{-# LANGUAGE TypeApplications #-} {-# LANGUAGE DeriveFunctor #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE ViewPatterns #-} {-# LANGUAGE DisambiguateRecordFields #-} {-# LANGUAGE MultiWayIf #-} {- (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 Renaming of patterns Basically dependency analysis. Handles @Match@, @GRHSs@, @HsExpr@, and @Qualifier@ datatypes. In general, all of these functions return a renamed thing, and a set of free variables. -} module GHC.Rename.Pat (-- main entry points rnPat, rnPats, rnBindPat, NameMaker, applyNameMaker, -- a utility for making names: localRecNameMaker, topRecNameMaker, -- sometimes we want to make local names, -- sometimes we want to make top (qualified) names. isTopRecNameMaker, rnHsRecFields, HsRecFieldContext(..), rnHsRecUpdFields, -- CpsRn monad CpsRn, liftCps, liftCpsWithCont, -- Literals rnLit, rnOverLit, ) where -- ENH: thin imports to only what is necessary for patterns import GHC.Prelude import {-# SOURCE #-} GHC.Rename.Expr ( rnLExpr ) import {-# SOURCE #-} GHC.Rename.Splice ( rnSplicePat ) import GHC.Hs import GHC.Tc.Errors.Types import GHC.Tc.Utils.Monad import GHC.Tc.Utils.TcMType ( hsOverLitName ) import GHC.Rename.Env import GHC.Rename.Fixity import GHC.Rename.Utils ( newLocalBndrRn, bindLocalNames , warnUnusedMatches, newLocalBndrRn , checkUnusedRecordWildcard , checkDupNames, checkDupAndShadowedNames , wrapGenSpan, genHsApps, genLHsVar, genHsIntegralLit, warnForallIdentifier ) import GHC.Rename.HsType import GHC.Builtin.Names import GHC.Types.Name import GHC.Types.Name.Set import GHC.Types.Name.Reader import GHC.Types.Unique.Set import GHC.Types.Basic import GHC.Types.SourceText import GHC.Utils.Misc import GHC.Data.FastString ( uniqCompareFS ) import GHC.Data.List.SetOps( removeDups ) import GHC.Utils.Outputable import GHC.Utils.Panic.Plain import GHC.Types.SrcLoc import GHC.Types.Literal ( inCharRange ) import GHC.Types.GREInfo ( ConInfo(..), conInfoFields ) import GHC.Builtin.Types ( nilDataCon ) import GHC.Core.DataCon import qualified GHC.LanguageExtensions as LangExt import Control.Monad ( when, ap, guard ) import Data.Foldable import Data.Function ( on ) import Data.Functor.Identity ( Identity (..) ) import qualified Data.List.NonEmpty as NE import Data.Maybe import Data.Ratio {- ********************************************************* * * The CpsRn Monad * * ********************************************************* Note [CpsRn monad] ~~~~~~~~~~~~~~~~~~ The CpsRn monad uses continuation-passing style to support this style of programming: do { ... ; ns <- bindNames rs ; ...blah... } where rs::[RdrName], ns::[Name] The idea is that '...blah...' a) sees the bindings of ns b) returns the free variables it mentions so that bindNames can report unused ones In particular, mapM rnPatAndThen [p1, p2, p3] has a *left-to-right* scoping: it makes the binders in p1 scope over p2,p3. -} newtype CpsRn b = CpsRn { unCpsRn :: forall r. (b -> RnM (r, FreeVars)) -> RnM (r, FreeVars) } deriving (Functor) -- See Note [CpsRn monad] instance Applicative CpsRn where pure x = CpsRn (\k -> k x) (<*>) = ap instance Monad CpsRn where (CpsRn m) >>= mk = CpsRn (\k -> m (\v -> unCpsRn (mk v) k)) runCps :: CpsRn a -> RnM (a, FreeVars) runCps (CpsRn m) = m (\r -> return (r, emptyFVs)) liftCps :: RnM a -> CpsRn a liftCps rn_thing = CpsRn (\k -> rn_thing >>= k) liftCpsFV :: RnM (a, FreeVars) -> CpsRn a liftCpsFV rn_thing = CpsRn (\k -> do { (v,fvs1) <- rn_thing ; (r,fvs2) <- k v ; return (r, fvs1 `plusFV` fvs2) }) liftCpsWithCont :: (forall r. (b -> RnM (r, FreeVars)) -> RnM (r, FreeVars)) -> CpsRn b liftCpsWithCont = CpsRn wrapSrcSpanCps :: (a -> CpsRn b) -> LocatedA a -> CpsRn (LocatedA b) -- Set the location, and also wrap it around the value returned wrapSrcSpanCps fn (L loc a) = CpsRn (\k -> setSrcSpanA loc $ unCpsRn (fn a) $ \v -> k (L loc v)) lookupConCps :: LocatedN RdrName -> CpsRn (LocatedN Name) lookupConCps con_rdr = CpsRn (\k -> do { con_name <- lookupLocatedOccRnConstr con_rdr ; (r, fvs) <- k con_name ; return (r, addOneFV fvs (unLoc con_name)) }) -- We add the constructor name to the free vars -- See Note [Patterns are uses] {- Note [Patterns are uses] ~~~~~~~~~~~~~~~~~~~~~~~~ Consider module Foo( f, g ) where data T = T1 | T2 f T1 = True f T2 = False g _ = T1 Arguably we should report T2 as unused, even though it appears in a pattern, because it never occurs in a constructed position. See #7336. However, implementing this in the face of pattern synonyms would be less straightforward, since given two pattern synonyms pattern P1 <- P2 pattern P2 <- () we need to observe the dependency between P1 and P2 so that type checking can be done in the correct order (just like for value bindings). Dependencies between bindings is analyzed in the renamer, where we don't know yet whether P2 is a constructor or a pattern synonym. So for now, we do report conid occurrences in patterns as