X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FdeSugar%2FMatch.lhs;h=d64a649b3717215fe2ee94381a5f33ea4bec0e5a;hp=f545930a48c44826faf1a38aaf5de112a27d880d;hb=7fc01c4671980ea3c66d549c0ece4d82fd3f5ade;hpb=860e92c1dd65f2a7a617c253849d7ce84ed9bbc9 diff --git a/compiler/deSugar/Match.lhs b/compiler/deSugar/Match.lhs index f545930..d64a649 100644 --- a/compiler/deSugar/Match.lhs +++ b/compiler/deSugar/Match.lhs @@ -26,6 +26,7 @@ import Check import CoreSyn import Literal import CoreUtils +import MkCore import DsMonad import DsBinds import DsGRHSs @@ -34,7 +35,6 @@ import Id import DataCon import MatchCon import MatchLit -import PrelInfo import Type import TysWiredIn import ListSetOps @@ -42,6 +42,7 @@ import SrcLoc import Maybes import Util import Name +import FiniteMap import Outputable import FastString \end{code} @@ -242,7 +243,7 @@ Make all constructor patterns in column~1 into @ConPats@, notably Handle any irrefutable (or ``twiddle'') @LazyPats@. \end{itemize} \item -Now {\em unmix} the equations into {\em blocks} [w/ local function +Now {\em unmix} the equations into {\em blocks} [w\/ local function @unmix_eqns@], in which the equations in a block all have variable patterns in column~1, or they all have constructor patterns in ... (see ``the mixture rule'' in SLPJ). @@ -268,7 +269,7 @@ Wadler-chapter @match@ (p.~93, last clause), and @match_unmixed_blk@ corresponds roughly to @matchVarCon@. \begin{code} -match :: [Id] -- Variables rep'ing the exprs we're matching with +match :: [Id] -- Variables rep\'ing the exprs we\'re matching with -> Type -- Type of the case expression -> [EquationInfo] -- Info about patterns, etc. (type synonym below) -> DsM MatchResult -- Desugared result! @@ -288,8 +289,7 @@ match vars@(v:_) ty eqns (aux_binds, tidy_eqns) <- mapAndUnzipM (tidyEqnInfo v) eqns -- Group the equations and match each group in turn - - ; let grouped = (groupEquations tidy_eqns) + ; let grouped = groupEquations tidy_eqns -- print the view patterns that are commoned up to help debug ; ifOptM Opt_D_dump_view_pattern_commoning (debug grouped) @@ -304,10 +304,11 @@ match vars@(v:_) ty eqns match_group :: [(PatGroup,EquationInfo)] -> DsM MatchResult match_group eqns@((group,_) : _) = case group of + PgCon _ -> matchConFamily vars ty (subGroup [(c,e) | (PgCon c, e) <- eqns]) + PgLit _ -> matchLiterals vars ty (subGroup [(l,e) | (PgLit l, e) <- eqns]) + PgAny -> matchVariables vars ty (dropGroup eqns) - PgCon _ -> matchConFamily vars ty (subGroups eqns) - PgLit _ -> matchLiterals vars ty (subGroups eqns) - PgN _ -> matchNPats vars ty (subGroups eqns) + PgN _ -> matchNPats vars ty (dropGroup eqns) PgNpK _ -> matchNPlusKPats vars ty (dropGroup eqns) PgBang -> matchBangs vars ty (dropGroup eqns) PgCo _ -> matchCoercion vars ty (dropGroup eqns) @@ -342,10 +343,11 @@ matchCoercion :: [Id] -> Type -> [EquationInfo] -> DsM MatchResult -- Apply the coercion to the match variable and then match that matchCoercion (var:vars) ty (eqns@(eqn1:_)) = do { let CoPat co pat _ = firstPat eqn1 - ; var' <- newUniqueId (idName var) (hsPatType pat) + ; var' <- newUniqueId var (hsPatType pat) ; match_result <- match (var':vars) ty (map decomposeFirst_Coercion eqns) - ; rhs <- dsCoercion co (return (Var var)) - ; return (mkCoLetMatchResult (NonRec var' rhs) match_result) } + ; co' <- dsHsWrapper