%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[PatSyntax]{Abstract Haskell syntax---patterns}
\begin{code}
-#include "HsVersions.h"
-
module HsPat (
- InPat(..),
- OutPat(..),
-
- irrefutablePat, irrefutablePats,
- failureFreePat,
- patsAreAllCons, isConPat,
- patsAreAllLits, isLitPat,
- collectPatBinders
+ Pat(..), InPat, OutPat, LPat,
+
+ HsConDetails(..), hsConArgs,
+
+ mkPrefixConPat, mkCharLitPat, mkNilPat,
+
+ isWildPat,
+ patsAreAllCons, isConPat, isSigPat,
+ patsAreAllLits, isLitPat, isIrrefutableHsPat
) where
-IMP_Ubiq()
+#include "HsVersions.h"
--- friends:
-import HsLit ( HsLit )
-IMPORT_DELOOPER(HsLoop) ( HsExpr )
+import {-# SOURCE #-} HsExpr ( SyntaxExpr )
+
+-- friends:
+import HsBinds ( DictBinds, emptyLHsBinds, pprLHsBinds )
+import HsLit ( HsLit(HsCharPrim), HsOverLit )
+import HsTypes ( LHsType, PostTcType )
+import BasicTypes ( Boxity, tupleParens )
-- others:
-import Id ( dataConTyCon, GenId )
-import Maybes ( maybeToBool )
-import Name ( pprSym, pprNonSym )
-import Outputable ( interppSP, interpp'SP, ifPprShowAll )
-import PprStyle ( PprStyle(..) )
-import Pretty
-import TyCon ( maybeTyConSingleCon )
-import PprType ( GenType )
+import PprCore ( {- instance OutputableBndr TyVar -} )
+import TysWiredIn ( nilDataCon, charDataCon, charTy )
+import Var ( TyVar )
+import DataCon ( DataCon, dataConTyCon )
+import TyCon ( isProductTyCon )
+import Outputable
+import Type ( Type )
+import SrcLoc ( Located(..), unLoc, noLoc )
\end{code}
-Patterns come in distinct before- and after-typechecking flavo(u)rs.
-\begin{code}
-data InPat name
- = WildPatIn -- wild card
- | VarPatIn name -- variable
- | LitPatIn HsLit -- literal
- | LazyPatIn (InPat name) -- lazy pattern
- | AsPatIn name -- as pattern
- (InPat name)
- | ConPatIn name -- constructed type
- [InPat name]
- | ConOpPatIn (InPat name)
- name
- (InPat name)
-
- -- We preserve prefix negation and parenthesis for the precedence parser.
-
- | NegPatIn (InPat name) -- negated pattern
- | ParPatIn (InPat name) -- parenthesised pattern
-
- | ListPatIn [InPat name] -- syntactic list
- -- must have >= 1 elements
- | TuplePatIn [InPat name] -- tuple
-
- | RecPatIn name -- record
- [(name, InPat name, Bool)] -- True <=> source used punning
-
-data OutPat tyvar uvar id
- = WildPat (GenType tyvar uvar) -- wild card
-
- | VarPat id -- variable (type is in the Id)
-
- | LazyPat (OutPat tyvar uvar id) -- lazy pattern
-
- | AsPat id -- as pattern
- (OutPat tyvar uvar id)
-
- | ConPat Id -- Constructor is always an Id
- (GenType tyvar uvar) -- the type of the pattern
- [OutPat tyvar uvar id]
-
- | ConOpPat (OutPat tyvar uvar id) -- just a special case...
- Id
- (OutPat tyvar uvar id)
- (GenType tyvar uvar)
- | ListPat -- syntactic list
- (GenType tyvar uvar) -- the type of the elements
- [OutPat tyvar uvar id]
-
- | TuplePat [OutPat tyvar uvar id] -- tuple
- -- UnitPat is TuplePat []
-
- | RecPat Id -- record constructor
- (GenType tyvar uvar) -- the type of the pattern
- [(Id, OutPat tyvar uvar id, Bool)] -- True <=> source used punning
-
- | LitPat -- Used for *non-overloaded* literal patterns:
- -- Int#, Char#, Int, Char, String, etc.
