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>
9 -- The above warning supression flag is a temporary kludge.
10 -- While working on this module you are encouraged to remove it and fix
11 -- any warnings in the module. See
12 -- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
15 module Check ( check , ExhaustivePat ) where
17 #include "HsVersions.h"
37 This module performs checks about if one list of equations are:
42 To discover that we go through the list of equations in a tree-like fashion.
44 If you like theory, a similar algorithm is described in:
46 {\em Two Techniques for Compiling Lazy Pattern Matching},
48 INRIA Rocquencourt (RR-2385, 1994)
50 The algorithm is based on the first technique, but there are some differences:
52 \item We don't generate code
53 \item We have constructors and literals (not only literals as in the
55 \item We don't use directions, we must select the columns from
58 (By the way the second technique is really similar to the one used in
59 @Match.lhs@ to generate code)
61 This function takes the equations of a pattern and returns:
63 \item The patterns that are not recognized
64 \item The equations that are not overlapped
66 It simplify the patterns and then call @check'@ (the same semantics), and it
67 needs to reconstruct the patterns again ....
69 The problem appear with things like:
74 We want to put the two patterns with the same syntax, (prefix form) and
75 then all the constructors are equal:
77 f (: x (: y [])) = ....
80 (more about that in @simplify_eqns@)
82 We would prefer to have a @WarningPat@ of type @String@, but Strings and the
83 Pretty Printer are not friends.
85 We use @InPat@ in @WarningPat@ instead of @OutPat@
86 because we need to print the
87 warning messages in the same way they are introduced, i.e. if the user
92 He don't want a warning message written:
94 f (: x (: y [])) ........
96 Then we need to use InPats.
98 Juan Quintela 5 JUL 1998\\
99 User-friendliness and compiler writers are no friends.
103 type WarningPat = InPat Name
104 type ExhaustivePat = ([WarningPat], [(Name, [HsLit])])
106 type EqnSet = UniqSet EqnNo
109 check :: [EquationInfo] -> ([ExhaustivePat], [EquationInfo])
110 -- Second result is the shadowed equations
111 check qs = (untidy_warns, shadowed_eqns)
113 (warns, used_nos) = check' ([1..] `zip` map simplify_eqn qs)
114 untidy_warns = map untidy_exhaustive warns
115 shadowed_eqns = [eqn | (eqn,i) <- qs `zip` [1..],
116 not (i `elementOfUniqSet` used_nos)]
118 untidy_exhaustive :: ExhaustivePat -> ExhaustivePat
119 untidy_exhaustive ([pat], messages) =
120 ([untidy_no_pars pat], map untidy_message messages)
121 untidy_exhaustive (pats, messages) =
122 (map untidy_pars pats, map untidy_message messages)
124 untidy_message :: (Name, [HsLit]) -> (Name, [HsLit])
125 untidy_message (string, lits) = (string, map untidy_lit lits)
128 The function @untidy@ does the reverse work of the @simplify_pat@ funcion.
134 untidy_no_pars :: WarningPat -> WarningPat
135 untidy_no_pars p = untidy False p
137 untidy_pars :: WarningPat -> WarningPat
138 untidy_pars p = untidy True p
140 untidy :: NeedPars -> WarningPat -> WarningPat
141 untidy b (L loc p) = L loc (untidy' b p)
143 untidy' _ p@(WildPat _) = p
144 untidy' _ p@(VarPat name) = p
145 untidy' _ (LitPat lit) = LitPat (untidy_lit lit)
146 untidy' _ p@(ConPatIn name (PrefixCon [])) = p
147 untidy' b (ConPatIn name ps) = pars b (L loc (ConPatIn name (untidy_con ps)))
148 untidy' _ (ListPat pats ty) = ListPat (map untidy_no_pars pats) ty
149 untidy' _ (TuplePat pats box ty) = TuplePat (map untidy_no_pars pats) box ty
150 untidy' _ (PArrPat _ _) = panic "Check.untidy: Shouldn't get a parallel array here!"
151 untidy' _ (SigPatIn _ _) = panic "Check.untidy: SigPat"
153 untidy_con (PrefixCon pats) = PrefixCon (map untidy_pars pats)
154 untidy_con (InfixCon p1 p2) = InfixCon (untidy_pars p1) (untidy_pars p2)
155 untidy_con (RecCon (HsRecFields flds dd))
156 = RecCon (HsRecFields [ fld { hsRecFieldArg = untidy_pars (hsRecFieldArg fld) }
159 pars :: NeedPars -> WarningPat -> Pat Name
160 pars True p = ParPat p
163 untidy_lit :: HsLit -> HsLit
164 untidy_lit (HsCharPrim c) = HsChar c
168 This equation is the same that check, the only difference is that the
169 boring work is done, that work needs to be done only once, this is
170 the reason top have two functions, check is the external interface,
171 @check'@ is called recursively.