co + ; let rhs' = co' (Var var) + ; return (mkCoLetMatchResult (NonRec var' rhs') match_result) } matchView :: [Id] -> Type -> [EquationInfo] -> DsM MatchResult -- Apply the view function to the match variable and then match that @@ -355,7 +357,7 @@ matchView (var:vars) ty (eqns@(eqn1:_)) -- to figure out the type of the fresh variable let ViewPat viewExpr (L _ pat) _ = firstPat eqn1 -- do the rest of the compilation - ; var' <- newUniqueId (idName var) (hsPatType pat) + ; var' <- newUniqueId var (hsPatType pat) ; match_result <- match (var':vars) ty (map decomposeFirst_View eqns) -- compile the view expressions ; viewExpr' <- dsLExpr viewExpr @@ -461,8 +463,8 @@ tidy1 v (VarPat var) = return (wrapBind var v, WildPat (idType var)) tidy1 v (VarPatOut var binds) - = do { prs <- dsLHsBinds binds - ; return (wrapBind var v . mkDsLet (Rec prs), + = do { ds_ev_binds <- dsTcEvBinds binds + ; return (wrapBind var v . wrapDsEvBinds ds_ev_binds, WildPat (idType var)) } -- case v of { x@p -> mr[] } @@ -485,7 +487,7 @@ tidy1 v (AsPat (L _ var) pat) tidy1 v (LazyPat pat) = do { sel_prs <- mkSelectorBinds pat (Var v) ; let sel_binds = [NonRec b rhs | (b,rhs) <- sel_prs] - ; return (mkDsLets sel_binds, WildPat (idType v)) } + ; return (mkCoreLets sel_binds, WildPat (idType v)) } tidy1 _ (ListPat pats ty) = return (idDsWrapper, unLoc list_ConPat) @@ -517,6 +519,21 @@ tidy1 _ (LitPat lit) tidy1 _ (NPat lit mb_neg eq) = return (idDsWrapper, tidyNPat lit mb_neg eq) +-- BangPatterns: Pattern matching is already strict in constructors, +-- tuples etc, so the last case strips off the bang for thoses patterns. +tidy1 v (BangPat (L _ (LazyPat p))) = tidy1 v (BangPat p) +tidy1 v (BangPat (L _ (ParPat p))) = tidy1 v (BangPat p) +tidy1 _ p@(BangPat (L _(VarPat _))) = return (idDsWrapper, p) +tidy1 _ p@(BangPat (L _(VarPatOut _ _))) = return (idDsWrapper, p) +tidy1 _ p@(BangPat (L _ (WildPat _))) = return (idDsWrapper, p) +tidy1 _ p@(BangPat (L _ (CoPat _ _ _))) = return (idDsWrapper, p) +tidy1 _ p@(BangPat (L _ (SigPatIn _ _))) = return (idDsWrapper, p) +tidy1 _ p@(BangPat (L _ (SigPatOut _ _))) = return (idDsWrapper, p) +tidy1 v (BangPat (L _ (AsPat (L _ var) pat))) + = do { (wrap, pat') <- tidy1 v (BangPat pat) + ; return (wrapBind var v . wrap, pat') } +tidy1 v (BangPat (L _ p)) = tidy1 v p + -- Everything else goes through unchanged... tidy1 _ non_interesting_pat @@ -685,11 +702,11 @@ matchEquations ctxt vars eqns_info rhs_ty = do { dflags <- getDOptsDs ; locn <- getSrcSpanDs ; let ds_ctxt = DsMatchContext ctxt locn - error_string = matchContextErrString ctxt + error_doc = matchContextErrString ctxt ; match_result <- match_fun dflags ds_ctxt vars rhs_ty eqns_info - ; fail_expr <- mkErrorAppDs pAT_ERROR_ID rhs_ty error_string + ; fail_expr <- mkErrorAppDs pAT_ERROR_ID rhs_ty error_doc ; extractMatchResult match_result fail_expr } where match_fun dflags ds_ctxt @@ -771,24 +788,39 @@ groupEquations :: [EquationInfo] -> [[(PatGroup, EquationInfo)]] -- If the result is of form [g1, g2, g3], -- (a) all the (pg,eq) pairs in g1 have the same pg -- (b) none of the gi are empty +-- The ordering of equations is unchanged groupEquations eqns = runs same_gp [(patGroup (firstPat eqn), eqn) | eqn <- eqns] where same_gp :: (PatGroup,EquationInfo) -> (PatGroup,EquationInfo) -> Bool (pg1,_) `same_gp` (pg2,_) = pg1 `sameGroup` pg2 -subGroups :: [(PatGroup, EquationInfo)] -> [[EquationInfo]] +subGroup :: Ord a => [(a, EquationInfo)] -> [[EquationInfo]] -- Input is a particular group. The result sub-groups the -- equations by with particular constructor, literal etc they match. --- The order may be swizzled, so the matching should be order-independent -subGroups groups = map (map snd) (equivClasses cmp groups) +-- Each sub-list in the result has the same PatGroup +-- See Note [Take care with pattern order] +subGroup group + = map reverse $ eltsFM $ foldl accumulate emptyFM group where - (pg1, _) `cmp` (pg2, _) = pg1 `cmp_pg` pg2 - (PgCon c1) `cmp_pg` (PgCon c2) = c1 `compare` c2 - (PgLit l1) `cmp_pg` (PgLit l2) = l1 `compare` l2 - (PgN l1) `cmp_pg` (PgN l2) = l1 `compare` l2 - -- These are the only cases that are every sub-grouped + accumulate pg_map (pg, eqn) + = case lookupFM pg_map pg of + Just eqns -> addToFM pg_map pg (eqn:eqns) + Nothing -> addToFM pg_map pg [eqn] + + -- pg_map :: FiniteMap a [EquationInfo] + -- Equations seen so far in reverse order of appearance +\end{code} +Note [Take care with pattern order] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +In the subGroup function we must be very careful about pattern re-ordering, +Consider the patterns [ (True, Nothing), (False, x), (True, y) ] +Then in bringing together the patterns for True, we must not +swap the Nothing and y! + + +\begin{code} sameGroup :: PatGroup -> PatGroup -> Bool -- Same group means that a single case expression -- or test will suffice to match both, *and* the order @@ -797,9 +829,8 @@ sameGroup PgAny PgAny = True sameGroup PgBang PgBang = True sameGroup (PgCon _) (PgCon _) = True -- One case expression sameGroup (PgLit _) (PgLit _) = True -- One case expression -sameGroup (PgN _) (PgN _) = True -- Needs conditionals -sameGroup (PgNpK l1) (PgNpK l2) = l1==l2 -- Order is significant - -- See Note [Order of n+k] +sameGroup (PgN l1) (PgN l2) = l1==l2 -- Order is significant +sameGroup (PgNpK l1) (PgNpK l2) = l1==l2 -- See Note [Grouping overloaded literal patterns] sameGroup (PgCo t1) (PgCo t2) = t1 `coreEqType` t2 -- CoPats are in the same goup only if the type of the -- enclosed pattern is the same. The patterns outside the CoPat @@ -810,12 +841,12 @@ sameGroup (PgView e1 t1) (PgView e2 t2) = viewLExprEq (e1,t1) (e2,t2) -- are "equal"---conservatively, we use syntactic equality sameGroup _ _ = False --- an approximation of syntactic equality used for determining when view +-- An approximation of syntactic equality used for determining when view -- exprs are in the same group. --- this function can always safely return false; +-- This function can always safely return false; -- but doing so will result in the application of the view function being repeated. -- --- currently: compare applications of literals and variables +-- Currently: compare applications of literals and variables -- and anything else that we can do without involving other -- HsSyn types in the recursion -- @@ -828,12 +859,11 @@ viewLExprEq (e1,_) (e2,_) = -- short name for recursive call on unLoc lexp e e' = exp (unLoc e) (unLoc e') - -- check that two lists have the same length - -- and that they match up pairwise - lexps [] [] = True - lexps [] (_:_) = False - lexps (_:_) [] = False - lexps (x:xs) (y:ys) = lexp x y && lexps xs