the precedences would yield such a parse. -- -- There is a complication to deal with bang patterns. -- -- ToDo: what about this? -- x + 1 `op` y = ... go e@(L loc (PatBuilderOpApp l (dL->L loc' op) r)) es ann | Just (e',es') <- splitBang e = do { bang_on <- getBit BangPatBit ; if bang_on then go e' (es' ++ es) ann else return (Just (cL loc' op, Infix, (l:r:es), ann)) } -- No bangs; behave just like the next case | not (isRdrDataCon op) -- We have found the function! = return (Just (cL loc' op, Infix, (l:r:es), ann)) | otherwise -- Infix data con; keep going = do { mb_l <- go l es ann ; case mb_l of Just (op', Infix, j : k : es', ann') -> return (Just (op', Infix, j : op_app : es', ann')) where op_app = cL loc (PatBuilderOpApp k (cL loc' op) r) _ -> return Nothing } go _ _ _ = return Nothing -- | Either an operator or an operand. data TyEl = TyElOpr RdrName | TyElOpd (HsType GhcPs) | TyElKindApp SrcSpan (LHsType GhcPs) -- See Note [TyElKindApp SrcSpan interpretation] | TyElTilde | TyElBang | TyElUnpackedness ([AddAnn], SourceText, SrcUnpackedness) | TyElDocPrev HsDocString {- Note [TyElKindApp SrcSpan interpretation] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ A TyElKindApp captures type application written in haskell as @ Foo where Foo is some type. The SrcSpan reflects both elements, and there are AnnAt and AnnVal API Annotations attached to this SrcSpan for the specific locations of each within it. -} instance Outputable TyEl where ppr (TyElOpr name) = ppr name ppr (TyElOpd ty) = ppr ty ppr (TyElKindApp _ ki) = text "@" <> ppr ki ppr TyElTilde = text "~" ppr TyElBang = text "!" ppr (TyElUnpackedness (_, _, unpk)) = ppr unpk ppr (TyElDocPrev doc) = ppr doc tyElStrictness :: TyEl -> Maybe (AnnKeywordId, SrcStrictness) tyElStrictness TyElTilde = Just (AnnTilde, SrcLazy) tyElStrictness TyElBang = Just (AnnBang, SrcStrict) tyElStrictness _ = Nothing -- | Extract a strictness/unpackedness annotation from the front of a reversed -- 'TyEl' list. pStrictMark :: [Located TyEl] -- reversed TyEl -> Maybe ( Located HsSrcBang {- a strictness/upnackedness marker -} , [AddAnn] , [Located TyEl] {- remaining TyEl -}) pStrictMark ((dL->L l1 x1) : (dL->L l2 x2) : xs) | Just (strAnnId, str) <- tyElStrictness x1 , TyElUnpackedness (unpkAnns, prag, unpk) <- x2 = Just ( cL (combineSrcSpans l1 l2) (HsSrcBang prag unpk str) , unpkAnns ++ [AddAnn strAnnId l1] , xs ) pStrictMark ((dL->L l x1) : xs) | Just (strAnnId, str) <- tyElStrictness x1 = Just ( cL l (HsSrcBang NoSourceText NoSrcUnpack str) , [AddAnn strAnnId l] , xs ) pStrictMark ((dL->L l x1) : xs) | TyElUnpackedness (anns, prag, unpk) <- x1 = Just ( cL l (HsSrcBang prag unpk NoSrcStrict) , anns , xs ) pStrictMark _ = Nothing pBangTy :: LHsType GhcPs -- a type to be wrapped inside HsBangTy -> [Located TyEl] -- reversed TyEl -> ( Bool {- has a strict mark been consumed? -} , LHsType GhcPs {- the resulting BangTy -} , P () {- add annotations -} , [Located TyEl] {- remaining TyEl -}) pBangTy lt@(dL->L l1 _) xs = case pStrictMark xs of Nothing -> (False, lt, pure (), xs) Just (dL->L l2 strictMark, anns, xs') -> let bl = combineSrcSpans l1 l2 bt = HsBangTy noExtField strictMark lt in (True, cL bl bt, addAnnsAt bl anns, xs') -- | Merge a /reversed/ and /non-empty/ soup of operators and operands -- into a type. -- -- User input: @F x y + G a b * X@ -- Input to 'mergeOps': [X, *, b, a, G, +, y, x, F] -- Output corresponds to what the user wrote assuming all operators are of the -- same fixity and right-associative. -- -- It's a bit silly that we're doing it at all, as the renamer will have to -- rearrange this, and it'd be easier to keep things separate. -- -- See Note [Parsing data constructors is hard] mergeOps :: [Located TyEl] -> P (LHsType GhcPs) mergeOps ((dL->L l1 (TyElOpd t)) : xs) | (_, t', addAnns, xs') <- pBangTy (cL l1 t) xs , null xs' -- We accept a BangTy only when there are no preceding TyEl. = addAnns >> return t' mergeOps all_xs = go (0 :: Int) [] id all_xs where -- NB. When modifying clauses in 'go', make sure that the reasoning in -- Note [Non-empty 'acc' in mergeOps clause [end]] is still correct. -- clause [unpk]: -- handle (NO)UNPACK pragmas go k acc ops_acc ((dL->L l (TyElUnpackedness (anns, unpkSrc, unpk))):xs) = if not (null acc) && null xs then do { acc' <- eitherToP $ mergeOpsAcc acc ; let a = ops_acc acc' strictMark = HsSrcBang unpkSrc unpk NoSrcStrict bl = combineSrcSpans l (getLoc a) bt = HsBangTy noExtField strictMark a ; addAnnsAt bl anns ; return (cL bl bt) } else addFatalError l unpkError where unpkSDoc = case unpkSrc of NoSourceText -> ppr unpk SourceText str -> text str <> text " #-}" unpkError | not (null xs) = unpkSDoc <+> text "cannot appear inside a type." | null acc && k == 0 = unpkSDoc <+> text "must be applied to a type." | otherwise = -- See Note [Impossible case in mergeOps clause [unpk]] panic "mergeOps.UNPACK: impossible position" -- clause [doc]: -- we do not expect to encounter any docs go _ _ _ ((dL->L l (TyElDocPrev _)):_) = failOpDocPrev l -- to improve error messages, we do a bit of guesswork to determine if the -- user intended a '!' or a '~' as a strictness annotation go k acc ops_acc ((dL->L l x) : xs) | Just (_, str) <- tyElStrictness x , let guess [] = True guess ((dL->L _ (TyElOpd _)):_) = False guess ((dL->L _ (TyElOpr _)):_) = True guess ((dL->L _ (TyElKindApp _ _)):_) = False guess ((dL->L _ (TyElTilde)):_) = True guess ((dL->L _ (TyElBang)):_) = True guess ((dL->L _ (TyElUnpackedness _)):_) = True guess ((dL->L _ (TyElDocPrev _)):xs') = guess xs' guess _ = panic "mergeOps.go.guess: Impossible Match" -- due to #15884 in guess xs = if not (null acc) && (k > 1 || length acc > 1) then do { a <- eitherToP (mergeOpsAcc acc) ; failOpStrictnessCompound (cL l str) (ops_acc a) } else