X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcExpr.lhs;h=e7c7f3b0d8dfadb9ccfb542afed2cec3931a223d;hb=cebe3ed020cfe403c809545d94bd6b416785f11d;hp=252d995669e0a0b76d384f53b6d7a86493551c42;hpb=469c3333ae5954cee58cdb1575b41fb1a3c34f06;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcExpr.lhs b/ghc/compiler/typecheck/TcExpr.lhs index 252d995..e7c7f3b 100644 --- a/ghc/compiler/typecheck/TcExpr.lhs +++ b/ghc/compiler/typecheck/TcExpr.lhs @@ -4,69 +4,81 @@ \section[TcExpr]{Typecheck an expression} \begin{code} -module TcExpr ( tcExpr, tcMonoExpr, tcId ) where +module TcExpr ( tcPolyExpr, tcPolyExprNC, + tcMonoExpr, tcInferRho, tcSyntaxOp ) where #include "HsVersions.h" -import HsSyn ( HsExpr(..), HsLit(..), ArithSeqInfo(..), - HsMatchContext(..), HsDoContext(..), mkMonoBind +#ifdef GHCI /* Only if bootstrapped */ +import {-# SOURCE #-} TcSplice( tcSpliceExpr, tcBracket ) +import HsSyn ( nlHsVar ) +import Id ( Id ) +import Name ( isExternalName ) +import TcType ( isTauTy ) +import TcEnv ( checkWellStaged ) +import HsSyn ( nlHsApp ) +import qualified DsMeta +#endif + +import HsSyn ( HsExpr(..), LHsExpr, ArithSeqInfo(..), recBindFields, + HsMatchContext(..), HsRecordBinds, + mkHsCoerce, mkHsApp, mkHsDictApp, mkHsTyApp ) +import TcHsSyn ( hsLitType ) +import TcRnMonad +import TcUnify ( tcInfer, tcSubExp, tcGen, boxyUnify, subFunTys, zapToMonotype, stripBoxyType, + boxySplitListTy, boxySplitTyConApp, wrapFunResCoercion, boxySubMatchType, + unBox ) +import BasicTypes ( Arity, isMarkedStrict ) +import Inst ( newMethodFromName, newIPDict, instToId, + newDicts, newMethodWithGivenTy, tcInstStupidTheta ) +import TcBinds ( tcLocalBinds ) +import TcEnv ( tcLookup, tcLookupId, + tcLookupDataCon, tcLookupGlobalId ) -import RnHsSyn ( RenamedHsExpr, RenamedRecordBinds ) -import TcHsSyn ( TcExpr, TcRecordBinds, simpleHsLitTy ) - -import TcMonad -import TcUnify ( tcSub, tcGen, (<$>), - unifyTauTy, unifyFunTy, unifyListTy, unifyPArrTy, - unifyTupleTy ) -import BasicTypes ( RecFlag(..), isMarkedStrict ) -import Inst ( InstOrigin(..), - LIE, mkLIE, emptyLIE, unitLIE, plusLIE, plusLIEs, - newOverloadedLit, newMethod, newIPDict, - newDicts, newMethodWithGivenTy, - instToId, tcInstCall - ) -import TcBinds ( tcBindsAndThen ) -import TcEnv ( tcLookupClass, tcLookupGlobalId, tcLookupGlobal_maybe, - tcLookupTyCon, tcLookupDataCon, tcLookupId - ) -import TcMatches ( tcMatchesCase, tcMatchLambda, tcStmts ) -import TcMonoType ( tcHsSigType, UserTypeCtxt(..) ) -import TcPat ( badFieldCon ) -import TcSimplify ( tcSimplifyIPs ) -import TcMType ( tcInstTyVars, tcInstType, newHoleTyVarTy, - newTyVarTy, newTyVarTys, zonkTcType ) -import TcType ( TcType, TcSigmaType, TcPhiType, - tcSplitFunTys, tcSplitTyConApp, mkTyVarTys, - isSigmaTy, mkFunTy, mkAppTy, mkTyConTy, - mkTyConApp, mkClassPred, tcFunArgTy, - tyVarsOfTypes, isLinearPred, - liftedTypeKind, openTypeKind, mkArrowKind, - tcSplitSigmaTy, tcTyConAppTyCon, - tidyOpenType - ) -import FieldLabel ( FieldLabel, fieldLabelName, fieldLabelType, fieldLabelTyCon ) -import Id ( idType, recordSelectorFieldLabel, isRecordSelector ) -import DataCon ( dataConFieldLabels, dataConSig, - dataConStrictMarks +import TcArrows ( tcProc ) +import TcMatches ( tcMatchesCase, tcMatchLambda, tcDoStmts, TcMatchCtxt(..) ) +import