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 module Check ( check , ExhaustivePat ) where
10 #include "HsVersions.h"
31 This module performs checks about if one list of equations are:
36 To discover that we go through the list of equations in a tree-like fashion.
38 If you like theory, a similar algorithm is described in:
40 {\em Two Techniques for Compiling Lazy Pattern Matching},
42 INRIA Rocquencourt (RR-2385, 1994)
44 The algorithm is based on the first technique, but there are some differences:
46 \item We don't generate code
47 \item We have constructors and literals (not only literals as in the
49 \item We don't use directions, we must select the columns from
52 (By the way the second technique is really similar to the one used in
53 @Match.lhs@ to generate code)
55 This function takes the equations of a pattern and returns:
57 \item The patterns that are not recognized
58 \item The equations that are not overlapped
60 It simplify the patterns and then call @check'@ (the same semantics), and it
61 needs to reconstruct the patterns again ....
63 The problem appear with things like:
68 We want to put the two patterns with the same syntax, (prefix form) and
69 then all the constructors are equal:
71 f (: x (: y [])) = ....
74 (more about that in @simplify_eqns@)
76 We would prefer to have a @WarningPat@ of type @String@, but Strings and the
77 Pretty Printer are not friends.
79 We use @InPat@ in @WarningPat@ instead of @OutPat@
80 because we need to print the
81 warning messages in the same way they are introduced, i.e. if the user
86 He don't want a warning message written:
88 f (: x (: y [])) ........
90 Then we need to use InPats.
92 Juan Quintela 5 JUL 1998\\
93 User-friendliness and compiler writers are no friends.
97 type WarningPat = InPat Name
98 type ExhaustivePat = ([WarningPat], [(Name, [HsLit])])
100 type EqnSet = UniqSet EqnNo
103 check :: [EquationInfo] -> ([ExhaustivePat], [EquationInfo])
104 -- Second result is the shadowed equations
105 check qs = (untidy_warns, shadowed_eqns)
107 (warns, used_nos) = check' ([1..] `zip` map simplify_eqn qs)
108 untidy_warns = map untidy_exhaustive warns
109 shadowed_eqns = [eqn | (eqn,i) <- qs `zip` [1..],
110 not (i `elementOfUniqSet` used_nos)]
112 untidy_exhaustive :: ExhaustivePat -> ExhaustivePat
113 untidy_exhaustive ([pat], messages) =
114 ([untidy_no_pars pat], map untidy_message messages)
115 untidy_exhaustive (pats, messages) =
116 (map untidy_pars pats, map untidy_message messages)
118 untidy_message :: (Name, [HsLit]) -> (Name, [HsLit])
119 untidy_message (string, lits) = (string, map untidy_lit lits)
122 The function @untidy@ does the reverse work of the @simplify_pat@ funcion.
128 untidy_no_pars :: WarningPat -> WarningPat
129 untidy_no_pars p = untidy False p
131 untidy_pars :: WarningPat -> WarningPat
132 untidy_pars p = untidy True p
134 untidy :: NeedPars -> WarningPat -> WarningPat
135 untidy b (L loc p) = L loc (untidy' b p)
137 untidy' _ p@(WildPat _) = p
138 untidy' _ p@(VarPat name) = p
139 untidy' _ (LitPat lit) = LitPat (untidy_lit lit)
140 untidy' _ p@(ConPatIn name (PrefixCon [])) = p
141 untidy' b (ConPatIn name ps) = pars b (L loc (ConPatIn name (untidy_con ps)))
142 untidy' _ (ListPat pats ty) = ListPat (map untidy_no_pars pats) ty
143 untidy' _ (TuplePat pats box ty) = TuplePat (map untidy_no_pars pats) box ty
144 untidy' _ (PArrPat _ _) = panic "Check.untidy: Shouldn't get a parallel array here!"
145 untidy' _ (SigPatIn _ _) = panic "Check.untidy: SigPat"
147 untidy_con (PrefixCon pats) = PrefixCon (map untidy_pars pats)
148 untidy_con (InfixCon p1 p2) = InfixCon (untidy_pars p1) (untidy_pars p2)
149 untidy_con (RecCon bs) = RecCon [ HsRecField f (untidy_pars p) d | HsRecField f p d <- bs ]
151 pars :: NeedPars -> WarningPat -> Pat Name
152 pars True p = ParPat p
155 untidy_lit :: HsLit -> HsLit
156 untidy_lit (HsCharPrim c) = HsChar c
160 This equation is the same that check, the only difference is that the
161 boring work is done, that work needs to be done only once, this is
162 the reason top have two functions, check is the external interface,
163 @check'@ is called recursively.
