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"
36 This module performs checks about if one list of equations are:
41 To discover that we go through the list of equations in a tree-like fashion.
43 If you like theory, a similar algorithm is described in:
45 {\em Two Techniques for Compiling Lazy Pattern Matching},
47 INRIA Rocquencourt (RR-2385, 1994)
49 The algorithm is based on the first technique, but there are some differences:
51 \item We don't generate code
52 \item We have constructors and literals (not only literals as in the
54 \item We don't use directions, we must select the columns from
57 (By the way the second technique is really similar to the one used in
58 @Match.lhs@ to generate code)
60 This function takes the equations of a pattern and returns:
62 \item The patterns that are not recognized
63 \item The equations that are not overlapped
65 It simplify the patterns and then call @check'@ (the same semantics), and it
66 needs to reconstruct the patterns again ....
68 The problem appear with things like:
73 We want to put the two patterns with the same syntax, (prefix form) and
74 then all the constructors are equal:
76 f (: x (: y [])) = ....
79 (more about that in @simplify_eqns@)
81 We would prefer to have a @WarningPat@ of type @String@, but Strings and the
82 Pretty Printer are not friends.
84 We use @InPat@ in @WarningPat@ instead of @OutPat@
85 because we need to print the
86 warning messages in the same way they are introduced, i.e. if the user
91 He don't want a warning message written:
93 f (: x (: y [])) ........
95 Then we need to use InPats.
97 Juan Quintela 5 JUL 1998\\
98 User-friendliness and compiler writers are no friends.
102 type WarningPat = InPat Name
103 type ExhaustivePat = ([WarningPat], [(Name, [HsLit])])
105 type EqnSet = UniqSet EqnNo
108 check :: [EquationInfo] -> ([ExhaustivePat], [EquationInfo])
109 -- Second result is the shadowed equations
110 check qs = (untidy_warns, shadowed_eqns)
112 (warns, used_nos) = check' ([1..] `zip` map simplify_eqn qs)
113 untidy_warns = map untidy_exhaustive warns
114 shadowed_eqns = [eqn | (eqn,i) <- qs `zip` [1..],
115 not (i `elementOfUniqSet` used_nos)]
117 untidy_exhaustive :: ExhaustivePat -> ExhaustivePat
118 untidy_exhaustive ([pat], messages) =
119 ([untidy_no_pars pat], map untidy_message messages)
120 untidy_exhaustive (pats, messages) =
121 (map untidy_pars pats, map untidy_message messages)
123 untidy_message :: (Name, [HsLit]) -> (Name, [HsLit])
124 untidy_message (string, lits) = (string, map untidy_lit lits)
127 The function @untidy@ does the reverse work of the @simplify_pat@ funcion.
133 untidy_no_pars :: WarningPat -> WarningPat
134 untidy_no_pars p = untidy False p
136 untidy_pars :: WarningPat -> WarningPat
137 untidy_pars p = untidy True p
139 untidy :: NeedPars -> WarningPat -> WarningPat
140 untidy b (L loc p) = L loc (untidy' b p)
142 untidy' _ p@(WildPat _) = p
143 untidy' _ p@(VarPat _) = p
144 untidy' _ (LitPat lit) = LitPat (untidy_lit lit)
145 untidy' _ p@(ConPatIn _ (PrefixCon [])) = p
146 untidy' b (ConPatIn name ps) = pars b (L loc (ConPatIn name (untidy_con ps)))
147 untidy' _ (ListPat pats ty) = ListPat (map untidy_no_pars pats) ty
148 untidy' _ (TuplePat pats box ty) = TuplePat (map untidy_no_pars pats) box ty
149 untidy' _ (PArrPat _ _) = panic "Check.untidy: Shouldn't get a parallel array here!"
