2 % (c) The GRASP/AQUA Project, Glasgow University, 1997-1998
4 % Author: Juan J. Quintela <quintela@krilin.dc.fi.udc.es>
5 \section{Module @Check@ in @deSugar@}
10 module Check ( check , ExhaustivePat ) where
14 import TcHsSyn ( hsPatType )
15 import TcType ( tcTyConAppTyCon )
16 import DsUtils ( EquationInfo(..), MatchResult(..),
17 CanItFail(..), firstPat )
18 import MatchLit ( tidyLitPat, tidyNPat )
19 import Id ( Id, idType )
20 import DataCon ( DataCon, dataConTyCon, dataConOrigArgTys, dataConFieldLabels )
21 import Name ( Name, mkInternalName, getOccName, isDataSymOcc, getName, mkVarOcc )
23 import PrelNames ( unboundKey )
24 import TyCon ( tyConDataCons, tupleTyConBoxity, isTupleTyCon )
25 import BasicTypes ( Boxity(..) )
26 import SrcLoc ( noSrcLoc, Located(..), unLoc, noLoc )
28 import Util ( takeList, splitAtList, notNull )
32 #include "HsVersions.h"
35 This module performs checks about if one list of equations are:
40 To discover that we go through the list of equations in a tree-like fashion.
42 If you like theory, a similar algorithm is described in:
44 {\em Two Techniques for Compiling Lazy Pattern Matching},
46 INRIA Rocquencourt (RR-2385, 1994)
48 The algorithm is based on the first technique, but there are some differences:
50 \item We don't generate code
51 \item We have constructors and literals (not only literals as in the
53 \item We don't use directions, we must select the columns from
56 (By the way the second technique is really similar to the one used in
57 @Match.lhs@ to generate code)
59 This function takes the equations of a pattern and returns:
61 \item The patterns that are not recognized
62 \item The equations that are not overlapped
64 It simplify the patterns and then call @check'@ (the same semantics), and it
65 needs to reconstruct the patterns again ....
67 The problem appear with things like:
72 We want to put the two patterns with the same syntax, (prefix form) and
73 then all the constructors are equal:
75 f (: x (: y [])) = ....
78 (more about that in @simplify_eqns@)
80 We would prefer to have a @WarningPat@ of type @String@, but Strings and the
81 Pretty Printer are not friends.
83 We use @InPat@ in @WarningPat@ instead of @OutPat@
84 because we need to print the
85 warning messages in the same way they are introduced, i.e. if the user
90 He don't want a warning message written:
92 f (: x (: y [])) ........
94 Then we need to use InPats.
96 Juan Quintela 5 JUL 1998\\
97 User-friendliness and compiler writers are no friends.
101 type WarningPat = InPat Name
102 type ExhaustivePat = ([WarningPat], [(Name, [HsLit])])
104 type EqnSet = UniqSet EqnNo
107 check :: [EquationInfo] -> ([ExhaustivePat], [EquationInfo])
108 -- Second result is the shadowed equations
109 check qs = (untidy_warns, shadowed_eqns)
111 (warns, used_nos) = check' ([1..] `zip` map simplify_eqn qs)
112 untidy_warns = map untidy_exhaustive warns
113 shadowed_eqns = [eqn | (eqn,i) <- qs `zip` [1..],
114 not (i `elementOfUniqSet` used_nos)]
116 untidy_exhaustive :: ExhaustivePat -> ExhaustivePat
117 untidy_exhaustive ([pat], messages) =
118 ([untidy_no_pars pat], map untidy_message messages)
119 untidy_exhaustive (pats, messages) =
120 (map untidy_pars pats, map untidy_message messages)
122 untidy_message :: (Name, [HsLit]) -> (Name, [HsLit])
123 untidy_message (string, lits) = (string, map untidy_lit lits)