165 There are several cases:
168 \item There are no equations: Everything is OK.
169 \item There are only one equation, that can fail, and all the patterns are
170 variables. Then that equation is used and the same equation is
172 \item All the patterns are variables, and the match can fail, there are
173 more equations then the results is the result of the rest of equations
174 and this equation is used also.
176 \item The general case, if all the patterns are variables (here the match
177 can't fail) then the result is that this equation is used and this
178 equation doesn't generate non-exhaustive cases.
180 \item In the general case, there can exist literals ,constructors or only
181 vars in the first column, we actuate in consequence.
188 check' :: [(EqnNo, EquationInfo)]
189 -> ([ExhaustivePat], -- Pattern scheme that might not be matched at all
190 EqnSet) -- Eqns that are used (others are overlapped)
192 check' [] = ([([],[])],emptyUniqSet)
194 check' ((n, EqnInfo { eqn_pats = ps, eqn_rhs = MatchResult can_fail _ }) : rs)
195 | first_eqn_all_vars && case can_fail of { CantFail -> True; CanFail -> False }
196 = ([], unitUniqSet n) -- One eqn, which can't fail
198 | first_eqn_all_vars && null rs -- One eqn, but it can fail
199 = ([(takeList ps (repeat nlWildPat),[])], unitUniqSet n)
201 | first_eqn_all_vars -- Several eqns, first can fail
202 = (pats, addOneToUniqSet indexs n)
204 first_eqn_all_vars = all_vars ps
205 (pats,indexs) = check' rs
208 | literals = split_by_literals qs
209 | constructors = split_by_constructor qs
210 | only_vars = first_column_only_vars qs
211 | otherwise = pprPanic "Check.check': Not implemented :-(" (ppr first_pats)
213 -- Note: RecPats will have been simplified to ConPats
215 first_pats = ASSERT2( okGroup qs, pprGroup qs ) map firstPatN qs
216 constructors = any is_con first_pats
217 literals = any is_lit first_pats
218 only_vars = all is_var first_pats
221 Here begins the code to deal with literals, we need to split the matrix
222 in different matrix beginning by each literal and a last matrix with the
226 split_by_literals :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet)
227 split_by_literals qs = process_literals used_lits qs
229 used_lits = get_used_lits qs
232 @process_explicit_literals@ is a function that process each literal that appears
233 in the column of the matrix.
236 process_explicit_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
237 process_explicit_literals lits qs = (concat pats, unionManyUniqSets indexs)
239 pats_indexs = map (\x -> construct_literal_matrix x qs) lits
240 (pats,indexs) = unzip pats_indexs
244 @process_literals@ calls @process_explicit_literals@ to deal with the literals
245 that appears in the matrix and deal also with the rest of the cases. It
246 must be one Variable to be complete.
250 process_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
251 process_literals used_lits qs
252 | null default_eqns = ([make_row_vars used_lits (head qs)] ++ pats,indexs)
253 | otherwise = (pats_default,indexs_default)
255 (pats,indexs) = process_explicit_literals used_lits qs
256 default_eqns = ASSERT2( okGroup qs, pprGroup qs )
257 [remove_var q | q <- qs, is_var (firstPatN q)]
258 (pats',indexs') = check' default_eqns
259 pats_default = [(nlWildPat:ps,constraints) | (ps,constraints) <- (pats')] ++ pats
260 indexs_default = unionUniqSets indexs' indexs
263 Here we have selected the literal and we will select all the equations that
264 begins for that literal and create a new matrix.
267 construct_literal_matrix :: HsLit -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
268 construct_literal_matrix lit qs =
269 (map (\ (xs,ys) -> (new_lit:xs,ys)) pats,indexs)
271 (pats,indexs) = (check' (remove_first_column_lit lit qs))
272 new_lit = nlLitPat lit
274 remove_first_column_lit :: HsLit
275 -> [(EqnNo, EquationInfo)]
276 -> [(EqnNo, EquationInfo)]
277 remove_first_column_lit lit qs
278 = ASSERT2( okGroup qs, pprGroup qs )
279 [(n, shift_pat eqn) | q@(n,eqn) <- qs, is_var_lit lit (firstPatN q)]
281 shift_pat eqn@(EqnInfo { eqn_pats = _:ps}) = eqn { eqn_pats = ps }
282 shift_pat eqn@(EqnInfo { eqn_pats = []}) = panic "Check.shift_var: no patterns"
285 This function splits the equations @qs@ in groups that deal with the
289 split_by_constructor :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet)
290 split_by_constructor qs
291 | notNull unused_cons = need_default_case used_cons unused_cons qs
292 | otherwise = no_need_default_case used_cons qs
294 used_cons = get_used_cons qs
295 unused_cons = get_unused_cons used_cons
298 The first column of the patterns matrix only have vars, then there is
302 first_column_only_vars :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
303 first_column_only_vars qs = (map (\ (xs,ys) -> (nlWildPat:xs,ys)) pats,indexs)
305 (pats, indexs) = check' (map remove_var qs)
308 This equation takes a matrix of patterns and split the equations by
309 constructor, using all the constructors that appears in the first column
310 of the pattern matching.
