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Diffstat (limited to 'compiler/deSugar/Check.lhs')
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diff --git a/compiler/deSugar/Check.lhs b/compiler/deSugar/Check.lhs new file mode 100644 index 0000000000..9aac5ce777 --- /dev/null +++ b/compiler/deSugar/Check.lhs @@ -0,0 +1,698 @@ +% +% (c) The GRASP/AQUA Project, Glasgow University, 1997-1998 +% +% Author: Juan J. Quintela <quintela@krilin.dc.fi.udc.es> +\section{Module @Check@ in @deSugar@} + +\begin{code} + + +module Check ( check , ExhaustivePat ) where + + +import HsSyn +import TcHsSyn ( hsPatType, mkVanillaTuplePat ) +import TcType ( tcTyConAppTyCon ) +import DsUtils ( EquationInfo(..), MatchResult(..), + CanItFail(..), firstPat ) +import MatchLit ( tidyLitPat, tidyNPat ) +import Id ( Id, idType ) +import DataCon ( DataCon, dataConTyCon, dataConOrigArgTys, dataConFieldLabels ) +import Name ( Name, mkInternalName, getOccName, isDataSymOcc, + getName, mkVarOccFS ) +import TysWiredIn +import PrelNames ( unboundKey ) +import TyCon ( tyConDataCons, tupleTyConBoxity, isTupleTyCon ) +import BasicTypes ( Boxity(..) ) +import SrcLoc ( noSrcLoc, Located(..), unLoc, noLoc ) +import UniqSet +import Util ( takeList, splitAtList, notNull ) +import Outputable +import FastString + +#include "HsVersions.h" +\end{code} + +This module performs checks about if one list of equations are: +\begin{itemize} +\item Overlapped +\item Non exhaustive +\end{itemize} +To discover that we go through the list of equations in a tree-like fashion. + +If you like theory, a similar algorithm is described in: +\begin{quotation} + {\em Two Techniques for Compiling Lazy Pattern Matching}, + Luc Maranguet, + INRIA Rocquencourt (RR-2385, 1994) +\end{quotation} +The algorithm is based on the first technique, but there are some differences: +\begin{itemize} +\item We don't generate code +\item We have constructors and literals (not only literals as in the + article) +\item We don't use directions, we must select the columns from + left-to-right +\end{itemize} +(By the way the second technique is really similar to the one used in + @Match.lhs@ to generate code) + +This function takes the equations of a pattern and returns: +\begin{itemize} +\item The patterns that are not recognized +\item The equations that are not overlapped +\end{itemize} +It simplify the patterns and then call @check'@ (the same semantics), and it +needs to reconstruct the patterns again .... + +The problem appear with things like: +\begin{verbatim} + f [x,y] = .... + f (x:xs) = ..... +\end{verbatim} +We want to put the two patterns with the same syntax, (prefix form) and +then all the constructors are equal: +\begin{verbatim} + f (: x (: y [])) = .... + f (: x xs) = ..... +\end{verbatim} +(more about that in @simplify_eqns@) + +We would prefer to have a @WarningPat@ of type @String@, but Strings and the +Pretty Printer are not friends. + +We use @InPat@ in @WarningPat@ instead of @OutPat@ +because we need to print the +warning messages in the same way they are introduced, i.e. if the user +wrote: +\begin{verbatim} + f [x,y] = .. +\end{verbatim} +He don't want a warning message written: +\begin{verbatim} + f (: x (: y [])) ........ +\end{verbatim} +Then we need to use InPats. +\begin{quotation} + Juan Quintela 5 JUL 1998\\ + User-friendliness and compiler writers are no friends. +\end{quotation} + +\begin{code} +type WarningPat = InPat Name +type ExhaustivePat = ([WarningPat], [(Name, [HsLit])]) +type EqnNo = Int +type EqnSet = UniqSet EqnNo + + +check :: [EquationInfo] -> ([ExhaustivePat], [EquationInfo]) + -- Second result is the shadowed equations +check qs = (untidy_warns, shadowed_eqns) + where + (warns, used_nos) = check' ([1..] `zip` map simplify_eqn qs) + untidy_warns = map untidy_exhaustive warns + shadowed_eqns = [eqn | (eqn,i) <- qs `zip` [1..], + not (i `elementOfUniqSet` used_nos)] + +untidy_exhaustive :: ExhaustivePat -> ExhaustivePat +untidy_exhaustive ([pat], messages) = + ([untidy_no_pars pat], map untidy_message messages) +untidy_exhaustive (pats, messages) = + (map untidy_pars pats, map untidy_message messages) + +untidy_message :: (Name, [HsLit]) -> (Name, [HsLit]) +untidy_message (string, lits) = (string, map untidy_lit lits) +\end{code} + +The function @untidy@ does the reverse work of the @simplify_pat@ funcion. + +\begin{code} + +type NeedPars = Bool + +untidy_no_pars :: WarningPat -> WarningPat +untidy_no_pars p = untidy False p + +untidy_pars :: WarningPat -> WarningPat +untidy_pars p = untidy True p + +untidy :: NeedPars -> WarningPat -> WarningPat +untidy b (L loc p) = L loc (untidy' b p) + where + untidy' _ p@(WildPat _) = p + untidy' _ p@(VarPat name) = p + untidy' _ (LitPat lit) = LitPat (untidy_lit lit) + untidy' _ p@(ConPatIn name (PrefixCon [])) = p + untidy' b (ConPatIn name ps) = pars b (L loc (ConPatIn name (untidy_con ps))) + untidy' _ (ListPat pats ty) = ListPat (map untidy_no_pars pats) ty + untidy' _ (TuplePat pats box ty) = TuplePat (map untidy_no_pars pats) box ty + untidy' _ (PArrPat _ _) = panic "Check.untidy: Shouldn't get a parallel array here!" + untidy' _ (SigPatIn _ _) = panic "Check.untidy: SigPat" + +untidy_con (PrefixCon pats) = PrefixCon (map untidy_pars pats) +untidy_con (InfixCon p1 p2) = InfixCon (untidy_pars p1) (untidy_pars p2) +untidy_con (RecCon bs) = RecCon [(f,untidy_pars p) | (f,p) <- bs] + +pars :: NeedPars -> WarningPat -> Pat Name +pars True p = ParPat p +pars _ p = unLoc p + +untidy_lit :: HsLit -> HsLit +untidy_lit (HsCharPrim c) = HsChar c +untidy_lit lit = lit +\end{code} + +This equation is the same that check, the only difference is that the +boring work is done, that work needs to be done only once, this is +the reason top have two functions, check is the external interface, +@check'@ is called recursively. + +There are several cases: + +\begin{itemize} +\item There are no equations: Everything is OK. +\item There are only one equation, that can fail, and all the patterns are + variables. Then that equation is used and the same equation is + non-exhaustive. +\item All the patterns are variables, and the match can fail, there are + more equations then the results is the result of the rest of equations + and this equation is used also. + +\item The general case, if all the patterns are variables (here the match + can't fail) then the result is that this equation is used and this + equation doesn't generate non-exhaustive cases. + +\item In the general case, there can exist literals ,constructors or only + vars in the first column, we actuate in consequence. + +\end{itemize} + + +\begin{code} + +check' :: [(EqnNo, EquationInfo)] + -> ([ExhaustivePat], -- Pattern scheme that might not be matched at all + EqnSet) -- Eqns that are used (others are overlapped) + +check' [] = ([([],[])],emptyUniqSet) + +check' ((n, EqnInfo { eqn_pats = ps, eqn_rhs = MatchResult can_fail _ }) : rs) + | first_eqn_all_vars && case can_fail of { CantFail -> True; CanFail -> False } + = ([], unitUniqSet n) -- One eqn, which can't fail + + | first_eqn_all_vars && null rs -- One eqn, but it can fail + = ([(takeList ps (repeat nlWildPat),[])], unitUniqSet n) + + | first_eqn_all_vars -- Several eqns, first can fail + = (pats, addOneToUniqSet indexs n) + where + first_eqn_all_vars = all_vars ps + (pats,indexs) = check' rs + +check' qs + | literals = split_by_literals qs + | constructors = split_by_constructor qs + | only_vars = first_column_only_vars qs + | otherwise = pprPanic "Check.check': Not implemented :-(" (ppr first_pats) + where + -- Note: RecPats will have been simplified to ConPats + -- at this stage. + first_pats = ASSERT2( okGroup qs, pprGroup qs ) map firstPatN qs + constructors = any is_con first_pats + literals = any is_lit first_pats + only_vars = all is_var first_pats +\end{code} + +Here begins the code to deal with literals, we need to split the matrix +in different matrix beginning by each literal and a last matrix with the +rest of values. + +\begin{code} +split_by_literals :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet) +split_by_literals qs = process_literals used_lits qs + where + used_lits = get_used_lits qs +\end{code} + +@process_explicit_literals@ is a function that process each literal that appears +in the column of the matrix. + +\begin{code} +process_explicit_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet) +process_explicit_literals lits qs = (concat pats, unionManyUniqSets indexs) + where + pats_indexs = map (\x -> construct_literal_matrix x qs) lits + (pats,indexs) = unzip pats_indexs +\end{code} + + +@process_literals@ calls @process_explicit_literals@ to deal with the literals +that appears in the matrix and deal also with the rest of the cases. It +must be one Variable to be complete. + +\begin{code} + +process_literals :: [HsLit] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet) +process_literals used_lits qs + | null default_eqns = ([make_row_vars used_lits (head qs)] ++ pats,indexs) + | otherwise = (pats_default,indexs_default) + where + (pats,indexs) = process_explicit_literals used_lits qs + default_eqns = ASSERT2( okGroup qs, pprGroup qs ) + [remove_var q | q <- qs, is_var (firstPatN q)] + (pats',indexs') = check' default_eqns + pats_default = [(nlWildPat:ps,constraints) | (ps,constraints) <- (pats')] ++ pats + indexs_default = unionUniqSets indexs' indexs +\end{code} + +Here we have selected the literal and we will select all the equations that +begins for that literal and create a new matrix. + +\begin{code} +construct_literal_matrix :: HsLit -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet) +construct_literal_matrix lit qs = + (map (\ (xs,ys) -> (new_lit:xs,ys)) pats,indexs) + where + (pats,indexs) = (check' (remove_first_column_lit lit qs)) + new_lit = nlLitPat lit + +remove_first_column_lit :: HsLit + -> [(EqnNo, EquationInfo)] + -> [(EqnNo, EquationInfo)] +remove_first_column_lit lit qs + = ASSERT2( okGroup qs, pprGroup qs ) + [(n, shift_pat eqn) | q@(n,eqn) <- qs, is_var_lit lit (firstPatN q)] + where + shift_pat eqn@(EqnInfo { eqn_pats = _:ps}) = eqn { eqn_pats = ps } + shift_pat eqn@(EqnInfo { eqn_pats = []}) = panic "Check.shift_var: no patterns" +\end{code} + +This function splits the equations @qs@ in groups that deal with the +same constructor. + +\begin{code} +split_by_constructor :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat], EqnSet) +split_by_constructor qs + | notNull unused_cons = need_default_case used_cons unused_cons qs + | otherwise = no_need_default_case used_cons qs + where + used_cons = get_used_cons qs + unused_cons = get_unused_cons used_cons +\end{code} + +The first column of the patterns matrix only have vars, then there is +nothing to do. + +\begin{code} +first_column_only_vars :: [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet) +first_column_only_vars qs = (map (\ (xs,ys) -> (nlWildPat:xs,ys)) pats,indexs) + where + (pats, indexs) = check' (map remove_var qs) +\end{code} + +This equation takes a matrix of patterns and split the equations by +constructor, using all the constructors that appears in the first column +of the pattern matching. + +We can need a default clause or not ...., it depends if we used all the +constructors or not explicitly. The reasoning is similar to @process_literals@, +the difference is that here the default case is not always needed. + +\begin{code} +no_need_default_case :: [Pat Id] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet) +no_need_default_case cons qs = (concat pats, unionManyUniqSets indexs) + where + pats_indexs = map (\x -> construct_matrix x qs) cons + (pats,indexs) = unzip pats_indexs + +need_default_case :: [Pat Id] -> [DataCon] -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet) +need_default_case used_cons unused_cons qs + | null default_eqns = (pats_default_no_eqns,indexs) + | otherwise = (pats_default,indexs_default) + where + (pats,indexs) = no_need_default_case used_cons qs + default_eqns = ASSERT2( okGroup qs, pprGroup qs ) + [remove_var q | q <- qs, is_var (firstPatN q)] + (pats',indexs') = check' default_eqns + pats_default = [(make_whole_con c:ps,constraints) | + c <- unused_cons, (ps,constraints) <- pats'] ++ pats + new_wilds = make_row_vars_for_constructor (head qs) + pats_default_no_eqns = [(make_whole_con c:new_wilds,[]) | c <- unused_cons] ++ pats + indexs_default = unionUniqSets indexs' indexs + +construct_matrix :: Pat Id -> [(EqnNo, EquationInfo)] -> ([ExhaustivePat],EqnSet) +construct_matrix con qs = + (map (make_con con) pats,indexs) + where + (pats,indexs) = (check' (remove_first_column con qs)) +\end{code} + +Here remove first column is more difficult that with literals due to the fact +that constructors can have arguments. + +For instance, the matrix +\begin{verbatim} + (: x xs) y + z y +\end{verbatim} +is transformed in: +\begin{verbatim} + x xs y + _ _ y +\end{verbatim} + +\begin{code} +remove_first_column :: Pat Id -- Constructor + -> [(EqnNo, EquationInfo)] + -> [(EqnNo, EquationInfo)] +remove_first_column (ConPatOut (L _ con) _ _ _ (PrefixCon con_pats) _) qs + = ASSERT2( okGroup qs, pprGroup qs ) + [(n, shift_var eqn) | q@(n, eqn) <- qs, is_var_con con (firstPatN q)] + where + new_wilds = [WildPat (hsPatType arg_pat) | arg_pat <- con_pats] + shift_var eqn@(EqnInfo { eqn_pats = ConPatOut _ _ _ _ (PrefixCon ps') _ : ps}) + = eqn { eqn_pats = map unLoc ps' ++ ps } + shift_var eqn@(EqnInfo { eqn_pats = WildPat _ : ps }) + = eqn { eqn_pats = new_wilds ++ ps } + shift_var _ = panic "Check.Shift_var:No done" + +make_row_vars :: [HsLit] -> (EqnNo, EquationInfo) -> ExhaustivePat +make_row_vars used_lits (_, EqnInfo { eqn_pats = pats}) + = (nlVarPat new_var:takeList (tail pats) (repeat nlWildPat),[(new_var,used_lits)]) + where + new_var = hash_x + +hash_x = mkInternalName unboundKey {- doesn't matter much -} + (mkVarOccFS FSLIT("#x")) + noSrcLoc + +make_row_vars_for_constructor :: (EqnNo, EquationInfo) -> [WarningPat] +make_row_vars_for_constructor (_, EqnInfo { eqn_pats = pats}) + = takeList (tail pats) (repeat nlWildPat) + +compare_cons :: Pat Id -> Pat Id -> Bool +compare_cons (ConPatOut (L _ id1) _ _ _ _ _) (ConPatOut (L _ id2) _ _ _ _ _) = id1 == id2 + +remove_dups :: [Pat Id] -> [Pat Id] +remove_dups [] = [] +remove_dups (x:xs) | or (map (\y -> compare_cons x y) xs) = remove_dups xs + | otherwise = x : remove_dups xs + +get_used_cons :: [(EqnNo, EquationInfo)] -> [Pat Id] +get_used_cons qs = remove_dups [pat | q <- qs, let pat = firstPatN q, + isConPatOut pat] + +isConPatOut (ConPatOut {}) = True +isConPatOut other = False + +remove_dups' :: [HsLit] -> [HsLit] +remove_dups' [] = [] +remove_dups' (x:xs) | x `elem` xs = remove_dups' xs + | otherwise = x : remove_dups' xs + + +get_used_lits :: [(EqnNo, EquationInfo)] -> [HsLit] +get_used_lits qs = remove_dups' all_literals + where + all_literals = get_used_lits' qs + +get_used_lits' :: [(EqnNo, EquationInfo)] -> [HsLit] +get_used_lits' [] = [] +get_used_lits' (q:qs) + | Just lit <- get_lit (firstPatN q) = lit : get_used_lits' qs + | otherwise = get_used_lits qs + +get_lit :: Pat id -> Maybe HsLit +-- Get a representative HsLit to stand for the OverLit +-- It doesn't matter which one, because they will only be compared +-- with other HsLits gotten in the same way +get_lit (LitPat lit) = Just lit +get_lit (NPat (HsIntegral i _) mb _ _) = Just (HsIntPrim (mb_neg mb i)) +get_lit (NPat (HsFractional f _) mb _ _) = Just (HsFloatPrim (mb_neg mb f)) +get_lit other_pat = Nothing + +mb_neg :: Num a => Maybe b -> a -> a +mb_neg Nothing v = v +mb_neg (Just _) v = -v + +get_unused_cons :: [Pat Id] -> [DataCon] +get_unused_cons used_cons = unused_cons + where + (ConPatOut _ _ _ _ _ ty) = head used_cons + ty_con = tcTyConAppTyCon ty -- Newtype observable + all_cons = tyConDataCons ty_con + used_cons_as_id = map (\ (ConPatOut (L _ d) _ _ _ _ _) -> d) used_cons + unused_cons = uniqSetToList + (mkUniqSet all_cons `minusUniqSet` mkUniqSet used_cons_as_id) + +all_vars :: [Pat Id] -> Bool +all_vars [] = True +all_vars (WildPat _:ps) = all_vars ps +all_vars _ = False + +remove_var :: (EqnNo, EquationInfo) -> (EqnNo, EquationInfo) +remove_var (n, eqn@(EqnInfo { eqn_pats = WildPat _ : ps})) = (n, eqn { eqn_pats = ps }) +remove_var _ = panic "Check.remove_var: equation does not begin with a variable" + +----------------------- +eqnPats :: (EqnNo, EquationInfo) -> [Pat Id] +eqnPats (_, eqn) = eqn_pats eqn + +okGroup :: [(EqnNo, EquationInfo)] -> Bool +-- True if all equations have at least one pattern, and +-- all have the same number of patterns +okGroup [] = True +okGroup (e:es) = n_pats > 0 && and [length (eqnPats e) == n_pats | e <- es] + where + n_pats = length (eqnPats e) + +-- Half-baked print +pprGroup es = vcat (map pprEqnInfo es) +pprEqnInfo e = ppr (eqnPats e) + + +firstPatN :: (EqnNo, EquationInfo) -> Pat Id +firstPatN (_, eqn) = firstPat eqn + +is_con :: Pat Id -> Bool +is_con (ConPatOut _ _ _ _ _ _) = True +is_con _ = False + +is_lit :: Pat Id -> Bool +is_lit (LitPat _) = True +is_lit (NPat _ _ _ _) = True +is_lit _ = False + +is_var :: Pat Id -> Bool +is_var (WildPat _) = True +is_var _ = False + +is_var_con :: DataCon -> Pat Id -> Bool +is_var_con con (WildPat _) = True +is_var_con con (ConPatOut (L _ id) _ _ _ _ _) | id == con = True +is_var_con con _ = False + +is_var_lit :: HsLit -> Pat Id -> Bool +is_var_lit lit (WildPat _) = True +is_var_lit lit pat + | Just lit' <- get_lit pat = lit == lit' + | otherwise = False +\end{code} + +The difference beteewn @make_con@ and @make_whole_con@ is that +@make_wole_con@ creates a new constructor with all their arguments, and +@make_con@ takes a list of argumntes, creates the contructor getting their +arguments from the list. See where \fbox{\ ???