failOpStrictnessPosition (cL l str) -- clause [opr]: -- when we encounter an operator, we must have accumulated -- something for its rhs, and there must be something left -- to build its lhs. go k acc ops_acc ((dL->L l (TyElOpr op)):xs) = if null acc || null (filter isTyElOpd xs) then failOpFewArgs (cL l op) else do { acc' <- eitherToP (mergeOpsAcc acc) ; go (k + 1) [] (\c -> mkLHsOpTy c (cL l op) (ops_acc acc')) xs } where isTyElOpd (dL->L _ (TyElOpd _)) = True isTyElOpd _ = False -- clause [opr.1]: interpret 'TyElTilde' as an operator go k acc ops_acc ((dL->L l TyElTilde):xs) = let op = eqTyCon_RDR in go k acc ops_acc (cL l (TyElOpr op):xs) -- clause [opr.2]: interpret 'TyElBang' as an operator go k acc ops_acc ((dL->L l TyElBang):xs) = let op = mkUnqual tcClsName (fsLit "!") in go k acc ops_acc (cL l (TyElOpr op):xs) -- clause [opd]: -- whenever an operand is encountered, it is added to the accumulator go k acc ops_acc ((dL->L l (TyElOpd a)):xs) = go k (HsValArg (cL l a):acc) ops_acc xs -- clause [tyapp]: -- whenever a type application is encountered, it is added to the accumulator go k acc ops_acc ((dL->L _ (TyElKindApp l a)):xs) = go k (HsTypeArg l a:acc) ops_acc xs -- clause [end] -- See Note [Non-empty 'acc' in mergeOps clause [end]] go _ acc ops_acc [] = do { acc' <- eitherToP (mergeOpsAcc acc) ; return (ops_acc acc') } go _ _ _ _ = panic "mergeOps.go: Impossible Match" -- due to #15884 mergeOpsAcc :: [HsArg (LHsType GhcPs) (LHsKind GhcPs)] -> Either (SrcSpan, SDoc) (LHsType GhcPs) mergeOpsAcc [] = panic "mergeOpsAcc: empty input" mergeOpsAcc (HsTypeArg _ (L loc ki):_) = Left (loc, text "Unexpected type application:" <+> ppr ki) mergeOpsAcc (HsValArg ty : xs) = go1 ty xs where go1 :: LHsType GhcPs -> [HsArg (LHsType GhcPs) (LHsKind GhcPs)] -> Either (SrcSpan, SDoc) (LHsType GhcPs) go1 lhs [] = Right lhs go1 lhs (x:xs) = case x of HsValArg ty -> go1 (mkHsAppTy lhs ty) xs HsTypeArg loc ki -> let ty = mkHsAppKindTy loc lhs ki in go1 ty xs HsArgPar _ -> go1 lhs xs mergeOpsAcc (HsArgPar _: xs) = mergeOpsAcc xs {- Note [Impossible case in mergeOps clause [unpk]] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ This case should never occur. Let us consider all possible variations of 'acc', 'xs', and 'k': acc xs k ============================== null | null 0 -- "must be applied to a type" null | not null 0 -- "must be applied to a type" not null | null 0 -- successful parse not null | not null 0 -- "cannot appear inside a type" null | null >0 -- handled in clause [opr] null | not null >0 -- "cannot appear inside a type" not null | null >0 -- successful parse not null | not null >0 -- "cannot appear inside a type" The (null acc && null xs && k>0) case is handled in clause [opr] by the following check: if ... || null (filter isTyElOpd xs) then failOpFewArgs (L l op) We know that this check has been performed because k>0, and by the time we reach the end of the list (null xs), the only way for (null acc) to hold is that there was not a single TyElOpd between the operator and the end of the list. But this case is caught by the check and reported as 'failOpFewArgs'. -} {- Note [Non-empty 'acc' in mergeOps clause [end]] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In clause [end] we need to know that 'acc' is non-empty to call 'mergeAcc' without a check. Running 'mergeOps' with an empty input list is forbidden, so we do not consider this possibility. This means we'll hit at least one other clause before we reach clause [end]. * Clauses [unpk] and [doc] do not call 'go' recursively, so we cannot hit clause [end] from there. * Clause [opd] makes 'acc' non-empty, so if we hit clause [end] after it, 'acc' will be non-empty. * Clause [opr] checks that (filter isTyElOpd xs) is not null - so we are going to hit clause [opd] at least once before we reach clause [end], making 'acc' non-empty. * There are no other clauses. Therefore, it is safe to omit a check for non-emptiness of 'acc' in clause [end]. -} pInfixSide :: [Located TyEl] -> Maybe (LHsType GhcPs, P (), [Located TyEl]) pInfixSide ((dL->L l (TyElOpd t)):xs) | (True, t', addAnns, xs') <- pBangTy (cL l t) xs = Just (t', addAnns, xs') pInfixSide (el:xs1) | Just t1 <- pLHsTypeArg el = go [t1] xs1 where go :: [HsArg (LHsType GhcPs) (LHsKind GhcPs)] -> [Located TyEl] -> Maybe (LHsType GhcPs, P (), [Located TyEl]) go acc (el:xs) | Just t <- pLHsTypeArg el = go (t:acc) xs go acc xs = case mergeOpsAcc acc of Left _ -> Nothing Right acc' -> Just (acc', pure (), xs) pInfixSide _ = Nothing pLHsTypeArg :: Located TyEl -> Maybe (HsArg (LHsType GhcPs) (LHsKind GhcPs)) pLHsTypeArg (dL->L l (TyElOpd a)) = Just (HsValArg (L l a)) pLHsTypeArg (dL->L _ (TyElKindApp l a)) = Just (HsTypeArg l a) pLHsTypeArg _ = Nothing pDocPrev :: [Located TyEl] -> (Maybe LHsDocString, [Located TyEl]) pDocPrev = go Nothing where go mTrailingDoc ((dL->L l (TyElDocPrev doc)):xs) = go (mTrailingDoc `mplus` Just (cL l doc)) xs go mTrailingDoc xs = (mTrailingDoc, xs) orErr :: Maybe a -> b -> Either b a orErr (Just a) _ = Right a orErr Nothing b = Left b {- Note [isFunLhs vs mergeDataCon] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ When parsing a function LHS, we do not know whether to treat (!) as a strictness annotation or an infix operator: f ! a = ... Without -XBangPatterns, this parses as (!) f a = ... with -XBangPatterns, this parses as f (!a) = ... So in function declarations we opted to always parse as if -XBangPatterns were off, and then rejig in 'isFunLhs'. There are two downsides to this approach: 1. It is not particularly elegant, as there's a point in our pipeline where the representation is awfully incorrect. For instance, f !a b !c = ... will be first parsed as (f ! a b) ! c = ... 