X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcPat.lhs;h=82ac5e3596a53c1558c6800ed3f58f2b7b09a5fd;hb=cc9a63c2552d74abc1fefae647aeba062ea76b71;hp=984b2e5481b9e9d5f6547c93a1ab2a0b6c96264b;hpb=5e5310b3cb4f78e30cc7b90879eb016e97c214cb;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcPat.lhs b/compiler/typecheck/TcPat.lhs index 984b2e5..82ac5e3 100644 --- a/compiler/typecheck/TcPat.lhs +++ b/compiler/typecheck/TcPat.lhs @@ -6,7 +6,7 @@ TcPat: Typechecking patterns \begin{code} -module TcPat ( tcLetPat, tcLamPat, tcLamPats, tcProcPat, tcOverloadedLit, +module TcPat ( tcLetPat, tcPat, tcPats, tcOverloadedLit, addDataConStupidTheta, badFieldCon, polyPatSig ) where #include "HsVersions.h" @@ -37,6 +37,7 @@ import TyCon import DataCon import PrelNames import BasicTypes hiding (SuccessFlag(..)) +import DynFlags ( DynFlag( Opt_GADTs ) ) import SrcLoc import ErrUtils import Util @@ -70,11 +71,12 @@ tcLetPat sig_fn pat pat_ty thing_inside ; return (pat', res) } ----------------- -tcLamPats :: [LPat Name] -- Patterns, - -> [BoxySigmaType] -- and their types - -> BoxyRhoType -- Result type, - -> (BoxyRhoType -> TcM a) -- and the checker for the body - -> TcM ([LPat TcId], a) +tcPats :: HsMatchContext Name + -> [LPat Name] -- Patterns, + -> [BoxySigmaType] -- and their types + -> BoxyRhoType -- Result type, + -> (BoxyRhoType -> TcM a) -- and the checker for the body + -> TcM ([LPat TcId], a) -- This is the externally-callable wrapper function -- Typecheck the patterns, extend the environment to bind the variables, @@ -87,17 +89,17 @@ tcLamPats :: [LPat Name] -- Patterns, -- 3. Check the body -- 4. Check that no existentials escape -tcLamPats pats tys res_ty thing_inside - = tc_lam_pats LamPat (zipEqual "tcLamPats" pats tys) +tcPats ctxt pats tys res_ty thing_inside + = tc_lam_pats (APat ctxt) (zipEqual "tcLamPats" pats tys) res_ty thing_inside -tcLamPat, tcProcPat :: LPat Name -> BoxySigmaType - -> BoxyRhoType -- Result type - -> (BoxyRhoType -> TcM a) -- Checker for body, given - -- its result type - -> TcM (LPat TcId, a) -tcLamPat = tc_lam_pat LamPat -tcProcPat = tc_lam_pat ProcPat +tcPat :: HsMatchContext Name + -> LPat Name -> BoxySigmaType + -> BoxyRhoType -- Result type + -> (BoxyRhoType -> TcM a) -- Checker for body, given + -- its result type + -> TcM (LPat TcId, a) +tcPat ctxt = tc_lam_pat (APat ctxt) tc_lam_pat :: PatCtxt -> LPat Name -> BoxySigmaType -> BoxyRhoType -> (BoxyRhoType -> TcM a) -> TcM (LPat TcId, a) @@ -117,7 +119,7 @@ tc_lam_pats ctxt pat_ty_prs res_ty thing_inside ; (pats', ex_tvs, res) <- do { traceTc (text "tc_lam_pats" <+> (ppr pat_ty_prs $$ ppr res_ty)) ; tcMultiple tc_lpat_pr pat_ty_prs init_state $ \ pstate' -> if (pat_eqs pstate' && (not $ isRigidTy res_ty)) - then nonRigidResult res_ty + then nonRigidResult ctxt res_ty else thing_inside res_ty } ; let tys = map snd pat_ty_prs @@ -154,11 +156,13 @@ data PatState = PS { } data PatCtxt - = LamPat - | ProcPat -- The pattern in (proc pat -> ...) - -- see Note [Arrows and patterns] + = APat (HsMatchContext Name) | LetPat (Name -> Maybe TcRhoType) -- Used for let(rec) bindings +notProcPat :: PatCtxt -> Bool +notProcPat (APat ProcExpr) = False +notProcPat _ = True + patSigCtxt :: PatState -> UserTypeCtxt patSigCtxt (PS { pat_ctxt = LetPat _ }) = BindPatSigCtxt patSigCtxt _ = LamPatSigCtxt @@ -424,7 +428,7 @@ tc_pat pstate (orig@(ViewPat expr pat _)) overall_pat_ty thing_inside tc_pat pstate (SigPatIn pat sig_ty) pat_ty thing_inside = do { (inner_ty, tv_binds, coi) <- tcPatSig (patSigCtxt pstate) sig_ty pat_ty - ; unless (isIdentityCoercion coi) $ + ; unless (isIdentityCoI coi) $ failWithTc (badSigPat pat_ty) ; (pat', tvs, res) <- tcExtendTyVarEnv2 tv_binds $ tc_lpat pat inner_ty pstate thing_inside @@ -647,8 +651,9 @@ tcConPat pstate con_span data_con tycon pat_ty