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"
37 This module performs checks about if one list of equations are:
42 To discover that we go through the list of equations in a tree-like fashion.
44 If you like theory, a similar algorithm is described in:
46 {\em Two Techniques for Compiling Lazy Pattern Matching},
48 INRIA Rocquencourt (RR-2385, 1994)
50 The algorithm is based on the first technique, but there are some differences:
52 \item We don't generate code
53 \item We have constructors and literals (not only literals as in the
55 \item We don't use directions, we must select the columns from
58 (By the way the second technique is really similar to the one used in
59 @Match.lhs@ to generate code)
61 This function takes the equations of a pattern and returns:
63 \item The patterns that are not recognized
64 \item The equations that are not overlapped
66 It simplify the patterns and then call @check'@ (the same semantics), and it
67 needs to reconstruct the patterns again ....
69 The problem appear with things like:
74 We want to put the two patterns with the same syntax, (prefix form) and
75 then all the constructors are equal:
77 f (: x (: y [])) = ....
80 (more about that in @tidy_eqns@)
82 We would prefer to have a @WarningPat@ of type @String@, but Strings and the
83 Pretty Printer are not friends.
85 We use @InPat@ in @WarningPat@ instead of @OutPat@
86 because we need to print the
87 warning messages in the same way they are introduced, i.e. if the user
92 He don't want a warning message written:
94 f (: x (: y [])) ........
96 Then we need to use InPats.
98 Juan Quintela 5 JUL 1998\\
99 User-friendliness and compiler writers are no friends.
103 type WarningPat = InPat Name
104 type ExhaustivePat = ([WarningPat], [(Name, [HsLit])])
106 type EqnSet = UniqSet EqnNo
109 check :: [EquationInfo] -> ([ExhaustivePat], [EquationInfo])
110 -- Second result is the shadowed equations
111 -- if there are view patterns, just give up - don't know what the function is
112 check qs = (untidy_warns, shadowed_eqns)
114 (warns, used_nos) = check' ([1..] `zip` map tidy_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 @tidy_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 | some_literals = split_by_literals qs
219 | some_constructors = split_by_constructor qs
220 | only_vars = first_column_only_vars qs
221 | otherwise = pprPanic "Check.check': Not implemented :-(" (ppr first_pats)
224 -- Note: RecPats will have been simplified to ConPats
226 first_pats = ASSERT2( okGroup qs, pprGroup qs ) map firstPatN qs
227 some_constructors = any is_con first_pats
228 some_literals = any is_lit first_pats
229 only_vars = all is_var first_pats
232 Here begins the code to deal with literals, we need to split the matrix
233 in different matrix beginning by each literal and a last matrix with the
237 split_by_literals :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet)
238 split_by_literals qs = process_literals used_lits qs
240 used_lits = get_used_lits qs
243 @process_explicit_literals@ is a function that process each literal that appears
244 in the column of the matrix.
247 process_explicit_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
248 process_explicit_literals lits qs = (concat pats, unionManyUniqSets indexs)
250 pats_indexs = map (\x -> construct_literal_matrix x qs) lits
251 (pats,indexs) = unzip pats_indexs
255 @process_literals@ calls @process_explicit_literals@ to deal with the literals
256 that appears in the matrix and deal also with the rest of the cases. It
257 must be one Variable to be complete.
261 process_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
262 process_literals used_lits qs
263 | null default_eqns = ASSERT( not (null qs) ) ([make_row_vars used_lits (head qs)] ++ pats,indexs)
264 | otherwise = (pats_default,indexs_default)
266 (pats,indexs) = process_explicit_literals used_lits qs
267 default_eqns = ASSERT2( okGroup qs, pprGroup qs )
268 [remove_var q | q <- qs, is_var (firstPatN q)]
269 (pats',indexs') = check' default_eqns
270 pats_default = [(nlWildPat:ps,constraints) | (ps,constraints) <- (pats')] ++ pats
271 indexs_default = unionUniqSets indexs' indexs
274 Here we have selected the literal and we will select all the equations that
275 begins for that literal and create a new matrix.
