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 {-# OPTIONS -fno-warn-incomplete-patterns #-}
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"
30 import Unify( dataConCannotMatch )
38 This module performs checks about if one list of equations are:
43 To discover that we go through the list of equations in a tree-like fashion.
45 If you like theory, a similar algorithm is described in:
47 {\em Two Techniques for Compiling Lazy Pattern Matching},
49 INRIA Rocquencourt (RR-2385, 1994)
51 The algorithm is based on the first technique, but there are some differences:
53 \item We don't generate code
54 \item We have constructors and literals (not only literals as in the
56 \item We don't use directions, we must select the columns from
59 (By the way the second technique is really similar to the one used in
60 @Match.lhs@ to generate code)
62 This function takes the equations of a pattern and returns:
64 \item The patterns that are not recognized
65 \item The equations that are not overlapped
67 It simplify the patterns and then call @check'@ (the same semantics), and it
68 needs to reconstruct the patterns again ....
70 The problem appear with things like:
75 We want to put the two patterns with the same syntax, (prefix form) and
76 then all the constructors are equal:
78 f (: x (: y [])) = ....
81 (more about that in @simplify_eqns@)
83 We would prefer to have a @WarningPat@ of type @String@, but Strings and the
84 Pretty Printer are not friends.
86 We use @InPat@ in @WarningPat@ instead of @OutPat@
87 because we need to print the
88 warning messages in the same way they are introduced, i.e. if the user
93 He don't want a warning message written:
95 f (: x (: y [])) ........
97 Then we need to use InPats.
99 Juan Quintela 5 JUL 1998\\
100 User-friendliness and compiler writers are no friends.
104 type WarningPat = InPat Name
105 type ExhaustivePat = ([WarningPat], [(Name, [HsLit])])
107 type EqnSet = UniqSet EqnNo
110 check :: [EquationInfo] -> ([ExhaustivePat], [EquationInfo])
111 -- Second result is the shadowed equations
112 check qs = (untidy_warns, shadowed_eqns)
114 (warns, used_nos) = check' ([1..] `zip` map simplify_eqn qs)
115 untidy_warns = map untidy_exhaustive warns
116 shadowed_eqns = [eqn | (eqn,i) <- qs `zip` [1..],
117 not (i `elementOfUniqSet` used_nos)]
119 untidy_exhaustive :: ExhaustivePat -> ExhaustivePat
120 untidy_exhaustive ([pat], messages) =
121 ([untidy_no_pars pat], map untidy_message messages)
122 untidy_exhaustive (pats, messages) =
123 (map untidy_pars pats, map untidy_message messages)
125 untidy_message :: (Name, [HsLit]) -> (Name, [HsLit])
126 untidy_message (string, lits) = (string, map untidy_lit lits)
129 The function @untidy@ does the reverse work of the @simplify_pat@ funcion.
135 untidy_no_pars :: WarningPat -> WarningPat
136 untidy_no_pars p = untidy False p
138 untidy_pars :: WarningPat -> WarningPat
139 untidy_pars p = untidy True p
141 untidy :: NeedPars -> WarningPat -> WarningPat
142 untidy b (L loc p) = L loc (untidy' b p)
144 untidy' _ p@(WildPat _) = p
145 untidy' _ p@(VarPat _) = p
146 untidy' _ (LitPat lit) = LitPat (untidy_lit lit)
147 untidy' _ p@(ConPatIn _ (PrefixCon [])) = p
148 untidy' b (ConPatIn name ps) = pars b (L loc (ConPatIn name (untidy_con ps)))
149 untidy' _ (ListPat pats ty) = ListPat (map untidy_no_pars pats) ty
150 untidy' _ (TuplePat pats box ty) = TuplePat (map untidy_no_pars pats) box ty
151 untidy' _ (PArrPat _ _) = panic "Check.untidy: Shouldn't get a parallel array here!"