312 We can need a default clause or not ...., it depends if we used all the
313 constructors or not explicitly. The reasoning is similar to @process_literals@,
314 the difference is that here the default case is not always needed.
317 no_need_default_case :: [Pat Id] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
318 no_need_default_case cons qs = (concat pats, unionManyUniqSets indexs)
320 pats_indexs = map (\x -> construct_matrix x qs) cons
321 (pats,indexs) = unzip pats_indexs
323 need_default_case :: [Pat Id] -> [DataCon] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
324 need_default_case used_cons unused_cons qs
325 | null default_eqns = (pats_default_no_eqns,indexs)
326 | otherwise = (pats_default,indexs_default)
328 (pats,indexs) = no_need_default_case used_cons qs
329 default_eqns = ASSERT2( okGroup qs, pprGroup qs )
330 [remove_var q | q <- qs, is_var (firstPatN q)]
331 (pats',indexs') = check' default_eqns
332 pats_default = [(make_whole_con c:ps,constraints) |
333 c <- unused_cons, (ps,constraints) <- pats'] ++ pats
334 new_wilds = make_row_vars_for_constructor (head qs)
335 pats_default_no_eqns = [(make_whole_con c:new_wilds,[]) | c <- unused_cons] ++ pats
336 indexs_default = unionUniqSets indexs' indexs
338 construct_matrix :: Pat Id -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet)
339 construct_matrix con qs =
340 (map (make_con con) pats,indexs)
342 (pats,indexs) = (check' (remove_first_column con qs))
345 Here remove first column is more difficult that with literals due to the fact
346 that constructors can have arguments.
348 For instance, the matrix
360 remove_first_column :: Pat Id -- Constructor
361 -> [(EqnNo, EquationInfo)]
362 -> [(EqnNo, EquationInfo)]
363 remove_first_column (ConPatOut{ pat_con = L _ con, pat_args = PrefixCon con_pats }) qs
364 = ASSERT2( okGroup qs, pprGroup qs )
365 [(n, shift_var eqn) | q@(n, eqn) <- qs, is_var_con con (firstPatN q)]
367 new_wilds = [WildPat (hsLPatType arg_pat) | arg_pat <- con_pats]
368 shift_var eqn@(EqnInfo { eqn_pats = ConPatOut{ pat_args = PrefixCon ps' } : ps})
369 = eqn { eqn_pats = map unLoc ps' ++ ps }
370 shift_var eqn@(EqnInfo { eqn_pats = WildPat _ : ps })
371 = eqn { eqn_pats = new_wilds ++ ps }
372 shift_var _ = panic "Check.Shift_var:No done"
374 make_row_vars :: [HsLit] -> (EqnNo, EquationInfo) -> ExhaustivePat
375 make_row_vars used_lits (_, EqnInfo { eqn_pats = pats})
376 = (nlVarPat new_var:takeList (tail pats) (repeat nlWildPat),[(new_var,used_lits)])
380 hash_x = mkInternalName unboundKey {- doesn't matter much -}
381 (mkVarOccFS FSLIT("#x"))
384 make_row_vars_for_constructor :: (EqnNo, EquationInfo) -> [WarningPat]
385 make_row_vars_for_constructor (_, EqnInfo { eqn_pats = pats})
386 = takeList (tail pats) (repeat nlWildPat)
388 compare_cons :: Pat Id -> Pat Id -> Bool
389 compare_cons (ConPatOut{ pat_con = L _ id1 }) (ConPatOut { pat_con = L _ id2 }) = id1 == id2
391 remove_dups :: [Pat Id] -> [Pat Id]
393 remove_dups (x:xs) | or (map (\y -> compare_cons x y) xs) = remove_dups xs
394 | otherwise = x : remove_dups xs
396 get_used_cons :: [(EqnNo, EquationInfo)] -> [Pat Id]
397 get_used_cons qs = remove_dups [pat | q <- qs, let pat = firstPatN q,
