X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcPat.lhs;h=064067534d434e8e99ec2259149948d97bf7f2d5;hb=a6fdf61f392cde7fdcb35bdb28250e99754d27eb;hp=c9b5d6e6503cb226a9af402ff3bba4af37e21245;hpb=1166c7d62f3fa9acd2084c90df6585cbbf868ceb;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcPat.lhs b/compiler/typecheck/TcPat.lhs index c9b5d6e..0640675 100644 --- a/compiler/typecheck/TcPat.lhs +++ b/compiler/typecheck/TcPat.lhs @@ -6,6 +6,13 @@ TcPat: Typechecking patterns \begin{code} +{-# OPTIONS -w #-} +-- 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 TcPat ( tcLetPat, tcLamPat, tcLamPats, tcOverloadedLit, addDataConStupidTheta, badFieldCon, polyPatSig ) where @@ -31,9 +38,11 @@ import TcHsType import TysWiredIn import TcGadt import Type +import Coercion import StaticFlags import TyCon import DataCon +import DynFlags import PrelNames import BasicTypes hiding (SuccessFlag(..)) import SrcLoc @@ -58,7 +67,8 @@ tcLetPat :: (Name -> Maybe TcRhoType) -> TcM (LPat TcId, a) tcLetPat sig_fn pat pat_ty thing_inside = do { let init_state = PS { pat_ctxt = LetPat sig_fn, - pat_reft = emptyRefinement } + pat_reft = emptyRefinement, + pat_eqs = False } ; (pat', ex_tvs, res) <- tc_lpat pat pat_ty init_state (\ _ -> thing_inside) -- Don't know how to deal with pattern-bound existentials yet @@ -103,11 +113,13 @@ tc_lam_pats :: [(LPat Name,BoxySigmaType)] -> ((Refinement,BoxyRhoType) -> TcM a) -- Checker for body, given its result type -> TcM ([LPat TcId], a) tc_lam_pats pat_ty_prs (reft, res_ty) thing_inside - = do { let init_state = PS { pat_ctxt = LamPat, pat_reft = reft } + = do { let init_state = PS { pat_ctxt = LamPat, pat_reft = reft, pat_eqs = False } ; (pats', ex_tvs, res) <- tcMultiple tc_lpat_pr pat_ty_prs init_state $ \ pstate' -> - refineEnvironment (pat_reft pstate') $ - thing_inside (pat_reft pstate', res_ty) + refineEnvironment (pat_reft pstate') (pat_eqs pstate') $ + if (pat_eqs pstate' && (not $ isRigidTy res_ty)) + then failWithTc (nonRigidResult res_ty) + else thing_inside (pat_reft pstate', res_ty) ; let tys = map snd pat_ty_prs ; tcCheckExistentialPat pats' ex_tvs tys res_ty @@ -132,12 +144,14 @@ tcCheckExistentialPat pats [] pat_tys body_ty = return () -- Short cut for case when there are no existentials tcCheckExistentialPat pats ex_tvs pat_tys body_ty - = addErrCtxtM (sigPatCtxt (collectPatsBinders pats) ex_tvs pat_tys body_ty) $ + = addErrCtxtM (sigPatCtxt pats ex_tvs pat_tys body_ty) $ checkSigTyVarsWrt (tcTyVarsOfTypes (body_ty:pat_tys)) ex_tvs data PatState = PS { pat_ctxt :: PatCtxt, - pat_reft :: Refinement -- Binds rigid TcTyVars to their refinements + pat_reft :: Refinement, -- Binds rigid TcTyVars to their refinements + pat_eqs :: Bool -- <=> there are GADT equational constraints + -- for refinement } data PatCtxt @@ -228,7 +242,7 @@ unBoxArgType ty pp_this Note [Nesting] ~~~~~~~~~~~~~~ -tcPat takes a "thing inside" over which the patter scopes. This is partly +tcPat takes a "thing inside" over which the pattern scopes. This is partly so that tcPat can extend the environment for the thing_inside, but also so that constraints arising in the thing_inside can be discharged by the pattern. @@ -332,11 +346,26 @@ tc_pat pstate (BangPat pat) pat_ty thing_inside -- -- Nor should a lazy pattern bind any existential type variables -- because they won't be in scope when we do the desugaring +-- +-- Note [Hopping the LIE in lazy patterns] +-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +-- In