2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1997-1998
5 % Author: Juan J. Quintela <quintela@krilin.dc.fi.udc.es>
8 module Check ( check , ExhaustivePat ) where
10 #include "HsVersions.h"
30 This module performs checks about if one list of equations are:
35 To discover that we go through the list of equations in a tree-like fashion.
37 If you like theory, a similar algorithm is described in:
39 {\em Two Techniques for Compiling Lazy Pattern Matching},
41 INRIA Rocquencourt (RR-2385, 1994)
43 The algorithm is based on the first technique, but there are some differences:
45 \item We don't generate code
46 \item We have constructors and literals (not only literals as in the
48 \item We don't use directions, we must select the columns from
51 (By the way the second technique is really similar to the one used in
52 @Match.lhs@ to generate code)
54 This function takes the equations of a pattern and returns:
56 \item The patterns that are not recognized
57 \item The equations that are not overlapped
59 It simplify the patterns and then call @check'@ (the same semantics), and it
60 needs to reconstruct the patterns again ....
62 The problem appear with things like:
67 We want to put the two patterns with the same syntax, (prefix form) and
68 then all the constructors are equal:
70 f (: x (: y [])) = ....
73 (more about that in @simplify_eqns@)
75 We would prefer to have a @WarningPat@ of type @String@, but Strings and the
76 Pretty Printer are not friends.
78 We use @InPat@ in @WarningPat@ instead of @OutPat@
79 because we need to print the
80 warning messages in the same way they are introduced, i.e. if the user
85 He don't want a warning message written:
87 f (: x (: y [])) ........
89 Then we need to use InPats.
91 Juan Quintela 5 JUL 1998\\
92 User-friendliness and compiler writers are no friends.
96 type WarningPat = InPat Name
97 type ExhaustivePat = ([WarningPat], [(Name, [HsLit])])
99 type EqnSet = UniqSet EqnNo
102 check :: [EquationInfo] -> ([ExhaustivePat], [EquationInfo])
103 -- Second result is the shadowed equations
104 check qs = (untidy_warns, shadowed_eqns)
106 (warns, used_nos) = check' ([1..] `zip` map simplify_eqn qs)
107 untidy_warns = map untidy_exhaustive warns
108 shadowed_eqns = [eqn | (eqn,i) <- qs `zip` [1..],
109 not (i `elementOfUniqSet` used_nos)]
111 untidy_exhaustive :: ExhaustivePat -> ExhaustivePat
112 untidy_exhaustive ([pat], messages) =
113 ([untidy_no_pars pat], map untidy_message messages)
114 untidy_exhaustive (pats, messages) =
115 (map untidy_pars pats, map untidy_message messages)
117 untidy_message :: (Name, [HsLit]) -> (Name, [HsLit])
118 untidy_message (string, lits) = (string, map untidy_lit lits)
121 The function @untidy@ does the reverse work of the @simplify_pat@ funcion.
127 untidy_no_pars :: WarningPat -> WarningPat
128 untidy_no_pars p = untidy False p
130 untidy_pars :: WarningPat -> WarningPat
131 untidy_pars p = untidy True p
133 untidy :: NeedPars -> WarningPat -> WarningPat
134 untidy b (L loc p) = L loc (untidy' b p)
136 untidy' _ p@(WildPat _) = p
137 untidy' _ p@(VarPat name) = p
138 untidy' _ (LitPat lit) = LitPat (untidy_lit lit)
139 untidy' _ p@(ConPatIn name (PrefixCon [])) = p
140 untidy' b (ConPatIn name ps) = pars b (L loc (ConPatIn name (untidy_con ps)))
141 untidy' _ (ListPat pats ty) = ListPat (map untidy_no_pars pats) ty
142 untidy' _ (TuplePat pats box ty) = TuplePat (map untidy_no_pars pats) box ty
143 untidy' _ (PArrPat _ _) = panic "Check.untidy: Shouldn't get a parallel array here!"
144 untidy' _ (SigPatIn _ _) = panic "Check.untidy: SigPat"
146 untidy_con (PrefixCon pats) = PrefixCon (map untidy_pars pats)
147 untidy_con (InfixCon p1 p2) = InfixCon (untidy_pars p1) (untidy_pars p2)
148 untidy_con (RecCon (HsRecFields flds dd))
149 = RecCon (HsRecFields [ fld { hsRecFieldArg = untidy_pars (hsRecFieldArg fld) }
152 pars :: NeedPars -> WarningPat -> Pat Name
153 pars True p = ParPat p
156 untidy_lit :: HsLit -> HsLit
157 untidy_lit (HsCharPrim c) = HsChar c
161 This equation is the same that check, the only difference is that the
162 boring work is done, that work needs to be done only once, this is
163 the reason top have two functions, check is the external interface,
164 @check'@ is called recursively.