152 untidy' _ (SigPatIn _ _) = panic "Check.untidy: SigPat"
154 untidy_con :: HsConPatDetails Name -> HsConPatDetails Name
155 untidy_con (PrefixCon pats) = PrefixCon (map untidy_pars pats)
156 untidy_con (InfixCon p1 p2) = InfixCon (untidy_pars p1) (untidy_pars p2)
157 untidy_con (RecCon (HsRecFields flds dd))
158 = RecCon (HsRecFields [ fld { hsRecFieldArg = untidy_pars (hsRecFieldArg fld) }
161 pars :: NeedPars -> WarningPat -> Pat Name
162 pars True p = ParPat p
165 untidy_lit :: HsLit -> HsLit
166 untidy_lit (HsCharPrim c) = HsChar c
170 This equation is the same that check, the only difference is that the
171 boring work is done, that work needs to be done only once, this is
172 the reason top have two functions, check is the external interface,
173 @check'@ is called recursively.
175 There are several cases:
178 \item There are no equations: Everything is OK.
179 \item There are only one equation, that can fail, and all the patterns are
180 variables. Then that equation is used and the same equation is
182 \item All the patterns are variables, and the match can fail, there are
183 more equations then the results is the result of the rest of equations
184 and this equation is used also.
186 \item The general case, if all the patterns are variables (here the match
187 can't fail) then the result is that this equation is used and this
188 equation doesn't generate non-exhaustive cases.
190 \item In the general case, there can exist literals ,constructors or only
191 vars in the first column, we actuate in consequence.
198 check' :: [(EqnNo, EquationInfo)]
199 -> ([ExhaustivePat], -- Pattern scheme that might not be matched at all
200 EqnSet) -- Eqns that are used (others are overlapped)
202 check' [] = ([([],[])],emptyUniqSet)
204 check' ((n, EqnInfo { eqn_pats = ps, eqn_rhs = MatchResult can_fail _ }) : rs)
205 | first_eqn_all_vars && case can_fail of { CantFail -> True; CanFail -> False }
206 = ([], unitUniqSet n) -- One eqn, which can't fail
208 | first_eqn_all_vars && null rs -- One eqn, but it can fail
209 = ([(takeList ps (repeat nlWildPat),[])], unitUniqSet n)
211 | first_eqn_all_vars -- Several eqns, first can fail
212 = (pats, addOneToUniqSet indexs n)
214 first_eqn_all_vars = all_vars ps
215 (pats,indexs) = check' rs
218 | literals = split_by_literals qs
219 | constructors = split_by_constructor qs
220 | only_vars = first_column_only_vars qs
221 -- FIXME: hack to get view patterns through for now
222 | otherwise = ([([],[])],emptyUniqSet)
223 -- pprPanic "Check.check': Not implemented :-(" (ppr first_pats)
225 -- Note: RecPats will have been simplified to ConPats
227 first_pats = ASSERT2( okGroup qs, pprGroup qs ) map firstPatN qs
228 constructors = any is_con first_pats
229 literals = any is_lit first_pats
230 only_vars = all is_var first_pats
233 Here begins the code to deal with literals, we need to split the matrix
234 in different matrix beginning by each literal and a last matrix with the
238 split_by_literals :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet)
239 split_by_literals qs = process_literals used_lits qs
241 used_lits = get_used_lits qs
244 @process_explicit_literals@ is a function that process each literal that appears
245 in the column of the matrix.
248 process_explicit_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
249 process_explicit_literals lits qs = (concat pats, unionManyUniqSets indexs)
251 pats_indexs = map (\x -> construct_literal_matrix x qs) lits
252 (pats,indexs) = unzip pats_indexs
256 @process_literals@ calls @process_explicit_literals@ to deal with the literals
257 that appears in the matrix and deal also with the rest of the cases. It
258 must be one Variable to be complete.