- HsLit
- (GenType tyvar uvar) -- type of pattern
-
- | NPat -- Used for *overloaded* literal patterns
- HsLit -- the literal is retained so that
- -- the desugarer can readily identify
- -- equations with identical literal-patterns
- (GenType tyvar uvar) -- type of pattern, t
- (HsExpr tyvar uvar id (OutPat tyvar uvar id))
- -- of type t -> Bool; detects match
+\begin{code}
+type InPat id = LPat id -- No 'Out' constructors
+type OutPat id = LPat id -- No 'In' constructors
+
+type LPat id = Located (Pat id)
+
+data Pat id
+ = ------------ Simple patterns ---------------
+ WildPat PostTcType -- Wild card
+ | VarPat id -- Variable
+ | VarPatOut id (DictBinds id) -- Used only for overloaded Ids; the
+ -- bindings give its overloaded instances
+ | LazyPat (LPat id) -- Lazy pattern
+ | AsPat (Located id) (LPat id) -- As pattern
+ | ParPat (LPat id) -- Parenthesised pattern
+
+ ------------ Lists, tuples, arrays ---------------
+ | ListPat [LPat id] -- Syntactic list
+ PostTcType -- The type of the elements
+
+ | TuplePat [LPat id] -- Tuple
+ Boxity -- UnitPat is TuplePat []
+ PostTcType
+ -- You might think that the PostTcType was redundant, 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
+
+ | PArrPat [LPat id] -- Syntactic parallel array
+ PostTcType -- The type of the elements
+
+ ------------ Constructor patterns ---------------
+ | ConPatIn (Located id)
+ (HsConDetails id (LPat id))
+
+ | ConPatOut (Located DataCon)
+ [TyVar] -- Existentially bound type variables
+ [id] -- Ditto dictionaries
+ (DictBinds id) -- Bindings involving those dictionaries
+ (HsConDetails id (LPat id))
+ Type -- The type of the pattern
+
+ ------------ Literal and n+k patterns ---------------
+ | LitPat HsLit -- Used for *non-overloaded* literal patterns:
+ -- Int#, Char#, Int, Char, String, etc.
+
+ | NPat (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
+ PostTcType -- Type of the pattern
+
+ | NPlusKPat (Located id) -- n+k pattern
+ (HsOverLit id) -- It'll always be an HsIntegral
+ (SyntaxExpr id) -- (>=) function, of type t->t->Bool
+ (SyntaxExpr id) -- Name of '-' (see RnEnv.lookupSyntaxName)
+
+ ------------ Generics ---------------
+ | TypePat (LHsType id) -- Type pattern for generic definitions
+ -- e.g f{| a+b |} = ...
+ -- These show up only in class declarations,
+ -- and should be a top-level pattern
+
+ ------------ Pattern type signatures ---------------
+ | SigPatIn (LPat id) -- Pattern with a type signature
+ (LHsType id)
+
+ | SigPatOut (LPat id) -- Pattern with a type signature
+ Type
+
+ ------------ Dictionary patterns (translation only) ---------------
| DictPat -- Used when destructing Dictionaries with an explicit case
[id] -- superclass dicts
[id] -- methods
\end{code}
+HsConDetails is use both for patterns and for data type declarations
+
\begin{code}
-instance (Outputable name, NamedThing name) => Outputable (InPat name) where
- ppr = pprInPat
-
-pprInPat :: (Outputable name, NamedThing name) => PprStyle -> InPat name -> Pretty
-
-pprInPat sty (WildPatIn) = ppStr "_"
-pprInPat sty (VarPatIn var) = pprNonSym sty var
-pprInPat sty (LitPatIn s) = ppr sty s
-pprInPat sty (LazyPatIn pat) = ppBeside (ppChar '~') (ppr sty pat)
-pprInPat sty (AsPatIn name pat)
- = ppBesides [ppLparen, ppr sty name, ppChar '@', ppr sty pat, ppRparen]
-
-pprInPat sty (ConPatIn c pats)
- = if null pats then
- ppr sty c
- else
- ppCat [ppr sty c, interppSP sty pats] -- ParPats put in the parens