126 The function @untidy@ does the reverse work of the @simplify_pat@ funcion.
132 untidy_no_pars :: WarningPat -> WarningPat
133 untidy_no_pars p = untidy False p
135 untidy_pars :: WarningPat -> WarningPat
136 untidy_pars p = untidy True p
138 untidy :: NeedPars -> WarningPat -> WarningPat
139 untidy b (L loc p) = L loc (untidy' b p)
141 untidy' _ p@(WildPat _) = p
142 untidy' _ p@(VarPat name) = p
143 untidy' _ (LitPat lit) = LitPat (untidy_lit lit)
144 untidy' _ p@(ConPatIn name (PrefixCon [])) = p
145 untidy' b (ConPatIn name ps) = pars b (L loc (ConPatIn name (untidy_con ps)))
146 untidy' _ (ListPat pats ty) = ListPat (map untidy_no_pars pats) ty
147 untidy' _ (TuplePat pats boxed) = TuplePat (map untidy_no_pars pats) boxed
148 untidy' _ (PArrPat _ _) = panic "Check.untidy: Shouldn't get a parallel array here!"
149 untidy' _ (SigPatIn _ _) = panic "Check.untidy: SigPat"
151 untidy_con (PrefixCon pats) = PrefixCon (map untidy_pars pats)
152 untidy_con (InfixCon p1 p2) = InfixCon (untidy_pars p1) (untidy_pars p2)
153 untidy_con (RecCon bs) = RecCon [(f,untidy_pars p) | (f,p) <- bs]
155 pars :: NeedPars -> WarningPat -> Pat Name
156 pars True p = ParPat p
159 untidy_lit :: HsLit -> HsLit
160 untidy_lit (HsCharPrim c) = HsChar c
164 This equation is the same that check, the only difference is that the
165 boring work is done, that work needs to be done only once, this is
166 the reason top have two functions, check is the external interface,
167 @check'@ is called recursively.
169 There are several cases:
172 \item There are no equations: Everything is OK.
173 \item There are only one equation, that can fail, and all the patterns are
174 variables. Then that equation is used and the same equation is
176 \item All the patterns are variables, and the match can fail, there are
177 more equations then the results is the result of the rest of equations
178 and this equation is used also.
180 \item The general case, if all the patterns are variables (here the match
181 can't fail) then the result is that this equation is used and this
182 equation doesn't generate non-exhaustive cases.
184 \item In the general case, there can exist literals ,constructors or only
185 vars in the first column, we actuate in consequence.
192 check' :: [(EqnNo, EquationInfo)]
193 -> ([ExhaustivePat], -- Pattern scheme that might not be matched at all
194 EqnSet) -- Eqns that are used (others are overlapped)
196 check' [] = ([([],[])],emptyUniqSet)
198 check' ((n, EqnInfo { eqn_pats = ps, eqn_rhs = MatchResult can_fail _ }) : rs)
199 | first_eqn_all_vars && case can_fail of { CantFail -> True; CanFail -> False }
200 = ([], unitUniqSet n) -- One eqn, which can't fail
202 | first_eqn_all_vars && null rs -- One eqn, but it can fail
203 = ([(takeList ps (repeat nlWildPat),[])], unitUniqSet n)
205 | first_eqn_all_vars -- Several eqns, first can fail
206 = (pats, addOneToUniqSet indexs n)
208 first_eqn_all_vars = all_vars ps
209 (pats,indexs) = check' rs
212 | literals = split_by_literals qs
213 | constructors = split_by_constructor qs
214 | only_vars = first_column_only_vars qs
215 | otherwise = pprPanic "Check.check': Not implemented :-(" (ppr first_pats)
217 -- Note: RecPats will have been simplified to ConPats
219 first_pats = ASSERT2( okGroup qs, pprGroup qs ) map firstPatN qs
220 constructors = any is_con first_pats
221 literals = any is_lit first_pats
222 only_vars = all is_var first_pats
225 Here begins the code to deal with literals, we need to split the matrix
226 in different matrix beginning by each literal and a last matrix with the
230 split_by_literals :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet)
231 split_by_literals qs = process_literals used_lits qs
233 used_lits = get_used_lits qs
236 @process_explicit_literals@ is a function that process each literal that appears
237 in the column of the matrix.
