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"
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 = (untidy_warns, shadowed_eqns)
115 tidy_qs = map tidy_eqn qs
116 (warns, used_nos) = check' ([1..] `zip` tidy_qs)
117 untidy_warns = map untidy_exhaustive warns
118 shadowed_eqns = [eqn | (eqn,i) <- qs `zip` [1..],
119 not (i `elementOfUniqSet` used_nos)]
121 untidy_exhaustive :: ExhaustivePat -> ExhaustivePat
122 untidy_exhaustive ([pat], messages) =
123 ([untidy_no_pars pat], map untidy_message messages)
124 untidy_exhaustive (pats, messages) =
125 (map untidy_pars pats, map untidy_message messages)
127 untidy_message :: (Name, [HsLit]) -> (Name, [HsLit])
128 untidy_message (string, lits) = (string, map untidy_lit lits)
131 The function @untidy@ does the reverse work of the @tidy_pat@ funcion.
137 untidy_no_pars :: WarningPat -> WarningPat
138 untidy_no_pars p = untidy False p
140 untidy_pars :: WarningPat -> WarningPat
141 untidy_pars p = untidy True p
143 untidy :: NeedPars -> WarningPat -> WarningPat
144 untidy b (L loc p) = L loc (untidy' b p)
146 untidy' _ p@(WildPat _) = p
147 untidy' _ p@(VarPat _) = p
148 untidy' _ (LitPat lit) = LitPat (untidy_lit lit)
149 untidy' _ p@(ConPatIn _ (PrefixCon [])) = p
150 untidy' b (ConPatIn name ps) = pars b (L loc (ConPatIn name (untidy_con ps)))
151 untidy' _ (ListPat pats ty) = ListPat (map untidy_no_pars pats) ty
152 untidy' _ (TuplePat pats box ty) = TuplePat (map untidy_no_pars pats) box ty
153 untidy' _ (PArrPat _ _) = panic "Check.untidy: Shouldn't get a parallel array here!"
154 untidy' _ (SigPatIn _ _) = panic "Check.untidy: SigPat"
156 untidy_con :: HsConPatDetails Name -> HsConPatDetails Name
157 untidy_con (PrefixCon pats) = PrefixCon (map untidy_pars pats)
158 untidy_con (InfixCon p1 p2) = InfixCon (untidy_pars p1) (untidy_pars p2)
159 untidy_con (RecCon (HsRecFields flds dd))
160 = RecCon (HsRecFields [ fld { hsRecFieldArg = untidy_pars (hsRecFieldArg fld) }
163 pars :: NeedPars -> WarningPat -> Pat Name
164 pars True p = ParPat p
167 untidy_lit :: HsLit -> HsLit
168 untidy_lit (HsCharPrim c) = HsChar c
172 This equation is the same that check, the only difference is that the
173 boring work is done, that work needs to be done only once, this is
174 the reason top have two functions, check is the external interface,
175 @check'@ is called recursively.
177 There are several cases:
180 \item There are no equations: Everything is OK.
181 \item There are only one equation, that can fail, and all the patterns are
182 variables. Then that equation is used and the same equation is
184 \item All the patterns are variables, and the match can fail, there are
185 more equations then the results is the result of the rest of equations
186 and this equation is used also.
188 \item The general case, if all the patterns are variables (here the match
189 can't fail) then the result is that this equation is used and this
190 equation doesn't generate non-exhaustive cases.
192 \item In the general case, there can exist literals ,constructors or only
193 vars in the first column, we actuate in consequence.