262 process_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
263 process_literals used_lits qs
264 | null default_eqns = ASSERT( not (null qs) ) ([make_row_vars used_lits (head qs)] ++ pats,indexs)
265 | otherwise = (pats_default,indexs_default)
267 (pats,indexs) = process_explicit_literals used_lits qs
268 default_eqns = ASSERT2( okGroup qs, pprGroup qs )
269 [remove_var q | q <- qs, is_var (firstPatN q)]
270 (pats',indexs') = check' default_eqns
271 pats_default = [(nlWildPat:ps,constraints) | (ps,constraints) <- (pats')] ++ pats
272 indexs_default = unionUniqSets indexs' indexs
275 Here we have selected the literal and we will select all the equations that
276 begins for that literal and create a new matrix.
279 construct_literal_matrix :: HsLit -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
280 construct_literal_matrix lit qs =
281 (map (\ (xs,ys) -> (new_lit:xs,ys)) pats,indexs)
283 (pats,indexs) = (check' (remove_first_column_lit lit qs))
284 new_lit = nlLitPat lit
286 remove_first_column_lit :: HsLit
287 -> [(EqnNo, EquationInfo)]
288 -> [(EqnNo, EquationInfo)]
289 remove_first_column_lit lit qs
290 = ASSERT2( okGroup qs, pprGroup qs )
291 [(n, shift_pat eqn) | q@(n,eqn) <- qs, is_var_lit lit (firstPatN q)]
293 shift_pat eqn@(EqnInfo { eqn_pats = _:ps}) = eqn { eqn_pats = ps }
294 shift_pat _ = panic "Check.shift_var: no patterns"
297 This function splits the equations @qs@ in groups that deal with the
301 split_by_constructor :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet)
302 split_by_constructor qs
303 | notNull unused_cons = need_default_case used_cons unused_cons qs
304 | otherwise = no_need_default_case used_cons qs
306 used_cons = get_used_cons qs
307 unused_cons = get_unused_cons used_cons
310 The first column of the patterns matrix only have vars, then there is
314 first_column_only_vars :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
315 first_column_only_vars qs = (map (\ (xs,ys) -> (nlWildPat:xs,ys)) pats,indexs)
317 (pats, indexs) = check' (map remove_var qs)
320 This equation takes a matrix of patterns and split the equations by
321 constructor, using all the constructors that appears in the first column
322 of the pattern matching.
324 We can need a default clause or not ...., it depends if we used all the
325 constructors or not explicitly. The reasoning is similar to @process_literals@,
326 the difference is that here the default case is not always needed.
329 no_need_default_case :: [Pat Id] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
330 no_need_default_case cons qs = (concat pats, unionManyUniqSets indexs)
332 pats_indexs = map (\x -> construct_matrix x qs) cons
333 (pats,indexs) = unzip pats_indexs
335 need_default_case :: [Pat Id] -> [DataCon] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
336 need_default_case used_cons unused_cons qs
337 | null default_eqns = (pats_default_no_eqns,indexs)
338 | otherwise = (pats_default,indexs_default)
340 (pats,indexs) = no_need_default_case used_cons qs
341 default_eqns = ASSERT2( okGroup qs, pprGroup qs )
342 [remove_var q | q <- qs, is_var (firstPatN q)]
343 (pats',indexs') = check' default_eqns
344 pats_default = [(make_whole_con c:ps,constraints) |
345 c <- unused_cons, (ps,constraints) <- pats'] ++ pats
346 new_wilds = ASSERT( not (null qs) ) make_row_vars_for_constructor (head qs)
347 pats_default_no_eqns = [(make_whole_con c:new_wilds,[]) | c <- unused_cons] ++ pats
348 indexs_default = unionUniqSets indexs' indexs
350 construct_matrix :: Pat Id -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
351 construct_matrix con qs =
352 (map (make_con con) pats,indexs)
354 (pats,indexs) = (check' (remove_first_column con qs))
357 Here remove first column is more difficult that with literals due to the fact
358 that constructors can have arguments.