400 isConPatOut (ConPatOut {}) = True
401 isConPatOut other = False
403 remove_dups' :: [HsLit] -> [HsLit]
405 remove_dups' (x:xs) | x `elem` xs = remove_dups' xs
406 | otherwise = x : remove_dups' xs
409 get_used_lits :: [(EqnNo, EquationInfo)] -> [HsLit]
410 get_used_lits qs = remove_dups' all_literals
412 all_literals = get_used_lits' qs
414 get_used_lits' :: [(EqnNo, EquationInfo)] -> [HsLit]
415 get_used_lits' [] = []
416 get_used_lits' (q:qs)
417 | Just lit <- get_lit (firstPatN q) = lit : get_used_lits' qs
418 | otherwise = get_used_lits qs
420 get_lit :: Pat id -> Maybe HsLit
421 -- Get a representative HsLit to stand for the OverLit
422 -- It doesn't matter which one, because they will only be compared
423 -- with other HsLits gotten in the same way
424 get_lit (LitPat lit) = Just lit
425 get_lit (NPat (HsIntegral i _) mb _ _) = Just (HsIntPrim (mb_neg mb i))
426 get_lit (NPat (HsFractional f _) mb _ _) = Just (HsFloatPrim (mb_neg mb f))
427 get_lit (NPat (HsIsString s _) _ _ _) = Just (HsStringPrim s)
428 get_lit other_pat = Nothing
430 mb_neg :: Num a => Maybe b -> a -> a
432 mb_neg (Just _) v = -v
434 get_unused_cons :: [Pat Id] -> [DataCon]
435 get_unused_cons used_cons = unused_cons
437 (ConPatOut { pat_con = l_con, pat_ty = ty }) = head used_cons
438 ty_con = dataConTyCon (unLoc l_con) -- Newtype observable
439 all_cons = tyConDataCons ty_con
440 used_cons_as_id = map (\ (ConPatOut{ pat_con = L _ d}) -> d) used_cons
441 unused_cons = uniqSetToList
442 (mkUniqSet all_cons `minusUniqSet` mkUniqSet used_cons_as_id)
444 all_vars :: [Pat Id] -> Bool
446 all_vars (WildPat _:ps) = all_vars ps
449 remove_var :: (EqnNo, EquationInfo) -> (EqnNo, EquationInfo)
450 remove_var (n, eqn@(EqnInfo { eqn_pats = WildPat _ : ps})) = (n, eqn { eqn_pats = ps })
451 remove_var _ = panic "Check.remove_var: equation does not begin with a variable"
453 -----------------------
454 eqnPats :: (EqnNo, EquationInfo) -> [Pat Id]
455 eqnPats (_, eqn) = eqn_pats eqn
457 okGroup :: [(EqnNo, EquationInfo)] -> Bool
458 -- True if all equations have at least one pattern, and
459 -- all have the same number of patterns
461 okGroup (e:es) = n_pats > 0 && and [length (eqnPats e) == n_pats | e <- es]
463 n_pats = length (eqnPats e)
466 pprGroup es = vcat (map pprEqnInfo es)
467 pprEqnInfo e = ppr (eqnPats e)
470 firstPatN :: (EqnNo, EquationInfo) -> Pat Id
471 firstPatN (_, eqn) = firstPat eqn
473 is_con :: Pat Id -> Bool
474 is_con (ConPatOut {}) = True
477 is_lit :: Pat Id -> Bool
478 is_lit (LitPat _) = True
479 is_lit (NPat _ _ _ _) = True
482 is_var :: Pat Id -> Bool
483 is_var (WildPat _) = True
486 is_var_con :: DataCon -> Pat Id -> Bool
487 is_var_con con (WildPat _) = True
488 is_var_con con (ConPatOut{ pat_con = L _ id }) | id == con = True
489 is_var_con con _ = False
491 is_var_lit :: HsLit -> Pat Id -> Bool
492 is_var_lit lit (WildPat _) = True
494 | Just lit' <- get_lit pat = lit == lit'
498 The difference beteewn @make_con@ and @make_whole_con@ is that
499 @make_wole_con@ creates a new constructor with all their arguments, and
500 @make_con@ takes a list of argumntes, creates the contructor getting their
501 arguments from the list. See where \fbox{\ ???\ } are used for details.