278 construct_literal_matrix :: HsLit -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
279 construct_literal_matrix lit qs =
280 (map (\ (xs,ys) -> (new_lit:xs,ys)) pats,indexs)
282 (pats,indexs) = (check' (remove_first_column_lit lit qs))
283 new_lit = nlLitPat lit
285 remove_first_column_lit :: HsLit
286 -> [(EqnNo, EquationInfo)]
287 -> [(EqnNo, EquationInfo)]
288 remove_first_column_lit lit qs
289 = ASSERT2( okGroup qs, pprGroup qs )
290 [(n, shift_pat eqn) | q@(n,eqn) <- qs, is_var_lit lit (firstPatN q)]
292 shift_pat eqn@(EqnInfo { eqn_pats = _:ps}) = eqn { eqn_pats = ps }
293 shift_pat _ = panic "Check.shift_var: no patterns"
296 This function splits the equations @qs@ in groups that deal with the
300 split_by_constructor :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet)
301 split_by_constructor qs
302 | notNull unused_cons = need_default_case used_cons unused_cons qs
303 | otherwise = no_need_default_case used_cons qs
305 used_cons = get_used_cons qs
306 unused_cons = get_unused_cons used_cons
309 The first column of the patterns matrix only have vars, then there is
313 first_column_only_vars :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
314 first_column_only_vars qs = (map (\ (xs,ys) -> (nlWildPat:xs,ys)) pats,indexs)
316 (pats, indexs) = check' (map remove_var qs)
319 This equation takes a matrix of patterns and split the equations by
320 constructor, using all the constructors that appears in the first column
321 of the pattern matching.
323 We can need a default clause or not ...., it depends if we used all the
324 constructors or not explicitly. The reasoning is similar to @process_literals@,
325 the difference is that here the default case is not always needed.
328 no_need_default_case :: [Pat Id] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
329 no_need_default_case cons qs = (concat pats, unionManyUniqSets indexs)
331 pats_indexs = map (\x -> construct_matrix x qs) cons
332 (pats,indexs) = unzip pats_indexs
334 need_default_case :: [Pat Id] -> [DataCon] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
335 need_default_case used_cons unused_cons qs
336 | null default_eqns = (pats_default_no_eqns,indexs)
337 | otherwise = (pats_default,indexs_default)
339 (pats,indexs) = no_need_default_case used_cons qs
340 default_eqns = ASSERT2( okGroup qs, pprGroup qs )
341 [remove_var q | q <- qs, is_var (firstPatN q)]
342 (pats',indexs') = check' default_eqns
343 pats_default = [(make_whole_con c:ps,constraints) |
344 c <- unused_cons, (ps,constraints) <- pats'] ++ pats
345 new_wilds = ASSERT( not (null qs) ) make_row_vars_for_constructor (head qs)
346 pats_default_no_eqns = [(make_whole_con c:new_wilds,[]) | c <- unused_cons] ++ pats
347 indexs_default = unionUniqSets indexs' indexs
349 construct_matrix :: Pat Id -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
350 construct_matrix con qs =
351 (map (make_con con) pats,indexs)
353 (pats,indexs) = (check' (remove_first_column con qs))
356 Here remove first column is more difficult that with literals due to the fact
357 that constructors can have arguments.
359 For instance, the matrix
371 remove_first_column :: Pat Id -- Constructor
372 -> [(EqnNo, EquationInfo)]
373 -> [(EqnNo, EquationInfo)]
374 remove_first_column (ConPatOut{ pat_con = L _ con, pat_args = PrefixCon con_pats }) qs
375 = ASSERT2( okGroup qs, pprGroup qs )
376 [(n, shift_var eqn) | q@(n, eqn) <- qs, is_var_con con (firstPatN q)]
378 new_wilds = [WildPat (hsLPatType arg_pat) | arg_pat <- con_pats]
379 shift_var eqn@(EqnInfo { eqn_pats = ConPatOut{ pat_args = PrefixCon ps' } : ps})
380 = eqn { eqn_pats = map unLoc ps' ++ ps }
381 shift_var eqn@(EqnInfo { eqn_pats = WildPat _ : ps })
382 = eqn { eqn_pats = new_wilds ++ ps }
383 shift_var _ = panic "Check.Shift_var:No done"
385 make_row_vars :: [HsLit] -> (EqnNo, EquationInfo) -> ExhaustivePat
386 make_row_vars used_lits (_, EqnInfo { eqn_pats = pats})
387 = (nlVarPat new_var:takeList (tail pats) (repeat nlWildPat),[(new_var,used_lits)])
392 hash_x = mkInternalName unboundKey {- doesn't matter much -}