360 For instance, the matrix
372 remove_first_column :: Pat Id -- Constructor
373 -> [(EqnNo, EquationInfo)]
374 -> [(EqnNo, EquationInfo)]
375 remove_first_column (ConPatOut{ pat_con = L _ con, pat_args = PrefixCon con_pats }) qs
376 = ASSERT2( okGroup qs, pprGroup qs )
377 [(n, shift_var eqn) | q@(n, eqn) <- qs, is_var_con con (firstPatN q)]
379 new_wilds = [WildPat (hsLPatType arg_pat) | arg_pat <- con_pats]
380 shift_var eqn@(EqnInfo { eqn_pats = ConPatOut{ pat_args = PrefixCon ps' } : ps})
381 = eqn { eqn_pats = map unLoc ps' ++ ps }
382 shift_var eqn@(EqnInfo { eqn_pats = WildPat _ : ps })
383 = eqn { eqn_pats = new_wilds ++ ps }
384 shift_var _ = panic "Check.Shift_var:No done"
386 make_row_vars :: [HsLit] -> (EqnNo, EquationInfo) -> ExhaustivePat
387 make_row_vars used_lits (_, EqnInfo { eqn_pats = pats})
388 = (nlVarPat new_var:takeList (tail pats) (repeat nlWildPat),[(new_var,used_lits)])
393 hash_x = mkInternalName unboundKey {- doesn't matter much -}
394 (mkVarOccFS (fsLit "#x"))
397 make_row_vars_for_constructor :: (EqnNo, EquationInfo) -> [WarningPat]
398 make_row_vars_for_constructor (_, EqnInfo { eqn_pats = pats})
399 = takeList (tail pats) (repeat nlWildPat)
401 compare_cons :: Pat Id -> Pat Id -> Bool
402 compare_cons (ConPatOut{ pat_con = L _ id1 }) (ConPatOut { pat_con = L _ id2 }) = id1 == id2
404 remove_dups :: [Pat Id] -> [Pat Id]
406 remove_dups (x:xs) | or (map (\y -> compare_cons x y) xs) = remove_dups xs
407 | otherwise = x : remove_dups xs
409 get_used_cons :: [(EqnNo, EquationInfo)] -> [Pat Id]
410 get_used_cons qs = remove_dups [pat | q <- qs, let pat = firstPatN q,
413 isConPatOut :: Pat Id -> Bool
414 isConPatOut (ConPatOut {}) = True
415 isConPatOut _ = False
417 remove_dups' :: [HsLit] -> [HsLit]
419 remove_dups' (x:xs) | x `elem` xs = remove_dups' xs
420 | otherwise = x : remove_dups' xs
423 get_used_lits :: [(EqnNo, EquationInfo)] -> [HsLit]
424 get_used_lits qs = remove_dups' all_literals
426 all_literals = get_used_lits' qs
428 get_used_lits' :: [(EqnNo, EquationInfo)] -> [HsLit]
429 get_used_lits' [] = []
430 get_used_lits' (q:qs)
431 | Just lit <- get_lit (firstPatN q) = lit : get_used_lits' qs
432 | otherwise = get_used_lits qs
434 get_lit :: Pat id -> Maybe HsLit
435 -- Get a representative HsLit to stand for the OverLit
436 -- It doesn't matter which one, because they will only be compared
437 -- with other HsLits gotten in the same way
438 get_lit (LitPat lit) = Just lit
439 get_lit (NPat (OverLit { ol_val = HsIntegral i}) mb _) = Just (HsIntPrim (mb_neg mb i))
440 get_lit (NPat (OverLit { ol_val = HsFractional f }) mb _) = Just (HsFloatPrim (mb_neg mb f))
441 get_lit (NPat (OverLit { ol_val = HsIsString s }) _ _) = Just (HsStringPrim s)
444 mb_neg :: Num a => Maybe b -> a -> a
446 mb_neg (Just _) v = -v
448 get_unused_cons :: [Pat Id] -> [DataCon]