173 There are several cases:
176 \item There are no equations: Everything is OK.
177 \item There are only one equation, that can fail, and all the patterns are
178 variables. Then that equation is used and the same equation is
180 \item All the patterns are variables, and the match can fail, there are
181 more equations then the results is the result of the rest of equations
182 and this equation is used also.
184 \item The general case, if all the patterns are variables (here the match
185 can't fail) then the result is that this equation is used and this
186 equation doesn't generate non-exhaustive cases.
188 \item In the general case, there can exist literals ,constructors or only
189 vars in the first column, we actuate in consequence.
196 check' :: [(EqnNo, EquationInfo)]
197 -> ([ExhaustivePat], -- Pattern scheme that might not be matched at all
198 EqnSet) -- Eqns that are used (others are overlapped)
200 check' [] = ([([],[])],emptyUniqSet)
202 check' ((n, EqnInfo { eqn_pats = ps, eqn_rhs = MatchResult can_fail _ }) : rs)
203 | first_eqn_all_vars && case can_fail of { CantFail -> True; CanFail -> False }
204 = ([], unitUniqSet n) -- One eqn, which can't fail
206 | first_eqn_all_vars && null rs -- One eqn, but it can fail
207 = ([(takeList ps (repeat nlWildPat),[])], unitUniqSet n)
209 | first_eqn_all_vars -- Several eqns, first can fail
210 = (pats, addOneToUniqSet indexs n)
212 first_eqn_all_vars = all_vars ps
213 (pats,indexs) = check' rs
216 | literals = split_by_literals qs
217 | constructors = split_by_constructor qs
218 | only_vars = first_column_only_vars qs
219 | otherwise = pprPanic "Check.check': Not implemented :-(" (ppr first_pats)
221 -- Note: RecPats will have been simplified to ConPats
223 first_pats = ASSERT2( okGroup qs, pprGroup qs ) map firstPatN qs
224 constructors = any is_con first_pats
225 literals = any is_lit first_pats
226 only_vars = all is_var first_pats
229 Here begins the code to deal with literals, we need to split the matrix
230 in different matrix beginning by each literal and a last matrix with the
234 split_by_literals :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet)
235 split_by_literals qs = process_literals used_lits qs
237 used_lits = get_used_lits qs
240 @process_explicit_literals@ is a function that process each literal that appears
241 in the column of the matrix.
244 process_explicit_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
245 process_explicit_literals lits qs = (concat pats, unionManyUniqSets indexs)
247 pats_indexs = map (\x -> construct_literal_matrix x qs) lits
248 (pats,indexs) = unzip pats_indexs
252 @process_literals@ calls @process_explicit_literals@ to deal with the literals
253 that appears in the matrix and deal also with the rest of the cases. It
254 must be one Variable to be complete.
258 process_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
259 process_literals used_lits qs
260 | null default_eqns = ASSERT( not (null qs) ) ([make_row_vars used_lits (head qs)] ++ pats,indexs)
261 | otherwise = (pats_default,indexs_default)
263 (pats,indexs) = process_explicit_literals used_lits qs
264 default_eqns = ASSERT2( okGroup qs, pprGroup qs )
265 [remove_var q | q <- qs, is_var (firstPatN q)]
266 (pats',indexs') = check' default_eqns
267 pats_default = [(nlWildPat:ps,constraints) | (ps,constraints) <- (pats')] ++ pats
268 indexs_default = unionUniqSets indexs' indexs
271 Here we have selected the literal and we will select all the equations that
272 begins for that literal and create a new matrix.