\ } are used for details. + +We need to reconstruct the patterns (make the constructors infix and +similar) at the same time that we create the constructors. + +You can tell tuple constructors using +\begin{verbatim} + Id.isTupleCon +\end{verbatim} +You can see if one constructor is infix with this clearer code :-)))))))))) +\begin{verbatim} + Lex.isLexConSym (Name.occNameString (Name.getOccName con)) +\end{verbatim} + + Rather clumsy but it works. (Simon Peyton Jones) + + +We don't mind the @nilDataCon@ because it doesn't change the way to +print the messsage, we are searching only for things like: @[1,2,3]@, +not @x:xs@ .... + +In @reconstruct_pat@ we want to ``undo'' the work +that we have done in @simplify_pat@. +In particular: +\begin{tabular}{lll} + @((,) x y)@ & returns to be & @(x, y)@ +\\ @((:) x xs)@ & returns to be & @(x:xs)@ +\\ @(x:(...:[])@ & returns to be & @[x,...]@ +\end{tabular} +% +The difficult case is the third one becouse we need to follow all the +contructors until the @[]@ to know that we need to use the second case, +not the second. \fbox{\ ???\ } +% +\begin{code} +isInfixCon con = isDataSymOcc (getOccName con) + +is_nil (ConPatIn con (PrefixCon [])) = unLoc con == getName nilDataCon +is_nil _ = False + +is_list (ListPat _ _) = True +is_list _ = False + +return_list id q = id == consDataCon && (is_nil q || is_list q) + +make_list p q | is_nil q = ListPat [p] placeHolderType +make_list p (ListPat ps ty) = ListPat (p:ps) ty +make_list _ _ = panic "Check.make_list: Invalid argument" + +make_con :: Pat Id -> ExhaustivePat -> ExhaustivePat +make_con (ConPatOut (L _ id) _ _ _ _ _) (lp:lq:ps, constraints) + | return_list id q = (noLoc (make_list lp q) : ps, constraints) + | isInfixCon id = (nlInfixConPat (getName id) lp lq : ps, constraints) + where q = unLoc lq + +make_con (ConPatOut (L _ id) _ _ _ (PrefixCon pats) ty) (ps, constraints) + | isTupleTyCon tc = (noLoc (TuplePat pats_con (tupleTyConBoxity tc) ty) : rest_pats, constraints) + | isPArrFakeCon id = (noLoc (PArrPat pats_con placeHolderType) : rest_pats, constraints) + | otherwise = (nlConPat name pats_con : rest_pats, constraints) + where + name = getName id + (pats_con, rest_pats) = splitAtList pats ps + tc = dataConTyCon id + +-- reconstruct parallel array pattern +-- +-- * don't check for the type only; we need to make sure that we are really +-- dealing with one of the fake constructors and not with the real +-- representation + +make_whole_con :: DataCon -> WarningPat +make_whole_con con | isInfixCon con = nlInfixConPat name nlWildPat nlWildPat + | otherwise = nlConPat name pats + where + name = getName con + pats = [nlWildPat | t <- dataConOrigArgTys con] +\end{code} + +This equation makes the same thing as @tidy@ in @Match.lhs@, the +difference is that here we can do all the tidy in one place and in the +@Match@ tidy it must be done one column each time due to bookkeeping +constraints. + +\begin{code} + +simplify_eqn :: EquationInfo -> EquationInfo +simplify_eqn eqn = eqn { eqn_pats = map simplify_pat (eqn_pats eqn), + eqn_rhs = simplify_rhs (eqn_rhs eqn) } + where + -- Horrible hack. The simplify_pat stuff converts NPlusK pats to WildPats + -- which of course loses the info that they can fail to match. So we + -- stick in a CanFail as if it were a guard. + -- The Right Thing to do is for the whole system to treat NPlusK pats properly + simplify_rhs (MatchResult can_fail body) + | any has_nplusk_pat (eqn_pats eqn) = MatchResult CanFail body + | otherwise = MatchResult can_fail body + +has_nplusk_lpat :: LPat Id -> Bool +has_nplusk_lpat (L _ p) = has_nplusk_pat p + +has_nplusk_pat :: Pat Id -> Bool +has_nplusk_pat (NPlusKPat _ _ _ _) = True +has_nplusk_pat (ParPat p) = has_nplusk_lpat p +has_nplusk_pat (AsPat _ p) = has_nplusk_lpat p +has_nplusk_pat (SigPatOut p _ ) = has_nplusk_lpat p +has_nplusk_pat (ConPatOut _ _ _ _ ps ty) = any has_nplusk_lpat (hsConArgs ps) +has_nplusk_pat (ListPat ps _) = any has_nplusk_lpat ps +has_nplusk_pat (TuplePat ps _ _) = any has_nplusk_lpat ps +has_nplusk_pat (PArrPat ps _) = any has_nplusk_lpat ps +has_nplusk_pat (LazyPat p) = False -- Why? +has_nplusk_pat (BangPat p) = has_nplusk_lpat p -- I think +has_nplusk_pat p = False -- VarPat, VarPatOut, WildPat, LitPat, NPat, TypePat, DictPat + +simplify_lpat :: LPat Id -> LPat Id +simplify_lpat p = fmap simplify_pat p + +simplify_pat :: Pat Id -> Pat Id +simplify_pat pat@(WildPat gt) = pat +simplify_pat (VarPat id) = WildPat (idType id) +simplify_pat (VarPatOut id _) = WildPat (idType id) -- Ignore the bindings +simplify_pat (ParPat p) = unLoc (simplify_lpat p) +simplify_pat (LazyPat p) = unLoc (simplify_lpat p) +simplify_pat (BangPat p) = unLoc (simplify_lpat p) +simplify_pat (AsPat id p) = unLoc (simplify_lpat p) +simplify_pat (SigPatOut p _) = unLoc (simplify_lpat p) -- I'm not sure this is right + +simplify_pat (ConPatOut (L loc id) tvs dicts binds ps ty) + = ConPatOut (L loc id) tvs dicts binds (simplify_con id ps) ty + +simplify_pat (ListPat ps ty) = + unLoc $ foldr (\ x y -> mkPrefixConPat consDataCon [x,y] list_ty) + (mkNilPat list_ty) + (map simplify_lpat ps) + where list_ty = mkListTy ty + +-- introduce fake parallel array constructors to be able to handle parallel +-- arrays with the existing machinery for constructor pattern +-- +simplify_pat (PArrPat ps ty) + = mk_simple_con_pat (parrFakeCon (length ps)) + (PrefixCon (map simplify_lpat ps)) + (mkPArrTy ty) + +simplify_pat (TuplePat ps boxity ty) + = mk_simple_con_pat (tupleCon boxity arity) + (PrefixCon (map simplify_lpat ps)) + ty + where + arity = length ps + +-- unpack string patterns fully, so we can see when they overlap with +-- each other, or even explicit lists of Chars. +simplify_pat pat@(LitPat (HsString s)) = + foldr (\c pat -> mk_simple_con_pat consDataCon (PrefixCon [mk_char_lit c,noLoc pat]) stringTy) + (mk_simple_con_pat nilDataCon (PrefixCon []) stringTy) (unpackFS s) + where + mk_char_lit c = noLoc (mk_simple_con_pat charDataCon (PrefixCon [nlLitPat (HsCharPrim c)]) charTy) + +simplify_pat pat@(LitPat lit) = unLoc (tidyLitPat lit (noLoc pat)) + +simplify_pat pat@(NPat lit mb_neg _ lit_ty) = unLoc (tidyNPat lit mb_neg lit_ty (noLoc pat)) + +simplify_pat (NPlusKPat id hslit hsexpr1 hsexpr2) + = WildPat (idType (unLoc id)) + +simplify_pat (DictPat dicts methods) + = case num_of_d_and_ms of + 0 -> simplify_pat (TuplePat [] Boxed unitTy) + 1 -> simplify_pat (head dict_and_method_pats) + _ -> simplify_pat (mkVanillaTuplePat (map noLoc dict_and_method_pats) Boxed) + where + num_of_d_and_ms = length dicts + length methods + dict_and_method_pats = map VarPat (dicts ++ methods) + +mk_simple_con_pat con args ty = ConPatOut (noLoc con) [] [] emptyLHsBinds args ty + +----------------- +simplify_con con (PrefixCon ps) = PrefixCon (map simplify_lpat ps) +simplify_con con (InfixCon p1 p2) = PrefixCon [simplify_lpat p1, simplify_lpat p2] +simplify_con con (RecCon fs) + | null fs = PrefixCon [nlWildPat | t <- dataConOrigArgTys con] + -- Special case for null patterns; maybe not a record at all + | otherwise = PrefixCon (map (simplify_lpat.snd) all_pats) + where + -- pad out all the missing fields with WildPats. + field_pats = map (\ f -> (f, nlWildPat)) (dataConFieldLabels con) + all_pats = foldr (\ (id,p) acc -> insertNm (getName (unLoc id)) p acc) + field_pats fs + + insertNm nm p [] = [(nm,p)] + insertNm nm p (x@(n,_):xs) + | nm == n = (nm,p):xs + | otherwise = x : insertNm nm p xs +\end{code} |