393 (mkVarOccFS (fsLit "#x"))
396 make_row_vars_for_constructor :: (EqnNo, EquationInfo) -> [WarningPat]
397 make_row_vars_for_constructor (_, EqnInfo { eqn_pats = pats})
398 = takeList (tail pats) (repeat nlWildPat)
400 compare_cons :: Pat Id -> Pat Id -> Bool
401 compare_cons (ConPatOut{ pat_con = L _ id1 }) (ConPatOut { pat_con = L _ id2 }) = id1 == id2
403 remove_dups :: [Pat Id] -> [Pat Id]
405 remove_dups (x:xs) | or (map (\y -> compare_cons x y) xs) = remove_dups xs
406 | otherwise = x : remove_dups xs
408 get_used_cons :: [(EqnNo, EquationInfo)] -> [Pat Id]
409 get_used_cons qs = remove_dups [pat | q <- qs, let pat = firstPatN q,
412 isConPatOut :: Pat Id -> Bool
413 isConPatOut (ConPatOut {}) = True
414 isConPatOut _ = False
416 remove_dups' :: [HsLit] -> [HsLit]
418 remove_dups' (x:xs) | x `elem` xs = remove_dups' xs
419 | otherwise = x : remove_dups' xs
422 get_used_lits :: [(EqnNo, EquationInfo)] -> [HsLit]
423 get_used_lits qs = remove_dups' all_literals
425 all_literals = get_used_lits' qs
427 get_used_lits' :: [(EqnNo, EquationInfo)] -> [HsLit]
428 get_used_lits' [] = []
429 get_used_lits' (q:qs)
430 | Just lit <- get_lit (firstPatN q) = lit : get_used_lits' qs
431 | otherwise = get_used_lits qs
433 get_lit :: Pat id -> Maybe HsLit
434 -- Get a representative HsLit to stand for the OverLit
435 -- It doesn't matter which one, because they will only be compared
436 -- with other HsLits gotten in the same way
437 get_lit (LitPat lit) = Just lit
438 get_lit (NPat (OverLit { ol_val = HsIntegral i}) mb _) = Just (HsIntPrim (mb_neg mb i))
439 get_lit (NPat (OverLit { ol_val = HsFractional f }) mb _) = Just (HsFloatPrim (mb_neg mb f))
440 get_lit (NPat (OverLit { ol_val = HsIsString s }) _ _) = Just (HsStringPrim s)
443 mb_neg :: Num a => Maybe b -> a -> a
445 mb_neg (Just _) v = -v
447 get_unused_cons :: [Pat Id] -> [DataCon]
448 get_unused_cons used_cons = ASSERT( not (null used_cons) ) unused_cons
450 used_set :: UniqSet DataCon
451 used_set = mkUniqSet [d | ConPatOut{ pat_con = L _ d} <- used_cons]
452 (ConPatOut { pat_ty = ty }) = head used_cons
453 Just (ty_con, inst_tys) = splitTyConApp_maybe ty
454 unused_cons = filterOut is_used (tyConDataCons ty_con)
455 is_used con = con `elementOfUniqSet` used_set
456 || dataConCannotMatch inst_tys con
458 all_vars :: [Pat Id] -> Bool
460 all_vars (WildPat _:ps) = all_vars ps
463 remove_var :: (EqnNo, EquationInfo) -> (EqnNo, EquationInfo)
464 remove_var (n, eqn@(EqnInfo { eqn_pats = WildPat _ : ps})) = (n, eqn { eqn_pats = ps })
465 remove_var _ = panic "Check.remove_var: equation does not begin with a variable"
467 -----------------------
468 eqnPats :: (EqnNo, EquationInfo) -> [Pat Id]
469 eqnPats (_, eqn) = eqn_pats eqn
471 okGroup :: [(EqnNo, EquationInfo)] -> Bool
472 -- True if all equations have at least one pattern, and
473 -- all have the same number of patterns
475 okGroup (e:es) = n_pats > 0 && and [length (eqnPats e) == n_pats | e <- es]
477 n_pats = length (eqnPats e)
480 pprGroup :: [(EqnNo, EquationInfo)] -> SDoc
481 pprEqnInfo :: (EqnNo, EquationInfo) -> SDoc
482 pprGroup es = vcat (map pprEqnInfo es)
483 pprEqnInfo e = ppr (eqnPats e)
486 firstPatN :: (EqnNo, EquationInfo) -> Pat Id
487 firstPatN (_, eqn) = firstPat eqn
489 is_con :: Pat Id -> Bool
490 is_con (ConPatOut {}) = True
493 is_lit :: Pat Id -> Bool
494 is_lit (LitPat _) = True
495 is_lit (NPat _ _ _) = True
498 is_var :: Pat Id -> Bool
499 is_var (WildPat _) = True
502 is_var_con :: DataCon -> Pat Id -> Bool
503 is_var_con _ (WildPat _) = True
504 is_var_con con (ConPatOut{ pat_con = L _ id }) | id == con = True
505 is_var_con _ _ = False
507 is_var_lit :: HsLit -> Pat Id -> Bool
508 is_var_lit _ (WildPat _) = True
510 | Just lit' <- get_lit pat = lit == lit'
514 The difference beteewn @make_con@ and @make_whole_con@ is that
515 @make_wole_con@ creates a new constructor with all their arguments, and
516 @make_con@ takes a list of argumntes, creates the contructor getting their
517 arguments from the list. See where \fbox{\ ???\ } are used for details.