240 process_explicit_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
241 process_explicit_literals lits qs = (concat pats, unionManyUniqSets indexs)
243 pats_indexs = map (\x -> construct_literal_matrix x qs) lits
244 (pats,indexs) = unzip pats_indexs
248 @process_literals@ calls @process_explicit_literals@ to deal with the literals
249 that appears in the matrix and deal also with the rest of the cases. It
250 must be one Variable to be complete.
254 process_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
255 process_literals used_lits qs
256 | null default_eqns = ([make_row_vars used_lits (head qs)] ++ pats,indexs)
257 | otherwise = (pats_default,indexs_default)
259 (pats,indexs) = process_explicit_literals used_lits qs
260 default_eqns = ASSERT2( okGroup qs, pprGroup qs )
261 [remove_var q | q <- qs, is_var (firstPatN q)]
262 (pats',indexs') = check' default_eqns
263 pats_default = [(nlWildPat:ps,constraints) | (ps,constraints) <- (pats')] ++ pats
264 indexs_default = unionUniqSets indexs' indexs
267 Here we have selected the literal and we will select all the equations that
268 begins for that literal and create a new matrix.
271 construct_literal_matrix :: HsLit -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
272 construct_literal_matrix lit qs =
273 (map (\ (xs,ys) -> (new_lit:xs,ys)) pats,indexs)
275 (pats,indexs) = (check' (remove_first_column_lit lit qs))
276 new_lit = nlLitPat lit
278 remove_first_column_lit :: HsLit
279 -> [(EqnNo, EquationInfo)]
280 -> [(EqnNo, EquationInfo)]
281 remove_first_column_lit lit qs
282 = ASSERT2( okGroup qs, pprGroup qs )
283 [(n, shift_pat eqn) | q@(n,eqn) <- qs, is_var_lit lit (firstPatN q)]
285 shift_pat eqn@(EqnInfo { eqn_pats = _:ps}) = eqn { eqn_pats = ps }
286 shift_pat eqn@(EqnInfo { eqn_pats = []}) = panic "Check.shift_var: no patterns"
289 This function splits the equations @qs@ in groups that deal with the
293 split_by_constructor :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet)
294 split_by_constructor qs
295 | notNull unused_cons = need_default_case used_cons unused_cons qs
296 | otherwise = no_need_default_case used_cons qs
298 used_cons = get_used_cons qs
299 unused_cons = get_unused_cons used_cons
302 The first column of the patterns matrix only have vars, then there is
306 first_column_only_vars :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
307 first_column_only_vars qs = (map (\ (xs,ys) -> (nlWildPat:xs,ys)) pats,indexs)
309 (pats, indexs) = check' (map remove_var qs)
312 This equation takes a matrix of patterns and split the equations by
313 constructor, using all the constructors that appears in the first column
314 of the pattern matching.
316 We can need a default clause or not ...., it depends if we used all the
317 constructors or not explicitly. The reasoning is similar to @process_literals@,
318 the difference is that here the default case is not always needed.
321 no_need_default_case :: [Pat Id] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
322 no_need_default_case cons qs = (concat pats, unionManyUniqSets indexs)
324 pats_indexs = map (\x -> construct_matrix x qs) cons
325 (pats,indexs) = unzip pats_indexs
327 need_default_case :: [Pat Id] -> [DataCon] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
328 need_default_case used_cons unused_cons qs
329 | null default_eqns = (pats_default_no_eqns,indexs)
330 | otherwise = (pats_default,indexs_default)
332 (pats,indexs) = no_need_default_case used_cons qs
333 default_eqns = ASSERT2( okGroup qs, pprGroup qs )
334 [remove_var q | q <- qs, is_var (firstPatN q)]
335 (pats',indexs') = check' default_eqns
336 pats_default = [(make_whole_con c:ps,constraints) |
337 c <- unused_cons, (ps,constraints) <- pats'] ++ pats
338 new_wilds = make_row_vars_for_constructor (head qs)
339 pats_default_no_eqns = [(make_whole_con c:new_wilds,[]) | c <- unused_cons] ++ pats
340 indexs_default = unionUniqSets indexs' indexs
342 construct_matrix :: Pat Id -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
343 construct_matrix con qs =
344 (map (make_con con) pats,indexs)
346 (pats,indexs) = (check' (remove_first_column con qs))
349 Here remove first column is more difficult that with literals due to the fact
350 that constructors can have arguments.