TcHsType ( tcHsSigType, UserTypeCtxt(..) ) +import TcPat ( tcOverloadedLit, badFieldCon ) +import TcMType ( tcInstTyVars, newFlexiTyVarTy, newBoxyTyVars, readFilledBox, + tcInstBoxyTyVar, tcInstTyVar, zonkTcType ) +import TcType ( TcType, TcSigmaType, TcRhoType, + BoxySigmaType, BoxyRhoType, ThetaType, + tcSplitFunTys, mkTyVarTys, mkFunTys, + tcMultiSplitSigmaTy, tcSplitFunTysN, + isSigmaTy, mkFunTy, mkTyConApp, isLinearPred, + exactTyVarsOfType, exactTyVarsOfTypes, mkTyVarTy, + tidyOpenType, + zipTopTvSubst, zipOpenTvSubst, substTys, substTyVar, lookupTyVar ) +import Kind ( argTypeKind ) + +import Id ( idType, idName, recordSelectorFieldLabel, isRecordSelector, + isNaughtyRecordSelector, isDataConId_maybe ) +import DataCon ( DataCon, dataConFieldLabels, dataConStrictMarks, dataConSourceArity, + dataConWrapId, isVanillaDataCon, dataConTyVars, dataConOrigArgTys ) import Name ( Name ) -import TyCon ( TyCon, tyConTyVars, isAlgTyCon, tyConDataCons ) -import Subst ( mkTopTyVarSubst, substTheta, substTy ) -import VarSet ( emptyVarSet, elemVarSet ) -import TysWiredIn ( boolTy, mkListTy, mkPArrTy, listTyCon, parrTyCon ) -import PrelNames ( cCallableClassName, - cReturnableClassName, - enumFromName, enumFromThenName, +import TyCon ( FieldLabel, tyConStupidTheta, tyConDataCons ) +import Type ( substTheta, substTy ) +import Var ( TyVar, tyVarKind ) +import VarSet ( emptyVarSet, elemVarSet, unionVarSet ) +import TysWiredIn ( boolTy, parrTyCon, tupleTyCon ) +import PrelNames ( enumFromName, enumFromThenName, enumFromToName, enumFromThenToName, - enumFromToPName, enumFromThenToPName, - thenMName, failMName, returnMName, ioTyConName + enumFromToPName, enumFromThenToPName, negateName ) -import Outputable -import ListSetOps ( minusList ) -import Util -import CmdLineOpts +import DynFlags +import StaticFlags ( opt_NoMethodSharing ) import HscTypes ( TyThing(..) ) +import SrcLoc ( Located(..), unLoc, noLoc, getLoc ) +import Util +import ListSetOps ( assocMaybe ) +import Maybes ( catMaybes ) +import Outputable +import FastString +#ifdef DEBUG +import TyCon ( tyConArity ) +#endif \end{code} %************************************************************************ @@ -76,315 +88,273 @@ import HscTypes ( TyThing(..) ) %************************************************************************ \begin{code} -tcExpr :: RenamedHsExpr -- Expession to type check - -> TcSigmaType -- Expected type (could be a polytpye) - -> TcM (TcExpr, LIE) -- Generalised expr with expected type, and LIE - -tcExpr expr expected_ty - | not (isSigmaTy expected_ty) -- Monomorphic case - = tcMonoExpr expr expected_ty +tcPolyExpr, tcPolyExprNC + :: LHsExpr Name -- Expession to type check + -> BoxySigmaType -- Expected type (could be a polytpye) + -> TcM (LHsExpr TcId) -- Generalised expr with expected type + +-- tcPolyExpr is a convenient place (frequent but not too frequent) place +-- to add context information. +-- The NC version does not do so, usually because the caller wants +-- to do so himself. + +tcPolyExpr expr res_ty + = addErrCtxt (exprCtxt (unLoc expr)) $ + tcPolyExprNC expr res_ty + +tcPolyExprNC expr res_ty + | isSigmaTy res_ty + = do { (gen_fn, expr') <- tcGen res_ty emptyVarSet (tcPolyExprNC expr) + -- Note the recursive call