519 We need to reconstruct the patterns (make the constructors infix and
520 similar) at the same time that we create the constructors.
522 You can tell tuple constructors using
526 You can see if one constructor is infix with this clearer code :-))))))))))
528 Lex.isLexConSym (Name.occNameString (Name.getOccName con))
531 Rather clumsy but it works. (Simon Peyton Jones)
534 We don't mind the @nilDataCon@ because it doesn't change the way to
535 print the messsage, we are searching only for things like: @[1,2,3]@,
538 In @reconstruct_pat@ we want to ``undo'' the work
539 that we have done in @tidy_pat@.
542 @((,) x y)@ & returns to be & @(x, y)@
543 \\ @((:) x xs)@ & returns to be & @(x:xs)@
544 \\ @(x:(...:[])@ & returns to be & @[x,...]@
547 The difficult case is the third one becouse we need to follow all the
548 contructors until the @[]@ to know that we need to use the second case,
549 not the second. \fbox{\ ???\ }
552 isInfixCon :: DataCon -> Bool
553 isInfixCon con = isDataSymOcc (getOccName con)
555 is_nil :: Pat Name -> Bool
556 is_nil (ConPatIn con (PrefixCon [])) = unLoc con == getName nilDataCon
559 is_list :: Pat Name -> Bool
560 is_list (ListPat _ _) = True
563 return_list :: DataCon -> Pat Name -> Bool
564 return_list id q = id == consDataCon && (is_nil q || is_list q)
566 make_list :: LPat Name -> Pat Name -> Pat Name
567 make_list p q | is_nil q = ListPat [p] placeHolderType
568 make_list p (ListPat ps ty) = ListPat (p:ps) ty
569 make_list _ _ = panic "Check.make_list: Invalid argument"
571 make_con :: Pat Id -> ExhaustivePat -> ExhaustivePat
572 make_con (ConPatOut{ pat_con = L _ id }) (lp:lq:ps, constraints)
573 | return_list id q = (noLoc (make_list lp q) : ps, constraints)
574 | isInfixCon id = (nlInfixConPat (getName id) lp lq : ps, constraints)
577 make_con (ConPatOut{ pat_con = L _ id, pat_args = PrefixCon pats, pat_ty = ty }) (ps, constraints)
578 | isTupleTyCon tc = (noLoc (TuplePat pats_con (tupleTyConBoxity tc) ty) : rest_pats, constraints)
579 | isPArrFakeCon id = (noLoc (PArrPat pats_con placeHolderType) : rest_pats, constraints)
580 | otherwise = (nlConPat name pats_con : rest_pats, constraints)
583 (pats_con, rest_pats) = splitAtList pats ps
586 -- reconstruct parallel array pattern
588 -- * don't check for the type only; we need to make sure that we are really
589 -- dealing with one of the fake constructors and not with the real
592 make_whole_con :: DataCon -> WarningPat
593 make_whole_con con | isInfixCon con = nlInfixConPat name nlWildPat nlWildPat
594 | otherwise = nlConPat name pats
597 pats = [nlWildPat | _ <- dataConOrigArgTys con]
600 ------------------------------------------------------------------------
602 ------------------------------------------------------------------------
604 tidy_eqn does more or less the same thing as @tidy@ in @Match.lhs@;
605 that is, it removes syntactic sugar, reducing the number of cases that
606 must be handled by the main checking algorithm. One difference is
607 that here we can do *all* the tidying at once (recursively), rather
608 than doing it incrementally.
611 tidy_eqn :: EquationInfo -> EquationInfo
612 tidy_eqn eqn = eqn { eqn_pats = map tidy_pat (eqn_pats eqn),
613 eqn_rhs = tidy_rhs (eqn_rhs eqn) }
615 -- Horrible hack. The tidy_pat stuff converts "might-fail" patterns to
616 -- WildPats which of course loses the info that they can fail to match.
617 -- So we stick in a CanFail as if it were a guard.