2. There are cases that it fails to cover, for instance infix declarations: !a + !b = ... will trigger an error. Unfortunately, we cannot define different productions in the 'happy' grammar depending on whether -XBangPatterns are enabled. When parsing data constructors, we face a similar issue: (a) data T1 = C ! D (b) data T2 = C ! D => ... In (a) the first bang is a strictness annotation, but in (b) it is a type operator. A 'happy'-based parser does not have unlimited lookahead to check for =>, so we must first parse (C ! D) into a common representation. If we tried to mirror the approach used in functions, we would parse both sides of => as types, and then rejig. However, we take a different route and use an intermediate data structure, a reversed list of 'TyEl'. See Note [Parsing data constructors is hard] for details. This approach does not suffer from the issues of 'isFunLhs': 1. A sequence of 'TyEl' is a dedicated intermediate representation, not an incorrectly parsed type. Therefore, we do not have confusing states in our pipeline. (Except for representing data constructors as type variables). 2. We can handle infix data constructors with strictness annotations: data T a b = !a :+ !b -} -- | Merge a /reversed/ and /non-empty/ soup of operators and operands -- into a data constructor. -- -- User input: @C !A B -- ^ doc@ -- Input to 'mergeDataCon': ["doc", B, !, A, C] -- Output: (C, PrefixCon [!A, B], "doc") -- -- See Note [Parsing data constructors is hard] -- See Note [isFunLhs vs mergeDataCon] mergeDataCon :: [Located TyEl] -> P ( Located RdrName -- constructor name , HsConDeclDetails GhcPs -- constructor field information , Maybe LHsDocString -- docstring to go on the constructor ) mergeDataCon all_xs = do { (addAnns, a) <- eitherToP res ; addAnns ; return a } where -- We start by splitting off the trailing documentation comment, -- if any exists. (mTrailingDoc, all_xs') = pDocPrev all_xs -- Determine whether the trailing documentation comment exists and is the -- only docstring in this constructor declaration. -- -- When true, it means that it applies to the constructor itself: -- data T = C -- A -- B -- ^ Comment on C (singleDoc == True) -- -- When false, it means that it applies to the last field: -- data T = C -- ^ Comment on C -- A -- ^ Comment on A -- B -- ^ Comment on B (singleDoc == False) singleDoc = isJust mTrailingDoc && null [ () | (dL->L _ (TyElDocPrev _)) <- all_xs' ] -- The result of merging the list of reversed TyEl into a -- data constructor, along with [AddAnn]. res = goFirst all_xs' -- Take the trailing docstring into account when interpreting -- the docstring near the constructor. -- -- data T = C -- ^ docstring right after C -- A -- B -- ^ trailing docstring -- -- 'mkConDoc' must be applied to the docstring right after C, so that it -- falls back to the trailing docstring when appropriate (see singleDoc). mkConDoc mDoc | singleDoc = mDoc `mplus` mTrailingDoc | otherwise = mDoc -- The docstring for the last field of a data constructor. trailingFieldDoc | singleDoc = Nothing | otherwise = mTrailingDoc goFirst [ dL->L l (TyElOpd (HsTyVar _ _ (dL->L _ tc))) ] = do { data_con <- tyConToDataCon l tc ; return (pure (), (data_con, PrefixCon [], mTrailingDoc)) } goFirst ((dL->L l (TyElOpd (HsRecTy _ fields))):xs) | (mConDoc, xs') <- pDocPrev xs , [ dL->L l' (TyElOpd (HsTyVar _ _ (dL->L _ tc))) ] <- xs' = do { data_con <- tyConToDataCon l' tc ; let mDoc = mTrailingDoc `mplus` mConDoc ; return (pure (), (data_con, RecCon (cL l fields), mDoc)) } goFirst [dL->L l (TyElOpd (HsTupleTy _ HsBoxedOrConstraintTuple ts))] = return ( pure () , ( cL l (getRdrName (tupleDataCon Boxed (length ts))) , PrefixCon ts , mTrailingDoc ) ) goFirst ((dL->L l (TyElOpd t)):xs) | (_, t', addAnns, xs') <- pBangTy (cL l t) xs = go addAnns Nothing [mkLHsDocTyMaybe t' trailingFieldDoc] xs' goFirst (L l (TyElKindApp _ _):_) = goInfix Monoid.<> Left (l, kindAppErr) goFirst xs = go (pure ()) mTrailingDoc [] xs go addAnns mLastDoc ts [ dL->L l (TyElOpd (HsTyVar _ _ (dL->L _ tc))) ] = do { data_con <- tyConToDataCon l tc ; return (addAnns, (data_con, PrefixCon ts, mkConDoc mLastDoc)) } go addAnns mLastDoc ts ((dL->L l (TyElDocPrev doc)):xs) = go addAnns (mLastDoc `mplus` Just (cL l doc)) ts xs go addAnns mLastDoc ts ((dL->L l (TyElOpd t)):xs) | (_, t', addAnns', xs') <- pBangTy (cL l t) xs , t'' <- mkLHsDocTyMaybe t' mLastDoc = go (addAnns >> addAnns') Nothing (t'':ts) xs' go _ _ _ ((dL->L _ (TyElOpr _)):_) = -- Encountered an operator: backtrack to the beginning and attempt -- to parse as an infix definition. goInfix go _ _ _ (L l (TyElKindApp _ _):_) = goInfix Monoid.<> Left (l, kindAppErr) go _ _ _ _ = Left malformedErr where malformedErr = ( foldr combineSrcSpans noSrcSpan (map getLoc all_xs') , text "Cannot parse data constructor" <+> text "in a data/newtype declaration:" $$ nest 2 (hsep . reverse $ map ppr all_xs')) goInfix = do { let xs0 = all_xs' ; (rhs_t, rhs_addAnns, xs1) <- pInfixSide xs0 `orErr` malformedErr ; let (mOpDoc, xs2) = pDocPrev xs1 ; (op, xs3) <- case xs2 of (dL->L l (TyElOpr op)) : xs3 -> do { data_con <- tyConToDataCon l op ; return (data_con, xs3) } _ -> Left malformedErr ; let (mLhsDoc, xs4) = pDocPrev xs3 ; (lhs_t, lhs_addAnns, xs5) <- pInfixSide xs4 `orErr` malformedErr ; unless (null xs5) (Left malformedErr) ; let rhs = mkLHsDocTyMaybe rhs_t trailingFieldDoc lhs = mkLHsDocTyMaybe lhs_t mLhsDoc addAnns = lhs_addAnns >> rhs_addAnns ; return (addAnns, (op, InfixCon lhs rhs, mkConDoc mOpDoc)) } where malformedErr = ( foldr combineSrcSpans noSrcSpan (map getLoc all_xs') , text "Cannot parse an infix data constructor" <+> text "in a data/newtype declaration:" $$ nest 2 (hsep . reverse $ map ppr all_xs')) kindAppErr = text "Unexpected kind application" <+> text "in a data/newtype declaration:" $$ nest 2 (hsep . reverse $ map ppr