503 We need to reconstruct the patterns (make the constructors infix and
504 similar) at the same time that we create the constructors.
506 You can tell tuple constructors using
510 You can see if one constructor is infix with this clearer code :-))))))))))
512 Lex.isLexConSym (Name.occNameString (Name.getOccName con))
515 Rather clumsy but it works. (Simon Peyton Jones)
518 We don't mind the @nilDataCon@ because it doesn't change the way to
519 print the messsage, we are searching only for things like: @[1,2,3]@,
522 In @reconstruct_pat@ we want to ``undo'' the work
523 that we have done in @simplify_pat@.
526 @((,) x y)@ & returns to be & @(x, y)@
527 \\ @((:) x xs)@ & returns to be & @(x:xs)@
528 \\ @(x:(...:[])@ & returns to be & @[x,...]@
531 The difficult case is the third one becouse we need to follow all the
532 contructors until the @[]@ to know that we need to use the second case,
533 not the second. \fbox{\ ???\ }
536 isInfixCon con = isDataSymOcc (getOccName con)
538 is_nil (ConPatIn con (PrefixCon [])) = unLoc con == getName nilDataCon
541 is_list (ListPat _ _) = True
544 return_list id q = id == consDataCon && (is_nil q || is_list q)
546 make_list p q | is_nil q = ListPat [p] placeHolderType
547 make_list p (ListPat ps ty) = ListPat (p:ps) ty
548 make_list _ _ = panic "Check.make_list: Invalid argument"
550 make_con :: Pat Id -> ExhaustivePat -> ExhaustivePat
551 make_con (ConPatOut{ pat_con = L _ id }) (lp:lq:ps, constraints)
552 | return_list id q = (noLoc (make_list lp q) : ps, constraints)
553 | isInfixCon id = (nlInfixConPat (getName id) lp lq : ps, constraints)
556 make_con (ConPatOut{ pat_con = L _ id, pat_args = PrefixCon pats, pat_ty = ty }) (ps, constraints)
557 | isTupleTyCon tc = (noLoc (TuplePat pats_con (tupleTyConBoxity tc) ty) : rest_pats, constraints)
558 | isPArrFakeCon id = (noLoc (PArrPat pats_con placeHolderType) : rest_pats, constraints)
559 | otherwise = (nlConPat name pats_con : rest_pats, constraints)
562 (pats_con, rest_pats) = splitAtList pats ps
565 -- reconstruct parallel array pattern
567 -- * don't check for the type only; we need to make sure that we are really
568 -- dealing with one of the fake constructors and not with the real
571 make_whole_con :: DataCon -> WarningPat
572 make_whole_con con | isInfixCon con = nlInfixConPat name nlWildPat nlWildPat
573 | otherwise = nlConPat name pats
576 pats = [nlWildPat | t <- dataConOrigArgTys con]
579 This equation makes the same thing as @tidy@ in @Match.lhs@, the
580 difference is that here we can do all the tidy in one place and in the
581 @Match@ tidy it must be done one column each time due to bookkeeping
586 simplify_eqn :: EquationInfo -> EquationInfo
587 simplify_eqn eqn = eqn { eqn_pats = map simplify_pat (eqn_pats eqn),
588 eqn_rhs = simplify_rhs (eqn_rhs eqn) }
590 -- Horrible hack. The simplify_pat stuff converts NPlusK pats to WildPats
591 -- which of course loses the info that they can fail to match. So we
592 -- stick in a CanFail as if it were a guard.
593 -- The Right Thing to do is for the whole system to treat NPlusK pats properly
594 simplify_rhs (MatchResult can_fail body)
595 | any has_nplusk_pat (eqn_pats eqn) = MatchResult CanFail body
596 | otherwise = MatchResult can_fail body
598 has_nplusk_lpat :: LPat Id -> Bool
599 has_nplusk_lpat (L _ p) = has_nplusk_pat p
601 has_nplusk_pat :: Pat Id -> Bool
602 has_nplusk_pat (NPlusKPat _ _ _ _) = True
603 has_nplusk_pat (ParPat p) = has_nplusk_lpat p
604 has_nplusk_pat (AsPat _ p) = has_nplusk_lpat p
605 has_nplusk_pat (SigPatOut p _ ) = has_nplusk_lpat p
606 has_nplusk_pat (ListPat ps _) = any has_nplusk_lpat ps
607 has_nplusk_pat (TuplePat ps _ _) = any has_nplusk_lpat ps
608 has_nplusk_pat (PArrPat ps _) = any has_nplusk_lpat ps
609 has_nplusk_pat (LazyPat p) = False -- Why?