618 tidy_rhs (MatchResult can_fail body)
619 | any might_fail_pat (eqn_pats eqn) = MatchResult CanFail body
620 | otherwise = MatchResult can_fail body
623 might_fail_pat :: Pat Id -> Bool
624 -- Returns True of patterns that might fail (i.e. fall through) in a way
625 -- that is not covered by the checking algorithm. Specifically:
627 -- ViewPat (if refutable)
629 -- First the two special cases
630 might_fail_pat (NPlusKPat {}) = True
631 might_fail_pat (ViewPat _ p _) = not (isIrrefutableHsPat p)
633 -- Now the recursive stuff
634 might_fail_pat (ParPat p) = might_fail_lpat p
635 might_fail_pat (AsPat _ p) = might_fail_lpat p
636 might_fail_pat (SigPatOut p _ ) = might_fail_lpat p
637 might_fail_pat (ListPat ps _) = any might_fail_lpat ps
638 might_fail_pat (TuplePat ps _ _) = any might_fail_lpat ps
639 might_fail_pat (PArrPat ps _) = any might_fail_lpat ps
640 might_fail_pat (BangPat p) = might_fail_lpat p
641 might_fail_pat (ConPatOut { pat_args = ps }) = any might_fail_lpat (hsConPatArgs ps)
643 -- Finally the ones that are sure to succeed, or which are covered by the checking algorithm
644 might_fail_pat (LazyPat _) = False -- Always succeeds
645 might_fail_pat _ = False -- VarPat, WildPat, LitPat, NPat, TypePat
648 might_fail_lpat :: LPat Id -> Bool
649 might_fail_lpat (L _ p) = might_fail_pat p
652 tidy_lpat :: LPat Id -> LPat Id
653 tidy_lpat p = fmap tidy_pat p
656 tidy_pat :: Pat Id -> Pat Id
657 tidy_pat pat@(WildPat _) = pat
658 tidy_pat (VarPat id) = WildPat (idType id)
659 tidy_pat (ParPat p) = tidy_pat (unLoc p)
660 tidy_pat (LazyPat p) = WildPat (hsLPatType p) -- For overlap and exhaustiveness checking
661 -- purposes, a ~pat is like a wildcard
662 tidy_pat (BangPat p) = tidy_pat (unLoc p)
663 tidy_pat (AsPat _ p) = tidy_pat (unLoc p)
664 tidy_pat (SigPatOut p _) = tidy_pat (unLoc p)
665 tidy_pat (CoPat _ pat _) = tidy_pat pat
667 -- These two are might_fail patterns, so we map them to
668 -- WildPats. The might_fail_pat stuff arranges that the
669 -- guard says "this equation might fall through".
670 tidy_pat (NPlusKPat id _ _ _) = WildPat (idType (unLoc id))
671 tidy_pat (ViewPat _ _ ty) = WildPat ty
673 tidy_pat (NPat lit mb_neg eq) = tidyNPat lit mb_neg eq
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 -- Unpack string patterns fully, so we can see when they overlap with
699 -- each other, or even explicit lists of Chars.
700 tidy_pat (LitPat lit)
702 = unLoc $ foldr (\c pat -> mkPrefixConPat consDataCon [mk_char_lit c, pat] stringTy)
703 (mkPrefixConPat nilDataCon [] stringTy) (unpackFS s)
707 mk_char_lit c = mkPrefixConPat charDataCon [nlLitPat (HsCharPrim c)] charTy
710 tidy_con :: DataCon -> HsConPatDetails Id -> HsConPatDetails Id
711 tidy_con _ (PrefixCon ps) = PrefixCon (map tidy_lpat ps)
712 tidy_con _ (InfixCon p1 p2) = PrefixCon [tidy_lpat p1, tidy_lpat p2]
713 tidy_con con (RecCon (HsRecFields fs _))
714 | null fs = PrefixCon [nlWildPat | _ <- dataConOrigArgTys con]
715 -- Special case for null patterns; maybe not a record at all
716 | otherwise = PrefixCon (map (tidy_lpat.snd) all_pats)
718 -- pad out all the missing fields with WildPats.
719 field_pats = map (\ f -> (f, nlWildPat)) (dataConFieldLabels con)
720 all_pats = foldr (\(HsRecField id p _) acc -> insertNm (getName (unLoc id)) p acc)
723 insertNm nm p [] = [(nm,p)]
724 insertNm nm p (x@(n,_):xs)
725 | nm == n = (nm,p):xs
726 | otherwise = x : insertNm nm p xs