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 @tidy_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 -- if there are view patterns, just give up - don't know what the function is
113 check qs = pprTrace "check" (ppr tidy_qs) $
114 (untidy_warns, shadowed_eqns)
116 tidy_qs = map tidy_eqn qs
117 (warns, used_nos) = check' ([1..] `zip` tidy_qs)
118 untidy_warns = map untidy_exhaustive warns
119 shadowed_eqns = [eqn | (eqn,i) <- qs `zip` [1..],
120 not (i `elementOfUniqSet` used_nos)]
122 untidy_exhaustive :: ExhaustivePat -> ExhaustivePat
123 untidy_exhaustive ([pat], messages) =
124 ([untidy_no_pars pat], map untidy_message messages)
125 untidy_exhaustive (pats, messages) =
126 (map untidy_pars pats, map untidy_message messages)
128 untidy_message :: (Name, [HsLit]) -> (Name, [HsLit])
129 untidy_message (string, lits) = (string, map untidy_lit lits)
132 The function @untidy@ does the reverse work of the @tidy_pat@ funcion.
138 untidy_no_pars :: WarningPat -> WarningPat
139 untidy_no_pars p = untidy False p
141 untidy_pars :: WarningPat -> WarningPat
142 untidy_pars p = untidy True p
144 untidy :: NeedPars -> WarningPat -> WarningPat
145 untidy b (L loc p) = L loc (untidy' b p)
147 untidy' _ p@(WildPat _) = p
148 untidy' _ p@(VarPat _) = p
149 untidy' _ (LitPat lit) = LitPat (untidy_lit lit)
150 untidy' _ p@(ConPatIn _ (PrefixCon [])) = p
151 untidy' b (ConPatIn name ps) = pars b (L loc (ConPatIn name (untidy_con ps)))
152 untidy' _ (ListPat pats ty) = ListPat (map untidy_no_pars pats) ty
153 untidy' _ (TuplePat pats box ty) = TuplePat (map untidy_no_pars pats) box ty
154 untidy' _ (PArrPat _ _) = panic "Check.untidy: Shouldn't get a parallel array here!"
155 untidy' _ (SigPatIn _ _) = panic "Check.untidy: SigPat"
157 untidy_con :: HsConPatDetails Name -> HsConPatDetails Name
158 untidy_con (PrefixCon pats) = PrefixCon (map untidy_pars pats)
159 untidy_con (InfixCon p1 p2) = InfixCon (untidy_pars p1) (untidy_pars p2)
160 untidy_con (RecCon (HsRecFields flds dd))
161 = RecCon (HsRecFields [ fld { hsRecFieldArg = untidy_pars (hsRecFieldArg fld) }
164 pars :: NeedPars -> WarningPat -> Pat Name
165 pars True p = ParPat p
168 untidy_lit :: HsLit -> HsLit
169 untidy_lit (HsCharPrim c) = HsChar c
173 This equation is the same that check, the only difference is that the
174 boring work is done, that work needs to be done only once, this is
175 the reason top have two functions, check is the external interface,
176 @check'@ is called recursively.
178 There are several cases:
181 \item There are no equations: Everything is OK.
182 \item There are only one equation, that can fail, and all the patterns are
183 variables. Then that equation is used and the same equation is
185 \item All the patterns are variables, and the match can fail, there are
186 more equations then the results is the result of the rest of equations
187 and this equation is used also.
189 \item The general case, if all the patterns are variables (here the match
190 can't fail) then the result is that this equation is used and this
191 equation doesn't generate non-exhaustive cases.
193 \item In the general case, there can exist literals ,constructors or only
194 vars in the first column, we actuate in consequence.