a lazy pattern, we must *not* discharge constraints from the RHS +-- from dictionaries bound in the pattern. E.g. +-- f ~(C x) = 3 +-- We can't discharge the Num constraint from dictionaries bound by +-- the pattern C! +-- +-- So we have to make the constraints from thing_inside "hop around" +-- the pattern. Hence the getLLE and extendLIEs later. + tc_pat pstate lpat@(LazyPat pat) pat_ty thing_inside - = do { (pat', pat_tvs, res) <- tc_lpat pat pat_ty pstate $ \ _ -> - thing_inside pstate - -- Ignore refined pstate', - -- revert to pstate + = do { (pat', pat_tvs, (res,lie)) + <- tc_lpat pat pat_ty pstate $ \ _ -> + getLIE (thing_inside pstate) + -- Ignore refined pstate', revert to pstate + ; extendLIEs lie + -- getLIE/extendLIEs: see Note [Hopping the LIE in lazy patterns] + -- Check no existentials ; if (null pat_tvs) then return () else lazyPatErr lpat pat_tvs @@ -418,9 +447,15 @@ tc_pat pstate pat_in@(ConPatIn (L con_span con_name) arg_pats) pat_ty thing_insi ------------------------ -- Literal patterns tc_pat pstate (LitPat simple_lit) pat_ty thing_inside - = do { boxyUnify (hsLitType simple_lit) pat_ty + = do { let lit_ty = hsLitType simple_lit + ; coi <- boxyUnify lit_ty pat_ty + -- coi is of kind: lit_ty ~ pat_ty ; res <- thing_inside pstate - ; returnM (LitPat simple_lit, [], res) } + ; span <- getSrcSpanM + -- pattern coercions have to + -- be of kind: pat_ty ~ lit_ty + -- hence, sym coi + ; returnM (wrapPatCoI (mkSymCoI coi) (LitPat simple_lit) pat_ty, [], res) } ------------------------ -- Overloaded patterns: n, and n+k @@ -455,7 +490,7 @@ tc_pat pstate pat@(NPlusKPat (L nm_loc name) lit ge minus) pat_ty thing_inside ; res <- tcExtendIdEnv1 name bndr_id (thing_inside pstate) ; returnM (NPlusKPat (L nm_loc bndr_id) lit' ge' minus', [], res) } -tc_pat _ _other_pat _ _ = panic "tc_pat" -- DictPat, ConPatOut, SigPatOut, VarPatOut +tc_pat _ _other_pat _ _ = panic "tc_pat" -- ConPatOut, SigPatOut, VarPatOut \end{code} @@ -528,32 +563,33 @@ further type refinement is local to the alternative. tcConPat :: PatState -> SrcSpan -> DataCon -> TyCon -> BoxySigmaType -- Type of the pattern - -> HsConDetails Name (LPat Name) -> (PatState -> TcM a) + -> HsConPatDetails Name -> (PatState -> TcM a) -> TcM (Pat TcId, [TcTyVar], a) tcConPat pstate con_span data_con tycon pat_ty arg_pats thing_inside - = do { span <- getSrcSpanM -- Span for the whole pattern - ; let (univ_tvs, ex_tvs, eq_spec, theta, arg_tys) = dataConFullSig data_con - skol_info = PatSkol data_con span + = do { let (univ_tvs, ex_tvs, eq_spec, eq_theta, dict_theta, arg_tys, _) = dataConFullSig data_con + skol_info = PatSkol data_con origin = SigOrigin skol_info -- Instantiate the constructor type variables [a->ty] ; ctxt_res_tys <- boxySplitTyConAppWithFamily tycon pat_ty - ; ex_tvs' <- tcInstSkolTyVars skol_info ex_tvs + ; ex_tvs' <- tcInstSkolTyVars skol_info ex_tvs -- Get location from monad, + -- not from ex_tvs ; let tenv = zipTopTvSubst (univ_tvs ++ ex_tvs) - (ctxt_res_tys ++ mkTyVarTys ex_tvs') + (ctxt_res_tys ++ mkTyVarTys ex_tvs') eq_spec' = substEqSpec tenv eq_spec - theta' = substTheta tenv theta + theta' = substTheta tenv (eq_theta ++ dict_theta) arg_tys' = substTys tenv arg_tys ; co_vars <- newCoVars eq_spec' -- Make coercion variables ; pstate' <- refineAlt data_con pstate ex_tvs' co_vars pat_ty - + ; ((arg_pats', inner_tvs, res), lie_req) <- getLIE $ tcConArgs data_con arg_tys' arg_pats