150 untidy' _ (SigPatIn _ _) = panic "Check.untidy: SigPat"
152 untidy_con :: HsConPatDetails Name -> HsConPatDetails Name
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 -- FIXME: hack to get view patterns through for now
220 | otherwise = ([([],[])],emptyUniqSet)
221 -- pprPanic "Check.check': Not implemented :-(" (ppr first_pats)
223 -- Note: RecPats will have been simplified to ConPats
225 first_pats = ASSERT2( okGroup qs, pprGroup qs ) map firstPatN qs
226 constructors = any is_con first_pats
227 literals = any is_lit first_pats
228 only_vars = all is_var first_pats
231 Here begins the code to deal with literals, we need to split the matrix
232 in different matrix beginning by each literal and a last matrix with the
236 split_by_literals :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet)
237 split_by_literals qs = process_literals used_lits qs
239 used_lits = get_used_lits qs
242 @process_explicit_literals@ is a function that process each literal that appears
243 in the column of the matrix.
246 process_explicit_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
247 process_explicit_literals lits qs = (concat pats, unionManyUniqSets indexs)
249 pats_indexs = map (\x -> construct_literal_matrix x qs) lits
250 (pats,indexs) = unzip pats_indexs
254 @process_literals@ calls @process_explicit_literals@ to deal with the literals
255 that appears in the matrix and deal also with the rest of the cases. It
256 must be one Variable to be complete.
260 process_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
261 process_literals used_lits qs
262 | null default_eqns = ASSERT( not (null qs) ) ([make_row_vars used_lits (head qs)] ++ pats,indexs)
263 | otherwise = (pats_default,indexs_default)
265 (pats,indexs) = process_explicit_literals used_lits qs
266 default_eqns = ASSERT2( okGroup qs, pprGroup qs )
267 [remove_var q | q <- qs, is_var (firstPatN q)]
268 (pats',indexs') = check' default_eqns
269 pats_default = [(nlWildPat:ps,constraints) | (ps,constraints) <- (pats')] ++ pats
270 indexs_default = unionUniqSets indexs' indexs
273 Here we have selected the literal and we will select all the equations that
274 begins for that literal and create a new matrix.
277 construct_literal_matrix :: HsLit -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
278 construct_literal_matrix lit qs =
279 (map (\ (xs,ys) -> (new_lit:xs,ys)) pats,indexs)
281 (pats,indexs) = (check' (remove_first_column_lit lit qs))
282 new_lit = nlLitPat lit
284 remove_first_column_lit :: HsLit
285 -> [(EqnNo, EquationInfo)]
286 -> [(EqnNo, EquationInfo)]
287 remove_first_column_lit lit qs
288 = ASSERT2( okGroup qs, pprGroup qs )
289 [(n, shift_pat eqn) | q@(n,eqn) <- qs, is_var_lit lit (firstPatN q)]
291 shift_pat eqn@(EqnInfo { eqn_pats = _:ps}) = eqn { eqn_pats = ps }
292 shift_pat _ = panic "Check.shift_var: no patterns"
295 This function splits the equations @qs@ in groups that deal with the
299 split_by_constructor :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet)
300 split_by_constructor qs
301 | notNull unused_cons = need_default_case used_cons unused_cons qs
302 | otherwise = no_need_default_case used_cons qs
304 used_cons = get_used_cons qs
305 unused_cons = get_unused_cons used_cons
308 The first column of the patterns matrix only have vars, then there is
312 first_column_only_vars :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
313 first_column_only_vars qs = (map (\ (xs,ys) -> (nlWildPat:xs,ys)) pats,indexs)
315 (pats, indexs) = check' (map remove_var qs)
318 This equation takes a matrix of patterns and split the equations by
319 constructor, using all the constructors that appears in the first column
320 of the pattern matching.
322 We can need a default clause or not ...., it depends if we used all the
323 constructors or not explicitly. The reasoning is similar to @process_literals@,
324 the difference is that here the default case is not always needed.