166 There are several cases:
169 \item There are no equations: Everything is OK.
170 \item There are only one equation, that can fail, and all the patterns are
171 variables. Then that equation is used and the same equation is
173 \item All the patterns are variables, and the match can fail, there are
174 more equations then the results is the result of the rest of equations
175 and this equation is used also.
177 \item The general case, if all the patterns are variables (here the match
178 can't fail) then the result is that this equation is used and this
179 equation doesn't generate non-exhaustive cases.
181 \item In the general case, there can exist literals ,constructors or only
182 vars in the first column, we actuate in consequence.
189 check' :: [(EqnNo, EquationInfo)]
190 -> ([ExhaustivePat], -- Pattern scheme that might not be matched at all
191 EqnSet) -- Eqns that are used (others are overlapped)
193 check' [] = ([([],[])],emptyUniqSet)
195 check' ((n, EqnInfo { eqn_pats = ps, eqn_rhs = MatchResult can_fail _ }) : rs)
196 | first_eqn_all_vars && case can_fail of { CantFail -> True; CanFail -> False }
197 = ([], unitUniqSet n) -- One eqn, which can't fail
199 | first_eqn_all_vars && null rs -- One eqn, but it can fail
200 = ([(takeList ps (repeat nlWildPat),[])], unitUniqSet n)
202 | first_eqn_all_vars -- Several eqns, first can fail
203 = (pats, addOneToUniqSet indexs n)
205 first_eqn_all_vars = all_vars ps
206 (pats,indexs) = check' rs
209 | literals = split_by_literals qs
210 | constructors = split_by_constructor qs
211 | only_vars = first_column_only_vars qs
212 | otherwise = pprPanic "Check.check': Not implemented :-(" (ppr first_pats)
214 -- Note: RecPats will have been simplified to ConPats
216 first_pats = ASSERT2( okGroup qs, pprGroup qs ) map firstPatN qs
217 constructors = any is_con first_pats
218 literals = any is_lit first_pats
219 only_vars = all is_var first_pats
222 Here begins the code to deal with literals, we need to split the matrix
223 in different matrix beginning by each literal and a last matrix with the
227 split_by_literals :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet)
228 split_by_literals qs = process_literals used_lits qs
230 used_lits = get_used_lits qs
233 @process_explicit_literals@ is a function that process each literal that appears
234 in the column of the matrix.
237 process_explicit_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
238 process_explicit_literals lits qs = (concat pats, unionManyUniqSets indexs)
240 pats_indexs = map (\x -> construct_literal_matrix x qs) lits
241 (pats,indexs) = unzip pats_indexs
245 @process_literals@ calls @process_explicit_literals@ to deal with the literals
246 that appears in the matrix and deal also with the rest of the cases. It
247 must be one Variable to be complete.
251 process_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
252 process_literals used_lits qs
253 | null default_eqns = ASSERT( not (null qs) ) ([make_row_vars used_lits (head qs)] ++ pats,indexs)
254 | otherwise = (pats_default,indexs_default)
256 (pats,indexs) = process_explicit_literals used_lits qs
257 default_eqns = ASSERT2( okGroup qs, pprGroup qs )
258 [remove_var q | q <- qs, is_var (firstPatN q)]
259 (pats',indexs') = check' default_eqns
260 pats_default = [(nlWildPat:ps,constraints) | (ps,constraints) <- (pats')] ++ pats
261 indexs_default = unionUniqSets indexs' indexs
264 Here we have selected the literal and we will select all the equations that
265 begins for that literal and create a new matrix.