uses. ********************************************************* * * Name makers * * ********************************************************* Externally abstract type of name makers, which is how you go from a RdrName to a Name -} data NameMaker = LamMk -- Lambdas Bool -- True <=> report unused bindings -- (even if True, the warning only comes out -- if -Wunused-matches is on) | LetMk -- Let bindings, incl top level -- Do *not* check for unused bindings TopLevelFlag MiniFixityEnv topRecNameMaker :: MiniFixityEnv -> NameMaker topRecNameMaker fix_env = LetMk TopLevel fix_env isTopRecNameMaker :: NameMaker -> Bool isTopRecNameMaker (LetMk TopLevel _) = True isTopRecNameMaker _ = False localRecNameMaker :: MiniFixityEnv -> NameMaker localRecNameMaker fix_env = LetMk NotTopLevel fix_env matchNameMaker :: HsMatchContext a -> NameMaker matchNameMaker ctxt = LamMk report_unused where -- Do not report unused names in interactive contexts -- i.e. when you type 'x <- e' at the GHCi prompt report_unused = case ctxt of StmtCtxt (HsDoStmt GhciStmtCtxt) -> False -- also, don't warn in pattern quotes, as there -- is no RHS where the variables can be used! ThPatQuote -> False _ -> True newPatLName :: NameMaker -> LocatedN RdrName -> CpsRn (LocatedN Name) newPatLName name_maker rdr_name@(L loc _) = do { name <- newPatName name_maker rdr_name ; return (L loc name) } newPatName :: NameMaker -> LocatedN RdrName -> CpsRn Name newPatName (LamMk report_unused) rdr_name = CpsRn (\ thing_inside -> do { warnForallIdentifier rdr_name ; name <- newLocalBndrRn rdr_name ; (res, fvs) <- bindLocalNames [name] (thing_inside name) ; when report_unused $ warnUnusedMatches [name] fvs ; return (res, name `delFV` fvs) }) newPatName (LetMk is_top fix_env) rdr_name = CpsRn (\ thing_inside -> do { warnForallIdentifier rdr_name ; name <- case is_top of NotTopLevel -> newLocalBndrRn rdr_name TopLevel -> newTopSrcBinder rdr_name ; bindLocalNames [name] $ -- Do *not* use bindLocalNameFV here; -- see Note [View pattern usage] -- For the TopLevel case -- see Note [bindLocalNames for an External name] addLocalFixities fix_env [name] $ thing_inside name }) {- Note [bindLocalNames for an External name] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In the TopLevel case, the use of bindLocalNames here is somewhat suspicious because it binds a top-level External name in the LocalRdrEnv. c.f. Note [LocalRdrEnv] in GHC.Types.Name.Reader. However, this only happens when renaming the LHS (only) of a top-level pattern binding. Even though this only the LHS, we need to bring the binder into scope in the pattern itself in case the binder is used in subsequent view patterns. A bit bizarre, something like (x, Just y <- f x) = e Anyway, bindLocalNames does work, and the binding only exists for the duration of the pattern; then the top-level name is added to the global env before going on to the RHSes (see GHC.Rename.Module). Note [View pattern usage] ~~~~~~~~~~~~~~~~~~~~~~~~~ Consider let (r, (r -> x)) = x in ... Here the pattern binds 'r', and then uses it *only* in the view pattern. We want to "see" this use, and in let-bindings we collect all uses and report unused variables at the binding level. So we must use bindLocalNames here, *not* bindLocalNameFV. #3943. Note [Don't report shadowing for pattern synonyms] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ There is one special context where a pattern doesn't introduce any new binders - pattern synonym declarations. Therefore we don't check to see if pattern variables shadow existing identifiers as they are never bound to anything and have no scope. Without this check, there would be quite a cryptic warning that the `x` in the RHS of the pattern synonym declaration shadowed the top level `x`. ``` x :: () x = () pattern P x = Just x ``` See #12615 for some more examples. Note [Handling overloaded and rebindable patterns] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Overloaded paterns and rebindable patterns are desugared in the renamer using the HsPatExpansion mechanism detailed in: Note [Rebindable syntax and HsExpansion] The approach is similar to that of expressions, which is further detailed in Note [Handling overloaded and rebindable constructs] in GHC.Rename.Expr. Here are the patterns that are currently desugared in this way: * ListPat (list patterns [p1,p2,p3]) When (and only when) OverloadedLists is on, desugar to a view pattern: [p1, p2, p3] ==> toList -> [p1, p2, p3] ^^^^^^^^^^^^ built-in (non-overloaded) list pattern NB: the type checker and desugarer still see ListPat, but to them it always means the built-in list pattern. See Note [Desugaring overloaded list patterns] below for more details. We expect to add to this list as we deal with more patterns via the expansion mechanism. Note [Desugaring overloaded list patterns] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ If OverloadedLists is enabled, we desugar a list pattern