327 no_need_default_case :: [Pat Id] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
328 no_need_default_case cons qs = (concat pats, unionManyUniqSets indexs)
330 pats_indexs = map (\x -> construct_matrix x qs) cons
331 (pats,indexs) = unzip pats_indexs
333 need_default_case :: [Pat Id] -> [DataCon] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
334 need_default_case used_cons unused_cons qs
335 | null default_eqns = (pats_default_no_eqns,indexs)
336 | otherwise = (pats_default,indexs_default)
338 (pats,indexs) = no_need_default_case used_cons qs
339 default_eqns = ASSERT2( okGroup qs, pprGroup qs )
340 [remove_var q | q <- qs, is_var (firstPatN q)]
341 (pats',indexs') = check' default_eqns
342 pats_default = [(make_whole_con c:ps,constraints) |
343 c <- unused_cons, (ps,constraints) <- pats'] ++ pats
344 new_wilds = ASSERT( not (null qs) ) make_row_vars_for_constructor (head qs)
345 pats_default_no_eqns = [(make_whole_con c:new_wilds,[]) | c <- unused_cons] ++ pats
346 indexs_default = unionUniqSets indexs' indexs
348 construct_matrix :: Pat Id -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
349 construct_matrix con qs =
350 (map (make_con con) pats,indexs)
352 (pats,indexs) = (check' (remove_first_column con qs))
355 Here remove first column is more difficult that with literals due to the fact
356 that constructors can have arguments.
358 For instance, the matrix
370 remove_first_column :: Pat Id -- Constructor
371 -> [(EqnNo, EquationInfo)]
372 -> [(EqnNo, EquationInfo)]
373 remove_first_column (ConPatOut{ pat_con = L _ con, pat_args = PrefixCon con_pats }) qs
374 = ASSERT2( okGroup qs, pprGroup qs )
375 [(n, shift_var eqn) | q@(n, eqn) <- qs, is_var_con con (firstPatN q)]
377 new_wilds = [WildPat (hsLPatType arg_pat) | arg_pat <- con_pats]
378 shift_var eqn@(EqnInfo { eqn_pats = ConPatOut{ pat_args = PrefixCon ps' } : ps})
379 = eqn { eqn_pats = map unLoc ps' ++ ps }
380 shift_var eqn@(EqnInfo { eqn_pats = WildPat _ : ps })
381 = eqn { eqn_pats = new_wilds ++ ps }
382 shift_var _ = panic "Check.Shift_var:No done"
384 make_row_vars :: [HsLit] -> (EqnNo, EquationInfo) -> ExhaustivePat
385 make_row_vars used_lits (_, EqnInfo { eqn_pats = pats})
386 = (nlVarPat new_var:takeList (tail pats) (repeat nlWildPat),[(new_var,used_lits)])
391 hash_x = mkInternalName unboundKey {- doesn't matter much -}
392 (mkVarOccFS (fsLit "#x"))
395 make_row_vars_for_constructor :: (EqnNo, EquationInfo) -> [WarningPat]
396 make_row_vars_for_constructor (_, EqnInfo { eqn_pats = pats})
397 = takeList (tail pats) (repeat nlWildPat)
399 compare_cons :: Pat Id -> Pat Id -> Bool
400 compare_cons (ConPatOut{ pat_con = L _ id1 }) (ConPatOut { pat_con = L _ id2 }) = id1 == id2
402 remove_dups :: [Pat Id] -> [Pat Id]
404 remove_dups (x:xs) | or (map (\y -> compare_cons x y) xs) = remove_dups xs
405 | otherwise = x : remove_dups xs
407 get_used_cons :: [(EqnNo, EquationInfo)] -> [Pat Id]
408 get_used_cons qs = remove_dups [pat | q <- qs, let pat = firstPatN q,
411 isConPatOut :: Pat Id -> Bool
412 isConPatOut (ConPatOut {}) = True
413 isConPatOut _ = False
415 remove_dups' :: [HsLit] -> [HsLit]
417 remove_dups' (x:xs) | x `elem` xs = remove_dups' xs
418 | otherwise = x : remove_dups' xs
421 get_used_lits :: [(EqnNo, EquationInfo)] -> [HsLit]
422 get_used_lits qs = remove_dups' all_literals
424 all_literals = get_used_lits' qs
426 get_used_lits' :: [(EqnNo, EquationInfo)] -> [HsLit]
427 get_used_lits' [] = []
428 get_used_lits' (q:qs)
