{- (c) The University of Glasgow 2006 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 \section[PatSyntax]{Abstract Haskell syntax---patterns} -} {-# LANGUAGE DeriveDataTypeable #-} {-# LANGUAGE DeriveFunctor #-} {-# LANGUAGE DeriveFoldable #-} {-# LANGUAGE DeriveTraversable #-} {-# LANGUAGE StandaloneDeriving #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE UndecidableInstances #-} -- Note [Pass sensitive types] -- in module PlaceHolder {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE TypeFamilies #-} module HsPat ( Pat(..), InPat, OutPat, LPat, HsConPatDetails, hsConPatArgs, HsRecFields(..), HsRecField'(..), LHsRecField', HsRecField, LHsRecField, HsRecUpdField, LHsRecUpdField, hsRecFields, hsRecFieldSel, hsRecFieldId, hsRecFieldsArgs, hsRecUpdFieldId, hsRecUpdFieldOcc, hsRecUpdFieldRdr, mkPrefixConPat, mkCharLitPat, mkNilPat, looksLazyPatBind, isBangedLPat, isBangedPatBind, hsPatNeedsParens, isIrrefutableHsPat, collectEvVarsPats, pprParendLPat, pprConArgs ) where import {-# SOURCE #-} HsExpr (SyntaxExpr, LHsExpr, HsSplice, pprLExpr, pprSplice) -- friends: import HsBinds import HsLit import PlaceHolder import HsTypes import TcEvidence import BasicTypes -- others: import PprCore ( {- instance OutputableBndr TyVar -} ) import TysWiredIn import Var import RdrName ( RdrName ) import ConLike import DataCon import TyCon import Outputable import Type import SrcLoc import Bag -- collect ev vars from pats import DynFlags( gopt, GeneralFlag(..) ) import Maybes -- libraries: import Data.Data hiding (TyCon,Fixity) type InPat id = LPat id -- No 'Out' constructors type OutPat id = LPat id -- No 'In' constructors type LPat id = Located (Pat id) -- | Pattern -- -- - 'ApiAnnotation.AnnKeywordId' : 'ApiAnnotation.AnnBang' -- For details on above see note [Api annotations] in ApiAnnotation data Pat id = ------------ Simple patterns --------------- WildPat (PostTc id Type) -- ^ Wildcard Pattern -- The sole reason for a type on a WildPat is to -- support hsPatType :: Pat Id -> Type | VarPat (Located id) -- ^ Variable Pattern -- See Note [Located RdrNames] in HsExpr | LazyPat (LPat id) -- ^ Lazy Pattern -- ^ - 'ApiAnnotation.AnnKeywordId' : 'ApiAnnotation.AnnTilde' -- For details on above see note [Api annotations] in ApiAnnotation | AsPat (Located id) (LPat id) -- ^ As pattern -- ^ - 'ApiAnnotation.AnnKeywordId' : 'ApiAnnotation.AnnAt' -- For details on above see note [Api annotations] in ApiAnnotation | ParPat (LPat id) -- ^ Parenthesised pattern -- See Note [Parens in HsSyn] in HsExpr -- ^ - 'ApiAnnotation.AnnKeywordId' : 'ApiAnnotation.AnnOpen' @'('@, -- 'ApiAnnotation.AnnClose' @')'@ -- For details on above see note [Api annotations] in ApiAnnotation | BangPat (LPat id) -- ^ Bang pattern -- ^ - 'ApiAnnotation.AnnKeywordId' : 'ApiAnnotation.AnnBang' -- For details on above see note [Api annotations] in ApiAnnotation ------------ Lists, tuples, arrays --------------- | ListPat [LPat id] (PostTc id Type) -- The type of the elements (Maybe (PostTc id Type, SyntaxExpr id)) -- For rebindable syntax -- For OverloadedLists a Just (ty,fn) gives -- overall type of the pattern, and the toList -- function to convert the scrutinee to a list value -- ^ Syntactic List -- -- - 'ApiAnnotation.AnnKeywordId' : 'ApiAnnotation.AnnOpen' @'['@, -- 'ApiAnnotation.AnnClose' @']'@ -- For details on above see note [Api annotations] in ApiAnnotation | TuplePat [LPat id] -- Tuple sub-patterns Boxity -- UnitPat is TuplePat [] [PostTc id Type] -- [] before typechecker, filled in afterwards -- with the types of the tuple components -- You might think that the PostTc id Type was redundant, because we can -- get the pattern type by getting the types of the sub-patterns. -- But it's essential -- data T a where -- T1 :: Int -> T Int -- f :: (T a, a) -> Int -- f (T1 x, z) = z -- When desugaring, we must generate -- f = /\a. \v::a. case v of (t::T a, w::a) -> -- case t of (T1 (x::Int)) -> -- Note the (w::a), NOT (w::Int), because we have not yet -- refined 'a' to Int. So we must know that the second component -- of the tuple is of type 'a' not Int. See selectMatchVar -- (June 14: I'm not sure this comment is right; the sub-patterns -- will be wrapped in CoPats, no?) -- ^ Tuple sub-patterns -- -- - 'ApiAnnotation.AnnKeywordId' : -- 'ApiAnnotation.AnnOpen' @'('@ or @'(#'@, -- 'ApiAnnotation.AnnClose' @')'@ or @'#)'@ | SumPat (LPat id) -- Sum sub-pattern ConTag -- Alternative (one-based) Arity -- Arity (PostTc id [Type]) -- PlaceHolder before typechecker, filled in -- afterwards with the types of the -- alternative -- ^ Anonymous sum pattern -- -- - 'ApiAnnotation.AnnKeywordId' : -- 'ApiAnnotation.AnnOpen' @'(#'@, -- 'ApiAnnotation.AnnClose' @'#)'@ -- For details on above see note [Api annotations] in ApiAnnotation | PArrPat [LPat id] -- Syntactic parallel array (PostTc id Type) -- The type of the elements -- ^ - 'ApiAnnotation.AnnKeywordId' : 'ApiAnnotation.AnnOpen' @'[:'@, -- 'ApiAnnotation.AnnClose' @':]'@ -- For details on above see note [Api annotations] in ApiAnnotation ------------ Constructor patterns --------------- | ConPatIn (Located id) (HsConPatDetails id) -- ^ Constructor Pattern In | ConPatOut { pat_con :: Located ConLike, pat_arg_tys :: [Type], -- The universal arg types, 1-1 with the universal -- tyvars of the constructor/pattern synonym -- Use (conLikeResTy pat_con pat_arg_tys) to get -- the type of the pattern pat_tvs :: [TyVar], -- Existentially bound type variables -- in correctly-scoped order e.g. [k:*, x:k] pat_dicts :: [EvVar], -- Ditto *coercion variables* and *dictionaries* -- One reason for putting coercion variable here, I think, -- is to ensure their kinds are zonked pat_binds :: TcEvBinds, -- Bindings involving those dictionaries pat_args :: HsConPatDetails id, pat_wrap :: HsWrapper -- Extra wrapper to pass to the matcher -- Only relevant for pattern-synonyms; -- ignored for data cons } -- ^ Constructor Pattern Out ------------ View patterns --------------- -- | - 'ApiAnnotation.AnnKeywordId' : 'ApiAnnotation.AnnRarrow' -- For details on above see note [Api annotations] in ApiAnnotation | ViewPat (LHsExpr id) (LPat id) (PostTc id Type) -- The overall type of the pattern -- (= the argument type of the view function) -- for hsPatType. -- ^ View Pattern ------------ Pattern splices --------------- -- | - 'ApiAnnotation.AnnKeywordId' : 'ApiAnnotation.AnnOpen' @'$('@ -- 'ApiAnnotation.AnnClose' @')'@ -- For details on above see note [Api annotations] in ApiAnnotation | SplicePat (HsSplice id) -- ^ Splice Pattern (Includes quasi-quotes) ------------ Literal and n+k patterns --------------- | LitPat HsLit -- ^ Literal Pattern -- Used for *non-overloaded* literal patterns: -- Int#, Char#, Int, Char, String, etc. | NPat -- Natural Pattern -- Used for all overloaded literals, -- including