The @match@ function
\begin{code}
-{-# OPTIONS -fno-warn-incomplete-patterns #-}
--- The above warning supression flag is a temporary kludge.
--- While working on this module you are encouraged to remove it and fix
--- any warnings in the module. See
--- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
--- for details
-
module Match ( match, matchEquations, matchWrapper, matchSimply, matchSinglePat ) where
#include "HsVersions.h"
import CoreSyn
import Literal
import CoreUtils
+import MkCore
import DsMonad
import DsBinds
import DsGRHSs
import DataCon
import MatchCon
import MatchLit
-import PrelInfo
import Type
+import Coercion
import TysWiredIn
import ListSetOps
import SrcLoc
import Name
import Outputable
import FastString
+
+import Control.Monad( when )
+import qualified Data.Map as Map
\end{code}
This function is a wrapper of @match@, it must be called from all the parts where
-> [EquationInfo] -- Info about patterns, etc. (type synonym below)
-> DsM MatchResult -- Desugared result!
-matchCheck ctx vars ty qs = do
- dflags <- getDOptsDs
- matchCheck_really dflags ctx vars ty qs
+matchCheck ctx vars ty qs
+ = do { dflags <- getDOptsDs
+ ; matchCheck_really dflags ctx vars ty qs }
matchCheck_really :: DynFlags
-> DsMatchContext
-> Type
-> [EquationInfo]
-> DsM MatchResult
-matchCheck_really dflags ctx vars ty qs
- | incomplete && shadow = do
- dsShadowWarn ctx eqns_shadow
- dsIncompleteWarn ctx pats
- match vars ty qs
- | incomplete = do
- dsIncompleteWarn ctx pats
- match vars ty qs
- | shadow = do
- dsShadowWarn ctx eqns_shadow
- match vars ty qs
- | otherwise =
- match vars ty qs
- where (pats, eqns_shadow) = check qs
- incomplete = want_incomplete && (notNull pats)
- want_incomplete = case ctx of
- DsMatchContext RecUpd _ ->
- dopt Opt_WarnIncompletePatternsRecUpd dflags
- _ ->
- dopt Opt_WarnIncompletePatterns dflags
- shadow = dopt Opt_WarnOverlappingPatterns dflags
- && not (null eqns_shadow)
+matchCheck_really dflags ctx@(DsMatchContext hs_ctx _) vars ty qs
+ = do { when shadow (dsShadowWarn ctx eqns_shadow)
+ ; when incomplete (dsIncompleteWarn ctx pats)
+ ; match vars ty qs }
+ where
+ (pats, eqns_shadow) = check qs
+ incomplete = incomplete_flag hs_ctx && (notNull pats)
+ shadow = dopt Opt_WarnOverlappingPatterns dflags
+ && notNull eqns_shadow
+
+ incomplete_flag :: HsMatchContext id -> Bool
+ incomplete_flag (FunRhs {}) = dopt Opt_WarnIncompletePatterns dflags
+ incomplete_flag CaseAlt = dopt Opt_WarnIncompletePatterns dflags
+
+ incomplete_flag LambdaExpr = dopt Opt_WarnIncompleteUniPatterns dflags
+ incomplete_flag PatBindRhs = dopt Opt_WarnIncompleteUniPatterns dflags
+ incomplete_flag ProcExpr = dopt Opt_WarnIncompleteUniPatterns dflags
+
+ incomplete_flag RecUpd = dopt Opt_WarnIncompletePatternsRecUpd dflags
+
+ incomplete_flag ThPatQuote = False
+ incomplete_flag (StmtCtxt {}) = False -- Don't warn about incomplete patterns
+ -- in list comprehensions, pattern guards
+ -- etc. They are often *supposed* to be
+ -- incomplete
\end{code}
This variable shows the maximum number of lines of output generated for warnings.
= putSrcSpanDs loc (warnDs warn)
where
warn | qs `lengthExceeds` maximum_output
- = pp_context ctx (ptext SLIT("are overlapped"))
+ = pp_context ctx (ptext (sLit "are overlapped"))
(\ f -> vcat (map (ppr_eqn f kind) (take maximum_output qs)) $$
- ptext SLIT("..."))