268 construct_literal_matrix :: HsLit -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
269 construct_literal_matrix lit qs =
270 (map (\ (xs,ys) -> (new_lit:xs,ys)) pats,indexs)
272 (pats,indexs) = (check' (remove_first_column_lit lit qs))
273 new_lit = nlLitPat lit
275 remove_first_column_lit :: HsLit
276 -> [(EqnNo, EquationInfo)]
277 -> [(EqnNo, EquationInfo)]
278 remove_first_column_lit lit qs
279 = ASSERT2( okGroup qs, pprGroup qs )
280 [(n, shift_pat eqn) | q@(n,eqn) <- qs, is_var_lit lit (firstPatN q)]
282 shift_pat eqn@(EqnInfo { eqn_pats = _:ps}) = eqn { eqn_pats = ps }
283 shift_pat eqn@(EqnInfo { eqn_pats = []}) = panic "Check.shift_var: no patterns"
286 This function splits the equations @qs@ in groups that deal with the
290 split_by_constructor :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet)
291 split_by_constructor qs
292 | notNull unused_cons = need_default_case used_cons unused_cons qs
293 | otherwise = no_need_default_case used_cons qs
295 used_cons = get_used_cons qs
296 unused_cons = get_unused_cons used_cons
299 The first column of the patterns matrix only have vars, then there is
303 first_column_only_vars :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
304 first_column_only_vars qs = (map (\ (xs,ys) -> (nlWildPat:xs,ys)) pats,indexs)
306 (pats, indexs) = check' (map remove_var qs)
309 This equation takes a matrix of patterns and split the equations by
310 constructor, using all the constructors that appears in the first column
311 of the pattern matching.
313 We can need a default clause or not ...., it depends if we used all the
314 constructors or not explicitly. The reasoning is similar to @process_literals@,
315 the difference is that here the default case is not always needed.
318 no_need_default_case :: [Pat Id] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
319 no_need_default_case cons qs = (concat pats, unionManyUniqSets indexs)
321 pats_indexs = map (\x -> construct_matrix x qs) cons
322 (pats,indexs) = unzip pats_indexs
324 need_default_case :: [Pat Id] -> [DataCon] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
325 need_default_case used_cons unused_cons qs
326 | null default_eqns = (pats_default_no_eqns,indexs)
327 | otherwise = (pats_default,indexs_default)
329 (pats,indexs) = no_need_default_case used_cons qs
330 default_eqns = ASSERT2( okGroup qs, pprGroup qs )
331 [remove_var q | q <- qs, is_var (firstPatN q)]
332 (pats',indexs') = check' default_eqns
333 pats_default = [(make_whole_con c:ps,constraints) |
334 c <- unused_cons, (ps,constraints) <- pats'] ++ pats
335 new_wilds = ASSERT( not (null qs) ) make_row_vars_for_constructor (head qs)
336 pats_default_no_eqns = [(make_whole_con c:new_wilds,[]) | c <- unused_cons] ++ pats
337 indexs_default = unionUniqSets indexs' indexs
339 construct_matrix :: Pat Id -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
340 construct_matrix con qs =
341 (map (make_con con) pats,indexs)
343 (pats,indexs) = (check' (remove_first_column con qs))
346 Here remove first column is more difficult that with literals due to the fact
347 that constructors can have arguments.
349 For instance, the matrix
361 remove_first_column :: Pat Id -- Constructor
362 -> [(EqnNo, EquationInfo)]
363 -> [(EqnNo, EquationInfo)]
364 remove_first_column (ConPatOut{ pat_con = L _ con, pat_args = PrefixCon con_pats }) qs
365 = ASSERT2( okGroup qs, pprGroup qs )
366 [(n, shift_var eqn) | q@(n, eqn) <- qs, is_var_con con (firstPatN q)]
368 new_wilds = [WildPat (hsLPatType arg_pat) | arg_pat <- con_pats]
369 shift_var eqn@(EqnInfo { eqn_pats = ConPatOut{ pat_args = PrefixCon ps' } : ps})
370 = eqn { eqn_pats = map unLoc ps' ++ ps }
371 shift_var eqn@(EqnInfo { eqn_pats = WildPat _ : ps })
372 = eqn { eqn_pats = new_wilds ++ ps }
373 shift_var _ = panic "Check.Shift_var:No done"
375 make_row_vars :: [HsLit] -> (EqnNo, EquationInfo) -> ExhaustivePat
376 make_row_vars used_lits (_, EqnInfo { eqn_pats = pats})
377 = (nlVarPat new_var:takeList (tail pats) (repeat nlWildPat),[(new_var,used_lits)])