275 construct_literal_matrix :: HsLit -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
276 construct_literal_matrix lit qs =
277 (map (\ (xs,ys) -> (new_lit:xs,ys)) pats,indexs)
279 (pats,indexs) = (check' (remove_first_column_lit lit qs))
280 new_lit = nlLitPat lit
282 remove_first_column_lit :: HsLit
283 -> [(EqnNo, EquationInfo)]
284 -> [(EqnNo, EquationInfo)]
285 remove_first_column_lit lit qs
286 = ASSERT2( okGroup qs, pprGroup qs )
287 [(n, shift_pat eqn) | q@(n,eqn) <- qs, is_var_lit lit (firstPatN q)]
289 shift_pat eqn@(EqnInfo { eqn_pats = _:ps}) = eqn { eqn_pats = ps }
290 shift_pat eqn@(EqnInfo { eqn_pats = []}) = panic "Check.shift_var: no patterns"
293 This function splits the equations @qs@ in groups that deal with the
297 split_by_constructor :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet)
298 split_by_constructor qs
299 | notNull unused_cons = need_default_case used_cons unused_cons qs
300 | otherwise = no_need_default_case used_cons qs
302 used_cons = get_used_cons qs
303 unused_cons = get_unused_cons used_cons
306 The first column of the patterns matrix only have vars, then there is
310 first_column_only_vars :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
311 first_column_only_vars qs = (map (\ (xs,ys) -> (nlWildPat:xs,ys)) pats,indexs)
313 (pats, indexs) = check' (map remove_var qs)
316 This equation takes a matrix of patterns and split the equations by
317 constructor, using all the constructors that appears in the first column
318 of the pattern matching.
320 We can need a default clause or not ...., it depends if we used all the
321 constructors or not explicitly. The reasoning is similar to @process_literals@,
322 the difference is that here the default case is not always needed.
325 no_need_default_case :: [Pat Id] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
326 no_need_default_case cons qs = (concat pats, unionManyUniqSets indexs)
328 pats_indexs = map (\x -> construct_matrix x qs) cons
329 (pats,indexs) = unzip pats_indexs
331 need_default_case :: [Pat Id] -> [DataCon] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
332 need_default_case used_cons unused_cons qs
333 | null default_eqns = (pats_default_no_eqns,indexs)
334 | otherwise = (pats_default,indexs_default)
336 (pats,indexs) = no_need_default_case used_cons qs
337 default_eqns = ASSERT2( okGroup qs, pprGroup qs )
338 [remove_var q | q <- qs, is_var (firstPatN q)]
339 (pats',indexs') = check' default_eqns
340 pats_default = [(make_whole_con c:ps,constraints) |
341 c <- unused_cons, (ps,constraints) <- pats'] ++ pats
342 new_wilds = ASSERT( not (null qs) ) make_row_vars_for_constructor (head qs)
343 pats_default_no_eqns = [(make_whole_con c:new_wilds,[]) | c <- unused_cons] ++ pats
344 indexs_default = unionUniqSets indexs' indexs
346 construct_matrix :: Pat Id -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
347 construct_matrix con qs =
348 (map (make_con con) pats,indexs)
350 (pats,indexs) = (check' (remove_first_column con qs))
353 Here remove first column is more difficult that with literals due to the fact
354 that constructors can have arguments.
356 For instance, the matrix
368 remove_first_column :: Pat Id -- Constructor
369 -> [(EqnNo, EquationInfo)]
370 -> [(EqnNo, EquationInfo)]
371 remove_first_column (ConPatOut{ pat_con = L _ con, pat_args = PrefixCon con_pats }) qs
372 = ASSERT2( okGroup qs, pprGroup qs )
373 [(n, shift_var eqn) | q@(n, eqn) <- qs, is_var_con con (firstPatN q)]
375 new_wilds = [WildPat (hsLPatType arg_pat) | arg_pat <- con_pats]
376 shift_var eqn@(EqnInfo { eqn_pats = ConPatOut{ pat_args = PrefixCon ps' } : ps})
377 = eqn { eqn_pats = map unLoc ps' ++ ps }
378 shift_var eqn@(EqnInfo { eqn_pats = WildPat _ : ps })
379 = eqn { eqn_pats = new_wilds ++ ps }
380 shift_var _ = panic "Check.Shift_var:No done"
382 make_row_vars :: [HsLit] -> (EqnNo, EquationInfo) -> ExhaustivePat
383 make_row_vars used_lits (_, EqnInfo { eqn_pats = pats})
384 = (nlVarPat new_var:takeList (tail pats) (repeat nlWildPat),[(new_var,used_lits)])