449 get_unused_cons used_cons = ASSERT( not (null used_cons) ) unused_cons
451 used_set :: UniqSet DataCon
452 used_set = mkUniqSet [d | ConPatOut{ pat_con = L _ d} <- used_cons]
453 (ConPatOut { pat_ty = ty }) = head used_cons
454 Just (ty_con, inst_tys) = splitTyConApp_maybe ty
455 unused_cons = filterOut is_used (tyConDataCons ty_con)
456 is_used con = con `elementOfUniqSet` used_set
457 || dataConCannotMatch inst_tys con
459 all_vars :: [Pat Id] -> Bool
461 all_vars (WildPat _:ps) = all_vars ps
464 remove_var :: (EqnNo, EquationInfo) -> (EqnNo, EquationInfo)
465 remove_var (n, eqn@(EqnInfo { eqn_pats = WildPat _ : ps})) = (n, eqn { eqn_pats = ps })
466 remove_var _ = panic "Check.remove_var: equation does not begin with a variable"
468 -----------------------
469 eqnPats :: (EqnNo, EquationInfo) -> [Pat Id]
470 eqnPats (_, eqn) = eqn_pats eqn
472 okGroup :: [(EqnNo, EquationInfo)] -> Bool
473 -- True if all equations have at least one pattern, and
474 -- all have the same number of patterns
476 okGroup (e:es) = n_pats > 0 && and [length (eqnPats e) == n_pats | e <- es]
478 n_pats = length (eqnPats e)
481 pprGroup :: [(EqnNo, EquationInfo)] -> SDoc
482 pprEqnInfo :: (EqnNo, EquationInfo) -> SDoc
483 pprGroup es = vcat (map pprEqnInfo es)
484 pprEqnInfo e = ppr (eqnPats e)
487 firstPatN :: (EqnNo, EquationInfo) -> Pat Id
488 firstPatN (_, eqn) = firstPat eqn
490 is_con :: Pat Id -> Bool
491 is_con (ConPatOut {}) = True
494 is_lit :: Pat Id -> Bool
495 is_lit (LitPat _) = True
496 is_lit (NPat _ _ _) = True
499 is_var :: Pat Id -> Bool
500 is_var (WildPat _) = True
503 is_var_con :: DataCon -> Pat Id -> Bool
504 is_var_con _ (WildPat _) = True
505 is_var_con con (ConPatOut{ pat_con = L _ id }) | id == con = True
506 is_var_con _ _ = False
508 is_var_lit :: HsLit -> Pat Id -> Bool
509 is_var_lit _ (WildPat _) = True
511 | Just lit' <- get_lit pat = lit == lit'
515 The difference beteewn @make_con@ and @make_whole_con@ is that
516 @make_wole_con@ creates a new constructor with all their arguments, and
517 @make_con@ takes a list of argumntes, creates the contructor getting their
518 arguments from the list. See where \fbox{\ ???\ } are used for details.
520 We need to reconstruct the patterns (make the constructors infix and
521 similar) at the same time that we create the constructors.
523 You can tell tuple constructors using
527 You can see if one constructor is infix with this clearer code :-))))))))))
529 Lex.isLexConSym (Name.occNameString (Name.getOccName con))
532 Rather clumsy but it works. (Simon Peyton Jones)
535 We don't mind the @nilDataCon@ because it doesn't change the way to
536 print the messsage, we are searching only for things like: @[1,2,3]@,
539 In @reconstruct_pat@ we want to ``undo'' the work
540 that we have done in @simplify_pat@.