+ ptext (sLit "..."))
| otherwise
- = pp_context ctx (ptext SLIT("are overlapped"))
+ = pp_context ctx (ptext (sLit "are overlapped"))
(\ f -> vcat $ map (ppr_eqn f kind) qs)
dsIncompleteWarn ctx@(DsMatchContext kind loc) pats
= putSrcSpanDs loc (warnDs warn)
where
- warn = pp_context ctx (ptext SLIT("are non-exhaustive"))
- (\_ -> hang (ptext SLIT("Patterns not matched:"))
+ warn = pp_context ctx (ptext (sLit "are non-exhaustive"))
+ (\_ -> hang (ptext (sLit "Patterns not matched:"))
4 ((vcat $ map (ppr_incomplete_pats kind)
(take maximum_output pats))
$$ dots))
- dots | pats `lengthExceeds` maximum_output = ptext SLIT("...")
+ dots | pats `lengthExceeds` maximum_output = ptext (sLit "...")
| otherwise = empty
pp_context :: DsMatchContext -> SDoc -> ((SDoc -> SDoc) -> SDoc) -> SDoc
pp_context (DsMatchContext kind _loc) msg rest_of_msg_fun
- = vcat [ptext SLIT("Pattern match(es)") <+> msg,
- sep [ptext SLIT("In") <+> ppr_match <> char ':', nest 4 (rest_of_msg_fun pref)]]
+ = vcat [ptext (sLit "Pattern match(es)") <+> msg,
+ sep [ptext (sLit "In") <+> ppr_match <> char ':', nest 4 (rest_of_msg_fun pref)]]
where
(ppr_match, pref)
= case kind of
ppr_shadow_pats :: HsMatchContext Name -> [Pat Id] -> SDoc
ppr_shadow_pats kind pats
- = sep [ppr_pats pats, matchSeparator kind, ptext SLIT("...")]
+ = sep [ppr_pats pats, matchSeparator kind, ptext (sLit "...")]
ppr_incomplete_pats :: HsMatchContext Name -> ExhaustivePat -> SDoc
ppr_incomplete_pats _ (pats,[]) = ppr_pats pats
ppr_incomplete_pats _ (pats,constraints) =
- sep [ppr_pats pats, ptext SLIT("with"),
+ sep [ppr_pats pats, ptext (sLit "with"),
sep (map ppr_constraint constraints)]
ppr_constraint :: (Name,[HsLit]) -> SDoc
-ppr_constraint (var,pats) = sep [ppr var, ptext SLIT("`notElem`"), ppr pats]
+ppr_constraint (var,pats) = sep [ppr var, ptext (sLit "`notElem`"), ppr pats]
ppr_eqn :: (SDoc -> SDoc) -> HsMatchContext Name -> EquationInfo -> SDoc
ppr_eqn prefixF kind eqn = prefixF (ppr_shadow_pats kind (eqn_pats eqn))
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).
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!