overloaded strings with -XOverloadedStrings (Located (HsOverLit id)) -- ALWAYS positive (Maybe (SyntaxExpr id)) -- Just (Name of 'negate') for negative -- patterns, Nothing otherwise (SyntaxExpr id) -- Equality checker, of type t->t->Bool (PostTc id Type) -- Overall type of pattern. Might be -- different than the literal's type -- if (==) or negate changes the type -- ^ Natural Pattern -- -- - 'ApiAnnotation.AnnKeywordId' : 'ApiAnnotation.AnnVal' @'+'@ -- For details on above see note [Api annotations] in ApiAnnotation | NPlusKPat (Located id) -- n+k pattern (Located (HsOverLit id)) -- It'll always be an HsIntegral (HsOverLit id) -- See Note [NPlusK patterns] in TcPat -- NB: This could be (PostTc ...), but that induced a -- a new hs-boot file. Not worth it. (SyntaxExpr id) -- (>=) function, of type t1->t2->Bool (SyntaxExpr id) -- Name of '-' (see RnEnv.lookupSyntaxName) (PostTc id Type) -- Type of overall pattern -- ^ n+k pattern ------------ Pattern type signatures --------------- -- | - 'ApiAnnotation.AnnKeywordId' : 'ApiAnnotation.AnnDcolon' -- For details on above see note [Api annotations] in ApiAnnotation | SigPatIn (LPat id) -- Pattern with a type signature (LHsSigWcType id) -- Signature can bind both -- kind and type vars -- ^ Pattern with a type signature | SigPatOut (LPat id) Type -- ^ Pattern with a type signature ------------ Pattern coercions (translation only) --------------- | CoPat HsWrapper -- Coercion Pattern -- If co :: t1 ~ t2, p :: t2, -- then (CoPat co p) :: t1 (Pat id) -- Why not LPat? Ans: existing locn will do Type -- Type of whole pattern, t1 -- During desugaring a (CoPat co pat) turns into a cast with 'co' on -- the scrutinee, followed by a match on 'pat' -- ^ Coercion Pattern deriving instance (DataId id) => Data (Pat id) -- | Haskell Constructor Pattern Details type HsConPatDetails id = HsConDetails (LPat id) (HsRecFields id (LPat id)) hsConPatArgs :: HsConPatDetails id -> [LPat id] hsConPatArgs (PrefixCon ps) = ps hsConPatArgs (RecCon fs) = map (hsRecFieldArg . unLoc) (rec_flds fs) hsConPatArgs (InfixCon p1 p2) = [p1,p2] -- | Haskell Record Fields -- -- HsRecFields is used only for patterns and expressions (not data type -- declarations) data HsRecFields id arg -- A bunch of record fields -- { x = 3, y = True } -- Used for both expressions and patterns = HsRecFields { rec_flds :: [LHsRecField id arg], rec_dotdot :: Maybe Int } -- Note [DotDot fields] deriving (Functor, Foldable, Traversable) deriving instance (DataId id, Data arg) => Data (HsRecFields id arg) -- Note [DotDot fields] -- ~~~~~~~~~~~~~~~~~~~~ -- The rec_dotdot field means this: -- Nothing => the normal case -- Just n => the group uses ".." notation, -- -- In the latter case: -- -- *before* renamer: rec_flds are exactly the n user-written fields -- -- *after* renamer: rec_flds includes *all* fields, with -- the first 'n' being the user-written ones -- and the remainder being 'filled in' implicitly -- | Located Haskell Record Field type LHsRecField' id arg = Located (HsRecField' id arg) -- | Located Haskell Record Field type LHsRecField id arg = Located (HsRecField id arg) -- | Located Haskell Record Update Field type LHsRecUpdField id = Located (HsRecUpdField id) -- | Haskell Record Field type HsRecField id arg = HsRecField' (FieldOcc id) arg -- | Haskell Record Update Field type HsRecUpdField id = HsRecField' (AmbiguousFieldOcc id) (LHsExpr