ys + eq_list :: (a->a->Bool) -> [a] -> [a] -> Bool + eq_list _ [] [] = True + eq_list _ [] (_:_) = False + eq_list _ (_:_) [] = False + eq_list eq (x:xs) (y:ys) = eq x y && eq_list eq xs ys -- conservative, in that it demands that wrappers be -- syntactically identical and doesn't look under binders @@ -844,7 +874,7 @@ viewLExprEq (e1,_) (e2,_) = wrap WpHole WpHole = True wrap (WpCompose w1 w2) (WpCompose w1' w2') = wrap w1 w1' && wrap w2 w2' wrap (WpCast c) (WpCast c') = tcEqType c c' - wrap (WpApp d) (WpApp d') = d == d' + wrap (WpEvApp _) (WpEvApp _) = panic "ToDo: Match.viewLExprEq" wrap (WpTyApp t) (WpTyApp t') = tcEqType t t' -- Enhancement: could implement equality for more wrappers -- if it seems useful (lams and lets) @@ -862,15 +892,13 @@ viewLExprEq (e1,_) (e2,_) = -- above does exp (HsIPVar i) (HsIPVar i') = i == i' exp (HsOverLit l) (HsOverLit l') = - -- overloaded lits are equal if they have the same type + -- Overloaded lits are equal if they have the same type -- and the data is the same. -- this is coarser than comparing the SyntaxExpr's in l and l', -- which resolve the overloading (e.g., fromInteger 1), -- because these expressions get written as a bunch of different variables -- (presumably to improve sharing) tcEqType (overLitType l) (overLitType l') && l == l' - -- comparing the constants seems right - exp (HsLit l) (HsLit l') = l == l' exp (HsApp e1 e2) (HsApp e1' e2') = lexp e1 e1' && lexp e2 e2' -- the fixities have been straightened out by now, so it's safe -- to ignore them? @@ -881,14 +909,20 @@ viewLExprEq (e1,_) (e2,_) = lexp e1 e1' && lexp e2 e2' exp (SectionR e1 e2) (SectionR e1' e2') = lexp e1 e1' && lexp e2 e2' + exp (ExplicitTuple es1 _) (ExplicitTuple es2 _) = + eq_list tup_arg es1 es2 exp (HsIf e e1 e2) (HsIf e' e1' e2') = lexp e e' && lexp e1 e1' && lexp e2 e2' - exp (ExplicitList _ ls) (ExplicitList _ ls') = lexps ls ls' - exp (ExplicitPArr _ ls) (ExplicitPArr _ ls') = lexps ls ls' - exp (ExplicitTuple ls _) (ExplicitTuple ls' _) = lexps ls ls' + -- Enhancement: could implement equality for more expressions -- if it seems useful + -- But no need for HsLit, ExplicitList, ExplicitTuple, + -- because they cannot be functions exp _ _ = False + + tup_arg (Present e1) (Present e2) = lexp e1 e2 + tup_arg (Missing t1) (Missing t2) = tcEqType t1 t2 + tup_arg _ _ = False in lexp e1 e2 @@ -904,8 +938,8 @@ patGroup (ViewPat expr p _) = PgView expr (hsPatType (unLoc p)) patGroup pat = pprPanic "patGroup" (ppr pat) \end{code} -Note [Order of n+k] -~~~~~~~~~~~~~~~~~~~ +Note [Grouping overloaded literal patterns] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ WATCH OUT! Consider f (n+1) = ... @@ -913,9 +947,11 @@ WATCH OUT! Consider f (n+1) = ... We can't group the first and third together, because the second may match -the same thing as the first. Contrast - f 1 = ... - f 2 = ... - f 1 = ... -where we can group the first and third. Hence we don't regard (n+1) and -(n+2) as part of the same group. +the same thing as the first. Same goes for *overloaded* literal patterns + f 1 True = ... + f 2 False = ... + f 1 False = ... +If the first arg matches '1' but the second does not match 'True', we +cannot jump to the third equation! Because the same argument might +match '2'! +Hence we don't regard 1 and 2, or (n+1) and (n+2), as part of the same group.