201 check' :: [(EqnNo, EquationInfo)]
202 -> ([ExhaustivePat], -- Pattern scheme that might not be matched at all
203 EqnSet) -- Eqns that are used (others are overlapped)
205 check' [] = ([([],[])],emptyUniqSet)
207 check' ((n, EqnInfo { eqn_pats = ps, eqn_rhs = MatchResult can_fail _ }) : rs)
208 | first_eqn_all_vars && case can_fail of { CantFail -> True; CanFail -> False }
209 = ([], unitUniqSet n) -- One eqn, which can't fail
211 | first_eqn_all_vars && null rs -- One eqn, but it can fail
212 = ([(takeList ps (repeat nlWildPat),[])], unitUniqSet n)
214 | first_eqn_all_vars -- Several eqns, first can fail
215 = (pats, addOneToUniqSet indexs n)
217 first_eqn_all_vars = all_vars ps
218 (pats,indexs) = check' rs
221 | some_literals = split_by_literals qs
222 | some_constructors = split_by_constructor qs
223 | only_vars = first_column_only_vars qs
224 | otherwise = pprPanic "Check.check': Not implemented :-(" (ppr first_pats)
227 -- Note: RecPats will have been simplified to ConPats
229 first_pats = ASSERT2( okGroup qs, pprGroup qs ) map firstPatN qs
230 some_constructors = any is_con first_pats
231 some_literals = any is_lit first_pats
232 only_vars = all is_var first_pats
235 Here begins the code to deal with literals, we need to split the matrix
236 in different matrix beginning by each literal and a last matrix with the
240 split_by_literals :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet)
241 split_by_literals qs = process_literals used_lits qs
243 used_lits = get_used_lits qs
246 @process_explicit_literals@ is a function that process each literal that appears
247 in the column of the matrix.
250 process_explicit_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
251 process_explicit_literals lits qs = (concat pats, unionManyUniqSets indexs)
253 pats_indexs = map (\x -> construct_literal_matrix x qs) lits
254 (pats,indexs) = unzip pats_indexs
258 @process_literals@ calls @process_explicit_literals@ to deal with the literals
259 that appears in the matrix and deal also with the rest of the cases. It
260 must be one Variable to be complete.
264 process_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
265 process_literals used_lits qs
266 | null default_eqns = ASSERT( not (null qs) ) ([make_row_vars used_lits (head qs)] ++ pats,indexs)
267 | otherwise = (pats_default,indexs_default)
269 (pats,indexs) = process_explicit_literals used_lits qs
270 default_eqns = ASSERT2( okGroup qs, pprGroup qs )
271 [remove_var q | q <- qs, is_var (firstPatN q)]
272 (pats',indexs') = check' default_eqns
273 pats_default = [(nlWildPat:ps,constraints) | (ps,constraints) <- (pats')] ++ pats
274 indexs_default = unionUniqSets indexs' indexs
277 Here we have selected the literal and we will select all the equations that
278 begins for that literal and create a new matrix.
281 construct_literal_matrix :: HsLit -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
282 construct_literal_matrix lit qs =
283 (map (\ (xs,ys) -> (new_lit:xs,ys)) pats,indexs)
285 (pats,indexs) = (check' (remove_first_column_lit lit qs))
286 new_lit = nlLitPat lit
288 remove_first_column_lit :: HsLit
289 -> [(EqnNo, EquationInfo)]
290 -> [(EqnNo, EquationInfo)]
291 remove_first_column_lit lit qs
292 = ASSERT2( okGroup qs, pprGroup qs )
293 [(n, shift_pat eqn) | q@(n,eqn) <- qs, is_var_lit lit (firstPatN q)]
295 shift_pat eqn@(EqnInfo { eqn_pats = _:ps}) = eqn { eqn_pats = ps }
296 shift_pat _ = panic "Check.shift_var: no patterns"
299 This function splits the equations @qs@ in groups that deal with the
303 split_by_constructor :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet)
304 split_by_constructor qs
305 | notNull unused_cons = need_default_case used_cons unused_cons qs
306 | otherwise = no_need_default_case used_cons qs
308 used_cons = get_used_cons qs
309 unused_cons = get_unused_cons used_cons
312 The first column of the patterns matrix only have vars, then there is
316 first_column_only_vars :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
317 first_column_only_vars qs = (map (\ (xs,ys) -> (nlWildPat:xs,ys)) pats,indexs)
319 (pats, indexs) = check' (map remove_var qs)
322 This equation takes a matrix of patterns and split the equations by
323 constructor, using all the constructors that appears in the first column
324 of the pattern matching.
326 We can need a default clause or not ...., it depends if we used all the
327 constructors or not explicitly. The reasoning is similar to @process_literals@,
328 the difference is that here the default case is not always needed.