id) -- | Haskell Record Field -- -- - 'ApiAnnotation.AnnKeywordId' : 'ApiAnnotation.AnnEqual', -- -- For details on above see note [Api annotations] in ApiAnnotation data HsRecField' id arg = HsRecField { hsRecFieldLbl :: Located id, hsRecFieldArg :: arg, -- ^ Filled in by renamer when punning hsRecPun :: Bool -- ^ Note [Punning] } deriving (Data, Functor, Foldable, Traversable) -- Note [Punning] -- ~~~~~~~~~~~~~~ -- If you write T { x, y = v+1 }, the HsRecFields will be -- HsRecField x x True ... -- HsRecField y (v+1) False ... -- That is, for "punned" field x is expanded (in the renamer) -- to x=x; but with a punning flag so we can detect it later -- (e.g. when pretty printing) -- -- If the original field was qualified, we un-qualify it, thus -- T { A.x } means T { A.x = x } -- Note [HsRecField and HsRecUpdField] -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -- A HsRecField (used for record construction and pattern matching) -- contains an unambiguous occurrence of a field (i.e. a FieldOcc). -- We can't just store the Name, because thanks to -- DuplicateRecordFields this may not correspond to the label the user -- wrote. -- -- A HsRecUpdField (used for record update) contains a potentially -- ambiguous occurrence of a field (an AmbiguousFieldOcc). The -- renamer will fill in the selector function if it can, but if the -- selector is ambiguous the renamer will defer to the typechecker. -- After the typechecker, a unique selector will have been determined. -- -- The renamer produces an Unambiguous result if it can, rather than -- just doing the lookup in the typechecker, so that completely -- unambiguous updates can be represented by 'DsMeta.repUpdFields'. -- -- For example, suppose we have: -- -- data S = MkS { x :: Int } -- data T = MkT { x :: Int } -- -- f z = (z { x = 3 }) :: S -- -- The parsed HsRecUpdField corresponding to the record update will have: -- -- hsRecFieldLbl = Unambiguous "x" PlaceHolder :: AmbiguousFieldOcc RdrName -- -- After the renamer, this will become: -- -- hsRecFieldLbl = Ambiguous "x" PlaceHolder :: AmbiguousFieldOcc Name -- -- (note that the Unambiguous constructor is not type-correct here). -- The typechecker will determine the particular selector: -- -- hsRecFieldLbl = Unambiguous "x" $sel:x:MkS :: AmbiguousFieldOcc Id -- -- See also Note [Disambiguating record fields] in TcExpr. hsRecFields :: HsRecFields id arg -> [PostRn id id] hsRecFields rbinds = map (unLoc . hsRecFieldSel . unLoc) (rec_flds rbinds) -- Probably won't typecheck at once, things have changed :/ hsRecFieldsArgs :: HsRecFields id arg -> [arg] hsRecFieldsArgs rbinds = map (hsRecFieldArg . unLoc) (rec_flds rbinds) hsRecFieldSel :: HsRecField name arg -> Located (PostRn name name) hsRecFieldSel = fmap selectorFieldOcc . hsRecFieldLbl hsRecFieldId :: HsRecField Id arg -> Located Id hsRecFieldId = hsRecFieldSel hsRecUpdFieldRdr :: HsRecUpdField id -> Located RdrName hsRecUpdFieldRdr = fmap rdrNameAmbiguousFieldOcc . hsRecFieldLbl hsRecUpdFieldId :: HsRecField' (AmbiguousFieldOcc Id) arg -> Located Id hsRecUpdFieldId = fmap selectorFieldOcc . hsRecUpdFieldOcc hsRecUpdFieldOcc :: HsRecField' (AmbiguousFieldOcc Id) arg -> LFieldOcc Id hsRecUpdFieldOcc = fmap unambiguousFieldOcc . hsRecFieldLbl {- ************************************************************************ * * * Printing patterns * * ************************************************************************ -} instance (OutputableBndrId name) => Outputable (Pat name) where ppr = pprPat pprPatBndr :: OutputableBndr name => name -> SDoc pprPatBndr var -- Print with type info if -dppr-debug is on = getPprStyle $ \ sty -> if debugStyle sty then parens (pprBndr LambdaBind var) -- Could pass the site to pprPat -- but is it worth it? else pprPrefixOcc var pprParendLPat :: (OutputableBndrId name) => LPat name -> SDoc pprParendLPat (L _ p) = pprParendPat p pprParendPat :: (OutputableBndrId name) => Pat name -> SDoc pprParendPat p = sdocWithDynFlags $ \ dflags -> if need_parens dflags p then parens (pprPat p) else pprPat p where need_parens dflags p | CoPat {} <- p = gopt Opt_PrintTypecheckerElaboration dflags | otherwise = hsPatNeedsParens p -- For a CoPat we need parens if we are going to show it, which -- we do if -fprint-typechecker-elaboration is on (c.f. pprHsWrapper) -- But otherwise the CoPat is discarded, so it -- is the pattern inside that matters. Sigh. pprPat :: (OutputableBndrId name) => Pat name -> SDoc pprPat (VarPat (L _ var)) = pprPatBndr var pprPat (WildPat _) = char '_' pprPat (LazyPat pat) = char '~' <> pprParendLPat pat pprPat (BangPat pat) = char '!' <> pprParendLPat pat pprPat (AsPat name pat) = hcat [pprPrefixOcc (unLoc name), char '@', pprParendLPat pat] pprPat (ViewPat expr pat _) = hcat [pprLExpr expr, text " -> ", ppr pat] pprPat (ParPat pat) = parens (ppr pat) pprPat (LitPat s) = ppr s pprPat (NPat l Nothing _ _) = ppr l pprPat (NPat l (Just _) _ _) = char '-' <> ppr l pprPat (NPlusKPat n k _ _ _ _)= hcat [ppr n, char '+', ppr k] pprPat (SplicePat splice) = pprSplice splice pprPat (CoPat co pat _) = pprHsWrapper co (\parens -> if parens then pprParendPat pat else pprPat pat) pprPat (SigPatIn pat ty) = ppr pat <+> dcolon <+> ppr ty pprPat (SigPatOut pat ty) = ppr pat <+> dcolon <+> ppr ty pprPat (ListPat pats _ _) = brackets (interpp'SP pats) pprPat (PArrPat pats _) = paBrackets (interpp'SP pats) pprPat (TuplePat pats bx _) = tupleParens (boxityTupleSort bx) (pprWithCommas ppr pats) pprPat (SumPat pat alt arity _) = sumParens (pprAlternative ppr pat alt arity) pprPat (ConPatIn con details) = pprUserCon (unLoc con) details pprPat (ConPatOut { pat_con = con, pat_tvs = tvs, pat_dicts = dicts, pat_binds = binds, pat_args = details }) = sdocWithDynFlags $ \dflags -> -- Tiresome; in TcBinds.tcRhs we print out a -- typechecked Pat in an error message, -- and we want to make sure it prints nicely if gopt Opt_PrintTypecheckerElaboration dflags then ppr con <> braces (sep [ hsep (map pprPatBndr (tvs ++ dicts)) , ppr binds]) <+> pprConArgs details else pprUserCon (unLoc con) details pprUserCon :: (OutputableBndr con, OutputableBndrId id) => con -> HsConPatDetails id -> SDoc pprUserCon c (InfixCon p1 p2) = ppr p1 <+> pprInfixOcc c <+> ppr p2 pprUserCon c details = pprPrefixOcc c <+> pprConArgs details pprConArgs :: (OutputableBndrId id) => HsConPatDetails id -> SDoc pprConArgs (PrefixCon pats) = sep (map pprParendLPat pats) pprConArgs (InfixCon p1 p2) = sep [pprParendLPat p1, pprParendLPat p2] pprConArgs (RecCon rpats) = ppr rpats instance (Outputable arg) => Outputable (HsRecFields id arg) where ppr (HsRecFields { rec_flds = flds, rec_dotdot = Nothing }) = braces (fsep (punctuate comma (map ppr flds))) ppr (HsRecFields { rec_flds = flds, rec_dotdot = Just n }) = braces (fsep (punctuate comma (map ppr (take