to a view pattern: [p1, p2, p3] ==> toList -> [p1, p2, p3] This happens directly in the renamer, using the HsPatExpansion mechanism detailed in Note [Rebindable syntax and HsExpansion]. Note that we emit a special view pattern: we additionally keep track of an inverse to the pattern. See Note [Invertible view patterns] in GHC.Tc.TyCl.PatSyn for details. == Wrinkle == This is all fine, except in one very specific case: - when RebindableSyntax is off, - and the type being matched on is already a list type. In this case, it is undesirable to desugar an overloaded list pattern into a view pattern. To illustrate, consider the following program: > {-# LANGUAGE OverloadedLists #-} > > f [] = True > f (_:_) = False Without any special logic, the pattern `[]` is desugared to `(toList -> [])`, whereas `(_:_)` remains a constructor pattern. This implies that the argument of `f` is necessarily a list (even though `OverloadedLists` is enabled). After desugaring the overloaded list pattern `[]`, and type-checking, we obtain: > f :: [a] -> Bool > f (toList -> []) = True > f (_:_) = False The pattern match checker then warns that the pattern `[]` is not covered, as it isn't able to look through view patterns. We can see that this is silly: as we are matching on a list, `toList` doesn't actually do anything. So we ignore it, and desugar the pattern to an explicit list pattern, instead of a view pattern. Note however that this is not necessarily sound, because it is possible to have a list `l` such that `toList l` is not the same as `l`. This can happen with an overlapping instance, such as the following: instance {-# OVERLAPPING #-} IsList [Int] where type Item [Int] = Int toList = reverse fromList = reverse We make the assumption that no such instance exists, in order to avoid worsening pattern-match warnings (see #14547). ********************************************************* * * External entry points * * ********************************************************* There are various entry points to renaming patterns, depending on (1) whether the names created should be top-level names or local names (2) whether the scope of the names is entirely given in a continuation (e.g., in a case or lambda, but not in a let or at the top-level, because of the way mutually recursive bindings are handled) (3) whether the a type signature in the pattern can bind lexically-scoped type variables (for unpacking existential type vars in data constructors) (4) whether we do duplicate and unused variable checking (5) whether there are fixity declarations associated with the names bound by the patterns that need to be brought into scope with them. Rather than burdening the clients of this module with all of these choices, we export the three points in this design space that we actually need: -} -- ----------- Entry point 1: rnPats ------------------- -- Binds local names; the scope of the bindings is entirely in the thing_inside -- * allows type sigs to bind type vars -- * local namemaker -- * unused and duplicate checking -- * no fixities rnPats :: Traversable f => HsMatchContext GhcRn -- for error messages -> f (LPat GhcPs) -> (f (LPat GhcRn) -> RnM (a, FreeVars)) -> RnM (a, FreeVars) rnPats ctxt pats thing_inside = do { envs_before <- getRdrEnvs -- (1) rename the patterns, bringing into scope all of the term variables -- (2) then do the thing inside. ; unCpsRn (rnLPatsAndThen (matchNameMaker ctxt) pats) $ \ pats' -> do { -- Check for duplicated and shadowed names -- Must do this *after* renaming the patterns -- See Note [Collect binders only after renaming] in GHC.Hs.Utils -- Because we don't bind the vars all at once, we can't -- check incrementally for duplicates; -- Nor can we check incrementally for shadowing, else we'll -- complain *twice* about duplicates e.g. f (x,x) = ... -- -- See Note [Don't report shadowing for pattern synonyms] ; let bndrs = collectPatsBinders CollNoDictBinders (toList pats') ; addErrCtxt doc_pat $ if isPatSynCtxt ctxt then checkDupNames bndrs else checkDupAndShadowedNames envs_before bndrs ; thing_inside pats' } } where doc_pat = text "In" <+> pprMatchContext ctxt {-# SPECIALIZE rnPats :: HsMatchContext GhcRn -> [LPat GhcPs] -> ([LPat GhcRn] -> RnM (a, FreeVars)) -> RnM (a, FreeVars) #-} {-# SPECIALIZE rnPats :: HsMatchContext GhcRn -> Identity (LPat GhcPs) -> (Identity (LPat GhcRn) -> RnM (a, FreeVars)) -> RnM (a, FreeVars) #-} rnPat :: HsMatchContext GhcRn -- for error messages -> LPat GhcPs -> (LPat GhcRn -> RnM (a, FreeVars)) -> RnM (a, FreeVars) -- Variables bound by pattern do not -- appear in the result FreeVars rnPat ctxt pat thing_inside = rnPats ctxt (Identity pat) (thing_inside . runIdentity) applyNameMaker :: NameMaker -> LocatedN RdrName -> RnM (LocatedN Name) applyNameMaker mk rdr = do { (n, _fvs) <- runCps (newPatLName mk rdr) ; return n } -- ----------- Entry point 2: rnBindPat ------------------- -- Binds local names; in a