381 hash_x = mkInternalName unboundKey {- doesn't matter much -}
382 (mkVarOccFS FSLIT("#x"))
385 make_row_vars_for_constructor :: (EqnNo, EquationInfo) -> [WarningPat]
386 make_row_vars_for_constructor (_, EqnInfo { eqn_pats = pats})
387 = takeList (tail pats) (repeat nlWildPat)
389 compare_cons :: Pat Id -> Pat Id -> Bool
390 compare_cons (ConPatOut{ pat_con = L _ id1 }) (ConPatOut { pat_con = L _ id2 }) = id1 == id2
392 remove_dups :: [Pat Id] -> [Pat Id]
394 remove_dups (x:xs) | or (map (\y -> compare_cons x y) xs) = remove_dups xs
395 | otherwise = x : remove_dups xs
397 get_used_cons :: [(EqnNo, EquationInfo)] -> [Pat Id]
398 get_used_cons qs = remove_dups [pat | q <- qs, let pat = firstPatN q,
401 isConPatOut (ConPatOut {}) = True
402 isConPatOut other = False
404 remove_dups' :: [HsLit] -> [HsLit]
406 remove_dups' (x:xs) | x `elem` xs = remove_dups' xs
407 | otherwise = x : remove_dups' xs
410 get_used_lits :: [(EqnNo, EquationInfo)] -> [HsLit]
411 get_used_lits qs = remove_dups' all_literals
413 all_literals = get_used_lits' qs
415 get_used_lits' :: [(EqnNo, EquationInfo)] -> [HsLit]
416 get_used_lits' [] = []
417 get_used_lits' (q:qs)
418 | Just lit <- get_lit (firstPatN q) = lit : get_used_lits' qs
419 | otherwise = get_used_lits qs
421 get_lit :: Pat id -> Maybe HsLit
422 -- Get a representative HsLit to stand for the OverLit
423 -- It doesn't matter which one, because they will only be compared
424 -- with other HsLits gotten in the same way
425 get_lit (LitPat lit) = Just lit
426 get_lit (NPat (HsIntegral i _) mb _ _) = Just (HsIntPrim (mb_neg mb i))
427 get_lit (NPat (HsFractional f _) mb _ _) = Just (HsFloatPrim (mb_neg mb f))
428 get_lit (NPat (HsIsString s _) _ _ _) = Just (HsStringPrim s)
429 get_lit other_pat = Nothing
431 mb_neg :: Num a => Maybe b -> a -> a
433 mb_neg (Just _) v = -v
435 get_unused_cons :: [Pat Id] -> [DataCon]
436 get_unused_cons used_cons = ASSERT( not (null used_cons) ) unused_cons
438 (ConPatOut { pat_con = l_con, pat_ty = ty }) = head used_cons
439 ty_con = dataConTyCon (unLoc l_con) -- Newtype observable
440 all_cons = tyConDataCons ty_con
441 used_cons_as_id = map (\ (ConPatOut{ pat_con = L _ d}) -> d) used_cons
442 unused_cons = uniqSetToList
443 (mkUniqSet all_cons `minusUniqSet` mkUniqSet used_cons_as_id)
445 all_vars :: [Pat Id] -> Bool
447 all_vars (WildPat _:ps) = all_vars ps
450 remove_var :: (EqnNo, EquationInfo) -> (EqnNo, EquationInfo)
451 remove_var (n, eqn@(EqnInfo { eqn_pats = WildPat _ : ps})) = (n, eqn { eqn_pats = ps })
452 remove_var _ = panic "Check.remove_var: equation does not begin with a variable"
454 -----------------------
455 eqnPats :: (EqnNo, EquationInfo) -> [Pat Id]
456 eqnPats (_, eqn) = eqn_pats eqn
458 okGroup :: [(EqnNo, EquationInfo)] -> Bool
459 -- True if all equations have at least one pattern, and
460 -- all have the same number of patterns
462 okGroup (e:es) = n_pats > 0 && and [length (eqnPats e) == n_pats | e <- es]
464 n_pats = length (eqnPats e)
467 pprGroup es = vcat (map pprEqnInfo es)
468 pprEqnInfo e = ppr (eqnPats e)
471 firstPatN :: (EqnNo, EquationInfo) -> Pat Id
472 firstPatN (_, eqn) = firstPat eqn
474 is_con :: Pat Id -> Bool
475 is_con (ConPatOut {}) = True
478 is_lit :: Pat Id -> Bool
479 is_lit (LitPat _) = True
480 is_lit (NPat _ _ _ _) = True
483 is_var :: Pat Id -> Bool
484 is_var (WildPat _) = True
487 is_var_con :: DataCon -> Pat Id -> Bool
488 is_var_con con (WildPat _) = True
489 is_var_con con (ConPatOut{ pat_con = L _ id }) | id == con = True
490 is_var_con con _ = False
492 is_var_lit :: HsLit -> Pat Id -> Bool
493 is_var_lit lit (WildPat _) = True
495 | Just lit' <- get_lit pat = lit == lit'
499 The difference beteewn @make_con@ and @make_whole_con@ is that
500 @make_wole_con@ creates a new constructor with all their arguments, and
501 @make_con@ takes a list of argumntes, creates the contructor getting their
502 arguments from the list. See where \fbox{\ ???\ } are used for details.