200 check' :: [(EqnNo, EquationInfo)]
201 -> ([ExhaustivePat], -- Pattern scheme that might not be matched at all
202 EqnSet) -- Eqns that are used (others are overlapped)
204 check' [] = ([([],[])],emptyUniqSet)
206 check' ((n, EqnInfo { eqn_pats = ps, eqn_rhs = MatchResult can_fail _ }) : rs)
207 | first_eqn_all_vars && case can_fail of { CantFail -> True; CanFail -> False }
208 = ([], unitUniqSet n) -- One eqn, which can't fail
210 | first_eqn_all_vars && null rs -- One eqn, but it can fail
211 = ([(takeList ps (repeat nlWildPat),[])], unitUniqSet n)
213 | first_eqn_all_vars -- Several eqns, first can fail
214 = (pats, addOneToUniqSet indexs n)
216 first_eqn_all_vars = all_vars ps
217 (pats,indexs) = check' rs
220 | some_literals = split_by_literals qs
221 | some_constructors = split_by_constructor qs
222 | only_vars = first_column_only_vars qs
223 | otherwise = pprPanic "Check.check': Not implemented :-(" (ppr first_pats)
226 -- Note: RecPats will have been simplified to ConPats
228 first_pats = ASSERT2( okGroup qs, pprGroup qs ) map firstPatN qs
229 some_constructors = any is_con first_pats
230 some_literals = any is_lit first_pats
231 only_vars = all is_var first_pats
234 Here begins the code to deal with literals, we need to split the matrix
235 in different matrix beginning by each literal and a last matrix with the
239 split_by_literals :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet)
240 split_by_literals qs = process_literals used_lits qs
242 used_lits = get_used_lits qs
245 @process_explicit_literals@ is a function that process each literal that appears
246 in the column of the matrix.
249 process_explicit_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
250 process_explicit_literals lits qs = (concat pats, unionManyUniqSets indexs)
252 pats_indexs = map (\x -> construct_literal_matrix x qs) lits
253 (pats,indexs) = unzip pats_indexs
257 @process_literals@ calls @process_explicit_literals@ to deal with the literals
258 that appears in the matrix and deal also with the rest of the cases. It
259 must be one Variable to be complete.
263 process_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
264 process_literals used_lits qs
265 | null default_eqns = ASSERT( not (null qs) ) ([make_row_vars used_lits (head qs)] ++ pats,indexs)
266 | otherwise = (pats_default,indexs_default)
268 (pats,indexs) = process_explicit_literals used_lits qs
269 default_eqns = ASSERT2( okGroup qs, pprGroup qs )
270 [remove_var q | q <- qs, is_var (firstPatN q)]
271 (pats',indexs') = check' default_eqns
272 pats_default = [(nlWildPat:ps,constraints) | (ps,constraints) <- (pats')] ++ pats
273 indexs_default = unionUniqSets indexs' indexs
276 Here we have selected the literal and we will select all the equations that
277 begins for that literal and create a new matrix.
280 construct_literal_matrix :: HsLit -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
281 construct_literal_matrix lit qs =
282 (map (\ (xs,ys) -> (new_lit:xs,ys)) pats,indexs)
284 (pats,indexs) = (check' (remove_first_column_lit lit qs))
285 new_lit = nlLitPat lit
287 remove_first_column_lit :: HsLit
288 -> [(EqnNo, EquationInfo)]
289 -> [(EqnNo, EquationInfo)]
290 remove_first_column_lit lit qs
291 = ASSERT2( okGroup qs, pprGroup qs )
292 [(n, shift_pat eqn) | q@(n,eqn) <- qs, is_var_lit lit (firstPatN q)]
294 shift_pat eqn@(EqnInfo { eqn_pats = _:ps}) = eqn { eqn_pats = ps }
295 shift_pat _ = panic "Check.shift_var: no patterns"
298 This function splits the equations @qs@ in groups that deal with the
302 split_by_constructor :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet)
303 split_by_constructor qs
304 | notNull unused_cons = need_default_case used_cons unused_cons qs
305 | otherwise = no_need_default_case used_cons qs
307 used_cons = get_used_cons qs
308 unused_cons = get_unused_cons used_cons
311 The first column of the patterns matrix only have vars, then there is
315 first_column_only_vars :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
316 first_column_only_vars qs = (map (\ (xs,ys) -> (nlWildPat:xs,ys)) pats,indexs)
318 (pats, indexs) = check' (map remove_var qs)
321 This equation takes a matrix of patterns and split the equations by
322 constructor, using all the constructors that appears in the first column
323 of the pattern matching.
325 We can need a default clause or not ...., it depends if we used all the
326 constructors or not explicitly. The reasoning is similar to @process_literals@,
327 the difference is that here the default case is not always needed.