331 no_need_default_case :: [Pat Id] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
332 no_need_default_case cons qs = (concat pats, unionManyUniqSets indexs)
334 pats_indexs = map (\x -> construct_matrix x qs) cons
335 (pats,indexs) = unzip pats_indexs
337 need_default_case :: [Pat Id] -> [DataCon] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
338 need_default_case used_cons unused_cons qs
339 | null default_eqns = (pats_default_no_eqns,indexs)
340 | otherwise = (pats_default,indexs_default)
342 (pats,indexs) = no_need_default_case used_cons qs
343 default_eqns = ASSERT2( okGroup qs, pprGroup qs )
344 [remove_var q | q <- qs, is_var (firstPatN q)]
345 (pats',indexs') = check' default_eqns
346 pats_default = [(make_whole_con c:ps,constraints) |
347 c <- unused_cons, (ps,constraints) <- pats'] ++ pats
348 new_wilds = ASSERT( not (null qs) ) make_row_vars_for_constructor (head qs)
349 pats_default_no_eqns = [(make_whole_con c:new_wilds,[]) | c <- unused_cons] ++ pats
350 indexs_default = unionUniqSets indexs' indexs
352 construct_matrix :: Pat Id -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
353 construct_matrix con qs =
354 (map (make_con con) pats,indexs)
356 (pats,indexs) = (check' (remove_first_column con qs))
359 Here remove first column is more difficult that with literals due to the fact
360 that constructors can have arguments.
362 For instance, the matrix
374 remove_first_column :: Pat Id -- Constructor
375 -> [(EqnNo, EquationInfo)]
376 -> [(EqnNo, EquationInfo)]
377 remove_first_column (ConPatOut{ pat_con = L _ con, pat_args = PrefixCon con_pats }) qs
378 = ASSERT2( okGroup qs, pprGroup qs )
379 [(n, shift_var eqn) | q@(n, eqn) <- qs, is_var_con con (firstPatN q)]
381 new_wilds = [WildPat (hsLPatType arg_pat) | arg_pat <- con_pats]
382 shift_var eqn@(EqnInfo { eqn_pats = ConPatOut{ pat_args = PrefixCon ps' } : ps})
383 = eqn { eqn_pats = map unLoc ps' ++ ps }
384 shift_var eqn@(EqnInfo { eqn_pats = WildPat _ : ps })
385 = eqn { eqn_pats = new_wilds ++ ps }
386 shift_var _ = panic "Check.Shift_var:No done"
388 make_row_vars :: [HsLit] -> (EqnNo, EquationInfo) -> ExhaustivePat
389 make_row_vars used_lits (_, EqnInfo { eqn_pats = pats})
390 = (nlVarPat new_var:takeList (tail pats) (repeat nlWildPat),[(new_var,used_lits)])
395 hash_x = mkInternalName unboundKey {- doesn't matter much -}
396 (mkVarOccFS (fsLit "#x"))
399 make_row_vars_for_constructor :: (EqnNo, EquationInfo) -> [WarningPat]
400 make_row_vars_for_constructor (_, EqnInfo { eqn_pats = pats})
401 = takeList (tail pats) (repeat nlWildPat)
403 compare_cons :: Pat Id -> Pat Id -> Bool
404 compare_cons (ConPatOut{ pat_con = L _ id1 }) (ConPatOut { pat_con = L _ id2 }) = id1 == id2
406 remove_dups :: [Pat Id] -> [Pat Id]
408 remove_dups (x:xs) | or (map (\y -> compare_cons x y) xs) = remove_dups xs
409 | otherwise = x : remove_dups xs
411 get_used_cons :: [(EqnNo, EquationInfo)] -> [Pat Id]
412 get_used_cons qs = remove_dups [pat | q <- qs, let pat = firstPatN q,
415 isConPatOut :: Pat Id -> Bool
416 isConPatOut (ConPatOut {}) = True
417 isConPatOut _ = False
419 remove_dups' :: [HsLit] -> [HsLit]
421 remove_dups' (x:xs) | x `elem` xs = remove_dups' xs
422 | otherwise = x : remove_dups' xs
425 get_used_lits :: [(EqnNo, EquationInfo)] -> [HsLit]
426 get_used_lits qs = remove_dups' all_literals
428 all_literals = get_used_lits' qs
430 get_used_lits' :: [(EqnNo, EquationInfo)] -> [HsLit]
431 get_used_lits' [] = []
432 get_used_lits' (q:qs)