388 hash_x = mkInternalName unboundKey {- doesn't matter much -}
389 (mkVarOccFS FSLIT("#x"))
392 make_row_vars_for_constructor :: (EqnNo, EquationInfo) -> [WarningPat]
393 make_row_vars_for_constructor (_, EqnInfo { eqn_pats = pats})
394 = takeList (tail pats) (repeat nlWildPat)
396 compare_cons :: Pat Id -> Pat Id -> Bool
397 compare_cons (ConPatOut{ pat_con = L _ id1 }) (ConPatOut { pat_con = L _ id2 }) = id1 == id2
399 remove_dups :: [Pat Id] -> [Pat Id]
401 remove_dups (x:xs) | or (map (\y -> compare_cons x y) xs) = remove_dups xs
402 | otherwise = x : remove_dups xs
404 get_used_cons :: [(EqnNo, EquationInfo)] -> [Pat Id]
405 get_used_cons qs = remove_dups [pat | q <- qs, let pat = firstPatN q,
408 isConPatOut (ConPatOut {}) = True
409 isConPatOut other = False
411 remove_dups' :: [HsLit] -> [HsLit]
413 remove_dups' (x:xs) | x `elem` xs = remove_dups' xs
414 | otherwise = x : remove_dups' xs
417 get_used_lits :: [(EqnNo, EquationInfo)] -> [HsLit]
418 get_used_lits qs = remove_dups' all_literals
420 all_literals = get_used_lits' qs
422 get_used_lits' :: [(EqnNo, EquationInfo)] -> [HsLit]
423 get_used_lits' [] = []
424 get_used_lits' (q:qs)
425 | Just lit <- get_lit (firstPatN q) = lit : get_used_lits' qs
426 | otherwise = get_used_lits qs
428 get_lit :: Pat id -> Maybe HsLit
429 -- Get a representative HsLit to stand for the OverLit
430 -- It doesn't matter which one, because they will only be compared
431 -- with other HsLits gotten in the same way
432 get_lit (LitPat lit) = Just lit
433 get_lit (NPat (HsIntegral i _) mb _ _) = Just (HsIntPrim (mb_neg mb i))
434 get_lit (NPat (HsFractional f _) mb _ _) = Just (HsFloatPrim (mb_neg mb f))
435 get_lit (NPat (HsIsString s _) _ _ _) = Just (HsStringPrim s)
436 get_lit other_pat = Nothing
438 mb_neg :: Num a => Maybe b -> a -> a
440 mb_neg (Just _) v = -v
442 get_unused_cons :: [Pat Id] -> [DataCon]
443 get_unused_cons used_cons = ASSERT( not (null used_cons) ) unused_cons
445 (ConPatOut { pat_con = l_con, pat_ty = ty }) = head used_cons
446 ty_con = dataConTyCon (unLoc l_con) -- Newtype observable
447 all_cons = tyConDataCons ty_con
448 used_cons_as_id = map (\ (ConPatOut{ pat_con = L _ d}) -> d) used_cons
449 unused_cons = uniqSetToList
450 (mkUniqSet all_cons `minusUniqSet` mkUniqSet used_cons_as_id)
452 all_vars :: [Pat Id] -> Bool
454 all_vars (WildPat _:ps) = all_vars ps
457 remove_var :: (EqnNo, EquationInfo) -> (EqnNo, EquationInfo)
458 remove_var (n, eqn@(EqnInfo { eqn_pats = WildPat _ : ps})) = (n, eqn { eqn_pats = ps })
459 remove_var _ = panic "Check.remove_var: equation does not begin with a variable"
461 -----------------------
462 eqnPats :: (EqnNo, EquationInfo) -> [Pat Id]
463 eqnPats (_, eqn) = eqn_pats eqn
465 okGroup :: [(EqnNo, EquationInfo)] -> Bool
466 -- True if all equations have at least one pattern, and
467 -- all have the same number of patterns
469 okGroup (e:es) = n_pats > 0 && and [length (eqnPats e) == n_pats | e <- es]
471 n_pats = length (eqnPats e)
474 pprGroup es = vcat (map pprEqnInfo es)
475 pprEqnInfo e = ppr (eqnPats e)
478 firstPatN :: (EqnNo, EquationInfo) -> Pat Id
479 firstPatN (_, eqn) = firstPat eqn
481 is_con :: Pat Id -> Bool
482 is_con (ConPatOut {}) = True
485 is_lit :: Pat Id -> Bool
486 is_lit (LitPat _) = True
487 is_lit (NPat _ _ _ _) = True
490 is_var :: Pat Id -> Bool
491 is_var (WildPat _) = True
494 is_var_con :: DataCon -> Pat Id -> Bool
495 is_var_con con (WildPat _) = True
496 is_var_con con (ConPatOut{ pat_con = L _ id }) | id == con = True
497 is_var_con con _ = False
499 is_var_lit :: HsLit -> Pat Id -> Bool
500 is_var_lit lit (WildPat _) = True
502 | Just lit' <- get_lit pat = lit == lit'
506 The difference beteewn @make_con@ and @make_whole_con@ is that
507 @make_wole_con@ creates a new constructor with all their arguments, and
508 @make_con@ takes a list of argumntes, creates the contructor getting their
509 arguments from the list. See where \fbox{\ ???\ } are used for details.