330 no_need_default_case :: [Pat Id] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
331 no_need_default_case cons qs = (concat pats, unionManyUniqSets indexs)
333 pats_indexs = map (\x -> construct_matrix x qs) cons
334 (pats,indexs) = unzip pats_indexs
336 need_default_case :: [Pat Id] -> [DataCon] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
337 need_default_case used_cons unused_cons qs
338 | null default_eqns = (pats_default_no_eqns,indexs)
339 | otherwise = (pats_default,indexs_default)
341 (pats,indexs) = no_need_default_case used_cons qs
342 default_eqns = ASSERT2( okGroup qs, pprGroup qs )
343 [remove_var q | q <- qs, is_var (firstPatN q)]
344 (pats',indexs') = check' default_eqns
345 pats_default = [(make_whole_con c:ps,constraints) |
346 c <- unused_cons, (ps,constraints) <- pats'] ++ pats
347 new_wilds = ASSERT( not (null qs) ) make_row_vars_for_constructor (head qs)
348 pats_default_no_eqns = [(make_whole_con c:new_wilds,[]) | c <- unused_cons] ++ pats
349 indexs_default = unionUniqSets indexs' indexs
351 construct_matrix :: Pat Id -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
352 construct_matrix con qs =
353 (map (make_con con) pats,indexs)
355 (pats,indexs) = (check' (remove_first_column con qs))
358 Here remove first column is more difficult that with literals due to the fact
359 that constructors can have arguments.
361 For instance, the matrix
373 remove_first_column :: Pat Id -- Constructor
374 -> [(EqnNo, EquationInfo)]
375 -> [(EqnNo, EquationInfo)]
376 remove_first_column (ConPatOut{ pat_con = L _ con, pat_args = PrefixCon con_pats }) qs
377 = ASSERT2( okGroup qs, pprGroup qs )
378 [(n, shift_var eqn) | q@(n, eqn) <- qs, is_var_con con (firstPatN q)]
380 new_wilds = [WildPat (hsLPatType arg_pat) | arg_pat <- con_pats]
381 shift_var eqn@(EqnInfo { eqn_pats = ConPatOut{ pat_args = PrefixCon ps' } : ps})
382 = eqn { eqn_pats = map unLoc ps' ++ ps }
383 shift_var eqn@(EqnInfo { eqn_pats = WildPat _ : ps })
384 = eqn { eqn_pats = new_wilds ++ ps }
385 shift_var _ = panic "Check.Shift_var:No done"
387 make_row_vars :: [HsLit] -> (EqnNo, EquationInfo) -> ExhaustivePat
388 make_row_vars used_lits (_, EqnInfo { eqn_pats = pats})
389 = (nlVarPat new_var:takeList (tail pats) (repeat nlWildPat),[(new_var,used_lits)])
394 hash_x = mkInternalName unboundKey {- doesn't matter much -}
395 (mkVarOccFS (fsLit "#x"))
398 make_row_vars_for_constructor :: (EqnNo, EquationInfo) -> [WarningPat]
399 make_row_vars_for_constructor (_, EqnInfo { eqn_pats = pats})
400 = takeList (tail pats) (repeat nlWildPat)
402 compare_cons :: Pat Id -> Pat Id -> Bool
403 compare_cons (ConPatOut{ pat_con = L _ id1 }) (ConPatOut { pat_con = L _ id2 }) = id1 == id2
405 remove_dups :: [Pat Id] -> [Pat Id]
407 remove_dups (x:xs) | or (map (\y -> compare_cons x y) xs) = remove_dups xs
408 | otherwise = x : remove_dups xs
410 get_used_cons :: [(EqnNo, EquationInfo)] -> [Pat Id]
411 get_used_cons qs = remove_dups [pat | q <- qs, let pat = firstPatN q,
414 isConPatOut :: Pat Id -> Bool
415 isConPatOut (ConPatOut {}) = True
416 isConPatOut _ = False
418 remove_dups' :: [HsLit] -> [HsLit]
420 remove_dups' (x:xs) | x `elem` xs = remove_dups' xs
421 | otherwise = x : remove_dups' xs
424 get_used_lits :: [(EqnNo, EquationInfo)] -> [HsLit]
425 get_used_lits qs = remove_dups' all_literals
427 all_literals = get_used_lits' qs
429 get_used_lits' :: [(EqnNo, EquationInfo)] -> [HsLit]
430 get_used_lits' [] = []
431 get_used_lits' (q:qs)
432 | Just lit <- get_lit (firstPatN q) = lit : get_used_lits' qs