-
-pprInPat sty (ConOpPatIn pat1 op pat2)
- = ppCat [ppr sty pat1, ppr sty op, ppr sty pat2] -- ParPats put in parens
-
- -- ToDo: use pprSym to print op (but this involves fiddling various
- -- contexts & I'm lazy...); *PatIns are *rarely* printed anyway... (WDP)
-
-pprInPat sty (NegPatIn pat)
- = let
- pp_pat = pprInPat sty pat
- in
- ppBeside (ppChar '-') (
- case pat of
- LitPatIn _ -> pp_pat
- _ -> ppParens pp_pat
- )
-
-pprInPat sty (ParPatIn pat)
- = ppParens (pprInPat sty pat)
-
-pprInPat sty (ListPatIn pats)
- = ppBesides [ppLbrack, interpp'SP sty pats, ppRbrack]
-pprInPat sty (TuplePatIn pats)
- = ppParens (interpp'SP sty pats)
-
-pprInPat sty (RecPatIn con rpats)
- = ppBesides [ppr sty con, ppSP, ppChar '{', ppInterleave ppComma (map (pp_rpat sty) rpats), ppChar '}']
- where
- pp_rpat PprForUser (v, _, True) = ppr PprForUser v
- pp_rpat sty (v, p, _) = ppCat [ppr sty v, ppStr "=", ppr sty p]
+data HsConDetails id arg
+ = PrefixCon [arg] -- C p1 p2 p3
+ | RecCon [(Located id, arg)] -- C { x = p1, y = p2 }
+ | InfixCon arg arg -- p1 `C` p2
+
+hsConArgs :: HsConDetails id arg -> [arg]
+hsConArgs (PrefixCon ps) = ps
+hsConArgs (RecCon fs) = map snd fs
+hsConArgs (InfixCon p1 p2) = [p1,p2]
\end{code}
+
+%************************************************************************
+%* *
+%* Printing patterns
+%* *
+%************************************************************************
+
\begin{code}
-instance (Eq tyvar, Outputable tyvar, Eq uvar, Outputable uvar,
- NamedThing id, Outputable id)
- => Outputable (OutPat tyvar uvar id) where
- ppr = pprOutPat
+instance (OutputableBndr 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
+ ppr var
+
+pprPat :: (OutputableBndr name) => Pat name -> SDoc
+
+pprPat (VarPat var) = pprPatBndr var
+pprPat (VarPatOut var bs) = parens (pprPatBndr var <+> braces (ppr bs))
+pprPat (WildPat _) = char '_'
+pprPat (LazyPat pat) = char '~' <> ppr pat
+pprPat (AsPat name pat) = parens (hcat [ppr name, char '@', ppr pat])
+pprPat (ParPat pat) = parens (ppr pat)
+
+pprPat (ListPat pats _) = brackets (interpp'SP pats)
+pprPat (PArrPat pats _) = pabrackets (interpp'SP pats)
+pprPat (TuplePat pats bx _) = tupleParens bx (interpp'SP pats)
+
+pprPat (ConPatIn con details) = pprUserCon con details
+pprPat (ConPatOut con tvs dicts binds details _)
+ = getPprStyle $ \ sty -> -- Tiresome; in TcBinds.tcRhs we print out a
+ if debugStyle sty then -- typechecked Pat in an error message,
+ -- and we want to make sure it prints nicely
+ ppr con <+> sep [ hsep (map pprPatBndr tvs) <+> hsep (map pprPatBndr dicts),
+ pprLHsBinds binds, pprConArgs details]
+ else pprUserCon con details
+
+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 (TypePat ty) = ptext SLIT("{|") <> ppr ty <> ptext SLIT("|}")
+pprPat (SigPatIn pat ty) = ppr pat <+> dcolon <+> ppr ty
+pprPat (SigPatOut pat ty) = ppr pat <+> dcolon <+> ppr ty
+pprPat (DictPat ds ms) = parens (sep [ptext SLIT("{-dict-}"),
+ brackets (interpp'SP ds),
+ brackets (interpp'SP ms)])
+
+pprUserCon c (InfixCon p1 p2) = ppr p1 <+> ppr c <+> ppr p2
+pprUserCon c details = ppr c <+> pprConArgs details
+
+pprConArgs (PrefixCon pats) = interppSP pats
+pprConArgs (InfixCon p1 p2) = interppSP [p1,p2]
+pprConArgs (RecCon rpats) = braces (hsep (punctuate comma (map (pp_rpat) rpats)))
+ where
+ pp_rpat (v, p) = hsep [ppr v, char '=', ppr p]
+
+
+-- add parallel array brackets around a document