504 We need to reconstruct the patterns (make the constructors infix and
505 similar) at the same time that we create the constructors.
507 You can tell tuple constructors using
511 You can see if one constructor is infix with this clearer code :-))))))))))
513 Lex.isLexConSym (Name.occNameString (Name.getOccName con))
516 Rather clumsy but it works. (Simon Peyton Jones)
519 We don't mind the @nilDataCon@ because it doesn't change the way to
520 print the messsage, we are searching only for things like: @[1,2,3]@,
523 In @reconstruct_pat@ we want to ``undo'' the work
524 that we have done in @simplify_pat@.
527 @((,) x y)@ & returns to be & @(x, y)@
528 \\ @((:) x xs)@ & returns to be & @(x:xs)@
529 \\ @(x:(...:[])@ & returns to be & @[x,...]@
532 The difficult case is the third one becouse we need to follow all the
533 contructors until the @[]@ to know that we need to use the second case,
534 not the second. \fbox{\ ???\ }
537 isInfixCon con = isDataSymOcc (getOccName con)
539 is_nil (ConPatIn con (PrefixCon [])) = unLoc con == getName nilDataCon
542 is_list (ListPat _ _) = True
545 return_list id q = id == consDataCon && (is_nil q || is_list q)
547 make_list p q | is_nil q = ListPat [p] placeHolderType
548 make_list p (ListPat ps ty) = ListPat (p:ps) ty
549 make_list _ _ = panic "Check.make_list: Invalid argument"
551 make_con :: Pat Id -> ExhaustivePat -> ExhaustivePat
552 make_con (ConPatOut{ pat_con = L _ id }) (lp:lq:ps, constraints)
553 | return_list id q = (noLoc (make_list lp q) : ps, constraints)
554 | isInfixCon id = (nlInfixConPat (getName id) lp lq : ps, constraints)
557 make_con (ConPatOut{ pat_con = L _ id, pat_args = PrefixCon pats, pat_ty = ty }) (ps, constraints)
558 | isTupleTyCon tc = (noLoc (TuplePat pats_con (tupleTyConBoxity tc) ty) : rest_pats, constraints)
559 | isPArrFakeCon id = (noLoc (PArrPat pats_con placeHolderType) : rest_pats, constraints)
560 | otherwise = (nlConPat name pats_con : rest_pats, constraints)
563 (pats_con, rest_pats) = splitAtList pats ps
566 -- reconstruct parallel array pattern
568 -- * don't check for the type only; we need to make sure that we are really
569 -- dealing with one of the fake constructors and not with the real
572 make_whole_con :: DataCon -> WarningPat
573 make_whole_con con | isInfixCon con = nlInfixConPat name nlWildPat nlWildPat
574 | otherwise = nlConPat name pats
577 pats = [nlWildPat | t <- dataConOrigArgTys con]
580 This equation makes the same thing as @tidy@ in @Match.lhs@, the
581 difference is that here we can do all the tidy in one place and in the
582 @Match@ tidy it must be done one column each time due to bookkeeping
587 simplify_eqn :: EquationInfo -> EquationInfo
588 simplify_eqn eqn = eqn { eqn_pats = map simplify_pat (eqn_pats eqn),
589 eqn_rhs = simplify_rhs (eqn_rhs eqn) }
591 -- Horrible hack. The simplify_pat stuff converts NPlusK pats to WildPats
592 -- which of course loses the info that they can fail to match. So we
593 -- stick in a CanFail as if it were a guard.