610 has_nplusk_pat (BangPat p) = has_nplusk_lpat p -- I think
611 has_nplusk_pat (ConPatOut { pat_args = ps }) = any has_nplusk_lpat (hsConArgs ps)
612 has_nplusk_pat p = False -- VarPat, VarPatOut, WildPat, LitPat, NPat, TypePat, DictPat
614 simplify_lpat :: LPat Id -> LPat Id
615 simplify_lpat p = fmap simplify_pat p
617 simplify_pat :: Pat Id -> Pat Id
618 simplify_pat pat@(WildPat gt) = pat
619 simplify_pat (VarPat id) = WildPat (idType id)
620 simplify_pat (VarPatOut id _) = WildPat (idType id) -- Ignore the bindings
621 simplify_pat (ParPat p) = unLoc (simplify_lpat p)
622 simplify_pat (LazyPat p) = WildPat (hsLPatType p) -- For overlap and exhaustiveness checking
623 -- purposes, a ~pat is like a wildcard
624 simplify_pat (BangPat p) = unLoc (simplify_lpat p)
625 simplify_pat (AsPat id p) = unLoc (simplify_lpat p)
626 simplify_pat (SigPatOut p _) = unLoc (simplify_lpat p) -- I'm not sure this is right
628 simplify_pat pat@(ConPatOut { pat_con = L loc id, pat_args = ps })
629 = pat { pat_args = simplify_con id ps }
631 simplify_pat (ListPat ps ty) =
632 unLoc $ foldr (\ x y -> mkPrefixConPat consDataCon [x,y] list_ty)
634 (map simplify_lpat ps)
635 where list_ty = mkListTy ty
637 -- introduce fake parallel array constructors to be able to handle parallel
638 -- arrays with the existing machinery for constructor pattern
640 simplify_pat (PArrPat ps ty)
641 = unLoc $ mkPrefixConPat (parrFakeCon (length ps))
642 (map simplify_lpat ps)
645 simplify_pat (TuplePat ps boxity ty)
646 = unLoc $ mkPrefixConPat (tupleCon boxity arity)
647 (map simplify_lpat ps) ty
651 -- unpack string patterns fully, so we can see when they overlap with
652 -- each other, or even explicit lists of Chars.
653 simplify_pat pat@(LitPat (HsString s)) =
654 unLoc $ foldr (\c pat -> mkPrefixConPat consDataCon [mk_char_lit c, pat] stringTy)
655 (mkPrefixConPat nilDataCon [] stringTy) (unpackFS s)
657 mk_char_lit c = mkPrefixConPat charDataCon [nlLitPat (HsCharPrim c)] charTy
659 simplify_pat (LitPat lit) = tidyLitPat lit
660 simplify_pat (NPat lit mb_neg eq lit_ty) = tidyNPat lit mb_neg eq lit_ty
662 simplify_pat (NPlusKPat id hslit hsexpr1 hsexpr2)
663 = WildPat (idType (unLoc id))
665 simplify_pat (DictPat dicts methods)
666 = case num_of_d_and_ms of
667 0 -> simplify_pat (TuplePat [] Boxed unitTy)
668 1 -> simplify_pat (head dict_and_method_pats)
669 _ -> simplify_pat (mkVanillaTuplePat (map noLoc dict_and_method_pats) Boxed)
671 num_of_d_and_ms = length dicts + length methods
672 dict_and_method_pats = map VarPat (dicts ++ methods)
674 simplify_pat (CoPat co pat ty) = simplify_pat pat
677 simplify_con con (PrefixCon ps) = PrefixCon (map simplify_lpat ps)
678 simplify_con con (InfixCon p1 p2) = PrefixCon [simplify_lpat p1, simplify_lpat p2]
679 simplify_con con (RecCon fs)
680 | null fs = PrefixCon [nlWildPat | t <- dataConOrigArgTys con]
681 -- Special case for null patterns; maybe not a record at all
682 | otherwise = PrefixCon (map (simplify_lpat.snd) all_pats)
684 -- pad out all the missing fields with WildPats.
685 field_pats = map (\ f -> (f, nlWildPat)) (dataConFieldLabels con)
686 all_pats = foldr (\(HsRecField id p _) acc -> insertNm (getName (unLoc id)) p acc)
689 insertNm nm p [] = [(nm,p)]
690 insertNm nm p (x@(n,_):xs)
691 | nm == n = (nm,p):xs
692 | otherwise = x : insertNm nm p xs