+--
+pabrackets :: SDoc -> SDoc
+pabrackets p = ptext SLIT("[:") <> p <> ptext SLIT(":]")
\end{code}
-\begin{code}
-pprOutPat sty (WildPat ty) = ppChar '_'
-pprOutPat sty (VarPat var) = pprNonSym sty var
-pprOutPat sty (LazyPat pat) = ppBesides [ppChar '~', ppr sty pat]
-pprOutPat sty (AsPat name pat)
- = ppBesides [ppLparen, ppr sty name, ppChar '@', ppr sty pat, ppRparen]
-
-pprOutPat sty (ConPat name ty [])
- = ppBeside (ppr sty name)
- (ifPprShowAll sty (pprConPatTy sty ty))
-
-pprOutPat sty (ConPat name ty pats)
- = ppBesides [ppLparen, ppr sty name, ppSP,
- interppSP sty pats, ppRparen,
- ifPprShowAll sty (pprConPatTy sty ty) ]
-
-pprOutPat sty (ConOpPat pat1 op pat2 ty)
- = ppBesides [ppLparen, ppr sty pat1, ppSP, pprSym sty op, ppSP, ppr sty pat2, ppRparen]
-
-pprOutPat sty (ListPat ty pats)
- = ppBesides [ppLbrack, interpp'SP sty pats, ppRbrack]
-pprOutPat sty (TuplePat pats)
- = ppParens (interpp'SP sty pats)
-
-pprOutPat sty (RecPat con ty rpats)
- = ppBesides [ppr sty con, ppChar '{', ppInterleave ppComma (map (pp_rpat sty) rpats), ppChar '}']
- where
- pp_rpat PprForUser (v, _, True) = ppr PprForUser v
- pp_rpat sty (v, p, _) = ppCat [ppr sty v, ppStr "=", ppr sty p]
-pprOutPat sty (LitPat l ty) = ppr sty l -- ToDo: print more
-pprOutPat sty (NPat l ty e) = ppr sty l -- ToDo: print more
+%************************************************************************
+%* *
+%* Building patterns
+%* *
+%************************************************************************
+
+\begin{code}
+mkPrefixConPat :: DataCon -> [OutPat id] -> Type -> OutPat id
+-- Make a vanilla Prefix constructor pattern
+mkPrefixConPat dc pats ty = noLoc $ ConPatOut (noLoc dc) [] [] emptyLHsBinds (PrefixCon pats) ty
-pprOutPat sty (DictPat dicts methods)
- = ppSep [ppBesides [ppLparen, ppPStr SLIT("{-dict-}")],
- ppBracket (interpp'SP sty dicts),
- ppBesides [ppBracket (interpp'SP sty methods), ppRparen]]
+mkNilPat :: Type -> OutPat id
+mkNilPat ty = mkPrefixConPat nilDataCon [] ty
-pprConPatTy sty ty
- = ppParens (ppr sty ty)
+mkCharLitPat :: Char -> OutPat id
+mkCharLitPat c = mkPrefixConPat charDataCon [noLoc $ LitPat (HsCharPrim c)] charTy
\end{code}
+
%************************************************************************
%* *
-%* predicates for checking things about pattern-lists in EquationInfo *
+%* 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''
The 1.3 report defines what ``irrefutable'' and ``failure-free'' patterns are.
\begin{code}
-irrefutablePats :: [OutPat a b c] -> Bool
-irrefutablePats pat_list = all irrefutablePat pat_list
-
-irrefutablePat (AsPat _ pat) = irrefutablePat pat
-irrefutablePat (WildPat _) = True
-irrefutablePat (VarPat _) = True
-irrefutablePat (LazyPat _) = True
-irrefutablePat (DictPat ds ms) = (length ds + length ms) <= 1
-irrefutablePat other = False
-
-failureFreePat :: OutPat a b c -> Bool
-
-failureFreePat (WildPat _) = True
-failureFreePat (VarPat _) = True
-failureFreePat (LazyPat _) = True
-failureFreePat (AsPat _ pat) = failureFreePat pat
-failureFreePat (ConPat con tys pats) = only_con con && all failureFreePat pats
-failureFreePat (ConOpPat pat1 con pat2 _) = only_con con && failureFreePat pat1 && failureFreePat pat1
-failureFreePat (RecPat con _ fields) = only_con con && and [ failureFreePat pat | (_,pat,_) <- fields ]
-failureFreePat (ListPat _ _) = False
-failureFreePat (TuplePat pats) = all failureFreePat pats