all_xs') --------------------------------------------------------------------------- -- | Check for monad comprehensions -- -- If the flag MonadComprehensions is set, return a 'MonadComp' context, -- otherwise use the usual 'ListComp' context checkMonadComp :: PV (HsStmtContext Name) checkMonadComp = do monadComprehensions <- getBit MonadComprehensionsBit return $ if monadComprehensions then MonadComp else ListComp -- ------------------------------------------------------------------------- -- Expression/command/pattern ambiguity. -- See Note [Ambiguous syntactic categories] -- -- See Note [Parser-Validator] -- See Note [Ambiguous syntactic categories] newtype ECP = ECP { runECP_PV :: forall b. DisambECP b => PV (Located b) } runECP_P :: DisambECP b => ECP -> P (Located b) runECP_P p = runPV (runECP_PV p) ecpFromExp :: LHsExpr GhcPs -> ECP ecpFromExp a = ECP (ecpFromExp' a) ecpFromCmd :: LHsCmd GhcPs -> ECP ecpFromCmd a = ECP (ecpFromCmd' a) -- | Disambiguate infix operators. -- See Note [Ambiguous syntactic categories] class DisambInfixOp b where mkHsVarOpPV :: Located RdrName -> PV (Located b) mkHsConOpPV :: Located RdrName -> PV (Located b) mkHsInfixHolePV :: SrcSpan -> PV (Located b) instance p ~ GhcPs => DisambInfixOp (HsExpr p) where mkHsVarOpPV v = return $ cL (getLoc v) (HsVar noExtField v) mkHsConOpPV v = return $ cL (getLoc v) (HsVar noExtField v) mkHsInfixHolePV l = return $ cL l hsHoleExpr instance DisambInfixOp RdrName where mkHsConOpPV (dL->L l v) = return $ cL l v mkHsVarOpPV (dL->L l v) = return $ cL l v mkHsInfixHolePV l = addFatalError l $ text "Invalid infix hole, expected an infix operator" -- | 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 => DisambECP b where -- | See Note [Body in DisambECP] type Body b :: * -> * -- | Return a command without ambiguity, or fail in a non-command context. ecpFromCmd' :: LHsCmd GhcPs -> PV (Located b) -- | Return an expression without ambiguity, or fail in a non-expression context. ecpFromExp' :: LHsExpr GhcPs -> PV (Located b) -- | Disambiguate "\... -> ..." (lambda) mkHsLamPV :: SrcSpan -> MatchGroup GhcPs (Located b) -> PV (Located b) -- | Disambiguate "let ... in ..." mkHsLetPV :: SrcSpan -> LHsLocalBinds GhcPs -> Located b -> PV (Located b) -- | Infix operator representation type InfixOp b -- | Bring superclass constraints on FunArg into scope. -- See Note [UndecidableSuperClasses for associated types] superInfixOp :: (DisambInfixOp (InfixOp b) => PV (Located b )) -> PV (Located b) -- | Disambiguate "f # x" (infix operator) mkHsOpAppPV :: SrcSpan -> Located b -> Located (InfixOp b) -> Located b -> PV (Located b) -- | Disambiguate "case ... of ..." mkHsCasePV :: SrcSpan -> LHsExpr GhcPs -> MatchGroup GhcPs (Located b) -> PV (Located 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 (Located b)) -> PV (Located b) -- | Disambiguate "f x" (function application) mkHsAppPV :: SrcSpan -> Located b -> Located (FunArg b) -> PV (Located b) -- | Disambiguate "if ... then ... else ..." mkHsIfPV :: SrcSpan -> LHsExpr GhcPs -> Bool -- semicolon? -> Located b -> Bool -- semicolon? -> Located b -> PV (Located b) -- | Disambiguate "do { ... }" (do notation) mkHsDoPV :: SrcSpan -> Located [LStmt GhcPs (Located b)] -> PV (Located b) -- | Disambiguate "( ... )" (parentheses) mkHsParPV :: SrcSpan -> Located b -> PV (Located b) -- | Disambiguate a variable "f" or a data constructor "MkF". mkHsVarPV :: Located RdrName -> PV (Located 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 :: SrcSpan -> Located b -> LHsType GhcPs -> PV (Located b) -- | Disambiguate "[a,b,c]" (list syntax) mkHsExplicitListPV :: SrcSpan -> [Located b] -> PV (Located b) -- | Disambiguate "$(...)" and "[quasi|...|]" (TH splices) mkHsSplicePV :: Located (HsSplice GhcPs) -> PV (Located b) -- | Disambiguate "f { a = b, ... }" syntax (record construction and record updates) mkHsRecordPV :: SrcSpan -> SrcSpan -> Located b -> ([LHsRecField GhcPs (Located b)], Maybe SrcSpan) -> PV (Located b) -- | Disambiguate "-a" (negation) mkHsNegAppPV :: SrcSpan -> Located b -> PV (Located b) -- | Disambiguate "(# a)" (right operator section) mkHsSectionR_PV :: SrcSpan -> Located (InfixOp b) -> Located b -> PV (Located b) -- | Disambiguate "(a -> b)" (view pattern) mkHsViewPatPV :: SrcSpan -> LHsExpr GhcPs -> Located b -> PV (Located b) -- | Disambiguate "a@b" (as-pattern) mkHsAsPatPV :: SrcSpan -> Located RdrName -> Located b -> PV (Located b) -- | Disambiguate "~a" (lazy pattern) mkHsLazyPatPV :: SrcSpan -> Located b -> PV (Located b) -- | Disambiguate tuple sections and unboxed sums mkSumOrTuplePV :: SrcSpan -> Boxity -> SumOrTuple b -> PV (Located b) {- Note [UndecidableSuperClasses for associated types] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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 :: * -> *). 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 p ~ GhcPs => DisambECP (HsCmd p) where type Body (HsCmd p) = HsCmd ecpFromCmd' = return ecpFromExp' (dL-> L l e) = cmdFail l (ppr e) mkHsLamPV l mg = return $ cL l (HsCmdLam noExtField mg) mkHsLetPV l bs e = return $ cL l (HsCmdLet noExtField bs e) type InfixOp (HsCmd p) = HsExpr p superInfixOp m = m mkHsOpAppPV l c1 op c2 = do let cmdArg c = cL (getLoc c) $ HsCmdTop noExtField c return $ cL l $ HsCmdArrForm noExtField op Infix Nothing [cmdArg c1, cmdArg c2] mkHsCasePV l c mg = return $ cL l (HsCmdCase noExtField c mg) type FunArg (HsCmd p) = HsExpr p superFunArg m = m mkHsAppPV l c e = do checkCmdBlockArguments c checkExpBlockArguments e return $ cL l (HsCmdApp noExtField c e) mkHsIfPV l c semi1 a semi2 b = do checkDoAndIfThenElse c semi1 a semi2 b return $ cL l (mkHsCmdIf c a b) mkHsDoPV l stmts = return $ cL l (HsCmdDo noExtField stmts) mkHsParPV l c = return $ cL l (HsCmdPar noExtField c) mkHsVarPV (dL->L l