recursive scope that involves other bound vars -- e.g let { (x, Just y) = e1; ... } in ... -- * does NOT allows type sig to bind type vars -- * local namemaker -- * no unused and duplicate checking -- * fixities might be coming in rnBindPat :: NameMaker -> LPat GhcPs -> RnM (LPat GhcRn, FreeVars) -- Returned FreeVars are the free variables of the pattern, -- of course excluding variables bound by this pattern rnBindPat name_maker pat = runCps (rnLPatAndThen name_maker pat) {- ********************************************************* * * The main event * * ********************************************************* -} -- ----------- Entry point 3: rnLPatAndThen ------------------- -- General version: parameterized by how you make new names rnLPatsAndThen :: Traversable f => NameMaker -> f (LPat GhcPs) -> CpsRn (f (LPat GhcRn)) rnLPatsAndThen mk = mapM (rnLPatAndThen mk) -- Despite the map, the monad ensures that each pattern binds -- variables that may be mentioned in subsequent patterns in the list -------------------- -- The workhorse rnLPatAndThen :: NameMaker -> LPat GhcPs -> CpsRn (LPat GhcRn) rnLPatAndThen nm lpat = wrapSrcSpanCps (rnPatAndThen nm) lpat rnPatAndThen :: NameMaker -> Pat GhcPs -> CpsRn (Pat GhcRn) rnPatAndThen _ (WildPat _) = return (WildPat noExtField) rnPatAndThen mk (ParPat x lpar pat rpar) = do { pat' <- rnLPatAndThen mk pat ; return (ParPat x lpar pat' rpar) } rnPatAndThen mk (LazyPat _ pat) = do { pat' <- rnLPatAndThen mk pat ; return (LazyPat noExtField pat') } rnPatAndThen mk (BangPat _ pat) = do { pat' <- rnLPatAndThen mk pat ; return (BangPat noExtField pat') } rnPatAndThen mk (VarPat x (L l rdr)) = do { loc <- liftCps getSrcSpanM ; name <- newPatName mk (L (noAnnSrcSpan loc) rdr) ; return (VarPat x (L l name)) } -- we need to bind pattern variables for view pattern expressions -- (e.g. in the pattern (x, x -> y) x needs to be bound in the rhs of the tuple) rnPatAndThen mk (SigPat _ pat sig) -- When renaming a pattern type signature (e.g. f (a :: T) = ...), it is -- important to rename its type signature _before_ renaming the rest of the -- pattern, so that type variables are first bound by the _outermost_ pattern -- type signature they occur in. This keeps the type checker happy when -- pattern type signatures happen to be nested (#7827) -- -- f ((Just (x :: a) :: Maybe a) -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~^ `a' is first bound here -- ~~~~~~~~~~~~~~~^ the same `a' then used here = do { sig' <- rnHsPatSigTypeAndThen sig ; pat' <- rnLPatAndThen mk pat ; return (SigPat noExtField pat' sig' ) } where rnHsPatSigTypeAndThen :: HsPatSigType GhcPs -> CpsRn (HsPatSigType GhcRn) rnHsPatSigTypeAndThen sig = liftCpsWithCont (rnHsPatSigType AlwaysBind PatCtx sig) rnPatAndThen mk (LitPat x lit) | HsString src s <- lit = do { ovlStr <- liftCps (xoptM LangExt.OverloadedStrings) ; if ovlStr then rnPatAndThen mk (mkNPat (noLocA (mkHsIsString src s)) Nothing noAnn) else normal_lit } | otherwise = normal_lit where normal_lit = do { liftCps (rnLit lit); return (LitPat x (convertLit lit)) } rnPatAndThen _ (NPat x (L l lit) mb_neg _eq) = do { (lit', mb_neg') <- liftCpsFV $ rnOverLit lit ; mb_neg' -- See Note [Negative zero] <- let negative = do { (neg, fvs) <- lookupSyntax negateName ; return (Just neg, fvs) } positive = return (Nothing, emptyFVs) in liftCpsFV $ case (mb_neg , mb_neg') of (Nothing, Just _ ) -> negative (Just _ , Nothing) -> negative (Nothing, Nothing) -> positive (Just _ , Just _ ) -> positive ; eq' <- liftCpsFV $ lookupSyntax eqName ; return (NPat x (L l lit') mb_neg' eq') } rnPatAndThen mk (NPlusKPat _ rdr (L l lit) _ _ _ ) = do { new_name <- newPatName mk (l2n rdr) ; (lit', _) <- liftCpsFV $ rnOverLit lit -- See Note [Negative zero] -- We skip negateName as -- negative zero doesn't make -- sense in n + k patterns ; minus <- liftCpsFV $ lookupSyntax minusName ; ge <- liftCpsFV $ lookupSyntax geName ; return (NPlusKPat noExtField (L (noAnnSrcSpan $ nameSrcSpan new_name) new_name) (L l lit') lit' ge minus) } -- The Report says that n+k patterns must be in Integral rnPatAndThen mk (AsPat _ rdr at pat) = do { new_name <- newPatLName mk rdr ; pat' <- rnLPatAndThen mk pat ; return (AsPat noExtField new_name at pat') } rnPatAndThen mk p@(ViewPat _ expr pat) = do { liftCps $ do { vp_flag <- xoptM LangExt.ViewPatterns ; checkErr vp_flag (TcRnIllegalViewPattern p) } -- Because of the way we're arranging the recursive calls, -- this will be in the right context ; expr' <- liftCpsFV $ rnLExpr expr ; pat' <- rnLPatAndThen mk pat -- Note: at this point the PreTcType in ty can only be a placeHolder -- ; return (ViewPat expr' pat' ty) } -- Note: we can't cook up an inverse for an arbitrary view pattern, -- so we pass 'Nothing'. ; return (ViewPat Nothing expr' pat') } rnPatAndThen mk (ConPat _ con args) -- rnConPatAndThen takes care of reconstructing the pattern -- The pattern for the empty list needs to be replaced