352 For instance, the matrix
364 remove_first_column :: Pat Id -- Constructor
365 -> [(EqnNo, EquationInfo)]
366 -> [(EqnNo, EquationInfo)]
367 remove_first_column (ConPatOut (L _ con) _ _ _ (PrefixCon con_pats) _) qs
368 = ASSERT2( okGroup qs, pprGroup qs )
369 [(n, shift_var eqn) | q@(n, eqn) <- qs, is_var_con con (firstPatN q)]
371 new_wilds = [WildPat (hsPatType arg_pat) | arg_pat <- con_pats]
372 shift_var eqn@(EqnInfo { eqn_pats = ConPatOut _ _ _ _ (PrefixCon ps') _ : ps})
373 = eqn { eqn_pats = map unLoc ps' ++ ps }
374 shift_var eqn@(EqnInfo { eqn_pats = WildPat _ : ps })
375 = eqn { eqn_pats = new_wilds ++ ps }
376 shift_var _ = panic "Check.Shift_var:No done"
378 make_row_vars :: [HsLit] -> (EqnNo, EquationInfo) -> ExhaustivePat
379 make_row_vars used_lits (_, EqnInfo { eqn_pats = pats})
380 = (nlVarPat new_var:takeList (tail pats) (repeat nlWildPat),[(new_var,used_lits)])
384 hash_x = mkInternalName unboundKey {- doesn't matter much -}
385 (mkVarOcc FSLIT("#x"))
388 make_row_vars_for_constructor :: (EqnNo, EquationInfo) -> [WarningPat]
389 make_row_vars_for_constructor (_, EqnInfo { eqn_pats = pats})
390 = takeList (tail pats) (repeat nlWildPat)
392 compare_cons :: Pat Id -> Pat Id -> Bool
393 compare_cons (ConPatOut (L _ id1) _ _ _ _ _) (ConPatOut (L _ id2) _ _ _ _ _) = id1 == id2
395 remove_dups :: [Pat Id] -> [Pat Id]
397 remove_dups (x:xs) | or (map (\y -> compare_cons x y) xs) = remove_dups xs
398 | otherwise = x : remove_dups xs
400 get_used_cons :: [(EqnNo, EquationInfo)] -> [Pat Id]
401 get_used_cons qs = remove_dups [pat | q <- qs, let pat = firstPatN q,
404 isConPatOut (ConPatOut {}) = True
405 isConPatOut other = False
407 remove_dups' :: [HsLit] -> [HsLit]
409 remove_dups' (x:xs) | x `elem` xs = remove_dups' xs
410 | otherwise = x : remove_dups' xs
413 get_used_lits :: [(EqnNo, EquationInfo)] -> [HsLit]
414 get_used_lits qs = remove_dups' all_literals
416 all_literals = get_used_lits' qs
418 get_used_lits' :: [(EqnNo, EquationInfo)] -> [HsLit]
419 get_used_lits' [] = []
420 get_used_lits' (q:qs)
421 | Just lit <- get_lit (firstPatN q) = lit : get_used_lits' qs
422 | otherwise = get_used_lits qs
424 get_lit :: Pat id -> Maybe HsLit
425 -- Get a representative HsLit to stand for the OverLit
426 -- It doesn't matter which one, because they will only be compared
427 -- with other HsLits gotten in the same way
428 get_lit (LitPat lit) = Just lit
429 get_lit (NPat (HsIntegral i _) mb _ _) = Just (HsIntPrim (mb_neg mb i))
430 get_lit (NPat (HsFractional f _) mb _ _) = Just (HsFloatPrim (mb_neg mb f))
431 get_lit other_pat = Nothing
433 mb_neg :: Num a => Maybe b -> a -> a
435 mb_neg (Just _) v = -v