v) = cmdFail l (ppr v) mkHsLitPV (dL->L l a) = cmdFail l (ppr a) mkHsOverLitPV (dL->L l a) = cmdFail l (ppr a) mkHsWildCardPV l = cmdFail l (text "_") mkHsTySigPV l a sig = cmdFail l (ppr a <+> text "::" <+> ppr sig) mkHsExplicitListPV l xs = cmdFail l $ brackets (fsep (punctuate comma (map ppr xs))) mkHsSplicePV (dL->L l sp) = cmdFail l (ppr sp) mkHsRecordPV l _ a (fbinds, ddLoc) = cmdFail l $ ppr a <+> ppr (mk_rec_fields fbinds 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 mkSumOrTuplePV l boxity a = cmdFail l (pprSumOrTuple boxity a) cmdFail :: SrcSpan -> SDoc -> PV a cmdFail loc e = addFatalError loc $ hang (text "Parse error in command:") 2 (ppr e) instance p ~ GhcPs => DisambECP (HsExpr p) where type Body (HsExpr p) = HsExpr ecpFromCmd' (dL -> L l c) = do addError l $ vcat [ text "Arrow command found where an expression was expected:", nest 2 (ppr c) ] return (cL l hsHoleExpr) ecpFromExp' = return mkHsLamPV l mg = return $ cL l (HsLam noExtField mg) mkHsLetPV l bs c = return $ cL l (HsLet noExtField bs c) type InfixOp (HsExpr p) = HsExpr p superInfixOp m = m mkHsOpAppPV l e1 op e2 = do return $ cL l $ OpApp noExtField e1 op e2 mkHsCasePV l e mg = return $ cL l (HsCase noExtField e mg) type FunArg (HsExpr p) = HsExpr p superFunArg m = m mkHsAppPV l e1 e2 = do checkExpBlockArguments e1 checkExpBlockArguments e2 return $ cL l (HsApp noExtField e1 e2) mkHsIfPV l c semi1 a semi2 b = do checkDoAndIfThenElse c semi1 a semi2 b return $ cL l (mkHsIf c a b) mkHsDoPV l stmts = return $ cL l (HsDo noExtField DoExpr stmts) mkHsParPV l e = return $ cL l (HsPar noExtField e) mkHsVarPV v@(getLoc -> l) = return $ cL l (HsVar noExtField v) mkHsLitPV (dL->L l a) = return $ cL l (HsLit noExtField a) mkHsOverLitPV (dL->L l a) = return $ cL l (HsOverLit noExtField a) mkHsWildCardPV l = return $ cL l hsHoleExpr mkHsTySigPV l a sig = return $ cL l (ExprWithTySig noExtField a (mkLHsSigWcType sig)) mkHsExplicitListPV l xs = return $ cL l (ExplicitList noExtField Nothing xs) mkHsSplicePV sp = return $ mapLoc (HsSpliceE noExtField) sp mkHsRecordPV l lrec a (fbinds, ddLoc) = do r <- mkRecConstrOrUpdate a lrec (fbinds, ddLoc) checkRecordSyntax (cL l r) mkHsNegAppPV l a = return $ cL l (NegApp noExtField a noSyntaxExpr) mkHsSectionR_PV l op e = return $ cL l (SectionR noExtField op e) mkHsViewPatPV l a b = patSynErr l (ppr a <+> text "->" <+> ppr b) empty mkHsAsPatPV l v e = do opt_TypeApplications <- getBit TypeApplicationsBit let msg | opt_TypeApplications = "Type application syntax requires a space before '@'" | otherwise = "Did you mean to enable TypeApplications?" patSynErr l (pprPrefixOcc (unLoc v) <> text "@" <> ppr e) (text msg) mkHsLazyPatPV l e = patSynErr l (text "~" <> ppr e) empty mkSumOrTuplePV = mkSumOrTupleExpr patSynErr :: SrcSpan -> SDoc -> SDoc -> PV (LHsExpr GhcPs) patSynErr l e explanation = do { addError l $ sep [text "Pattern syntax in expression context:", nest 4 (ppr e)] $$ explanation ; return (cL l hsHoleExpr) } hsHoleExpr :: HsExpr (GhcPass id) hsHoleExpr = HsUnboundVar noExtField (TrueExprHole (mkVarOcc "_")) -- | See Note [Ambiguous syntactic categories] and Note [PatBuilder] data PatBuilder p = PatBuilderPat (Pat p) | PatBuilderBang SrcSpan (Located (PatBuilder p)) | PatBuilderPar (Located (PatBuilder p)) | PatBuilderApp (Located (PatBuilder p)) (Located (PatBuilder p)) | PatBuilderOpApp (Located (PatBuilder p)) (Located RdrName) (Located (PatBuilder p)) | PatBuilderVar (Located RdrName) | PatBuilderOverLit (HsOverLit GhcPs) patBuilderBang :: SrcSpan -> Located (PatBuilder p) -> Located (PatBuilder p) patBuilderBang bang p = cL (bang `combineSrcSpans` getLoc p) $ PatBuilderBang bang p instance Outputable (PatBuilder GhcPs) where ppr (PatBuilderPat p) = ppr p ppr (PatBuilderBang _ (L _ p)) = text "!" <+> ppr p ppr (PatBuilderPar (L _ p)) = parens (ppr p) ppr (PatBuilderApp (L _ p1) (L _ p2)) = ppr p1 <+> ppr p2 ppr (PatBuilderOpApp (L _ p1) op (L _ p2)) = ppr p1 <+> ppr op <+> ppr p2 ppr (PatBuilderVar v) = ppr v ppr (PatBuilderOverLit l) = ppr l instance DisambECP (PatBuilder GhcPs) where type Body (PatBuilder GhcPs) = PatBuilder ecpFromCmd' (dL-> L l c) = addFatalError l $ text "Command syntax in pattern:" <+> ppr c ecpFromExp' (dL-> L l e) = addFatalError l $ text "Expression syntax in pattern:" <+> ppr e mkHsLamPV l _ = addFatalError l $ text "Lambda-syntax in pattern." $$ text "Pattern matching on functions is not possible." mkHsLetPV l _ _ = addFatalError l $ text "(let ... in ...)-syntax in pattern" type InfixOp (PatBuilder GhcPs) = RdrName superInfixOp m = m mkHsOpAppPV l p1 op p2 = do warnSpaceAfterBang op (getLoc p2) return $ cL l $ PatBuilderOpApp p1 op p2 mkHsCasePV l _ _ = addFatalError l $ text "(case ... of ...)-syntax in pattern" type FunArg (PatBuilder GhcPs) = PatBuilder GhcPs superFunArg m = m mkHsAppPV l p1 p2 = return $ cL l (PatBuilderApp p1 p2) mkHsIfPV l _ _ _ _ _ = addFatalError l $ text "(if ... then ... else ...)