433 | Just lit <- get_lit (firstPatN q) = lit : get_used_lits' qs
434 | otherwise = get_used_lits qs
436 get_lit :: Pat id -> Maybe HsLit
437 -- Get a representative HsLit to stand for the OverLit
438 -- It doesn't matter which one, because they will only be compared
439 -- with other HsLits gotten in the same way
440 get_lit (LitPat lit) = Just lit
441 get_lit (NPat (OverLit { ol_val = HsIntegral i}) mb _) = Just (HsIntPrim (mb_neg mb i))
442 get_lit (NPat (OverLit { ol_val = HsFractional f }) mb _) = Just (HsFloatPrim (mb_neg mb f))
443 get_lit (NPat (OverLit { ol_val = HsIsString s }) _ _) = Just (HsStringPrim s)
446 mb_neg :: Num a => Maybe b -> a -> a
448 mb_neg (Just _) v = -v
450 get_unused_cons :: [Pat Id] -> [DataCon]
451 get_unused_cons used_cons = ASSERT( not (null used_cons) ) unused_cons
453 used_set :: UniqSet DataCon
454 used_set = mkUniqSet [d | ConPatOut{ pat_con = L _ d} <- used_cons]
455 (ConPatOut { pat_ty = ty }) = head used_cons
456 Just (ty_con, inst_tys) = splitTyConApp_maybe ty
457 unused_cons = filterOut is_used (tyConDataCons ty_con)
458 is_used con = con `elementOfUniqSet` used_set
459 || dataConCannotMatch inst_tys con
461 all_vars :: [Pat Id] -> Bool
463 all_vars (WildPat _:ps) = all_vars ps
466 remove_var :: (EqnNo, EquationInfo) -> (EqnNo, EquationInfo)
467 remove_var (n, eqn@(EqnInfo { eqn_pats = WildPat _ : ps})) = (n, eqn { eqn_pats = ps })
468 remove_var _ = panic "Check.remove_var: equation does not begin with a variable"
470 -----------------------
471 eqnPats :: (EqnNo, EquationInfo) -> [Pat Id]
472 eqnPats (_, eqn) = eqn_pats eqn
474 okGroup :: [(EqnNo, EquationInfo)] -> Bool
475 -- True if all equations have at least one pattern, and
476 -- all have the same number of patterns
478 okGroup (e:es) = n_pats > 0 && and [length (eqnPats e) == n_pats | e <- es]
480 n_pats = length (eqnPats e)
483 pprGroup :: [(EqnNo, EquationInfo)] -> SDoc
484 pprEqnInfo :: (EqnNo, EquationInfo) -> SDoc
485 pprGroup es = vcat (map pprEqnInfo es)
486 pprEqnInfo e = ppr (eqnPats e)
489 firstPatN :: (EqnNo, EquationInfo) -> Pat Id
490 firstPatN (_, eqn) = firstPat eqn
492 is_con :: Pat Id -> Bool
493 is_con (ConPatOut {}) = True
496 is_lit :: Pat Id -> Bool
497 is_lit (LitPat _) = True
498 is_lit (NPat _ _ _) = True
501 is_var :: Pat Id -> Bool
502 is_var (WildPat _) = True
505 is_var_con :: DataCon -> Pat Id -> Bool
506 is_var_con _ (WildPat _) = True
507 is_var_con con (ConPatOut{ pat_con = L _ id }) | id == con = True
508 is_var_con _ _ = False
510 is_var_lit :: HsLit -> Pat Id -> Bool
511 is_var_lit _ (WildPat _) = True
513 | Just lit' <- get_lit pat = lit == lit'
517 The difference beteewn @make_con@ and @make_whole_con@ is that
518 @make_wole_con@ creates a new constructor with all their arguments, and
519 @make_con@ takes a list of argumntes, creates the contructor getting their
520 arguments from the list. See where \fbox{\ ???\ } are used for details.
522 We need to reconstruct the patterns (make the constructors infix and
523 similar) at the same time that we create the constructors.
525 You can tell tuple constructors using
529 You can see if one constructor is infix with this clearer code :-))))))))))
531 Lex.isLexConSym (Name.occNameString (Name.getOccName con))
534 Rather clumsy but it works. (Simon Peyton Jones)
537 We don't mind the @nilDataCon@ because it doesn't change the way to
538 print the messsage, we are searching only for things like: @[1,2,3]@,
541 In @reconstruct_pat@ we want to ``undo'' the work
542 that we have done in @tidy_pat@.