= ASSERT( not (null eqns ) )
do { -- Tidy the first pattern, generating
-- auxiliary bindings if necessary
- (aux_binds, tidy_eqns) <- mapAndUnzipM (tidyEqnInfo v) 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)
+ ; ifDOptM Opt_D_dump_view_pattern_commoning (debug grouped)
; match_results <- mapM match_group grouped
; return (adjustMatchResult (foldr1 (.) aux_binds) $
dropGroup = map snd
match_group :: [(PatGroup,EquationInfo)] -> DsM MatchResult
+ match_group [] = panic "match_group"
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)
-- Real true variables, just like in matchVar, SLPJ p 94
-- No binding to do: they'll all be wildcards by now (done in tidy)
matchVariables (_:vars) ty eqns = match vars ty (shiftEqns eqns)
+matchVariables [] _ _ = panic "matchVariables"
matchBangs :: [Id] -> Type -> [EquationInfo] -> DsM MatchResult
matchBangs (var:vars) ty eqns
- = do { match_result <- match (var:vars) ty (map decomposeFirst_Bang eqns)
+ = do { match_result <- match (var:vars) ty $
+ map (decomposeFirstPat getBangPat) eqns
; return (mkEvalMatchResult var ty match_result) }
+matchBangs [] _ _ = panic "matchBangs"
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)
- ; match_result <- match (var':vars) ty (map decomposeFirst_Coercion eqns)
- ; rhs <- dsCoercion co (return (Var var))
- ; return (mkCoLetMatchResult (NonRec var' rhs) match_result) }
+ ; var' <- newUniqueId var (hsPatType pat)
+ ; match_result <- match (var':vars) ty $
+ map (decomposeFirstPat getCoPat) eqns
+ ; co' <- dsHsWrapper co
+ ; let rhs' = co' (Var var)
+ ; return (mkCoLetMatchResult (NonRec var' rhs') match_result) }
+matchCoercion _ _ _ = panic "matchCoercion"
matchView :: [Id] -> Type -> [EquationInfo] -> DsM MatchResult
-- Apply the view function to the match variable and then match that
-- 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)
- ; match_result <- match (var':vars) ty (map decomposeFirst_View eqns)
+ ; var' <- newUniqueId var (hsPatType pat)
+ ; match_result <- match (var':vars) ty $
+ map (decomposeFirstPat getViewPat) eqns
-- compile the view expressions
- ; viewExpr' <- dsLExpr viewExpr
+ ; viewExpr' <- dsLExpr viewExpr
; return (mkViewMatchResult var' viewExpr' var match_result) }
+matchView _ _ _ = panic "matchView"
-- decompose the first pattern and leave the rest alone
decomposeFirstPat :: (Pat Id -> Pat Id) -> EquationInfo -> EquationInfo
decomposeFirstPat extractpat (eqn@(EqnInfo { eqn_pats = pat : pats }))
= eqn { eqn_pats = extractpat pat : pats}
-
-decomposeFirst_Coercion, decomposeFirst_Bang, decomposeFirst_View :: EquationInfo -> EquationInfo
-
-decomposeFirst_Coercion = decomposeFirstPat (\ (CoPat _ pat _) -> pat)
-decomposeFirst_Bang = decomposeFirstPat (\ (BangPat pat ) -> unLoc pat)
-decomposeFirst_View = decomposeFirstPat (\ (ViewPat _ pat _) -> unLoc pat)
-
+decomposeFirstPat _ _ = panic "decomposeFirstPat"
+
+getCoPat, getBangPat, getViewPat :: Pat Id -> Pat Id
+getCoPat (CoPat _ pat _) = pat
+getCoPat _ = panic "getCoPat"
+getBangPat (BangPat pat ) = unLoc pat
+getBangPat _ = panic "getBangPat"
+getViewPat (ViewPat _ pat _) = unLoc pat
+getViewPat _ = panic "getBangPat"
\end{code}
%************************************************************************
-- NPlusKPat
-- but no other
-tidyEqnInfo v eqn@(EqnInfo { eqn_pats = pat : pats }) = do
- (wrap, pat') <- tidy1 v pat
- return (wrap, eqn { eqn_pats = do pat' : pats })
+tidyEqnInfo _ (EqnInfo { eqn_pats = [] })
+ = panic "tidyEqnInfo"
+
+tidyEqnInfo v eqn@(EqnInfo { eqn_pats = pat : pats })
+ = do { (wrap, pat') <- tidy1 v pat
+ ; return (wrap, eqn { eqn_pats = do pat' : pats }) }
tidy1 :: Id -- The Id being scrutinised
-> Pat Id -- The pattern against which it is to be matched
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),
- WildPat (idType var)) }
-
-- case v of { x@p -> mr[] }
-- = case v of { p -> let x=v in mr[] }
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)
-- NPats: we *might* be able to replace these w/ a simpler form
tidy1 _ (NPat lit mb_neg eq)
- = return (idDsWrapper, tidyNPat lit mb_neg eq)
+ = return (idDsWrapper, tidyNPat tidyLitPat 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 _ (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...