n flds) ++ [dotdot]))) where dotdot = text ".." <+> ifPprDebug (ppr (drop n flds)) instance (Outputable id, Outputable arg) => Outputable (HsRecField' id arg) where ppr (HsRecField { hsRecFieldLbl = f, hsRecFieldArg = arg, hsRecPun = pun }) = ppr f <+> (ppUnless pun $ equals <+> ppr arg) {- ************************************************************************ * * * Building patterns * * ************************************************************************ -} mkPrefixConPat :: DataCon -> [OutPat id] -> [Type] -> OutPat id -- Make a vanilla Prefix constructor pattern mkPrefixConPat dc pats tys = noLoc $ ConPatOut { pat_con = noLoc (RealDataCon dc), pat_tvs = [], pat_dicts = [], pat_binds = emptyTcEvBinds, pat_args = PrefixCon pats, pat_arg_tys = tys, pat_wrap = idHsWrapper } mkNilPat :: Type -> OutPat id mkNilPat ty = mkPrefixConPat nilDataCon [] [ty] mkCharLitPat :: SourceText -> Char -> OutPat id mkCharLitPat src c = mkPrefixConPat charDataCon [noLoc $ LitPat (HsCharPrim src c)] [] {- ************************************************************************ * * * Predicates for checking things about pattern-lists in EquationInfo * * * ************************************************************************ \subsection[Pat-list-predicates]{Look for interesting things in patterns} Unlike in the Wadler chapter, where patterns are either ``variables'' or ``constructors,'' here we distinguish between: \begin{description} \item[unfailable:] Patterns that cannot fail to match: variables, wildcards, and lazy patterns. These are the irrefutable patterns; the two other categories are refutable patterns. \item[constructor:] A non-literal constructor pattern (see next category). \item[literal patterns:] At least the numeric ones may be overloaded. \end{description} A pattern is in {\em exactly one} of the above three categories; `as' patterns are treated specially, of course. The 1.3 report defines what ``irrefutable'' and ``failure-free'' patterns are. -} isBangedPatBind :: HsBind id -> Bool isBangedPatBind (PatBind {pat_lhs = pat}) = isBangedLPat pat isBangedPatBind _ = False isBangedLPat :: LPat id -> Bool isBangedLPat (L _ (ParPat p)) = isBangedLPat p isBangedLPat (L _ (BangPat {})) = True isBangedLPat _ = False looksLazyPatBind :: HsBind id -> Bool -- Returns True of anything *except* -- a StrictHsBind (as above) or -- a VarPat -- In particular, returns True of a pattern binding with a compound pattern, like (I# x) -- Looks through AbsBinds looksLazyPatBind (PatBind { pat_lhs = p }) = looksLazyLPat p looksLazyPatBind (AbsBinds { abs_binds = binds }) = anyBag (looksLazyPatBind . unLoc) binds looksLazyPatBind (AbsBindsSig { abs_sig_bind = L _ bind }) = looksLazyPatBind bind looksLazyPatBind _ = False looksLazyLPat :: LPat id -> Bool looksLazyLPat (L _ (ParPat p)) = looksLazyLPat p looksLazyLPat (L _ (AsPat _ p)) = looksLazyLPat p looksLazyLPat (L _ (BangPat {})) = False looksLazyLPat (L _ (VarPat {})) = False looksLazyLPat (L _ (WildPat {})) = False looksLazyLPat _ = True isIrrefutableHsPat :: (OutputableBndrId id) => LPat id -> Bool -- (isIrrefutableHsPat p) is true if matching against p cannot fail, -- in the sense of falling through to the next pattern. -- (NB: this is not quite the same as the (silly) defn -- in 3.17.2 of the Haskell 98 report.) -- -- WARNING: isIrrefutableHsPat returns False if it's in doubt. -- Specifically on a