511 We need to reconstruct the patterns (make the constructors infix and
512 similar) at the same time that we create the constructors.
514 You can tell tuple constructors using
518 You can see if one constructor is infix with this clearer code :-))))))))))
520 Lex.isLexConSym (Name.occNameString (Name.getOccName con))
523 Rather clumsy but it works. (Simon Peyton Jones)
526 We don't mind the @nilDataCon@ because it doesn't change the way to
527 print the messsage, we are searching only for things like: @[1,2,3]@,
530 In @reconstruct_pat@ we want to ``undo'' the work
531 that we have done in @simplify_pat@.
534 @((,) x y)@ & returns to be & @(x, y)@
535 \\ @((:) x xs)@ & returns to be & @(x:xs)@
536 \\ @(x:(...:[])@ & returns to be & @[x,...]@
539 The difficult case is the third one becouse we need to follow all the
540 contructors until the @[]@ to know that we need to use the second case,
541 not the second. \fbox{\ ???\ }
544 isInfixCon con = isDataSymOcc (getOccName con)
546 is_nil (ConPatIn con (PrefixCon [])) = unLoc con == getName nilDataCon
549 is_list (ListPat _ _) = True
552 return_list id q = id == consDataCon && (is_nil q || is_list q)
554 make_list p q | is_nil q = ListPat [p] placeHolderType
555 make_list p (ListPat ps ty) = ListPat (p:ps) ty
556 make_list _ _ = panic "Check.make_list: Invalid argument"
558 make_con :: Pat Id -> ExhaustivePat -> ExhaustivePat
559 make_con (ConPatOut{ pat_con = L _ id }) (lp:lq:ps, constraints)
560 | return_list id q = (noLoc (make_list lp q) : ps, constraints)
561 | isInfixCon id = (nlInfixConPat (getName id) lp lq : ps, constraints)
564 make_con (ConPatOut{ pat_con = L _ id, pat_args = PrefixCon pats, pat_ty = ty }) (ps, constraints)
565 | isTupleTyCon tc = (noLoc (TuplePat pats_con (tupleTyConBoxity tc) ty) : rest_pats, constraints)
566 | isPArrFakeCon id = (noLoc (PArrPat pats_con placeHolderType) : rest_pats, constraints)
567 | otherwise = (nlConPat name pats_con : rest_pats, constraints)
570 (pats_con, rest_pats) = splitAtList pats ps
573 -- reconstruct parallel array pattern
575 -- * don't check for the type only; we need to make sure that we are really
576 -- dealing with one of the fake constructors and not with the real
579 make_whole_con :: DataCon -> WarningPat
580 make_whole_con con | isInfixCon con = nlInfixConPat name nlWildPat nlWildPat
581 | otherwise = nlConPat name pats
584 pats = [nlWildPat | t <- dataConOrigArgTys con]
587 This equation makes the same thing as @tidy@ in @Match.lhs@, the
588 difference is that here we can do all the tidy in one place and in the
589 @Match@ tidy it must be done one column each time due to bookkeeping
594 simplify_eqn :: EquationInfo -> EquationInfo
595 simplify_eqn eqn = eqn { eqn_pats = map simplify_pat (eqn_pats eqn),
596 eqn_rhs = simplify_rhs (eqn_rhs eqn) }
598 -- Horrible hack. The simplify_pat stuff converts NPlusK pats to WildPats
599 -- which of course loses the info that they can fail to match. So we
600 -- stick in a CanFail as if it were a guard.
601 -- The Right Thing to do is for the whole system to treat NPlusK pats properly
602 simplify_rhs (MatchResult can_fail body)
603 | any has_nplusk_pat (eqn_pats eqn) = MatchResult CanFail body
604 | otherwise = MatchResult can_fail body
606 has_nplusk_lpat :: LPat Id -> Bool
607 has_nplusk_lpat (L _ p) = has_nplusk_pat p
609 has_nplusk_pat :: Pat Id -> Bool
610 has_nplusk_pat (NPlusKPat _ _ _ _) = True
611 has_nplusk_pat (ParPat p) = has_nplusk_lpat p
612 has_nplusk_pat (AsPat _ p) = has_nplusk_lpat p
613 has_nplusk_pat (SigPatOut p _ ) = has_nplusk_lpat p
614 has_nplusk_pat (ListPat ps _) = any has_nplusk_lpat ps
615 has_nplusk_pat (TuplePat ps _ _) = any has_nplusk_lpat ps
616 has_nplusk_pat (PArrPat ps _) = any has_nplusk_lpat ps
617 has_nplusk_pat (LazyPat p) = False -- Why?