-syntax in pattern" mkHsDoPV l _ = addFatalError l $ text "do-notation in pattern" mkHsParPV l p = return $ cL l (PatBuilderPar p) mkHsVarPV v@(getLoc -> l) = return $ cL l (PatBuilderVar v) mkHsLitPV lit@(dL->L l a) = do checkUnboxedStringLitPat lit return $ cL l (PatBuilderPat (LitPat noExtField a)) mkHsOverLitPV (dL->L l a) = return $ cL l (PatBuilderOverLit a) mkHsWildCardPV l = return $ cL l (PatBuilderPat (WildPat noExtField)) mkHsTySigPV l b sig = do p <- checkLPat b return $ cL l (PatBuilderPat (SigPat noExtField p (mkLHsSigWcType sig))) mkHsExplicitListPV l xs = do ps <- traverse checkLPat xs return (cL l (PatBuilderPat (ListPat noExtField ps))) mkHsSplicePV (dL->L l sp) = return $ cL l (PatBuilderPat (SplicePat noExtField sp)) mkHsRecordPV l _ a (fbinds, ddLoc) = do r <- mkPatRec a (mk_rec_fields fbinds ddLoc) checkRecordSyntax (cL l r) mkHsNegAppPV l (dL->L lp p) = do lit <- case p of PatBuilderOverLit pos_lit -> return (cL lp pos_lit) _ -> patFail l (text "-" <> ppr p) return $ cL l (PatBuilderPat (mkNPat lit (Just noSyntaxExpr))) mkHsSectionR_PV l op p | isBangRdr (unLoc op) = return $ cL l $ PatBuilderBang (getLoc op) p | otherwise = patFail l (pprInfixOcc (unLoc op) <> ppr p) mkHsViewPatPV l a b = do p <- checkLPat b return $ cL l (PatBuilderPat (ViewPat noExtField a p)) mkHsAsPatPV l v e = do p <- checkLPat e return $ cL l (PatBuilderPat (AsPat noExtField v p)) mkHsLazyPatPV l e = do p <- checkLPat e return $ cL l (PatBuilderPat (LazyPat noExtField p)) mkSumOrTuplePV = mkSumOrTuplePat checkUnboxedStringLitPat :: Located (HsLit GhcPs) -> PV () checkUnboxedStringLitPat (dL->L loc lit) = case lit of HsStringPrim _ _ -- Trac #13260 -> addFatalError loc (text "Illegal unboxed string literal in pattern:" $$ ppr lit) _ -> return () mkPatRec :: Located (PatBuilder GhcPs) -> HsRecFields GhcPs (Located (PatBuilder GhcPs)) -> PV (PatBuilder GhcPs) mkPatRec (unLoc -> PatBuilderVar c) (HsRecFields fs dd) | isRdrDataCon (unLoc c) = do fs <- mapM checkPatField fs return (PatBuilderPat (ConPatIn c (RecCon (HsRecFields fs dd)))) mkPatRec p _ = addFatalError (getLoc p) $ text "Not a record constructor:" <+> ppr p -- | Warn about missing space after bang warnSpaceAfterBang :: Located RdrName -> SrcSpan -> PV () warnSpaceAfterBang (dL->L opLoc op) argLoc = do bang_on <- getBit BangPatBit when (not bang_on && noSpace && isBangRdr op) $ addWarning Opt_WarnSpaceAfterBang span msg where span = combineSrcSpans opLoc argLoc noSpace = srcSpanEnd opLoc == srcSpanStart argLoc msg = text "Did you forget to enable BangPatterns?" $$ text "If you mean to bind (!) then perhaps you want" $$ text "to add a space after the bang for clarity." {- 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 an infix operator, or if it's a function declaration where ! is a strictness annotation. 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 p ~ GhcPs => DisambECP (HsCmd p) where ... instance p ~ GhcPs => DisambECP (HsExp p) where ... instance p ~ GhcPs => DisambECP (PatBuilder p) 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 ([AddAnn],[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 ([AddAnn],[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 [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? * We cannot handle corner cases. For instance, the following function declaration LHS is not a valid expression (see #1087): !a + !b = ... * There are points in the pipeline where the representation was awfully incorrect. For instance, f !a b !c = ... is first parsed as (f ! a b) ! c = ... 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 Name) [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: -- See Note [Parser-Validator] 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: -- See Note [Parser-Validator] 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 ([AddAnn],[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 ([AddAnn],[LMatch GhcPs (LHsExpr GhcPs)])) -- as an expression , PV (Located ([AddAnn],[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 ([AddAnn],[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 ([AddAnn],[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 ([AddAnn],[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 accomodate 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. Worse yet, some intermediate forms are not valid patterns at all. For example: Con !a !b c This is parsed as ((Con ! a) ! (b c)) with ! as an infix operator, and then rearranged in 'splitBang'. But of course, neither (b c) nor (Con ! a) are valid patterns, so we cannot represent them as Pat. 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 (Located (PatBuilder p)) (Located (PatBuilder p)) | PatBuilderOpApp (Located (PatBuilder p)) (Located RdrName) (Located (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'. For example, in 'splitBang' we need to match on space-separated and bang-separated patterns, so these are represented with dedicated constructors 'PatBuilderApp' and 'PatBuilderOpApp'. In 'isFunLhs', we pattern match on variables, so we have a dedicated 'PatBuilderVar' constructor for this despite the existence of 'VarPat'. -} --------------------------------------------------------------------------- -- 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 (Located RdrName)) -- ^ operators -> P () checkPrecP (dL->L l (_,i)) (dL->L _ ol) | 0 <= i, i <= maxPrecedence = pure () | all specialOp ol = pure () | otherwise = addFatalError l (text ("Precedence out of range: " ++ show i)) where specialOp op = unLoc op `elem` [ eqTyCon_RDR , getRdrName funTyCon ] mkRecConstrOrUpdate :: LHsExpr GhcPs -> SrcSpan -> ([LHsRecField GhcPs (LHsExpr GhcPs)], Maybe SrcSpan) -> PV (HsExpr GhcPs) mkRecConstrOrUpdate (dL->L l (HsVar _ (dL->L _ c))) _ (fs,dd) | isRdrDataCon c = return (mkRdrRecordCon (cL l c) (mk_rec_fields fs dd)) mkRecConstrOrUpdate exp _ (fs,dd) | Just dd_loc <- dd = addFatalError dd_loc (text "You cannot use `..' in a record update") | otherwise = return (mkRdrRecordUpd exp (map (fmap mk_rec_upd_field) fs)) mkRdrRecordUpd :: LHsExpr GhcPs -> [LHsRecUpdField GhcPs] -> HsExpr GhcPs mkRdrRecordUpd exp flds = RecordUpd { rupd_ext = noExtField , rupd_expr = exp , rupd_flds = flds } mkRdrRecordCon :: Located RdrName -> HsRecordBinds GhcPs -> HsExpr GhcPs mkRdrRecordCon con flds = RecordCon { rcon_ext = noExtField, rcon_con_name = con, rcon_flds = flds } mk_rec_fields :: [LHsRecField id arg] -> Maybe SrcSpan -> HsRecFields id 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 (cL s (length fs)) } mk_rec_upd_field :: HsRecField GhcPs (LHsExpr GhcPs) -> HsRecUpdField GhcPs mk_rec_upd_field (HsRecField (dL->L loc (FieldOcc _ rdr)) arg pun) = HsRecField (L loc (Unambiguous noExtField rdr)) arg pun mk_rec_upd_field (HsRecField (dL->L _ (XFieldOcc nec)) _ _) = noExtCon nec mk_rec_upd_field (HsRecField _ _ _) = panic "mk_rec_upd_field: Impossible Match" -- due to #15884 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 BasicTypes , 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, Located RdrName, LHsSigType GhcPs) -> P (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 (cL loc esrc) of Nothing -> addFatalError loc (text "Malformed entity string") 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 (cL loc esrc) returnSpec spec = return $ ForD noExtField $ ForeignImport { fd_i_ext = noExtField , 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, Located RdrName, LHsSigType GhcPs) -> P (HsDecl GhcPs) mkExport (dL->L lc cconv) (dL->L le (StringLiteral esrc entity), v, ty) = return $ ForD noExtField $ ForeignExport { fd_e_ext = noExtField, fd_name = v, fd_sig_ty = ty , fd_fe = CExport (cL lc (CExportStatic esrc entity' cconv)) (cL 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 [Located ImpExpQcSpec] | ImpExpAllWith [Located ImpExpQcSpec] data ImpExpQcSpec = ImpExpQcName (Located RdrName) | ImpExpQcType (Located RdrName) | ImpExpQcWildcard mkModuleImpExp :: Located ImpExpQcSpec -> ImpExpSubSpec -> P (IE GhcPs) mkModuleImpExp (dL->L l specname) subs = case subs of ImpExpAbs | isVarNameSpace (rdrNameSpace name) -> return $ IEVar noExtField (cL l (ieNameFromSpec specname)) | otherwise -> IEThingAbs noExtField . cL l <$> nameT ImpExpAll -> IEThingAll noExtField . cL l <$> nameT ImpExpList xs -> (\newName -> IEThingWith noExtField (cL 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 = wrapped $ filter (not . isImpExpQcWildcard . unLoc) xs in (\newName -> IEThingWith noExtField (cL l newName) pos ies []) <$> nameT else addFatalError l (text "Illegal export form (use PatternSynonyms to enable)") where name = ieNameVal specname nameT = if isVarNameSpace (rdrNameSpace name) then addFatalError l (text "Expecting a type constructor but found a variable," <+> quotes (ppr name) <> text "." $$ if isSymOcc $ rdrNameOcc name then text "If" <+> quotes (ppr name) <+> text "is a type constructor" <+> text "then enable ExplicitNamespaces and use the 'type' keyword." else empty) 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 ln) = IEType ln ieNameFromSpec (ImpExpQcWildcard) = panic "ieName got wildcard" wrapped = map (onHasSrcSpan ieNameFromSpec) mkTypeImpExp :: Located RdrName -- TcCls or Var name space -> P (Located RdrName) mkTypeImpExp name = do allowed <- getBit ExplicitNamespacesBit unless allowed $ addError (getLoc name) $ text "Illegal keyword 'type' (use ExplicitNamespaces to enable)" return (fmap (`setRdrNameSpace` tcClsName) name) checkImportSpec :: Located [LIE GhcPs] -> P (Located [LIE GhcPs]) checkImportSpec ie@(dL->L _ specs) = case [l | (dL->L l (IEThingWith _ _ (IEWildcard _) _ _)) <- specs] of [] -> return ie (l:_) -> importSpecError l where importSpecError l = addFatalError l (text "Illegal import form, this syntax can only be used to bundle" $+$ text "pattern synonyms with types in module exports.") -- In the correct order mkImpExpSubSpec :: [Located ImpExpQcSpec] -> P ([AddAnn], ImpExpSubSpec) mkImpExpSubSpec [] = return ([], ImpExpList []) mkImpExpSubSpec [dL->L _ ImpExpQcWildcard] = return ([], 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 span msg where msg = text "Found" <+> quotes (text "qualified") <+> text "in prepositive position" $$ text "Suggested fix: place " <+> quotes (text "qualified") <+> text "after the module name instead." failOpNotEnabledImportQualifiedPost :: SrcSpan -> P () failOpNotEnabledImportQualifiedPost loc = addError loc msg where msg = text "Found" <+> quotes (text "qualified") <+> text "in postpositive position. " $$ text "To allow this, enable language extension 'ImportQualifiedPost'" failOpImportQualifiedTwice :: SrcSpan -> P () failOpImportQualifiedTwice loc = addError loc msg where msg = text "Multiple occurences of 'qualified'" warnStarIsType :: SrcSpan -> P () warnStarIsType span = addWarning Opt_WarnStarIsType span msg where msg = text "Using" <+> quotes (text "*") <+> text "(or its Unicode variant) to mean" <+> quotes (text "Data.Kind.Type") $$ text "relies on the StarIsType extension, which will become" $$ text "deprecated in the future." $$ text "Suggested fix: use" <+> quotes (text "Type") <+> text "from" <+> quotes (text "Data.Kind") <+> text "instead." warnStarBndr :: SrcSpan -> P () warnStarBndr span = addWarning Opt_WarnStarBinder span msg where msg = text "Found binding occurrence of" <+> quotes (text "*") <+> text "yet StarIsType is enabled." $$ text "NB. To use (or export) this operator in" <+> text "modules with StarIsType," $$ text " including the definition module, you must qualify it." failOpFewArgs :: Located RdrName -> P a failOpFewArgs (dL->L loc op) = do { star_is_type <- getBit StarIsTypeBit ; let msg = too_few $$ starInfo star_is_type op ; addFatalError loc msg } where too_few = text "Operator applied to too few arguments:" <+> ppr op failOpDocPrev :: SrcSpan -> P a failOpDocPrev loc = addFatalError loc msg where msg = text "Unexpected documentation comment." failOpStrictnessCompound :: Located SrcStrictness -> LHsType GhcPs -> P a failOpStrictnessCompound (dL->L _ str) (dL->L loc ty) = addFatalError loc msg where msg = text "Strictness annotation applied to a compound type." $$ text "Did you mean to add parentheses?" $$ nest 2 (ppr str <> parens (ppr ty)) failOpStrictnessPosition :: Located SrcStrictness -> P a failOpStrictnessPosition (dL->L loc _) = addFatalError loc msg where msg = text "Strictness annotation cannot appear in this