545 @((,) x y)@ & returns to be & @(x, y)@
546 \\ @((:) x xs)@ & returns to be & @(x:xs)@
547 \\ @(x:(...:[])@ & returns to be & @[x,...]@
550 The difficult case is the third one becouse we need to follow all the
551 contructors until the @[]@ to know that we need to use the second case,
552 not the second. \fbox{\ ???\ }
555 isInfixCon :: DataCon -> Bool
556 isInfixCon con = isDataSymOcc (getOccName con)
558 is_nil :: Pat Name -> Bool
559 is_nil (ConPatIn con (PrefixCon [])) = unLoc con == getName nilDataCon
562 is_list :: Pat Name -> Bool
563 is_list (ListPat _ _) = True
566 return_list :: DataCon -> Pat Name -> Bool
567 return_list id q = id == consDataCon && (is_nil q || is_list q)
569 make_list :: LPat Name -> Pat Name -> Pat Name
570 make_list p q | is_nil q = ListPat [p] placeHolderType
571 make_list p (ListPat ps ty) = ListPat (p:ps) ty
572 make_list _ _ = panic "Check.make_list: Invalid argument"
574 make_con :: Pat Id -> ExhaustivePat -> ExhaustivePat
575 make_con (ConPatOut{ pat_con = L _ id }) (lp:lq:ps, constraints)
576 | return_list id q = (noLoc (make_list lp q) : ps, constraints)
577 | isInfixCon id = (nlInfixConPat (getName id) lp lq : ps, constraints)
580 make_con (ConPatOut{ pat_con = L _ id, pat_args = PrefixCon pats, pat_ty = ty }) (ps, constraints)
581 | isTupleTyCon tc = (noLoc (TuplePat pats_con (tupleTyConBoxity tc) ty) : rest_pats, constraints)
582 | isPArrFakeCon id = (noLoc (PArrPat pats_con placeHolderType) : rest_pats, constraints)
583 | otherwise = (nlConPat name pats_con : rest_pats, constraints)
586 (pats_con, rest_pats) = splitAtList pats ps
589 -- reconstruct parallel array pattern
591 -- * don't check for the type only; we need to make sure that we are really
592 -- dealing with one of the fake constructors and not with the real
595 make_whole_con :: DataCon -> WarningPat
596 make_whole_con con | isInfixCon con = nlInfixConPat name nlWildPat nlWildPat
597 | otherwise = nlConPat name pats
600 pats = [nlWildPat | _ <- dataConOrigArgTys con]
603 ------------------------------------------------------------------------
605 ------------------------------------------------------------------------
607 tidy_eqn does more or less the same thing as @tidy@ in @Match.lhs@;
608 that is, it removes syntactic sugar, reducing the number of cases that
609 must be handled by the main checking algorithm. One difference is
610 that here we can do *all* the tidying at once (recursively), rather
611 than doing it incrementally.
614 tidy_eqn :: EquationInfo -> EquationInfo
615 tidy_eqn eqn = eqn { eqn_pats = map tidy_pat (eqn_pats eqn),
616 eqn_rhs = tidy_rhs (eqn_rhs eqn) }
618 -- Horrible hack. The tidy_pat stuff converts "might-fail" patterns to
619 -- WildPats which of course loses the info that they can fail to match.
620 -- So we stick in a CanFail as if it were a guard.