-> [Id] -> [EquationInfo] -> Type
-> DsM CoreExpr
matchEquations ctxt vars eqns_info rhs_ty
- = do { dflags <- getDOptsDs
- ; locn <- getSrcSpanDs
- ; let ds_ctxt = DsMatchContext ctxt locn
- error_string = matchContextErrString ctxt
+ = do { locn <- getSrcSpanDs
+ ; let ds_ctxt = DsMatchContext ctxt locn
+ error_doc = matchContextErrString ctxt
- ; match_result <- match_fun dflags ds_ctxt vars rhs_ty eqns_info
+ ; match_result <- matchCheck 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
- = case ctxt of
- LambdaExpr | dopt Opt_WarnSimplePatterns dflags -> matchCheck ds_ctxt
- | otherwise -> match
- _ -> matchCheck ds_ctxt
\end{code}
%************************************************************************
-> CoreExpr -- Return this if it matches
-> CoreExpr -- Return this if it doesn't
-> DsM CoreExpr
-
+-- Do not warn about incomplete patterns; see matchSinglePat comments
matchSimply scrut hs_ctx pat result_expr fail_expr = do
let
match_result = cantFailMatchResult result_expr
match_result' <- matchSinglePat scrut hs_ctx pat rhs_ty match_result
extractMatchResult match_result' fail_expr
-
matchSinglePat :: CoreExpr -> HsMatchContext Name -> LPat Id
-> Type -> MatchResult -> DsM MatchResult
-matchSinglePat (Var var) hs_ctx (L _ pat) ty match_result = do
- dflags <- getDOptsDs
- locn <- getSrcSpanDs
- let
- match_fn dflags
- | dopt Opt_WarnSimplePatterns dflags = matchCheck ds_ctx
- | otherwise = match
- where
- ds_ctx = DsMatchContext hs_ctx locn
- match_fn dflags [var] ty [EqnInfo { eqn_pats = [pat], eqn_rhs = match_result }]
-
-matchSinglePat scrut hs_ctx pat ty match_result = do
- var <- selectSimpleMatchVarL pat
- match_result' <- matchSinglePat (Var var) hs_ctx pat ty match_result
- return (adjustMatchResult (bindNonRec var scrut) match_result')
+-- Do not warn about incomplete patterns
+-- Used for things like [ e | pat <- stuff ], where
+-- incomplete patterns are just fine
+matchSinglePat (Var var) ctx (L _ pat) ty match_result
+ = do { locn <- getSrcSpanDs
+ ; matchCheck (DsMatchContext ctx locn)
+ [var] ty
+ [EqnInfo { eqn_pats = [pat], eqn_rhs = match_result }] }
+
+matchSinglePat scrut hs_ctx pat ty match_result
+ = do { var <- selectSimpleMatchVarL pat
+ ; match_result' <- matchSinglePat (Var var) hs_ctx pat ty match_result
+ ; return (adjustMatchResult (bindNonRec var scrut) match_result') }
\end{code}
-- 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 $ Map.elems $ foldl accumulate Map.empty 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 Map.lookup pg pg_map of
+ Just eqns -> Map.insert pg (eqn:eqns) pg_map
+ Nothing -> Map.insert pg [eqn] pg_map
+
+ -- pg_map :: Map 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
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 (PgCo t1) (PgCo t2) = t1 `coreEqType` t2
+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 `eqType` t2
-- CoPats are in the same goup only if the type of the
-- enclosed pattern is the same. The patterns outside the CoPat
-- always have the same type, so this boils down to saying that
-- 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
--
-- f (e1 -> True) = ...
-- f (e2 -> "hi") = ...
viewLExprEq :: (LHsExpr Id,Type) -> (LHsExpr Id,Type) -> Bool
-viewLExprEq (e1,_) (e2,_) =
- let
- -- 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
-
- -- conservative, in that it demands that wrappers be
- -- syntactically identical and doesn't look under binders
- --
- -- coarser notions of equality are possible
- -- (e.g., reassociating compositions,
- -- equating different ways of writing a coercion)
- 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 (WpTyApp t) (WpTyApp t') = tcEqType t t'
- -- Enhancement: could implement equality for more wrappers
- -- if it seems useful (lams and lets)
- wrap _ _ = False
-
- -- real comparison is on HsExpr's
- -- strip parens
- exp (HsPar (L _ e)) e' = exp e e'
- exp e (HsPar (L _ e')) = exp e e'
- -- because the expressions do not necessarily have the same type,
- -- we have to compare the wrappers
- exp (HsWrap h e) (HsWrap h' e') = wrap h h' && exp e e'
- exp (HsVar i) (HsVar i') = i == i'
- -- the instance for IPName derives using the id, so this works if the
- -- above does
- exp (HsIPVar i) (HsIPVar i') = i == i'
- exp (HsOverLit l) (HsOverLit l') =
- -- 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?