position." ----------------------------------------------------------------------------- -- Misc utils data PV_Context = PV_Context { pv_options :: ParserFlags , pv_hint :: SDoc -- See Note [Parser-Validator Hint] } data PV_Accum = PV_Accum { pv_messages :: DynFlags -> Messages , pv_annotations :: [(ApiAnnKey,[SrcSpan])] , pv_comment_q :: [Located AnnotationComment] , pv_annotations_comments :: [(SrcSpan,[Located AnnotationComment])] } data PV_Result a = PV_Ok PV_Accum a | PV_Failed PV_Accum -- See Note [Parser-Validator] 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_msg empty runPV_msg :: SDoc -> PV a -> P a runPV_msg msg m = P $ \s -> let pv_ctx = PV_Context { pv_options = options s , pv_hint = msg } pv_acc = PV_Accum { pv_messages = messages s , pv_annotations = annotations s , pv_comment_q = comment_q s , pv_annotations_comments = annotations_comments s } mkPState acc' = s { messages = pv_messages acc' , annotations = pv_annotations acc' , comment_q = pv_comment_q acc' , annotations_comments = pv_annotations_comments acc' } in case unPV m pv_ctx pv_acc of PV_Ok acc' a -> POk (mkPState acc') a PV_Failed acc' -> PFailed (mkPState acc') localPV_msg :: (SDoc -> SDoc) -> PV a -> PV a localPV_msg f m = let modifyHint ctx = ctx{pv_hint = f (pv_hint ctx)} in PV (\ctx acc -> unPV m (modifyHint ctx) acc) instance MonadP PV where addError srcspan msg = PV $ \ctx acc@PV_Accum{pv_messages=m} -> let msg' = msg $$ pv_hint ctx in PV_Ok acc{pv_messages=appendError srcspan msg' m} () addWarning option srcspan warning = PV $ \PV_Context{pv_options=o} acc@PV_Accum{pv_messages=m} -> PV_Ok acc{pv_messages=appendWarning o option srcspan warning m} () addFatalError srcspan msg = addError srcspan msg >> PV (const PV_Failed) getBit ext = PV $ \ctx acc -> let b = ext `xtest` pExtsBitmap (pv_options ctx) in PV_Ok acc $! b addAnnotation l a v = PV $ \_ acc -> let (comment_q', new_ann_comments) = allocateComments l (pv_comment_q acc) annotations_comments' = new_ann_comments ++ pv_annotations_comments acc annotations' = ((l,a), [v]) : pv_annotations acc acc' = acc { pv_annotations = annotations' , pv_comment_q = comment_q' , pv_annotations_comments = annotations_comments' } in PV_Ok acc' () {- Note [Parser-Validator] ~~~~~~~~~~~~~~~~~~~~~~~~~~ When resolving ambiguities, we need to postpone failure to make a choice later. For example, if we have ambiguity between some A and B, our parser could be abParser :: P (Maybe A, Maybe B) This way we can represent four possible outcomes of parsing: (Just a, Nothing) -- definitely A (Nothing, Just b) -- definitely B (Just a, Just b) -- either A or B (Nothing, Nothing) -- neither A nor B However, if we want to report informative parse errors, accumulate warnings, and add API annotations, we are better off using 'P' instead of 'Maybe': abParser :: P (P A, P B) So we have an outer layer of P that consumes the input and builds the inner layer, which validates the 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 :: P (PV A, PV B) -} {- 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_hint' 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 -> PatBuilder GhcPs -> PV () hintBangPat span e = do bang_on <- getBit BangPatBit unless bang_on $ addFatalError span (text "Illegal bang-pattern (use BangPatterns):" $$ ppr e) data SumOrTuple b = Sum ConTag Arity (Located b) | Tuple [Located (Maybe (Located b))] pprSumOrTuple :: Outputable b => Boxity -> SumOrTuple b -> SDoc pprSumOrTuple boxity = \case Sum alt arity e -> parOpen <+> ppr_bars (alt - 1) <+> ppr e <+> ppr_bars (arity - alt) <+> parClose Tuple xs -> parOpen <> (fcat . punctuate comma $ map (maybe empty ppr . unLoc) xs) <> parClose where ppr_bars n = hsep (replicate n (Outputable.char '|')) (parOpen, parClose) = case boxity of Boxed -> (text "(", text ")") Unboxed -> (text "(#", text "#)") mkSumOrTupleExpr :: SrcSpan -> Boxity -> SumOrTuple (HsExpr GhcPs) -> PV (LHsExpr GhcPs) -- Tuple mkSumOrTupleExpr l boxity (Tuple es) = return $ cL l (ExplicitTuple noExtField (map toTupArg es) boxity) where toTupArg :: Located (Maybe (LHsExpr GhcPs)) -> LHsTupArg GhcPs toTupArg = mapLoc (maybe missingTupArg (Present noExtField)) -- Sum mkSumOrTupleExpr l Unboxed (Sum alt arity e) = return $ cL l (ExplicitSum noExtField alt arity e) mkSumOrTupleExpr l Boxed a@Sum{} = addFatalError l (hang (text "Boxed sums not supported:") 2 (pprSumOrTuple Boxed a)) mkSumOrTuplePat :: SrcSpan -> Boxity -> SumOrTuple (PatBuilder GhcPs) -> PV (Located (PatBuilder GhcPs)) -- Tuple mkSumOrTuplePat l boxity (Tuple ps) = do ps' <- traverse toTupPat ps return $ cL l (PatBuilderPat (TuplePat noExtField ps' boxity)) where toTupPat :: Located (Maybe (Located (PatBuilder GhcPs))) -> PV (LPat GhcPs) toTupPat (dL -> L l p) = case p of Nothing -> addFatalError l (text "Tuple section in pattern context") Just p' -> checkLPat p' -- Sum mkSumOrTuplePat l Unboxed (Sum alt arity p) = do p' <- checkLPat p return $ cL l (PatBuilderPat (SumPat noExtField p' alt arity)) mkSumOrTuplePat l Boxed a@Sum{} = addFatalError l (hang (text "Boxed sums not supported:") 2 (pprSumOrTuple Boxed a)) mkLHsOpTy :: LHsType GhcPs -> Located RdrName -> LHsType GhcPs -> LHsType GhcPs mkLHsOpTy x op y = let loc = getLoc x `combineSrcSpans` getLoc op `combineSrcSpans` getLoc y in cL loc (mkHsOpTy x op y) mkLHsDocTy :: LHsType GhcPs -> LHsDocString -> LHsType GhcPs mkLHsDocTy t doc = let loc = getLoc t `combineSrcSpans` getLoc doc in cL loc (HsDocTy noExtField t doc) mkLHsDocTyMaybe :: LHsType GhcPs -> Maybe LHsDocString -> LHsType GhcPs mkLHsDocTyMaybe t = maybe t (mkLHsDocTy t) ----------------------------------------------------------------------------- -- Token symbols starSym :: Bool -> String starSym True = "★" starSym False = "*" forallSym :: Bool -> String forallSym True = "∀" forallSym False = "forall"