543 @((,) x y)@ & returns to be & @(x, y)@
544 \\ @((:) x xs)@ & returns to be & @(x:xs)@
545 \\ @(x:(...:[])@ & returns to be & @[x,...]@
548 The difficult case is the third one becouse we need to follow all the
549 contructors until the @[]@ to know that we need to use the second case,
550 not the second. \fbox{\ ???\ }
553 isInfixCon :: DataCon -> Bool
554 isInfixCon con = isDataSymOcc (getOccName con)
556 is_nil :: Pat Name -> Bool
557 is_nil (ConPatIn con (PrefixCon [])) = unLoc con == getName nilDataCon
560 is_list :: Pat Name -> Bool
561 is_list (ListPat _ _) = True
564 return_list :: DataCon -> Pat Name -> Bool
565 return_list id q = id == consDataCon && (is_nil q || is_list q)
567 make_list :: LPat Name -> Pat Name -> Pat Name
568 make_list p q | is_nil q = ListPat [p] placeHolderType
569 make_list p (ListPat ps ty) = ListPat (p:ps) ty
570 make_list _ _ = panic "Check.make_list: Invalid argument"
572 make_con :: Pat Id -> ExhaustivePat -> ExhaustivePat
573 make_con (ConPatOut{ pat_con = L _ id }) (lp:lq:ps, constraints)
574 | return_list id q = (noLoc (make_list lp q) : ps, constraints)
575 | isInfixCon id = (nlInfixConPat (getName id) lp lq : ps, constraints)
578 make_con (ConPatOut{ pat_con = L _ id, pat_args = PrefixCon pats, pat_ty = ty }) (ps, constraints)
579 | isTupleTyCon tc = (noLoc (TuplePat pats_con (tupleTyConBoxity tc) ty) : rest_pats, constraints)
580 | isPArrFakeCon id = (noLoc (PArrPat pats_con placeHolderType) : rest_pats, constraints)
581 | otherwise = (nlConPat name pats_con : rest_pats, constraints)
584 (pats_con, rest_pats) = splitAtList pats ps
587 -- reconstruct parallel array pattern
589 -- * don't check for the type only; we need to make sure that we are really
590 -- dealing with one of the fake constructors and not with the real
593 make_whole_con :: DataCon -> WarningPat
594 make_whole_con con | isInfixCon con = nlInfixConPat name nlWildPat nlWildPat
595 | otherwise = nlConPat name pats
598 pats = [nlWildPat | _ <- dataConOrigArgTys con]
601 This equation makes the same thing as @tidy@ in @Match.lhs@, the
602 difference is that here we can do all the tidy in one place and in the
603 @Match@ tidy it must be done one column each time due to bookkeeping
608 simplify_eqn :: EquationInfo -> EquationInfo
609 simplify_eqn eqn = eqn { eqn_pats = map simplify_pat (eqn_pats eqn),
610 eqn_rhs = simplify_rhs (eqn_rhs eqn) }
612 -- Horrible hack. The simplify_pat stuff converts NPlusK pats to WildPats
613 -- which of course loses the info that they can fail to match. So we
614 -- stick in a CanFail as if it were a guard.
615 -- The Right Thing to do is for the whole system to treat NPlusK pats properly
616 simplify_rhs (MatchResult can_fail body)
617 | any has_nplusk_pat (eqn_pats eqn) = MatchResult CanFail body
618 | otherwise = MatchResult can_fail body
620 has_nplusk_lpat :: LPat Id -> Bool
621 has_nplusk_lpat (L _ p) = has_nplusk_pat p
623 has_nplusk_pat :: Pat Id -> Bool
624 has_nplusk_pat (NPlusKPat _ _ _ _) = True
625 has_nplusk_pat (ParPat p) = has_nplusk_lpat p
626 has_nplusk_pat (AsPat _ p) = has_nplusk_lpat p
627 has_nplusk_pat (ViewPat _ p _) = has_nplusk_lpat p
628 has_nplusk_pat (SigPatOut p _ ) = has_nplusk_lpat p
629 has_nplusk_pat (ListPat ps _) = any has_nplusk_lpat ps
630 has_nplusk_pat (TuplePat ps _ _) = any has_nplusk_lpat ps
631 has_nplusk_pat (PArrPat ps _) = any has_nplusk_lpat ps
632 has_nplusk_pat (LazyPat _) = False -- Why?