pstate' thing_inside ; loc <- getInstLoc origin ; dicts <- newDictBndrs loc theta' - ; dict_binds <- tcSimplifyCheck doc ex_tvs' dicts lie_req + ; dict_binds <- tcSimplifyCheckPat loc co_vars (pat_reft pstate') + ex_tvs' dicts lie_req ; addDataConStupidTheta data_con ctxt_res_tys @@ -561,17 +597,14 @@ tcConPat pstate con_span data_con tycon pat_ty arg_pats thing_inside (unwrapFamInstScrutinee tycon ctxt_res_tys $ ConPatOut { pat_con = L con_span data_con, pat_tvs = ex_tvs' ++ co_vars, - pat_dicts = map instToId dicts, + pat_dicts = map instToVar dicts, pat_binds = dict_binds, pat_args = arg_pats', pat_ty = pat_ty }, ex_tvs' ++ inner_tvs, res) } where - doc = ptext SLIT("existential context for") <+> quotes (ppr data_con) - - -- Split against the family tycon if the pattern constructor belongs to a - -- representation tycon. - -- + -- Split against the family tycon if the pattern constructor + -- belongs to a family instance tycon. boxySplitTyConAppWithFamily tycon pat_ty = traceTc traceMsg >> case tyConFamInst_maybe tycon of @@ -608,8 +641,7 @@ tcConPat pstate con_span data_con tycon pat_ty arg_pats thing_inside tcConArgs :: DataCon -> [TcSigmaType] - -> Checker (HsConDetails Name (LPat Name)) - (HsConDetails Id (LPat Id)) + -> Checker (HsConPatDetails Name) (HsConPatDetails Id) tcConArgs data_con arg_tys (PrefixCon arg_pats) pstate thing_inside = do { checkTc (con_arity == no_of_args) -- Check correct arity @@ -634,16 +666,15 @@ tcConArgs data_con [arg_ty1,arg_ty2] (InfixCon p1 p2) pstate thing_inside tcConArgs data_con other_args (InfixCon p1 p2) pstate thing_inside = pprPanic "tcConArgs" (ppr data_con) -- InfixCon always has two arguments -tcConArgs data_con arg_tys (RecCon rpats) pstate thing_inside +tcConArgs data_con arg_tys (RecCon (HsRecFields rpats dd)) pstate thing_inside = do { (rpats', tvs, res) <- tcMultiple tc_field rpats pstate thing_inside - ; return (RecCon rpats', tvs, res) } + ; return (RecCon (HsRecFields rpats' dd), tvs, res) } where - -- doc comments are typechecked to Nothing here tc_field :: Checker (HsRecField FieldLabel (LPat Name)) (HsRecField TcId (LPat TcId)) - tc_field (HsRecField field_lbl pat _) pstate thing_inside + tc_field (HsRecField field_lbl pat pun) pstate thing_inside = do { (sel_id, pat_ty) <- wrapLocFstM find_field_ty field_lbl ; (pat', tvs, res) <- tcConArg (pat, pat_ty) pstate thing_inside - ; return (mkRecField sel_id pat', tvs, res) } + ; return (HsRecField sel_id pat' pun, tvs, res) } find_field_ty :: FieldLabel -> TcM (Id, TcType) find_field_ty field_lbl @@ -713,11 +744,15 @@ refineAlt :: DataCon -- For tracing only -> TcM PatState refineAlt con pstate ex_tvs [] pat_ty + | null $ dataConEqTheta con = return pstate -- Common case: no equational constraints refineAlt con pstate ex_tvs co_vars pat_ty - | not (isRigidTy pat_ty) - = failWithTc (nonRigidMatch con) + = do { opt_gadt <- doptM Opt_GADTs -- No type-refinement unless GADTs are on + ; if (not opt_gadt) then return pstate + else do + + { checkTc (isRigidTy pat_ty) (nonRigidMatch con) -- We are matching against a GADT constructor with non-trivial -- constraints, but pattern type is wobbly. For now we fail. -- We can make sense of this, however: @@ -732,11 +767,11 @@ refineAlt con pstate ex_tvs co_vars pat_ty -- then unify these constraints to make pat_ty the right shape; -- then proceed exactly as in the rigid case - | otherwise -- In the rigid case, we perform type refinement - = case