-failureFreePat (DictPat _ _) = True
-failureFreePat other_pat = False -- Literals, NPat
-
-only_con con = maybeToBool (maybeTyConSingleCon (dataConTyCon con))
-\end{code}
+isWildPat (WildPat _) = True
+isWildPat other = False
-\begin{code}
-patsAreAllCons :: [OutPat a b c] -> Bool
+patsAreAllCons :: [Pat id] -> Bool
patsAreAllCons pat_list = all isConPat pat_list
-isConPat (AsPat _ pat) = isConPat pat
-isConPat (ConPat _ _ _) = True
-isConPat (ConOpPat _ _ _ _) = True
-isConPat (ListPat _ _) = True
-isConPat (TuplePat _) = True
-isConPat (RecPat _ _ _) = True
-isConPat (DictPat ds ms) = (length ds + length ms) > 1
-isConPat other = False
+isConPat (AsPat _ pat) = isConPat (unLoc pat)
+isConPat (ConPatIn _ _) = True
+isConPat (ConPatOut _ _ _ _ _ _) = True
+isConPat (ListPat _ _) = True
+isConPat (PArrPat _ _) = True
+isConPat (TuplePat _ _ _) = True
+isConPat (DictPat ds ms) = (length ds + length ms) > 1
+isConPat other = False
-patsAreAllLits :: [OutPat a b c] -> Bool
+isSigPat (SigPatIn _ _) = True
+isSigPat (SigPatOut _ _) = True
+isSigPat other = False
+
+patsAreAllLits :: [Pat id] -> Bool
patsAreAllLits pat_list = all isLitPat pat_list
-isLitPat (AsPat _ pat) = isLitPat pat
-isLitPat (LitPat _ _) = True
-isLitPat (NPat _ _ _) = True
-isLitPat other = False
+isLitPat (AsPat _ pat) = isLitPat (unLoc pat)
+isLitPat (LitPat _) = True
+isLitPat (NPat _ _ _ _) = True
+isLitPat (NPlusKPat _ _ _ _) = True
+isLitPat other = False
+
+isIrrefutableHsPat :: LPat id -> Bool
+-- This function returns False if it's in doubt; specifically
+-- on a ConPatIn it doesn't know the size of the constructor family
+-- 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 (VarPatOut _ _) = True
+ go1 (LazyPat pat) = True
+ go1 (ParPat pat) = go pat
+ go1 (AsPat _ pat) = go pat
+ go1 (SigPatIn pat _) = go pat
+ go1 (SigPatOut pat _) = go pat
+ go1 (TuplePat pats _ _) = all go pats
+ go1 (ListPat pats _) = False
+ go1 (PArrPat pats _) = False -- ?
+
+ go1 (ConPatIn _ _) = False -- Conservative
+ go1 (ConPatOut (L _ con) _ _ _ details _)
+ = isProductTyCon (dataConTyCon con)
+ && all go (hsConArgs details)
+
+ go1 (LitPat _) = False
+ go1 (NPat _ _ _ _) = False
+ go1 (NPlusKPat _ _ _ _) = False
+
+ go1 (TypePat _) = panic "isIrrefutableHsPat: type pattern"
+ go1 (DictPat _ _) = panic "isIrrefutableHsPat: type pattern"
\end{code}
-This function @collectPatBinders@ works with the ``collectBinders''
-functions for @HsBinds@, etc. The order in which the binders are
-collected is important; see @HsBinds.lhs@.
-\begin{code}
-collectPatBinders :: InPat a -> [a]
-
-collectPatBinders WildPatIn = []
-collectPatBinders (VarPatIn var) = [var]
-collectPatBinders (LitPatIn _) = []
-collectPatBinders (LazyPatIn pat) = collectPatBinders pat
-collectPatBinders (AsPatIn a pat) = a : collectPatBinders pat
-collectPatBinders (ConPatIn c pats) = concat (map collectPatBinders pats)
-collectPatBinders (ConOpPatIn p1 c p2)= collectPatBinders p1 ++ collectPatBinders p2
-collectPatBinders (NegPatIn pat) = collectPatBinders pat
-collectPatBinders (ParPatIn pat) = collectPatBinders pat
-collectPatBinders (ListPatIn pats) = concat (map collectPatBinders pats)
-collectPatBinders (TuplePatIn pats) = concat (map collectPatBinders pats)
-collectPatBinders (RecPatIn c fields) = concat (map (\ (f,pat,_) -> collectPatBinders pat) fields)
-\end{code}
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