by an empty explicit list pattern when overloaded lists is turned on. = case unLoc con == nameRdrName (dataConName nilDataCon) of True -> do { ol_flag <- liftCps $ xoptM LangExt.OverloadedLists ; if ol_flag then rnPatAndThen mk (ListPat noAnn []) else rnConPatAndThen mk con args} False -> rnConPatAndThen mk con args rnPatAndThen mk (ListPat _ pats) = do { opt_OverloadedLists <- liftCps $ xoptM LangExt.OverloadedLists ; pats' <- rnLPatsAndThen mk pats ; if not opt_OverloadedLists then return (ListPat noExtField pats') else -- If OverloadedLists is enabled, desugar to a view pattern. -- See Note [Desugaring overloaded list patterns] do { (to_list_name,_) <- liftCps $ lookupSyntaxName toListName -- Use 'fromList' as proof of invertibility of the view pattern. -- See Note [Invertible view patterns] in GHC.Tc.TyCl.PatSyn ; (from_list_n_name,_) <- liftCps $ lookupSyntaxName fromListNName ; let lit_n = mkIntegralLit (length pats) hs_lit = genHsIntegralLit lit_n inverse = genHsApps from_list_n_name [hs_lit] rn_list_pat = ListPat noExtField pats' exp_expr = genLHsVar to_list_name exp_list_pat = ViewPat (Just inverse) exp_expr (wrapGenSpan rn_list_pat) ; return $ mkExpandedPat rn_list_pat exp_list_pat }} rnPatAndThen mk (TuplePat _ pats boxed) = do { pats' <- rnLPatsAndThen mk pats ; return (TuplePat noExtField pats' boxed) } rnPatAndThen mk (SumPat _ pat alt arity) = do { pat <- rnLPatAndThen mk pat ; return (SumPat noExtField pat alt arity) } rnPatAndThen mk (SplicePat _ splice) = do { eith <- liftCpsFV $ rnSplicePat splice ; case eith of -- See Note [rnSplicePat] in GHC.Rename.Splice (rn_splice, HsUntypedSpliceTop mfs pat) -> -- Splice was top-level and thus run, creating Pat GhcPs gParPat . (fmap (flip SplicePat rn_splice . HsUntypedSpliceTop mfs)) <$> rnLPatAndThen mk pat (rn_splice, HsUntypedSpliceNested splice_name) -> return (SplicePat (HsUntypedSpliceNested splice_name) rn_splice) -- Splice was nested and thus already renamed } -------------------- rnConPatAndThen :: NameMaker -> LocatedN RdrName -- the constructor -> HsConPatDetails GhcPs -> CpsRn (Pat GhcRn) rnConPatAndThen mk con (PrefixCon tyargs pats) = do { con' <- lookupConCps con ; liftCps check_lang_exts ; tyargs' <- mapM rnConPatTyArg tyargs ; pats' <- rnLPatsAndThen mk pats ; return $ ConPat { pat_con_ext = noExtField , pat_con = con' , pat_args = PrefixCon tyargs' pats' } } where check_lang_exts :: RnM () check_lang_exts = for_ (listToMaybe tyargs) $ \ arg -> do { type_abs <- xoptM LangExt.TypeAbstractions ; type_app <- xoptM LangExt.TypeApplications ; scoped_tvs <- xoptM LangExt.ScopedTypeVariables ; if | type_abs -> return () -- As per [GHC Proposal 604](https://github.com/ghc-proposals/ghc-proposals/pull/604/), -- we allow type applications in constructor patterns when -XTypeApplications and -- -XScopedTypeVariables are both enabled, but we emit a warning when doing so. -- -- This warning is scheduled to become an error in GHC 9.12, in -- which case we will get the usual error (below), -- which suggests enabling -XTypeAbstractions. | type_app && scoped_tvs -> addDiagnostic TcRnDeprecatedInvisTyArgInConPat | otherwise -> addErrTc $ TcRnTypeApplicationsDisabled (TypeApplicationInPattern arg) } rnConPatTyArg (HsConPatTyArg at t) = do t' <- liftCpsWithCont $ rnHsPatSigTypeBindingVars HsTypeCtx t return (HsConPatTyArg at t') rnConPatAndThen mk con (InfixCon pat1 pat2) = do { con' <- lookupConCps con ; pat1' <- rnLPatAndThen mk pat1 ; pat2' <- rnLPatAndThen mk pat2 ; fixity <- liftCps $ lookupFixityRn (unLoc con') ; liftCps $ mkConOpPatRn con' fixity pat1' pat2' } rnConPatAndThen mk con (RecCon rpats) = do { con' <- lookupConCps con ; rpats' <- rnHsRecPatsAndThen mk con' rpats ; return $ ConPat { pat_con_ext = noExtField , pat_con = con' , pat_args = RecCon rpats' } } checkUnusedRecordWildcardCps :: SrcSpan -> Maybe [Name] -> CpsRn () checkUnusedRecordWildcardCps loc dotdot_names = CpsRn (\thing -> do (r, fvs) <- thing () checkUnusedRecordWildcard loc fvs dotdot_names return (r, fvs) ) -------------------- rnHsRecPatsAndThen :: NameMaker -> LocatedN Name -- Constructor -> HsRecFields GhcPs (LPat GhcPs) -> CpsRn (HsRecFields GhcRn (LPat GhcRn)) rnHsRecPatsAndThen mk (L _ con) hs_rec_fields@(HsRecFields { rec_dotdot = dd }) = do { flds <- liftCpsFV $ rnHsRecFields (HsRecFieldPat con) mkVarPat hs_rec_fields ; flds' <- mapM rn_field (flds `zip` [1..]) ; check_unused_wildcard (implicit_binders flds' <$> dd) ; return (HsRecFields { rec_flds = flds', rec_dotdot = dd }) } where mkVarPat l n = VarPat noExtField (L (noAnnSrcSpan l) n) rn_field (L l fld, n') = do { arg' <- rnLPatAndThen (nested_mk dd mk (RecFieldsDotDot n')) (hfbRHS fld) ; return (L l (fld { hfbRHS = arg' })) } loc = maybe noSrcSpan getLoc dd -- Get the arguments of the implicit binders implicit_binders fs (unLoc -> RecFieldsDotDot n) = collectPatsBinders CollNoDictBinders implicit_pats where implicit_pats = map (hfbRHS . unLoc) (drop n fs) -- Don't warn for let P{..