437 get_unused_cons :: [Pat Id] -> [DataCon]
438 get_unused_cons used_cons = unused_cons
440 (ConPatOut _ _ _ _ _ ty) = head used_cons
441 ty_con = tcTyConAppTyCon ty -- Newtype observable
442 all_cons = tyConDataCons ty_con
443 used_cons_as_id = map (\ (ConPatOut (L _ d) _ _ _ _ _) -> d) used_cons
444 unused_cons = uniqSetToList
445 (mkUniqSet all_cons `minusUniqSet` mkUniqSet used_cons_as_id)
447 all_vars :: [Pat Id] -> Bool
449 all_vars (WildPat _:ps) = all_vars ps
452 remove_var :: (EqnNo, EquationInfo) -> (EqnNo, EquationInfo)
453 remove_var (n, eqn@(EqnInfo { eqn_pats = WildPat _ : ps})) = (n, eqn { eqn_pats = ps })
454 remove_var _ = panic "Check.remove_var: equation does not begin with a variable"
456 -----------------------
457 eqnPats :: (EqnNo, EquationInfo) -> [Pat Id]
458 eqnPats (_, eqn) = eqn_pats eqn
460 okGroup :: [(EqnNo, EquationInfo)] -> Bool
461 -- True if all equations have at least one pattern, and
462 -- all have the same number of patterns
464 okGroup (e:es) = n_pats > 0 && and [length (eqnPats e) == n_pats | e <- es]
466 n_pats = length (eqnPats e)
469 pprGroup es = vcat (map pprEqnInfo es)
470 pprEqnInfo e = ppr (eqnPats e)
473 firstPatN :: (EqnNo, EquationInfo) -> Pat Id
474 firstPatN (_, eqn) = firstPat eqn
476 is_con :: Pat Id -> Bool
477 is_con (ConPatOut _ _ _ _ _ _) = True
480 is_lit :: Pat Id -> Bool
481 is_lit (LitPat _) = True
482 is_lit (NPat _ _ _ _) = True
485 is_var :: Pat Id -> Bool
486 is_var (WildPat _) = True
489 is_var_con :: DataCon -> Pat Id -> Bool
490 is_var_con con (WildPat _) = True
491 is_var_con con (ConPatOut (L _ id) _ _ _ _ _) | id == con = True
492 is_var_con con _ = False
494 is_var_lit :: HsLit -> Pat Id -> Bool
495 is_var_lit lit (WildPat _) = True
497 | Just lit' <- get_lit pat = lit == lit'
501 The difference beteewn @make_con@ and @make_whole_con@ is that
502 @make_wole_con@ creates a new constructor with all their arguments, and
503 @make_con@ takes a list of argumntes, creates the contructor getting their
504 arguments from the list. See where \fbox{\ ???\ } are used for details.
506 We need to reconstruct the patterns (make the constructors infix and
507 similar) at the same time that we create the constructors.
509 You can tell tuple constructors using
513 You can see if one constructor is infix with this clearer code :-))))))))))
515 Lex.isLexConSym (Name.occNameString (Name.getOccName con))
518 Rather clumsy but it works. (Simon Peyton Jones)
521 We don't mind the @nilDataCon@ because it doesn't change the way to
522 print the messsage, we are searching only for things like: @[1,2,3]@,
525 In @reconstruct_pat@ we want to ``undo'' the work
526 that we have done in @simplify_pat@.