429 | Just lit <- get_lit (firstPatN q) = lit : get_used_lits' qs
430 | otherwise = get_used_lits qs
432 get_lit :: Pat id -> Maybe HsLit
433 -- Get a representative HsLit to stand for the OverLit
434 -- It doesn't matter which one, because they will only be compared
435 -- with other HsLits gotten in the same way
436 get_lit (LitPat lit) = Just lit
437 get_lit (NPat (OverLit { ol_val = HsIntegral i}) mb _) = Just (HsIntPrim (mb_neg mb i))
438 get_lit (NPat (OverLit { ol_val = HsFractional f }) mb _) = Just (HsFloatPrim (mb_neg mb f))
439 get_lit (NPat (OverLit { ol_val = HsIsString s }) _ _) = Just (HsStringPrim s)
442 mb_neg :: Num a => Maybe b -> a -> a
444 mb_neg (Just _) v = -v
446 get_unused_cons :: [Pat Id] -> [DataCon]
447 get_unused_cons used_cons = ASSERT( not (null used_cons) ) unused_cons
449 (ConPatOut { pat_con = l_con }) = head used_cons
450 ty_con = dataConTyCon (unLoc l_con) -- Newtype observable
451 all_cons = tyConDataCons ty_con
452 used_cons_as_id = map (\ (ConPatOut{ pat_con = L _ d}) -> d) used_cons
453 unused_cons = uniqSetToList
454 (mkUniqSet all_cons `minusUniqSet` mkUniqSet used_cons_as_id)
456 all_vars :: [Pat Id] -> Bool
458 all_vars (WildPat _:ps) = all_vars ps
461 remove_var :: (EqnNo, EquationInfo) -> (EqnNo, EquationInfo)
462 remove_var (n, eqn@(EqnInfo { eqn_pats = WildPat _ : ps})) = (n, eqn { eqn_pats = ps })
463 remove_var _ = panic "Check.remove_var: equation does not begin with a variable"
465 -----------------------
466 eqnPats :: (EqnNo, EquationInfo) -> [Pat Id]
467 eqnPats (_, eqn) = eqn_pats eqn
469 okGroup :: [(EqnNo, EquationInfo)] -> Bool
470 -- True if all equations have at least one pattern, and
471 -- all have the same number of patterns
473 okGroup (e:es) = n_pats > 0 && and [length (eqnPats e) == n_pats | e <- es]
475 n_pats = length (eqnPats e)
478 pprGroup :: [(EqnNo, EquationInfo)] -> SDoc
479 pprEqnInfo :: (EqnNo, EquationInfo) -> SDoc
480 pprGroup es = vcat (map pprEqnInfo es)
481 pprEqnInfo e = ppr (eqnPats e)
484 firstPatN :: (EqnNo, EquationInfo) -> Pat Id
485 firstPatN (_, eqn) = firstPat eqn
487 is_con :: Pat Id -> Bool
488 is_con (ConPatOut {}) = True
491 is_lit :: Pat Id -> Bool
492 is_lit (LitPat _) = True
493 is_lit (NPat _ _ _) = True
496 is_var :: Pat Id -> Bool
497 is_var (WildPat _) = True
500 is_var_con :: DataCon -> Pat Id -> Bool
501 is_var_con _ (WildPat _) = True
502 is_var_con con (ConPatOut{ pat_con = L _ id }) | id == con = True
503 is_var_con _ _ = False
505 is_var_lit :: HsLit -> Pat Id -> Bool
506 is_var_lit _ (WildPat _) = True
508 | Just lit' <- get_lit pat = lit == lit'
512 The difference beteewn @make_con@ and @make_whole_con@ is that
513 @make_wole_con@ creates a new constructor with all their arguments, and
514 @make_con@ takes a list of argumntes, creates the contructor getting their
515 arguments from the list. See where \fbox{\ ???\ } are used for details.
517 We need to reconstruct the patterns (make the constructors infix and
518 similar) at the same time that we create the constructors.
520 You can tell tuple constructors using
524 You can see if one constructor is infix with this clearer code :-))))))))))
526 Lex.isLexConSym (Name.occNameString (Name.getOccName con))
529 Rather clumsy but it works. (Simon Peyton Jones)
532 We don't mind the @nilDataCon@ because it doesn't change the way to
533 print the messsage, we are searching only for things like: @[1,2,3]@,
536 In @reconstruct_pat@ we want to ``undo'' the work
537 that we have done in @simplify_pat@.