594 -- The Right Thing to do is for the whole system to treat NPlusK pats properly
595 simplify_rhs (MatchResult can_fail body)
596 | any has_nplusk_pat (eqn_pats eqn) = MatchResult CanFail body
597 | otherwise = MatchResult can_fail body
599 has_nplusk_lpat :: LPat Id -> Bool
600 has_nplusk_lpat (L _ p) = has_nplusk_pat p
602 has_nplusk_pat :: Pat Id -> Bool
603 has_nplusk_pat (NPlusKPat _ _ _ _) = True
604 has_nplusk_pat (ParPat p) = has_nplusk_lpat p
605 has_nplusk_pat (AsPat _ p) = has_nplusk_lpat p
606 has_nplusk_pat (SigPatOut p _ ) = has_nplusk_lpat p
607 has_nplusk_pat (ListPat ps _) = any has_nplusk_lpat ps
608 has_nplusk_pat (TuplePat ps _ _) = any has_nplusk_lpat ps
609 has_nplusk_pat (PArrPat ps _) = any has_nplusk_lpat ps
610 has_nplusk_pat (LazyPat p) = False -- Why?
611 has_nplusk_pat (BangPat p) = has_nplusk_lpat p -- I think
612 has_nplusk_pat (ConPatOut { pat_args = ps }) = any has_nplusk_lpat (hsConPatArgs ps)
613 has_nplusk_pat p = False -- VarPat, VarPatOut, WildPat, LitPat, NPat, TypePat
615 simplify_lpat :: LPat Id -> LPat Id
616 simplify_lpat p = fmap simplify_pat p
618 simplify_pat :: Pat Id -> Pat Id
619 simplify_pat pat@(WildPat gt) = pat
620 simplify_pat (VarPat id) = WildPat (idType id)
621 simplify_pat (VarPatOut id _) = WildPat (idType id) -- Ignore the bindings
622 simplify_pat (ParPat p) = unLoc (simplify_lpat p)
623 simplify_pat (LazyPat p) = WildPat (hsLPatType p) -- For overlap and exhaustiveness checking
624 -- purposes, a ~pat is like a wildcard
625 simplify_pat (BangPat p) = unLoc (simplify_lpat p)
626 simplify_pat (AsPat id p) = unLoc (simplify_lpat p)
627 simplify_pat (SigPatOut p _) = unLoc (simplify_lpat p) -- I'm not sure this is right
629 simplify_pat pat@(ConPatOut { pat_con = L loc id, pat_args = ps })
630 = pat { pat_args = simplify_con id ps }
632 simplify_pat (ListPat ps ty) =
633 unLoc $ foldr (\ x y -> mkPrefixConPat consDataCon [x,y] list_ty)
635 (map simplify_lpat ps)
636 where list_ty = mkListTy ty
638 -- introduce fake parallel array constructors to be able to handle parallel
639 -- arrays with the existing machinery for constructor pattern
641 simplify_pat (PArrPat ps ty)
642 = unLoc $ mkPrefixConPat (parrFakeCon (length ps))
643 (map simplify_lpat ps)
646 simplify_pat (TuplePat ps boxity ty)
647 = unLoc $ mkPrefixConPat (tupleCon boxity arity)
648 (map simplify_lpat ps) ty
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 unLoc $ foldr (\c pat -> mkPrefixConPat consDataCon [mk_char_lit c, pat] stringTy)
656 (mkPrefixConPat nilDataCon [] stringTy) (unpackFS s)
658 mk_char_lit c = mkPrefixConPat charDataCon [nlLitPat (HsCharPrim c)] charTy
660 simplify_pat (LitPat lit) = tidyLitPat lit
661 simplify_pat (NPat lit mb_neg eq lit_ty) = tidyNPat lit mb_neg eq lit_ty
663 simplify_pat (NPlusKPat id hslit hsexpr1 hsexpr2)
664 = WildPat (idType (unLoc id))
666 simplify_pat (CoPat co pat ty) = simplify_pat pat
669 simplify_con con (PrefixCon ps) = PrefixCon (map simplify_lpat ps)
670 simplify_con con (InfixCon p1 p2) = PrefixCon [simplify_lpat p1, simplify_lpat p2]
671 simplify_con con (RecCon (HsRecFields fs _))
672 | null fs = PrefixCon [nlWildPat | t <- dataConOrigArgTys con]
673 -- Special case for null patterns; maybe not a record at all
674 | otherwise = PrefixCon (map (simplify_lpat.snd) all_pats)
676 -- pad out all the missing fields with WildPats.
677 field_pats = map (\ f -> (f, nlWildPat)) (dataConFieldLabels con)
678 all_pats = foldr (\(HsRecField id p _) acc -> insertNm (getName (unLoc id)) p acc)
681 insertNm nm p [] = [(nm,p)]
682 insertNm nm p (x@(n,_):xs)
683 | nm == n = (nm,p):xs
684 | otherwise = x : insertNm nm p xs