} = ... in ... check_unused_wildcard = case mk of LetMk{} -> const (return ()) LamMk{} -> checkUnusedRecordWildcardCps loc -- Suppress unused-match reporting for fields introduced by ".." nested_mk Nothing mk _ = mk nested_mk (Just _) mk@(LetMk {}) _ = mk nested_mk (Just (unLoc -> n)) (LamMk report_unused) n' = LamMk (report_unused && (n' <= n)) {- ********************************************************************* * * Generating code for HsPatExpanded See Note [Handling overloaded and rebindable constructs] * * ********************************************************************* -} -- | Build a 'HsPatExpansion' out of an extension constructor, -- and the two components of the expansion: original and -- desugared patterns mkExpandedPat :: Pat GhcRn -- ^ source pattern -> Pat GhcRn -- ^ expanded pattern -> Pat GhcRn -- ^ suitably wrapped 'HsPatExpansion' mkExpandedPat a b = XPat (HsPatExpanded a b) {- ************************************************************************ * * Record fields * * ************************************************************************ -} data HsRecFieldContext = HsRecFieldCon Name | HsRecFieldPat Name | HsRecFieldUpd rnHsRecFields :: forall arg. HsRecFieldContext -> (SrcSpan -> RdrName -> arg) -- When punning, use this to build a new field -> HsRecFields GhcPs (LocatedA arg) -> RnM ([LHsRecField GhcRn (LocatedA arg)], FreeVars) -- This surprisingly complicated pass -- a) looks up the field name (possibly using disambiguation) -- b) fills in puns and dot-dot stuff -- When we've finished, we've renamed the LHS, but not the RHS, -- of each x=e binding -- -- This is used for record construction and pattern-matching, but not updates. rnHsRecFields ctxt mk_arg (HsRecFields { rec_flds = flds, rec_dotdot = dotdot }) = do { pun_ok <- xoptM LangExt.NamedFieldPuns ; disambig_ok <- xoptM LangExt.DisambiguateRecordFields ; let parent = guard disambig_ok >> mb_con ; flds1 <- mapM (rn_fld pun_ok parent) flds ; mapM_ (addErr . dupFieldErr ctxt) dup_flds ; dotdot_flds <- rn_dotdot dotdot mb_con flds1 ; let all_flds | null dotdot_flds = flds1 | otherwise = flds1 ++ dotdot_flds ; return (all_flds, mkFVs (getFieldIds all_flds)) } where mb_con = case ctxt of HsRecFieldCon con -> Just con HsRecFieldPat con -> Just con HsRecFieldUpd -> Nothing rn_fld :: Bool -> Maybe Name -> LHsRecField GhcPs (LocatedA arg) -> RnM (LHsRecField GhcRn (LocatedA arg)) rn_fld pun_ok parent (L l (HsFieldBind { hfbLHS = L loc (FieldOcc _ (L ll lbl)) , hfbRHS = arg , hfbPun = pun })) = do { sel <- setSrcSpanA loc $ lookupRecFieldOcc parent lbl ; let arg_rdr = mkRdrUnqual $ recFieldToVarOcc $ occName sel -- Discard any module qualifier (#11662) ; arg' <- if pun then do { checkErr pun_ok $ TcRnIllegalFieldPunning (L (locA loc) arg_rdr) ; return $ L (l2l loc) $ mk_arg (locA loc) arg_rdr } else return arg ; return $ L l $ HsFieldBind { hfbAnn = noAnn , hfbLHS = L loc (FieldOcc sel (L ll arg_rdr)) , hfbRHS = arg' , hfbPun = pun } } rn_dotdot :: Maybe (Located RecFieldsDotDot) -- See Note [DotDot fields] in GHC.Hs.Pat -> Maybe Name -- The constructor (Nothing for an -- out of scope constructor) -> [LHsRecField GhcRn (LocatedA arg)] -- Explicit fields -> RnM ([LHsRecField GhcRn (LocatedA arg)]) -- Field Labels we need to fill in rn_dotdot (Just (L loc (RecFieldsDotDot n))) (Just con) flds -- ".." on record construction / pat match | not (isUnboundName con) -- This test is because if the constructor -- isn't in scope the constructor lookup will add -- an error but still return an unbound name. We -- don't want that to screw up the dot-dot fill-in stuff. = assert (flds `lengthIs` n) $ do { dd_flag <- xoptM LangExt.RecordWildCards ; checkErr dd_flag (needFlagDotDot ctxt) ; (rdr_env, lcl_env) <- getRdrEnvs ; conInfo <- lookupConstructorInfo con ; when (conInfo == ConHasPositionalArgs) (addErr (TcRnIllegalWildcardsInConstructor con)) ; let present_flds = mkOccSet $ map rdrNameOcc (getFieldLbls flds) -- For constructor uses (but not patterns) -- the arg should be in scope locally; -- i.e. not top level or imported -- Eg. data R = R { x,y :: Int } -- f x = R { .. } -- Should expand to R {x=x}, not R{x=x,y=y} arg_in_scope lbl = mkRdrUnqual lbl `elemLocalRdrEnv` lcl_env (dot_dot_fields, dot_dot_gres) = unzip [ (fl, gre) | fl <- conInfoFields conInfo , let lbl = recFieldToVarOcc $ occName $ flSelector fl , not (lbl `elemOccSet` present_flds) , Just gre <- [lookupGRE_FieldLabel rdr_env fl] -- Check selector is in scope , case ctxt of HsRecFieldCon {} -> arg_in_scope lbl _other -> True ] ; addUsedGREs NoDeprecationWarnings dot_dot_gres ; let locn = noAnnSrcSpan loc ; return [ L (noAnnSrcSpan loc) (HsFieldBind { hfbAnn = noAnn , hfbLHS = L (noAnnSrcSpan loc) (FieldOcc sel (L (noAnnSrcSpan loc) arg_rdr)) , hfbRHS = L locn (mk_arg loc arg_rdr) , hfbPun = False }) | fl <- dot_dot_fields , let sel = flSelector fl arg_rdr = mkRdrUnqual $ recFieldToVarOcc $ nameOccName sel ] } rn_dotdot _dotdot _mb_con _flds = return [] -- _dotdot = Nothing => No ".." at all -- _mb_con = Nothing => Record update -- _mb_con = Just unbound => Out of scope data constructor dup_flds :: [NE.NonEmpty RdrName] -- Each list represents a RdrName that occurred more than once -- (the list contains all occurrences) -- Each list in dup_fields is non-empty (_, dup_flds) = removeDups (uniqCompareFS `on` (occNameFS . rdrNameOcc)) (getFieldLbls flds) -- See the same duplicate handling logic in rnHsRecUpdFields below for further context. -- | Rename a regular (non-overloaded) record field update, -- disambiguating the fields if necessary. rnHsRecUpdFields :: [LHsRecUpdField GhcPs GhcPs] -> RnM (XLHsRecUpdLabels GhcRn, [LHsRecUpdField GhcRn GhcRn], FreeVars) rnHsRecUpdFields flds = do { pun_ok <- xoptM LangExt.NamedFieldPuns -- Check for an empty record update: e {} -- NB: don't complain about e { .. }, because rn_dotdot has done that already ; case flds of { [] -> failWithTc TcRnEmptyRecordUpdate ; fld:other_flds -> do { let dup_lbls :: [NE.NonEmpty RdrName] (_, dup_lbls) = removeDups (uniqCompareFS `on` (occNameFS . rdrNameOcc)) (fmap (unLoc . getFieldUpdLbl) flds) -- NB: we compare using the underlying field label FastString, -- in order to catch duplicates involving qualified names, -- as in the record update `r { fld = x, Mod.fld = y }`. -- See #21959. -- Note that this test doesn't correctly handle exact Names, but those -- aren't handled properly by the rest of the compiler anyway. See #22122. ; mapM_ (addErr . dupFieldErr HsRecFieldUpd) dup_lbls -- See Note [Disambiguating record updates] ; possible_parents <- lookupRecUpdFields (fld NE.:| other_flds) ; let mb_unambig_lbls :: Maybe [FieldLabel] fvs :: FreeVars (mb_unambig_lbls, fvs) = case possible_parents of RnRecUpdParent { rnRecUpdLabels = gres } NE.:| [] | let lbls = map fieldGRELabel $ NE.toList gres -> ( Just lbls, mkFVs $ map flSelector lbls) _ -> ( Nothing , plusFVs $ map (plusFVs . map pat_syn_free_vars . NE.toList . rnRecUpdLabels) $ NE.toList possible_parents -- See Note [Using PatSyn FreeVars] ) -- Rename each field. ; (upd_flds, fvs') <- rn_flds pun_ok mb_unambig_lbls flds ; let all_fvs = fvs `plusFV` fvs' ; return (possible_parents, upd_flds, all_fvs) } } } where -- For an ambiguous record update involving pattern synonym record fields, -- we must add all the possibly-relevant field selector names to ensure that -- we typecheck the record update **after** we typecheck the pattern synonym -- definition. See Note [Using PatSyn FreeVars]. pat_syn_free_vars :: FieldGlobalRdrElt -> FreeVars pat_syn_free_vars (GRE { gre_info = info }) | IAmRecField fld_info <- info , RecFieldInfo { recFieldLabel = fl, recFieldCons = cons } <- fld_info , uniqSetAny is_PS cons = unitFV (flSelector fl) pat_syn_free_vars _ = emptyFVs is_PS :: ConLikeName -> Bool is_PS (PatSynName {}) = True is_PS (DataConName {}) = False rn_flds :: Bool -> Maybe [FieldLabel] -> [LHsRecUpdField GhcPs GhcPs] -> RnM ([LHsRecUpdField GhcRn GhcRn], FreeVars) rn_flds _ _ [] = return ([], emptyFVs) rn_flds pun_ok mb_unambig_lbls ((L l (HsFieldBind { hfbLHS = L loc f , hfbRHS = arg , hfbPun = pun })):flds) = do { let lbl = ambiguousFieldOccRdrName f ; (arg' :: LHsExpr GhcPs) <- if pun then do { setSrcSpanA loc $ checkErr pun_ok (TcRnIllegalFieldPunning (L (locA loc) lbl)) -- Discard any module qualifier (#11662) ; let arg_rdr = mkRdrUnqual (rdrNameOcc lbl) ; return (L (l2l loc) (HsVar noExtField (L (l2l loc) arg_rdr))) } else return arg ; (arg'', fvs) <- rnLExpr arg' ; let lbl' :: AmbiguousFieldOcc GhcRn lbl' = case mb_unambig_lbls of { Just (fl:_) -> let sel_name = flSelector fl in Unambiguous sel_name (L (l2l loc) lbl) ; _ -> Ambiguous noExtField (L (l2l loc) lbl) } fld' :: LHsRecUpdField GhcRn GhcRn fld' = L l (HsFieldBind { hfbAnn = noAnn , hfbLHS = L loc lbl' , hfbRHS = arg'' , hfbPun = pun }) ; (flds', fvs') <- rn_flds pun_ok (tail <$> mb_unambig_lbls) flds ; return (fld' : flds', fvs `plusFV` fvs') } getFieldIds :: [LHsRecField GhcRn arg] -> [Name] getFieldIds flds = map (hsRecFieldSel . unLoc) flds getFieldLbls :: forall p arg . UnXRec p => [LHsRecField p arg] -> [RdrName] getFieldLbls flds = map (unXRec @p . foLabel . unXRec @p . hfbLHS . unXRec @p) flds needFlagDotDot :: HsRecFieldContext -> TcRnMessage needFlagDotDot = TcRnIllegalWildcardsInRecord . toRecordFieldPart dupFieldErr :: HsRecFieldContext -> NE.NonEmpty RdrName -> TcRnMessage dupFieldErr ctxt = TcRnDuplicateFieldName (toRecordFieldPart ctxt) toRecordFieldPart :: HsRecFieldContext -> RecordFieldPart toRecordFieldPart (HsRecFieldCon n) = RecordFieldConstructor n toRecordFieldPart (HsRecFieldPat n) = RecordFieldPattern n toRecordFieldPart (HsRecFieldUpd {}) = RecordFieldUpdate {- Note [Disambiguating record updates] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ When the -XDuplicateRecordFields extension is used, to