529 @((,) x y)@ & returns to be & @(x, y)@
530 \\ @((:) x xs)@ & returns to be & @(x:xs)@
531 \\ @(x:(...:[])@ & returns to be & @[x,...]@
534 The difficult case is the third one becouse we need to follow all the
535 contructors until the @[]@ to know that we need to use the second case,
536 not the second. \fbox{\ ???\ }
539 isInfixCon con = isDataSymOcc (getOccName con)
541 is_nil (ConPatIn con (PrefixCon [])) = unLoc con == getName nilDataCon
544 is_list (ListPat _ _) = True
547 return_list id q = id == consDataCon && (is_nil q || is_list q)
549 make_list p q | is_nil q = ListPat [p] placeHolderType
550 make_list p (ListPat ps ty) = ListPat (p:ps) ty
551 make_list _ _ = panic "Check.make_list: Invalid argument"
553 make_con :: Pat Id -> ExhaustivePat -> ExhaustivePat
554 make_con (ConPatOut (L _ id) _ _ _ _ _) (lp:lq:ps, constraints)
555 | return_list id q = (noLoc (make_list lp q) : ps, constraints)
556 | isInfixCon id = (nlInfixConPat (getName id) lp lq : ps, constraints)
559 make_con (ConPatOut (L _ id) _ _ _ (PrefixCon pats) _) (ps, constraints)
560 | isTupleTyCon tc = (noLoc (TuplePat pats_con (tupleTyConBoxity tc)) : rest_pats, constraints)
561 | isPArrFakeCon id = (noLoc (PArrPat pats_con placeHolderType) : rest_pats, constraints)
562 | otherwise = (nlConPat name pats_con : rest_pats, constraints)
565 (pats_con, rest_pats) = splitAtList pats ps
568 -- reconstruct parallel array pattern
570 -- * don't check for the type only; we need to make sure that we are really
571 -- dealing with one of the fake constructors and not with the real
574 make_whole_con :: DataCon -> WarningPat
575 make_whole_con con | isInfixCon con = nlInfixConPat name nlWildPat nlWildPat
576 | otherwise = nlConPat name pats
579 pats = [nlWildPat | t <- dataConOrigArgTys con]
582 This equation makes the same thing as @tidy@ in @Match.lhs@, the
583 difference is that here we can do all the tidy in one place and in the
584 @Match@ tidy it must be done one column each time due to bookkeeping
589 simplify_eqn :: EquationInfo -> EquationInfo
590 simplify_eqn eqn = eqn { eqn_pats = map simplify_pat (eqn_pats eqn),
591 eqn_rhs = simplify_rhs (eqn_rhs eqn) }
593 -- Horrible hack. The simplify_pat stuff converts NPlusK pats to WildPats
594 -- which of course loses the info that they can fail to match. So we
595 -- stick in a CanFail as if it were a guard.
596 -- The Right Thing to do is for the whole system to treat NPlusK pats properly
597 simplify_rhs (MatchResult can_fail body)
598 | any has_nplusk_pat (eqn_pats eqn) = MatchResult CanFail body
599 | otherwise = MatchResult can_fail body
601 has_nplusk_lpat :: LPat Id -> Bool
602 has_nplusk_lpat (L _ p) = has_nplusk_pat p
604 has_nplusk_pat :: Pat Id -> Bool
605 has_nplusk_pat (NPlusKPat _ _ _ _) = True
606 has_nplusk_pat (ParPat p) = has_nplusk_lpat p
607 has_nplusk_pat (AsPat _ p) = has_nplusk_lpat p
608 has_nplusk_pat (SigPatOut p _ ) = has_nplusk_lpat p
609 has_nplusk_pat (ConPatOut _ _ _ _ ps ty) = any has_nplusk_lpat (hsConArgs ps)
610 has_nplusk_pat (ListPat ps _) = any has_nplusk_lpat ps
611 has_nplusk_pat (TuplePat ps _) = any has_nplusk_lpat ps
612 has_nplusk_pat (PArrPat ps _) = any has_nplusk_lpat ps
613 has_nplusk_pat (LazyPat p) = False