gadtRefine (pat_reft pstate) ex_tvs co_vars of { + -- In the rigid case, we perform type refinement + ; case gadtRefine (pat_reft pstate) ex_tvs co_vars of { Failed msg -> failWithTc (inaccessibleAlt msg) ; Succeeded reft -> do { traceTc trace_msg - ; return (pstate { pat_reft = reft }) } + ; return (pstate { pat_reft = reft, pat_eqs = (pat_eqs pstate || not (null $ dataConEqTheta con)) }) } -- DO NOT refine the envt right away, because we -- might be inside a lazy pattern. Instead, refine pstate where @@ -745,7 +780,7 @@ refineAlt con pstate ex_tvs co_vars pat_ty vcat [ ppr con <+> ppr ex_tvs, ppr [(v, tyVarKind v) | v <- co_vars], ppr reft] - } + } } } \end{code} @@ -799,6 +834,19 @@ tcOverloadedLit orig lit@(HsFractional r fr) res_ty = do { expr <- newLitInst orig lit res_ty ; return (HsFractional r expr) } +tcOverloadedLit orig lit@(HsIsString s fr) res_ty + | not (fr `isHsVar` fromStringName) -- c.f. HsIntegral case + = do { str_ty <- tcMetaTy stringTyConName + ; fr' <- tcSyntaxOp orig fr (mkFunTy str_ty res_ty) + ; return (HsIsString s (HsApp (noLoc fr') (nlHsLit (HsString s)))) } + + | Just expr <- shortCutStringLit s res_ty + = return (HsIsString s expr) + + | otherwise + = do { expr <- newLitInst orig lit res_ty + ; return (HsIsString s expr) } + newLitInst :: InstOrigin -> HsOverLit Name -> BoxyRhoType -> TcM (HsExpr TcId) newLitInst orig lit res_ty -- Make a LitInst = do { loc <- getInstLoc orig @@ -892,10 +940,11 @@ patCtxt pat = Just (hang (ptext SLIT("In the pattern:")) existentialExplode pat = hang (vcat [text "My brain just exploded.", text "I can't handle pattern bindings for existentially-quantified constructors.", + text "Instead, use a case-expression, or do-notation, to unpack the constructor.", text "In the binding group for"]) 4 (ppr pat) -sigPatCtxt bound_ids bound_tvs pat_tys body_ty tidy_env +sigPatCtxt pats bound_tvs pat_tys body_ty tidy_env = do { pat_tys' <- mapM zonkTcType pat_tys ; body_ty' <- zonkTcType body_ty ; let (env1, tidy_tys) = tidyOpenTypes tidy_env (map idType show_ids) @@ -908,8 +957,9 @@ sigPatCtxt bound_ids bound_tvs pat_tys body_ty tidy_env ptext SLIT("The body has type:") <+> ppr tidy_body_ty ]) } where + bound_ids = collectPatsBinders pats show_ids = filter is_interesting bound_ids - is_interesting id = any (`elemVarSet` idFreeTyVars id) bound_tvs + is_interesting id = any (`elemVarSet` varTypeTyVars id) bound_tvs ppr_id id ty = ppr id <+> dcolon <+> ppr ty -- Don't zonk the types so we get the separate, un-unified versions @@ -928,13 +978,23 @@ badTypePat pat = ptext SLIT("Illegal type pattern") <+> ppr pat lazyPatErr pat tvs = failWithTc $ - hang (ptext SLIT("A lazy (~) pattern connot bind existential type variables")) + hang (ptext SLIT("A lazy (~) pattern cannot bind existential type variables")) 2 (vcat (map pprSkolTvBinding tvs)) nonRigidMatch con = hang (ptext SLIT("GADT pattern match in non-rigid context for") <+> quotes (ppr con)) 2 (ptext SLIT("Tell GHC HQ if you'd like this to unify the context")) +nonRigidResult res_ty + = hang (ptext SLIT("GADT pattern match with non-rigid result type") <+> quotes (ppr res_ty)) + 2 (ptext SLIT("Tell GHC HQ if you'd like this to unify the context")) + inaccessibleAlt msg = hang (ptext SLIT("Inaccessible case alternative:")) 2 msg \end{code} + +\begin{code} +wrapPatCoI :: CoercionI -> Pat a -> TcType -> Pat a +wrapPatCoI IdCo pat ty = pat +wrapPatCoI (ACo co) pat ty = CoPat (WpCo co) pat ty +\end{code}