rename and typecheck a non-overloaded record update, we might need to disambiguate the field labels. Consider the following definitions: {-# LANGUAGE DuplicateRecordFields #-} data R = MkR1 { fld1 :: Int, fld2 :: Char } | MKR2 { fld1 :: Int, fld2 :: Char, fld3 :: Bool } data S = MkS1 { fld1 :: Int } | MkS2 { fld2 :: Char } In a record update, the `lookupRecUpdFields` function tries to determine the parent datatype by computing the parents (TyCon/PatSyn) which have at least one constructor (DataCon/PatSyn) with all of the fields. For example, in the (non-overloaded) record update r { fld1 = 3, fld2 = 'x' } only the TyCon R contains at least one DataCon which has both of the fields being updated: in this case, MkR1 and MkR2 have both of the updated fields. The TyCon S also has both fields fld1 and fld2, but no single constructor has both of those fields, so S is not a valid parent for this record update. Note that this check is namespace-aware, so that a record update such as import qualified M ( R (fld1, fld2) ) f r = r { M.fld1 = 3 } is unambiguous, as only R contains the field fld1 in the M namespace. (See however #22122 for issues relating to the usage of exact Names in record fields.) See also Note [Type-directed record disambiguation] in GHC.Tc.Gen.Expr. Note [Using PatSyn FreeVars] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ When we are disambiguating a non-overloaded record update, as per Note [Disambiguating record updates], and have determined that this record update might involve pattern synonym record fields, it is important to declare usage of all these pattern synonyms record fields in the returned FreeVars of rnHsRecUpdFields. This ensures that the typechecker sees that the typechecking of the record update depends on the typechecking of the pattern synonym, and typechecks the pattern synonyms first. Not doing so caused #21898. Note that this can be removed once GHC proposal #366 is implemented, as we will be able to fully disambiguate the record update in the renamer, and can immediately declare the correct used FreeVars instead of having to over-estimate in case of ambiguity. ************************************************************************ * * \subsubsection{Literals} * * ************************************************************************ When literals occur we have to make sure that the types and classes they involve are made available. -} rnLit :: HsLit p -> RnM () rnLit (HsChar _ c) = checkErr (inCharRange c) (TcRnCharLiteralOutOfRange c) rnLit _ = return () -- | Turn a Fractional-looking literal which happens to be an integer into an -- Integer-looking literal. -- We only convert numbers where the exponent is between 0 and 100 to avoid -- converting huge numbers and incurring long compilation times. See #15646. generalizeOverLitVal :: OverLitVal -> OverLitVal generalizeOverLitVal (HsFractional fl@(FL {fl_text=src,fl_neg=neg,fl_exp=e})) | e >= -100 && e <= 100 , let val = rationalFromFractionalLit fl , denominator val == 1 = HsIntegral (IL {il_text=src,il_neg=neg,il_value=numerator val}) generalizeOverLitVal lit = lit isNegativeZeroOverLit :: (XXOverLit t ~ DataConCantHappen) => HsOverLit t -> Bool isNegativeZeroOverLit lit = case ol_val lit of HsIntegral i -> 0 == il_value i && il_neg i -- For HsFractional, the value of fl is n * (b ^^ e) so it is sufficient -- to check if n = 0. b is equal to either 2 or 10. We don't call -- rationalFromFractionalLit here as it is expensive when e is big. HsFractional fl -> 0 == fl_signi fl && fl_neg fl _ -> False {- Note [Negative zero] ~~~~~~~~~~~~~~~~~~~~~~~~~ There were problems with negative zero in conjunction with Negative Literals extension. Numeric literal value is contained in Integer and Rational types inside IntegralLit and FractionalLit. These types cannot represent negative zero value. So we had to add explicit field 'neg' which would hold information about literal sign. Here in rnOverLit we use it to detect negative zeroes and in this case return not only literal itself but also negateName so that users can apply it explicitly. In this case it stays negative zero. #13211 -} rnOverLit :: (XXOverLit t ~ DataConCantHappen) => HsOverLit t -> RnM ((HsOverLit GhcRn, Maybe (HsExpr GhcRn)), FreeVars) rnOverLit origLit = do { opt_NumDecimals <- xoptM LangExt.NumDecimals ; let { lit@(OverLit {ol_val=val}) | opt_NumDecimals = origLit {ol_val = generalizeOverLitVal (ol_val origLit)} | otherwise = origLit } ; let std_name = hsOverLitName val ; (from_thing_name, fvs1) <- lookupSyntaxName std_name ; let rebindable = from_thing_name /= std_name lit' = lit { ol_ext = OverLitRn { ol_rebindable = rebindable , ol_from_fun = noLocA from_thing_name } } ; if isNegativeZeroOverLit lit' then do { (negate_name, fvs2) <- lookupSyntaxExpr negateName ; return ((lit' { ol_val = negateOverLitVal val }, Just negate_name) , fvs1 `plusFV` fvs2) } else return ((lit', Nothing), fvs1) }