433 | otherwise = get_used_lits qs
435 get_lit :: Pat id -> Maybe HsLit
436 -- Get a representative HsLit to stand for the OverLit
437 -- It doesn't matter which one, because they will only be compared
438 -- with other HsLits gotten in the same way
439 get_lit (LitPat lit) = Just lit
440 get_lit (NPat (OverLit { ol_val = HsIntegral i}) mb _) = Just (HsIntPrim (mb_neg negate mb i))
441 get_lit (NPat (OverLit { ol_val = HsFractional f }) mb _) = Just (HsFloatPrim (mb_neg negateFractionalLit mb f))
442 get_lit (NPat (OverLit { ol_val = HsIsString s }) _ _) = Just (HsStringPrim s)
445 mb_neg :: (a -> a) -> Maybe b -> a -> a
446 mb_neg _ Nothing v = v
447 mb_neg negate (Just _) v = negate v
449 get_unused_cons :: [Pat Id] -> [DataCon]
450 get_unused_cons used_cons = ASSERT( not (null used_cons) ) unused_cons
452 used_set :: UniqSet DataCon
453 used_set = mkUniqSet [d | ConPatOut{ pat_con = L _ d} <- used_cons]
454 (ConPatOut { pat_ty = ty }) = head used_cons
455 Just (ty_con, inst_tys) = splitTyConApp_maybe ty
456 unused_cons = filterOut is_used (tyConDataCons ty_con)
457 is_used con = con `elementOfUniqSet` used_set
458 || dataConCannotMatch inst_tys con
460 all_vars :: [Pat Id] -> Bool
462 all_vars (WildPat _:ps) = all_vars ps
465 remove_var :: (EqnNo, EquationInfo) -> (EqnNo, EquationInfo)
466 remove_var (n, eqn@(EqnInfo { eqn_pats = WildPat _ : ps})) = (n, eqn { eqn_pats = ps })
467 remove_var _ = panic "Check.remove_var: equation does not begin with a variable"
469 -----------------------
470 eqnPats :: (EqnNo, EquationInfo) -> [Pat Id]
471 eqnPats (_, eqn) = eqn_pats eqn
473 okGroup :: [(EqnNo, EquationInfo)] -> Bool
474 -- True if all equations have at least one pattern, and
475 -- all have the same number of patterns
477 okGroup (e:es) = n_pats > 0 && and [length (eqnPats e) == n_pats | e <- es]
479 n_pats = length (eqnPats e)
482 pprGroup :: [(EqnNo, EquationInfo)] -> SDoc
483 pprEqnInfo :: (EqnNo, EquationInfo) -> SDoc
484 pprGroup es = vcat (map pprEqnInfo es)
485 pprEqnInfo e = ppr (eqnPats e)
488 firstPatN :: (EqnNo, EquationInfo) -> Pat Id
489 firstPatN (_, eqn) = firstPat eqn
491 is_con :: Pat Id -> Bool
492 is_con (ConPatOut {}) = True
495 is_lit :: Pat Id -> Bool
496 is_lit (LitPat _) = True
497 is_lit (NPat _ _ _) = True
500 is_var :: Pat Id -> Bool
501 is_var (WildPat _) = True
504 is_var_con :: DataCon -> Pat Id -> Bool
505 is_var_con _ (WildPat _) = True
506 is_var_con con (ConPatOut{ pat_con = L _ id }) | id == con = True
507 is_var_con _ _ = False
509 is_var_lit :: HsLit -> Pat Id -> Bool
510 is_var_lit _ (WildPat _) = True
512 | Just lit' <- get_lit pat = lit == lit'
516 The difference beteewn @make_con@ and @make_whole_con@ is that
517 @make_wole_con@ creates a new constructor with all their arguments, and
518 @make_con@ takes a list of argumntes, creates the contructor getting their
519 arguments from the list. See where \fbox{\ ???\ } are used for details.
521 We need to reconstruct the patterns (make the constructors infix and
522 similar) at the same time that we create the constructors.
524 You can tell tuple constructors using
528 You can see if one constructor is infix with this clearer code :-))))))))))
530 Lex.isLexConSym (Name.occNameString (Name.getOccName con))
533 Rather clumsy but it works. (Simon Peyton Jones)
536 We don't mind the @nilDataCon@ because it doesn't change the way to
537 print the messsage, we are searching only for things like: @[1,2,3]@,
540 In @reconstruct_pat@ we want to ``undo'' the work
541 that we have done in @tidy_pat@.