540 @((,) x y)@ & returns to be & @(x, y)@
541 \\ @((:) x xs)@ & returns to be & @(x:xs)@
542 \\ @(x:(...:[])@ & returns to be & @[x,...]@
545 The difficult case is the third one becouse we need to follow all the
546 contructors until the @[]@ to know that we need to use the second case,
547 not the second. \fbox{\ ???\ }
550 isInfixCon :: DataCon -> Bool
551 isInfixCon con = isDataSymOcc (getOccName con)
553 is_nil :: Pat Name -> Bool
554 is_nil (ConPatIn con (PrefixCon [])) = unLoc con == getName nilDataCon
557 is_list :: Pat Name -> Bool
558 is_list (ListPat _ _) = True
561 return_list :: DataCon -> Pat Name -> Bool
562 return_list id q = id == consDataCon && (is_nil q || is_list q)
564 make_list :: LPat Name -> Pat Name -> Pat Name
565 make_list p q | is_nil q = ListPat [p] placeHolderType
566 make_list p (ListPat ps ty) = ListPat (p:ps) ty
567 make_list _ _ = panic "Check.make_list: Invalid argument"
569 make_con :: Pat Id -> ExhaustivePat -> ExhaustivePat
570 make_con (ConPatOut{ pat_con = L _ id }) (lp:lq:ps, constraints)
571 | return_list id q = (noLoc (make_list lp q) : ps, constraints)
572 | isInfixCon id = (nlInfixConPat (getName id) lp lq : ps, constraints)
575 make_con (ConPatOut{ pat_con = L _ id, pat_args = PrefixCon pats, pat_ty = ty }) (ps, constraints)
576 | isTupleTyCon tc = (noLoc (TuplePat pats_con (tupleTyConBoxity tc) ty) : rest_pats, constraints)
577 | isPArrFakeCon id = (noLoc (PArrPat pats_con placeHolderType) : rest_pats, constraints)
578 | otherwise = (nlConPat name pats_con : rest_pats, constraints)
581 (pats_con, rest_pats) = splitAtList pats ps
584 -- reconstruct parallel array pattern
586 -- * don't check for the type only; we need to make sure that we are really
587 -- dealing with one of the fake constructors and not with the real
590 make_whole_con :: DataCon -> WarningPat
591 make_whole_con con | isInfixCon con = nlInfixConPat name nlWildPat nlWildPat
592 | otherwise = nlConPat name pats
595 pats = [nlWildPat | _ <- dataConOrigArgTys con]
598 This equation makes the same thing as @tidy@ in @Match.lhs@, the
599 difference is that here we can do all the tidy in one place and in the
600 @Match@ tidy it must be done one column each time due to bookkeeping
605 simplify_eqn :: EquationInfo -> EquationInfo
606 simplify_eqn eqn = eqn { eqn_pats = map simplify_pat (eqn_pats eqn),
607 eqn_rhs = simplify_rhs (eqn_rhs eqn) }
609 -- Horrible hack. The simplify_pat stuff converts NPlusK pats to WildPats
610 -- which of course loses the info that they can fail to match. So we
611 -- stick in a CanFail as if it were a guard.
612 -- The Right Thing to do is for the whole system to treat NPlusK pats properly
613 simplify_rhs (MatchResult can_fail body)
614 | any has_nplusk_pat (eqn_pats eqn) = MatchResult CanFail body
615 | otherwise = MatchResult can_fail body
617 has_nplusk_lpat :: LPat Id -> Bool
618 has_nplusk_lpat (L _ p) = has_nplusk_pat p
620 has_nplusk_pat :: Pat Id -> Bool
621 has_nplusk_pat (NPlusKPat _ _ _ _) = True
622 has_nplusk_pat (ParPat p) = has_nplusk_lpat p
623 has_nplusk_pat (AsPat _ p) = has_nplusk_lpat p
624 has_nplusk_pat (ViewPat _ p _) = has_nplusk_lpat p
625 has_nplusk_pat (SigPatOut p _ ) = has_nplusk_lpat p
626 has_nplusk_pat (ListPat ps _) = any has_nplusk_lpat ps
627 has_nplusk_pat (TuplePat ps _ _) = any has_nplusk_lpat ps
628 has_nplusk_pat (PArrPat ps _) = any has_nplusk_lpat ps
629 has_nplusk_pat (LazyPat _) = False -- Why?