621 tidy_rhs (MatchResult can_fail body)
622 | any might_fail_pat (eqn_pats eqn) = MatchResult CanFail body
623 | otherwise = MatchResult can_fail body
626 might_fail_pat :: Pat Id -> Bool
627 -- Returns True of patterns that might fail (i.e. fall through) in a way
628 -- that is not covered by the checking algorithm. Specifically:
630 -- ViewPat (if refutable)
632 -- First the two special cases
633 might_fail_pat (NPlusKPat {}) = True
634 might_fail_pat (ViewPat _ p _) = not (isIrrefutableHsPat p)
636 -- Now the recursive stuff
637 might_fail_pat (ParPat p) = might_fail_lpat p
638 might_fail_pat (AsPat _ p) = might_fail_lpat p
639 might_fail_pat (SigPatOut p _ ) = might_fail_lpat p
640 might_fail_pat (ListPat ps _) = any might_fail_lpat ps
641 might_fail_pat (TuplePat ps _ _) = any might_fail_lpat ps
642 might_fail_pat (PArrPat ps _) = any might_fail_lpat ps
643 might_fail_pat (BangPat p) = might_fail_lpat p
644 might_fail_pat (ConPatOut { pat_args = ps }) = any might_fail_lpat (hsConPatArgs ps)
646 -- Finally the ones that are sure to succeed, or which are covered by the checking algorithm
647 might_fail_pat (LazyPat _) = False -- Always succeeds
648 might_fail_pat _ = False -- VarPat, WildPat, LitPat, NPat
651 might_fail_lpat :: LPat Id -> Bool
652 might_fail_lpat (L _ p) = might_fail_pat p
655 tidy_lpat :: LPat Id -> LPat Id
656 tidy_lpat p = fmap tidy_pat p
659 tidy_pat :: Pat Id -> Pat Id
660 tidy_pat pat@(WildPat _) = pat
661 tidy_pat (VarPat id) = WildPat (idType id)
662 tidy_pat (ParPat p) = tidy_pat (unLoc p)
663 tidy_pat (LazyPat p) = WildPat (hsLPatType p) -- For overlap and exhaustiveness checking
664 -- purposes, a ~pat is like a wildcard
665 tidy_pat (BangPat p) = tidy_pat (unLoc p)
666 tidy_pat (AsPat _ p) = tidy_pat (unLoc p)
667 tidy_pat (SigPatOut p _) = tidy_pat (unLoc p)
668 tidy_pat (CoPat _ pat _) = tidy_pat pat
670 -- These two are might_fail patterns, so we map them to
671 -- WildPats. The might_fail_pat stuff arranges that the
672 -- guard says "this equation might fall through".
673 tidy_pat (NPlusKPat id _ _ _) = WildPat (idType (unLoc id))
674 tidy_pat (ViewPat _ _ ty) = WildPat ty
676 tidy_pat pat@(ConPatOut { pat_con = L _ id, pat_args = ps })
677 = pat { pat_args = tidy_con id ps }
679 tidy_pat (ListPat ps ty)
680 = unLoc $ foldr (\ x y -> mkPrefixConPat consDataCon [x,y] list_ty)
683 where list_ty = mkListTy ty
685 -- introduce fake parallel array constructors to be able to handle parallel
686 -- arrays with the existing machinery for constructor pattern
688 tidy_pat (PArrPat ps ty)
689 = unLoc $ mkPrefixConPat (parrFakeCon (length ps))
693 tidy_pat (TuplePat ps boxity ty)
694 = unLoc $ mkPrefixConPat (tupleCon boxity arity)
695 (map tidy_lpat ps) ty
699 tidy_pat (NPat lit mb_neg eq) = tidyNPat tidy_lit_pat lit mb_neg eq
700 tidy_pat (LitPat lit) = tidy_lit_pat lit
702 tidy_lit_pat :: HsLit -> Pat Id
703 -- Unpack string patterns fully, so we can see when they
704 -- overlap with each other, or even explicit lists of Chars.
707 = unLoc $ foldr (\c pat -> mkPrefixConPat consDataCon [mkCharLitPat c, pat] stringTy)
708 (mkPrefixConPat nilDataCon [] stringTy) (unpackFS s)
713 tidy_con :: DataCon -> HsConPatDetails Id -> HsConPatDetails Id
714 tidy_con _ (PrefixCon ps) = PrefixCon (map tidy_lpat ps)
715 tidy_con _ (InfixCon p1 p2) = PrefixCon [tidy_lpat p1, tidy_lpat p2]
716 tidy_con con (RecCon (HsRecFields fs _))
717 | null fs = PrefixCon [nlWildPat | _ <- dataConOrigArgTys con]
718 -- Special case for null patterns; maybe not a record at all
719 | otherwise = PrefixCon (map (tidy_lpat.snd) all_pats)
721 -- pad out all the missing fields with WildPats.
722 field_pats = map (\ f -> (f, nlWildPat)) (dataConFieldLabels con)
723 all_pats = foldr (\(HsRecField id p _) acc -> insertNm (getName (unLoc id)) p acc)
726 insertNm nm p [] = [(nm,p)]
727 insertNm nm p (x@(n,_):xs)
728 | nm == n = (nm,p):xs
729 | otherwise = x : insertNm nm p xs