544 @((,) x y)@ & returns to be & @(x, y)@
545 \\ @((:) x xs)@ & returns to be & @(x:xs)@
546 \\ @(x:(...:[])@ & returns to be & @[x,...]@
549 The difficult case is the third one becouse we need to follow all the
550 contructors until the @[]@ to know that we need to use the second case,
551 not the second. \fbox{\ ???\ }
554 isInfixCon :: DataCon -> Bool
555 isInfixCon con = isDataSymOcc (getOccName con)
557 is_nil :: Pat Name -> Bool
558 is_nil (ConPatIn con (PrefixCon [])) = unLoc con == getName nilDataCon
561 is_list :: Pat Name -> Bool
562 is_list (ListPat _ _) = True
565 return_list :: DataCon -> Pat Name -> Bool
566 return_list id q = id == consDataCon && (is_nil q || is_list q)
568 make_list :: LPat Name -> Pat Name -> Pat Name
569 make_list p q | is_nil q = ListPat [p] placeHolderType
570 make_list p (ListPat ps ty) = ListPat (p:ps) ty
571 make_list _ _ = panic "Check.make_list: Invalid argument"
573 make_con :: Pat Id -> ExhaustivePat -> ExhaustivePat
574 make_con (ConPatOut{ pat_con = L _ id }) (lp:lq:ps, constraints)
575 | return_list id q = (noLoc (make_list lp q) : ps, constraints)
576 | isInfixCon id = (nlInfixConPat (getName id) lp lq : ps, constraints)
579 make_con (ConPatOut{ pat_con = L _ id, pat_args = PrefixCon pats, pat_ty = ty }) (ps, constraints)
580 | isTupleTyCon tc = (noLoc (TuplePat pats_con (tupleTyConBoxity tc) ty) : rest_pats, constraints)
581 | isPArrFakeCon id = (noLoc (PArrPat pats_con placeHolderType) : rest_pats, constraints)
582 | otherwise = (nlConPat name pats_con : rest_pats, constraints)
585 (pats_con, rest_pats) = splitAtList pats ps
588 -- reconstruct parallel array pattern
590 -- * don't check for the type only; we need to make sure that we are really
591 -- dealing with one of the fake constructors and not with the real
594 make_whole_con :: DataCon -> WarningPat
595 make_whole_con con | isInfixCon con = nlInfixConPat name nlWildPat nlWildPat
596 | otherwise = nlConPat name pats
599 pats = [nlWildPat | _ <- dataConOrigArgTys con]
602 ------------------------------------------------------------------------
604 ------------------------------------------------------------------------
606 tidy_eqn does more or less the same thing as @tidy@ in @Match.lhs@;
607 that is, it removes syntactic sugar, reducing the number of cases that
608 must be handled by the main checking algorithm. One difference is
609 that here we can do *all* the tidying at once (recursively), rather
610 than doing it incrementally.
613 tidy_eqn :: EquationInfo -> EquationInfo
614 tidy_eqn eqn = eqn { eqn_pats = map tidy_pat (eqn_pats eqn),
615 eqn_rhs = tidy_rhs (eqn_rhs eqn) }
617 -- Horrible hack. The tidy_pat stuff converts "might-fail" patterns to
618 -- WildPats which of course loses the info that they can fail to match.
619 -- So we stick in a CanFail as if it were a guard.