arg_pats thing_inside else do -- The general case, with existential, and local equality -- constraints - { checkTc (case pat_ctxt pstate of { ProcPat -> False; _ -> True }) + { checkTc (notProcPat (pat_ctxt pstate)) (existentialProcPat data_con) + -- See Note [Arrows and patterns] -- Need to test for rigidity if *any* constraints in theta as class -- constraints may have superclass equality constraints. However, @@ -666,8 +671,14 @@ tcConPat pstate con_span data_con tycon pat_ty arg_pats thing_inside pstate' | no_equalities = pstate | otherwise = pstate { pat_eqs = True } - ; unless no_equalities $ - checkTc (isRigidTy pat_ty) (nonRigidMatch data_con) + ; gadts_on <- doptM Opt_GADTs + ; checkTc (no_equalities || gadts_on) + (ptext (sLit "A pattern match on a GADT requires -XGADTs")) + -- Trac #2905 decided that a *pattern-match* of a GADT + -- should require the GADT language flag + + ; unless no_equalities $ checkTc (isRigidTy pat_ty) $ + nonRigidMatch (pat_ctxt pstate) data_con ; ((arg_pats', inner_tvs, res), lie_req) <- getLIE $ tcConArgs data_con arg_tys' arg_pats pstate' thing_inside @@ -698,7 +709,7 @@ tcConPat pstate con_span data_con tycon pat_ty arg_pats thing_inside ; (_, freshTvs, subst) <- tcInstTyVars (tyConTyVars tycon) ; let instTys' = substTys subst instTys ; cois <- boxyUnifyList instTys' scrutinee_arg_tys - ; let coi = if isIdentityCoercion coi1 + ; let coi = if isIdentityCoI coi1 then -- pat_ty was splittable -- => boxyUnifyList had real work to do mkTyConAppCoI fam_tycon instTys' cois @@ -974,7 +985,7 @@ patCtxt pat = Just (hang (ptext (sLit "In the pattern:")) existentialExplode :: LPat Name -> SDoc existentialExplode pat = hang (vcat [text "My brain just exploded.", - text "I can't handle pattern bindings for existentially-quantified constructors.", + text "I can't handle pattern bindings for existential or GADT data constructors.", text "Instead, use a case-expression, or do-notation, to unpack the constructor.", text "In the binding group for"]) 4 (ppr pat) @@ -1026,20 +1037,33 @@ existentialProcPat con lazyPatErr :: Pat name -> [TcTyVar] -> TcM () lazyPatErr _ tvs = failWithTc $ - hang (ptext (sLit "A lazy (~) pattern cannot bind existential type variables")) + hang (ptext (sLit "A lazy (~) pattern cannot match existential or GADT data constructors")) 2 (vcat (map pprSkolTvBinding tvs)) -nonRigidMatch :: DataCon -> SDoc -nonRigidMatch con +nonRigidMatch :: PatCtxt -> DataCon -> SDoc +nonRigidMatch ctxt con = hang (ptext (sLit "GADT pattern match in non-rigid context for") <+> quotes (ppr con)) - 2 (ptext (sLit "Solution: add a type signature")) - -nonRigidResult :: Type -> TcM a -nonRigidResult res_ty + 2 (ptext (sLit "Probable solution: add a type signature for") <+> what ctxt) + where + what (APat (FunRhs f _)) = quotes (ppr f) + what (APat CaseAlt) = ptext (sLit "the scrutinee of the case expression") + what (APat LambdaExpr ) = ptext (sLit "the lambda expression") + what (APat (StmtCtxt _)) = ptext (sLit "the right hand side of a do/comprehension binding") + what _other = ptext (sLit "something") + +nonRigidResult :: PatCtxt -> Type -> TcM a +nonRigidResult ctxt res_ty = do { env0 <- tcInitTidyEnv ; let (env1, res_ty') = tidyOpenType env0 res_ty msg = hang (ptext (sLit "GADT pattern match with non-rigid result type") <+> quotes (ppr res_ty')) - 2 (ptext (sLit "Solution: add a type signature")) + 2 (ptext (sLit "Solution: add a type signature for") + <+> what ctxt ) ; failWithTcM (env1, msg) } + where + what (APat (FunRhs f _)) = quotes (ppr f) + what (APat CaseAlt) = ptext (sLit "the entire case expression") + what (APat LambdaExpr) = ptext (sLit "the lambda exression") + what (APat (StmtCtxt _)) = ptext (sLit "the entire do/comprehension expression") + what _other = ptext (sLit "something") \end{code}