614 has_nplusk_pat p = False -- VarPat, VarPatOut, WildPat, LitPat, NPat, TypePat, DictPat
616 simplify_lpat :: LPat Id -> LPat Id
617 simplify_lpat p = fmap simplify_pat p
619 simplify_pat :: Pat Id -> Pat Id
620 simplify_pat pat@(WildPat gt) = pat
621 simplify_pat (VarPat id) = WildPat (idType id)
622 simplify_pat (VarPatOut id _) = WildPat (idType id) -- Ignore the bindings
623 simplify_pat (ParPat p) = unLoc (simplify_lpat p)
624 simplify_pat (LazyPat p) = unLoc (simplify_lpat p)
625 simplify_pat (AsPat id p) = unLoc (simplify_lpat p)
626 simplify_pat (SigPatOut p _) = unLoc (simplify_lpat p) -- I'm not sure this is right
628 simplify_pat (ConPatOut (L loc id) tvs dicts binds ps ty)
629 = ConPatOut (L loc id) tvs dicts binds (simplify_con id ps) ty
631 simplify_pat (ListPat ps ty) =
632 unLoc $ foldr (\ x y -> mkPrefixConPat consDataCon [x,y] list_ty)
634 (map simplify_lpat ps)
635 where list_ty = mkListTy ty
637 -- introduce fake parallel array constructors to be able to handle parallel
638 -- arrays with the existing machinery for constructor pattern
640 simplify_pat (PArrPat ps ty)
641 = mk_simple_con_pat (parrFakeCon (length ps))
642 (PrefixCon (map simplify_lpat ps))
645 simplify_pat (TuplePat ps boxity)
646 = mk_simple_con_pat (tupleCon boxity arity)
647 (PrefixCon (map simplify_lpat ps))
648 (mkTupleTy boxity arity (map hsPatType ps))
652 -- unpack string patterns fully, so we can see when they overlap with
653 -- each other, or even explicit lists of Chars.
654 simplify_pat pat@(LitPat (HsString s)) =
655 foldr (\c pat -> mk_simple_con_pat consDataCon (PrefixCon [mk_char_lit c,noLoc pat]) stringTy)
656 (mk_simple_con_pat nilDataCon (PrefixCon []) stringTy) (unpackFS s)
658 mk_char_lit c = noLoc (mk_simple_con_pat charDataCon (PrefixCon [nlLitPat (HsCharPrim c)]) charTy)
660 simplify_pat pat@(LitPat lit) = unLoc (tidyLitPat lit (noLoc pat))
662 simplify_pat pat@(NPat lit mb_neg _ lit_ty) = unLoc (tidyNPat lit mb_neg lit_ty (noLoc pat))
664 simplify_pat (NPlusKPat id hslit hsexpr1 hsexpr2)
665 = WildPat (idType (unLoc id))
667 simplify_pat (DictPat dicts methods)
668 = case num_of_d_and_ms of
669 0 -> simplify_pat (TuplePat [] Boxed)
670 1 -> simplify_pat (head dict_and_method_pats)
671 _ -> simplify_pat (TuplePat (map noLoc dict_and_method_pats) Boxed)
673 num_of_d_and_ms = length dicts + length methods
674 dict_and_method_pats = map VarPat (dicts ++ methods)
676 mk_simple_con_pat con args ty = ConPatOut (noLoc con) [] [] emptyLHsBinds args ty
679 simplify_con con (PrefixCon ps) = PrefixCon (map simplify_lpat ps)
680 simplify_con con (InfixCon p1 p2) = PrefixCon [simplify_lpat p1, simplify_lpat p2]
681 simplify_con con (RecCon fs)
682 | null fs = PrefixCon [nlWildPat | t <- dataConOrigArgTys con]
683 -- Special case for null patterns; maybe not a record at all
684 | otherwise = PrefixCon (map (simplify_lpat.snd) all_pats)
686 -- pad out all the missing fields with WildPats.
687 field_pats = map (\ f -> (f, nlWildPat)) (dataConFieldLabels con)
688 all_pats = foldr (\ (id,p) acc -> insertNm (getName (unLoc id)) p acc)
691 insertNm nm p [] = [(nm,p)]
692 insertNm nm p (x@(n,_):xs)
693 | nm == n = (nm,p):xs
694 | otherwise = x : insertNm nm p xs