620 tidy_rhs (MatchResult can_fail body)
621 | any might_fail_pat (eqn_pats eqn) = MatchResult CanFail body
622 | otherwise = MatchResult can_fail body
625 might_fail_pat :: Pat Id -> Bool
626 -- Returns True of patterns that might fail (i.e. fall through) in a way
627 -- that is not covered by the checking algorithm. Specifically:
629 -- ViewPat (if refutable)
631 -- First the two special cases
632 might_fail_pat (NPlusKPat {}) = True
633 might_fail_pat (ViewPat _ p _) = not (isIrrefutableHsPat p)
635 -- Now the recursive stuff
636 might_fail_pat (ParPat p) = might_fail_lpat p
637 might_fail_pat (AsPat _ p) = might_fail_lpat p
638 might_fail_pat (SigPatOut p _ ) = might_fail_lpat p
639 might_fail_pat (ListPat ps _) = any might_fail_lpat ps
640 might_fail_pat (TuplePat ps _ _) = any might_fail_lpat ps
641 might_fail_pat (PArrPat ps _) = any might_fail_lpat ps
642 might_fail_pat (BangPat p) = might_fail_lpat p
643 might_fail_pat (ConPatOut { pat_args = ps }) = any might_fail_lpat (hsConPatArgs ps)
645 -- Finally the ones that are sure to succeed, or which are covered by the checking algorithm
646 might_fail_pat (LazyPat _) = False -- Always succeeds
647 might_fail_pat _ = False -- VarPat, WildPat, LitPat, NPat, TypePat
650 might_fail_lpat :: LPat Id -> Bool
651 might_fail_lpat (L _ p) = might_fail_pat p
654 tidy_lpat :: LPat Id -> LPat Id
655 tidy_lpat p = fmap tidy_pat p
658 tidy_pat :: Pat Id -> Pat Id
659 tidy_pat pat@(WildPat _) = pat
660 tidy_pat (VarPat id) = WildPat (idType id)
661 tidy_pat (ParPat p) = tidy_pat (unLoc p)
662 tidy_pat (LazyPat p) = WildPat (hsLPatType p) -- For overlap and exhaustiveness checking
663 -- purposes, a ~pat is like a wildcard
664 tidy_pat (BangPat p) = tidy_pat (unLoc p)
665 tidy_pat (AsPat _ p) = tidy_pat (unLoc p)
666 tidy_pat (SigPatOut p _) = tidy_pat (unLoc p)
667 tidy_pat (CoPat _ pat _) = tidy_pat pat
669 -- These two are might_fail patterns, so we map them to
670 -- WildPats. The might_fail_pat stuff arranges that the
671 -- guard says "this equation might fall through".
672 tidy_pat (NPlusKPat id _ _ _) = WildPat (idType (unLoc id))
673 tidy_pat (ViewPat _ _ ty) = WildPat ty
675 tidy_pat pat@(ConPatOut { pat_con = L _ id, pat_args = ps })
676 = pat { pat_args = tidy_con id ps }
678 tidy_pat (ListPat ps ty)
679 = unLoc $ foldr (\ x y -> mkPrefixConPat consDataCon [x,y] list_ty)
682 where list_ty = mkListTy ty
684 -- introduce fake parallel array constructors to be able to handle parallel
685 -- arrays with the existing machinery for constructor pattern
687 tidy_pat (PArrPat ps ty)
688 = unLoc $ mkPrefixConPat (parrFakeCon (length ps))
692 tidy_pat (TuplePat ps boxity ty)
693 = unLoc $ mkPrefixConPat (tupleCon boxity arity)
694 (map tidy_lpat ps) ty
698 tidy_pat (NPat lit mb_neg eq) = tidyNPat tidy_lit_pat lit mb_neg eq
699 tidy_pat (LitPat lit) = tidy_lit_pat lit
701 tidy_lit_pat :: HsLit -> Pat Id
702 -- Unpack string patterns fully, so we can see when they
703 -- overlap with each other, or even explicit lists of Chars.
706 = unLoc $ foldr (\c pat -> mkPrefixConPat consDataCon [mkCharLitPat c, pat] stringTy)
707 (mkPrefixConPat nilDataCon [] stringTy) (unpackFS s)
712 tidy_con :: DataCon -> HsConPatDetails Id -> HsConPatDetails Id
713 tidy_con _ (PrefixCon ps) = PrefixCon (map tidy_lpat ps)
714 tidy_con _ (InfixCon p1 p2) = PrefixCon [tidy_lpat p1, tidy_lpat p2]
715 tidy_con con (RecCon (HsRecFields fs _))
716 | null fs = PrefixCon [nlWildPat | _ <- dataConOrigArgTys con]
717 -- Special case for null patterns; maybe not a record at all
718 | otherwise = PrefixCon (map (tidy_lpat.snd) all_pats)
720 -- pad out all the missing fields with WildPats.
721 field_pats = map (\ f -> (f, nlWildPat)) (dataConFieldLabels con)
722 all_pats = foldr (\(HsRecField id p _) acc -> insertNm (getName (unLoc id)) p acc)
725 insertNm nm p [] = [(nm,p)]
726 insertNm nm p (x@(n,_):xs)
727 | nm == n = (nm,p):xs
728 | otherwise = x : insertNm nm p xs