630 has_nplusk_pat (BangPat p) = has_nplusk_lpat p -- I think
631 has_nplusk_pat (ConPatOut { pat_args = ps }) = any has_nplusk_lpat (hsConPatArgs ps)
632 has_nplusk_pat _ = False -- VarPat, VarPatOut, WildPat, LitPat, NPat, TypePat
634 simplify_lpat :: LPat Id -> LPat Id
635 simplify_lpat p = fmap simplify_pat p
637 simplify_pat :: Pat Id -> Pat Id
638 simplify_pat pat@(WildPat _) = pat
639 simplify_pat (VarPat id) = WildPat (idType id)
640 simplify_pat (VarPatOut id _) = WildPat (idType id) -- Ignore the bindings
641 simplify_pat (ParPat p) = unLoc (simplify_lpat p)
642 simplify_pat (LazyPat p) = WildPat (hsLPatType p) -- For overlap and exhaustiveness checking
643 -- purposes, a ~pat is like a wildcard
644 simplify_pat (BangPat p) = unLoc (simplify_lpat p)
645 simplify_pat (AsPat _ p) = unLoc (simplify_lpat p)
647 simplify_pat (ViewPat expr p ty) = ViewPat expr (simplify_lpat p) ty
649 simplify_pat (SigPatOut p _) = unLoc (simplify_lpat p) -- I'm not sure this is right
651 simplify_pat pat@(ConPatOut { pat_con = L _ id, pat_args = ps })
652 = pat { pat_args = simplify_con id ps }
654 simplify_pat (ListPat ps ty) =
655 unLoc $ foldr (\ x y -> mkPrefixConPat consDataCon [x,y] list_ty)
657 (map simplify_lpat ps)
658 where list_ty = mkListTy ty
660 -- introduce fake parallel array constructors to be able to handle parallel
661 -- arrays with the existing machinery for constructor pattern
663 simplify_pat (PArrPat ps ty)
664 = unLoc $ mkPrefixConPat (parrFakeCon (length ps))
665 (map simplify_lpat ps)
668 simplify_pat (TuplePat ps boxity ty)
669 = unLoc $ mkPrefixConPat (tupleCon boxity arity)
670 (map simplify_lpat ps) ty
674 -- unpack string patterns fully, so we can see when they overlap with
675 -- each other, or even explicit lists of Chars.
676 simplify_pat (LitPat (HsString s)) =
677 unLoc $ foldr (\c pat -> mkPrefixConPat consDataCon [mk_char_lit c, pat] stringTy)
678 (mkPrefixConPat nilDataCon [] stringTy) (unpackFS s)
680 mk_char_lit c = mkPrefixConPat charDataCon [nlLitPat (HsCharPrim c)] charTy
682 simplify_pat (LitPat lit) = tidyLitPat lit
683 simplify_pat (NPat lit mb_neg eq) = tidyNPat lit mb_neg eq
685 simplify_pat (NPlusKPat id _ _ _)
686 = WildPat (idType (unLoc id))
688 simplify_pat (CoPat _ pat _) = simplify_pat pat
691 simplify_con :: DataCon -> HsConPatDetails Id -> HsConPatDetails Id
692 simplify_con _ (PrefixCon ps) = PrefixCon (map simplify_lpat ps)
693 simplify_con _ (InfixCon p1 p2) = PrefixCon [simplify_lpat p1, simplify_lpat p2]
694 simplify_con con (RecCon (HsRecFields fs _))
695 | null fs = PrefixCon [nlWildPat | _ <- dataConOrigArgTys con]
696 -- Special case for null patterns; maybe not a record at all
697 | otherwise = PrefixCon (map (simplify_lpat.snd) all_pats)
699 -- pad out all the missing fields with WildPats.
700 field_pats = map (\ f -> (f, nlWildPat)) (dataConFieldLabels con)
701 all_pats = foldr (\(HsRecField id p _) acc -> insertNm (getName (unLoc id)) p acc)
704 insertNm nm p [] = [(nm,p)]
705 insertNm nm p (x@(n,_):xs)
706 | nm == n = (nm,p):xs
707 | otherwise = x : insertNm nm p xs