- exp (OpApp l o _ ri) (OpApp l' o' _ ri') =
- lexp l l' && lexp o o' && lexp ri ri'
- exp (NegApp e n) (NegApp e' n') = lexp e e' && exp n n'
- exp (SectionL e1 e2) (SectionL e1' e2') =
- lexp e1 e1' && lexp e2 e2'
- exp (SectionR e1 e2) (SectionR e1' e2') =
- lexp e1 e1' && lexp e2 e2'
- 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
- exp _ _ = False
- in
- lexp e1 e2
+viewLExprEq (e1,_) (e2,_) = lexp e1 e2
+ where
+ lexp :: LHsExpr Id -> LHsExpr Id -> Bool
+ lexp e e' = exp (unLoc e) (unLoc e')
+
+ ---------
+ exp :: HsExpr Id -> HsExpr Id -> Bool
+ -- real comparison is on HsExpr's
+ -- strip parens
+ exp (HsPar (L _ e)) e' = exp e e'
+ exp e (HsPar (L _ e')) = exp e e'
+ -- because the expressions do not necessarily have the same type,
+ -- we have to compare the wrappers
+ exp (HsWrap h e) (HsWrap h' e') = wrap h h' && exp e e'
+ exp (HsVar i) (HsVar i') = i == i'
+ -- the instance for IPName derives using the id, so this works if the
+ -- above does
+ exp (HsIPVar i) (HsIPVar i') = i == i'
+ exp (HsOverLit l) (HsOverLit l') =
+ -- 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)
+ eqType (overLitType l) (overLitType 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?
+ exp (OpApp l o _ ri) (OpApp l' o' _ ri') =
+ lexp l l' && lexp o o' && lexp ri ri'
+ exp (NegApp e n) (NegApp e' n') = lexp e e' && exp n n'
+ exp (SectionL e1 e2) (SectionL 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'
+
+ -- 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) = eqType t1 t2
+ tup_arg _ _ = False
+
+ ---------
+ wrap :: HsWrapper -> HsWrapper -> Bool
+ -- Conservative, in that it demands that wrappers be
+ -- syntactically identical and doesn't look under binders
+ --
+ -- Coarser notions of equality are possible
+ -- (e.g., reassociating compositions,
+ -- equating different ways of writing a coercion)
+ wrap WpHole WpHole = True
+ wrap (WpCompose w1 w2) (WpCompose w1' w2') = wrap w1 w1' && wrap w2 w2'
+ wrap (WpCast c) (WpCast c') = coreEqCoercion c c'
+ wrap (WpEvApp et1) (WpEvApp et2) = ev_term et1 et2
+ wrap (WpTyApp t) (WpTyApp t') = eqType t t'
+ -- Enhancement: could implement equality for more wrappers
+ -- if it seems useful (lams and lets)
+ wrap _ _ = False
+
+ ---------
+ ev_term :: EvTerm -> EvTerm -> Bool
+ ev_term (EvId a) (EvId b) = a==b
+ ev_term (EvCoercion a) (EvCoercion b) = coreEqCoercion a b
+ ev_term _ _ = False
+
+ ---------
+ 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
patGroup :: Pat Id -> PatGroup
patGroup (WildPat {}) = PgAny
patGroup pat = pprPanic "patGroup" (ppr pat)
\end{code}
-Note [Order of n+k]
-~~~~~~~~~~~~~~~~~~~
+Note [Grouping overloaded literal patterns]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
WATCH OUT! Consider
f (n+1) = ...
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.
+
projects / ghc-hetmet.git / blobdiff