618 has_nplusk_pat (BangPat p) = has_nplusk_lpat p -- I think
619 has_nplusk_pat (ConPatOut { pat_args = ps }) = any has_nplusk_lpat (hsConPatArgs ps)
620 has_nplusk_pat p = False -- VarPat, VarPatOut, WildPat, LitPat, NPat, TypePat
622 simplify_lpat :: LPat Id -> LPat Id
623 simplify_lpat p = fmap simplify_pat p
625 simplify_pat :: Pat Id -> Pat Id
626 simplify_pat pat@(WildPat gt) = pat
627 simplify_pat (VarPat id) = WildPat (idType id)
628 simplify_pat (VarPatOut id _) = WildPat (idType id) -- Ignore the bindings
629 simplify_pat (ParPat p) = unLoc (simplify_lpat p)
630 simplify_pat (LazyPat p) = WildPat (hsLPatType p) -- For overlap and exhaustiveness checking
631 -- purposes, a ~pat is like a wildcard
632 simplify_pat (BangPat p) = unLoc (simplify_lpat p)
633 simplify_pat (AsPat id p) = unLoc (simplify_lpat p)
634 simplify_pat (SigPatOut p _) = unLoc (simplify_lpat p) -- I'm not sure this is right
636 simplify_pat pat@(ConPatOut { pat_con = L loc id, pat_args = ps })
637 = pat { pat_args = simplify_con id ps }
639 simplify_pat (ListPat ps ty) =
640 unLoc $ foldr (\ x y -> mkPrefixConPat consDataCon [x,y] list_ty)
642 (map simplify_lpat ps)
643 where list_ty = mkListTy ty
645 -- introduce fake parallel array constructors to be able to handle parallel
646 -- arrays with the existing machinery for constructor pattern
648 simplify_pat (PArrPat ps ty)
649 = unLoc $ mkPrefixConPat (parrFakeCon (length ps))
650 (map simplify_lpat ps)
653 simplify_pat (TuplePat ps boxity ty)
654 = unLoc $ mkPrefixConPat (tupleCon boxity arity)
655 (map simplify_lpat ps) ty
659 -- unpack string patterns fully, so we can see when they overlap with
660 -- each other, or even explicit lists of Chars.
661 simplify_pat pat@(LitPat (HsString s)) =
662 unLoc $ foldr (\c pat -> mkPrefixConPat consDataCon [mk_char_lit c, pat] stringTy)
663 (mkPrefixConPat nilDataCon [] stringTy) (unpackFS s)
665 mk_char_lit c = mkPrefixConPat charDataCon [nlLitPat (HsCharPrim c)] charTy
667 simplify_pat (LitPat lit) = tidyLitPat lit
668 simplify_pat (NPat lit mb_neg eq lit_ty) = tidyNPat lit mb_neg eq lit_ty
670 simplify_pat (NPlusKPat id hslit hsexpr1 hsexpr2)
671 = WildPat (idType (unLoc id))
673 simplify_pat (CoPat co pat ty) = simplify_pat pat
676 simplify_con con (PrefixCon ps) = PrefixCon (map simplify_lpat ps)
677 simplify_con con (InfixCon p1 p2) = PrefixCon [simplify_lpat p1, simplify_lpat p2]
678 simplify_con con (RecCon (HsRecFields fs _))
679 | null fs = PrefixCon [nlWildPat | t <- dataConOrigArgTys con]
680 -- Special case for null patterns; maybe not a record at all
681 | otherwise = PrefixCon (map (simplify_lpat.snd) all_pats)
683 -- pad out all the missing fields with WildPats.
684 field_pats = map (\ f -> (f, nlWildPat)) (dataConFieldLabels con)
685 all_pats = foldr (\(HsRecField id p _) acc -> insertNm (getName (unLoc id)) p acc)
688 insertNm nm p [] = [(nm,p)]
689 insertNm nm p (x@(n,_):xs)
690 | nm == n = (nm,p):xs
691 | otherwise = x : insertNm nm p xs