ConPatIn, which is what it sees for a -- (LPat Name) in the renamer, it doesn't know the size of the -- constructor family, so it returns False. Result: only -- tuple patterns are considered irrefuable at the renamer stage. -- -- But if it returns True, the pattern is definitely irrefutable isIrrefutableHsPat pat = go pat where go (L _ pat) = go1 pat go1 (WildPat {}) = True go1 (VarPat {}) = True go1 (LazyPat {}) = True go1 (BangPat pat) = go pat go1 (CoPat _ pat _) = go1 pat go1 (ParPat pat) = go pat go1 (AsPat _ pat) = go pat go1 (ViewPat _ pat _) = go pat go1 (SigPatIn pat _) = go pat go1 (SigPatOut pat _) = go pat go1 (TuplePat pats _ _) = all go pats go1 (SumPat pat _ _ _) = go pat go1 (ListPat {}) = False go1 (PArrPat {}) = False -- ? go1 (ConPatIn {}) = False -- Conservative go1 (ConPatOut{ pat_con = L _ (RealDataCon con), pat_args = details }) = isJust (tyConSingleDataCon_maybe (dataConTyCon con)) -- NB: tyConSingleDataCon_maybe, *not* isProductTyCon, because -- the latter is false of existentials. See Trac #4439 && all go (hsConPatArgs details) go1 (ConPatOut{ pat_con = L _ (PatSynCon _pat) }) = False -- Conservative go1 (LitPat {}) = False go1 (NPat {}) = False go1 (NPlusKPat {}) = False -- We conservatively assume that no TH splices are irrefutable -- since we cannot know until the splice is evaluated. go1 (SplicePat {}) = False hsPatNeedsParens :: Pat a -> Bool hsPatNeedsParens (NPlusKPat {}) = True hsPatNeedsParens (SplicePat {}) = False hsPatNeedsParens (ConPatIn _ ds) = conPatNeedsParens ds hsPatNeedsParens p@(ConPatOut {}) = conPatNeedsParens (pat_args p) hsPatNeedsParens (SigPatIn {}) = True hsPatNeedsParens (SigPatOut {}) = True hsPatNeedsParens (ViewPat {}) = True hsPatNeedsParens (CoPat _ p _) = hsPatNeedsParens p hsPatNeedsParens (WildPat {}) = False hsPatNeedsParens (VarPat {}) = False hsPatNeedsParens (LazyPat {}) = False hsPatNeedsParens (BangPat {}) = False hsPatNeedsParens (ParPat {}) = False hsPatNeedsParens (AsPat {}) = False hsPatNeedsParens (TuplePat {}) = False hsPatNeedsParens (SumPat {}) = False hsPatNeedsParens (ListPat {}) = False hsPatNeedsParens (PArrPat {}) = False hsPatNeedsParens (LitPat {}) = False hsPatNeedsParens (NPat {}) = False conPatNeedsParens :: HsConDetails a b -> Bool conPatNeedsParens (PrefixCon {}) = False conPatNeedsParens (InfixCon {}) = True conPatNeedsParens (RecCon {}) = False {- % Collect all EvVars from all constructor patterns -} -- May need to add more cases collectEvVarsPats :: [Pat id] -> Bag EvVar collectEvVarsPats = unionManyBags . map collectEvVarsPat collectEvVarsLPat :: LPat id -> Bag EvVar collectEvVarsLPat (L _ pat) = collectEvVarsPat pat collectEvVarsPat :: Pat id -> Bag EvVar collectEvVarsPat pat = case pat of LazyPat p -> collectEvVarsLPat p AsPat _ p -> collectEvVarsLPat p ParPat p -> collectEvVarsLPat p BangPat p -> collectEvVarsLPat p ListPat ps _ _ -> unionManyBags $ map collectEvVarsLPat ps TuplePat ps _ _ -> unionManyBags $ map collectEvVarsLPat ps SumPat p _ _ _ -> collectEvVarsLPat p PArrPat ps _ -> unionManyBags $ map collectEvVarsLPat ps ConPatOut {pat_dicts = dicts, pat_args = args} -> unionBags (listToBag dicts) $ unionManyBags $ map collectEvVarsLPat $ hsConPatArgs args SigPatOut p _ -> collectEvVarsLPat p CoPat _ p _ -> collectEvVarsPat p ConPatIn _ _ -> panic "foldMapPatBag: ConPatIn" SigPatIn _ _ -> panic "foldMapPatBag: SigPatIn" _other_pat -> emptyBag