633 has_nplusk_pat (BangPat p) = has_nplusk_lpat p -- I think
634 has_nplusk_pat (ConPatOut { pat_args = ps }) = any has_nplusk_lpat (hsConPatArgs ps)
635 has_nplusk_pat _ = False -- VarPat, VarPatOut, WildPat, LitPat, NPat, TypePat
637 simplify_lpat :: LPat Id -> LPat Id
638 simplify_lpat p = fmap simplify_pat p
640 simplify_pat :: Pat Id -> Pat Id
641 simplify_pat pat@(WildPat _) = pat
642 simplify_pat (VarPat id) = WildPat (idType id)
643 simplify_pat (VarPatOut id _) = WildPat (idType id) -- Ignore the bindings
644 simplify_pat (ParPat p) = unLoc (simplify_lpat p)
645 simplify_pat (LazyPat p) = WildPat (hsLPatType p) -- For overlap and exhaustiveness checking
646 -- purposes, a ~pat is like a wildcard
647 simplify_pat (BangPat p) = unLoc (simplify_lpat p)
648 simplify_pat (AsPat _ p) = unLoc (simplify_lpat p)
650 simplify_pat (ViewPat expr p ty) = ViewPat expr (simplify_lpat p) ty
652 simplify_pat (SigPatOut p _) = unLoc (simplify_lpat p) -- I'm not sure this is right
654 simplify_pat pat@(ConPatOut { pat_con = L _ id, pat_args = ps })
655 = pat { pat_args = simplify_con id ps }
657 simplify_pat (ListPat ps ty) =
658 unLoc $ foldr (\ x y -> mkPrefixConPat consDataCon [x,y] list_ty)
660 (map simplify_lpat ps)
661 where list_ty = mkListTy ty
663 -- introduce fake parallel array constructors to be able to handle parallel
664 -- arrays with the existing machinery for constructor pattern
666 simplify_pat (PArrPat ps ty)
667 = unLoc $ mkPrefixConPat (parrFakeCon (length ps))
668 (map simplify_lpat ps)
671 simplify_pat (TuplePat ps boxity ty)
672 = unLoc $ mkPrefixConPat (tupleCon boxity arity)
673 (map simplify_lpat ps) ty
677 -- unpack string patterns fully, so we can see when they overlap with
678 -- each other, or even explicit lists of Chars.
679 simplify_pat (LitPat (HsString s)) =
680 unLoc $ foldr (\c pat -> mkPrefixConPat consDataCon [mk_char_lit c, pat] stringTy)
681 (mkPrefixConPat nilDataCon [] stringTy) (unpackFS s)
683 mk_char_lit c = mkPrefixConPat charDataCon [nlLitPat (HsCharPrim c)] charTy
685 simplify_pat (LitPat lit) = tidyLitPat lit
686 simplify_pat (NPat lit mb_neg eq) = tidyNPat lit mb_neg eq
688 simplify_pat (NPlusKPat id _ _ _)
689 = WildPat (idType (unLoc id))
691 simplify_pat (CoPat _ pat _) = simplify_pat pat
694 simplify_con :: DataCon -> HsConPatDetails Id -> HsConPatDetails Id
695 simplify_con _ (PrefixCon ps) = PrefixCon (map simplify_lpat ps)
696 simplify_con _ (InfixCon p1 p2) = PrefixCon [simplify_lpat p1, simplify_lpat p2]
697 simplify_con con (RecCon (HsRecFields fs _))
698 | null fs = PrefixCon [nlWildPat | _ <- dataConOrigArgTys con]
699 -- Special case for null patterns; maybe not a record at all
700 | otherwise = PrefixCon (map (simplify_lpat.snd) all_pats)
702 -- pad out all the missing fields with WildPats.
703 field_pats = map (\ f -> (f, nlWildPat)) (dataConFieldLabels con)
704 all_pats = foldr (\(HsRecField id p _) acc -> insertNm (getName (unLoc id)) p acc)
707 insertNm nm p [] = [(nm,p)]
708 insertNm nm p (x@(n,_):xs)
709 | nm == n = (nm,p):xs
710 | otherwise = x : insertNm nm p xs