to tcPolyExpr, because the + -- type may have multiple layers of for-alls + ; return (L (getLoc expr') (mkHsCoerce gen_fn (unLoc expr'))) } | otherwise - = tcGen expected_ty emptyVarSet ( - tcMonoExpr expr - ) `thenTc` \ (gen_fn, expr', lie) -> - returnTc (gen_fn <$> expr', lie) + = tcMonoExpr expr res_ty + +--------------- +tcPolyExprs :: [LHsExpr Name] -> [TcType] -> TcM [LHsExpr TcId] +tcPolyExprs [] [] = returnM [] +tcPolyExprs (expr:exprs) (ty:tys) + = do { expr' <- tcPolyExpr expr ty + ; exprs' <- tcPolyExprs exprs tys + ; returnM (expr':exprs') } +tcPolyExprs exprs tys = pprPanic "tcPolyExprs" (ppr exprs $$ ppr tys) + +--------------- +tcMonoExpr :: LHsExpr Name -- Expression to type check + -> BoxyRhoType -- Expected type (could be a type variable) + -- Definitely no foralls at the top + -- Can contain boxes, which will be filled in + -> TcM (LHsExpr TcId) + +tcMonoExpr (L loc expr) res_ty + = ASSERT( not (isSigmaTy res_ty) ) + setSrcSpan loc $ + do { expr' <- tcExpr expr res_ty + ; return (L loc expr') } + +--------------- +tcInferRho :: LHsExpr Name -> TcM (LHsExpr TcId, TcRhoType) +tcInferRho expr = tcInfer (tcMonoExpr expr) \end{code} -%************************************************************************ -%* * -\subsection{The TAUT rules for variables} -%* * -%************************************************************************ - -\begin{code} -tcMonoExpr :: RenamedHsExpr -- Expession to type check - -> TcPhiType -- Expected type (could be a type variable) - -- Definitely no foralls at the top - -- Can be a 'hole'. - -> TcM (TcExpr, LIE) - -tcMonoExpr (HsVar name) res_ty - = tcId name `thenNF_Tc` \ (expr', lie1, id_ty) -> - tcSub res_ty id_ty `thenTc` \ (co_fn, lie2) -> - returnTc (co_fn <$> expr', lie1 `plusLIE` lie2) - -tcMonoExpr (HsIPVar ip) res_ty - = -- Implicit parameters must have a *tau-type* not a - -- type scheme. We enforce this by creating a fresh - -- type variable as its type. (Because res_ty may not - -- be a tau-type.) - newTyVarTy openTypeKind `thenNF_Tc` \ ip_ty -> - newIPDict (IPOcc ip) ip ip_ty `thenNF_Tc` \ (ip', inst) -> - tcSub res_ty ip_ty `thenTc` \ (co_fn, lie) -> - returnNF_Tc (co_fn <$> HsIPVar ip', lie `plusLIE` unitLIE inst) -\end{code} - %************************************************************************ %* * -\subsection{Expressions type signatures} + tcExpr: the main expression typechecker %* * %************************************************************************ \begin{code} -tcMonoExpr in_expr@(ExprWithTySig expr poly_ty) res_ty - = tcHsSigType ExprSigCtxt poly_ty `thenTc` \ sig_tc_ty -> - tcExpr expr sig_tc_ty `thenTc` \ (expr', lie1) -> - - -- Must instantiate the outer for-alls of sig_tc_ty - -- else we risk instantiating a ? res_ty to a forall-type - -- which breaks the invariant that tcMonoExpr only returns phi-types - tcAddErrCtxt (exprSigCtxt in_expr) $ - tcInstCall SignatureOrigin sig_tc_ty `thenNF_Tc` \ (inst_fn, lie2, inst_sig_ty) -> - tcSub res_ty inst_sig_ty `thenTc` \ (co_fn, lie3) -> - - returnTc (co_fn <$> inst_fn expr', lie1 `plusLIE` lie2 `plusLIE` lie3) +tcExpr :: HsExpr Name -> BoxyRhoType -> TcM (HsExpr TcId) +tcExpr (HsVar name) res_ty = tcId (OccurrenceOf name) name res_ty + +tcExpr (HsLit lit) res_ty = do { boxyUnify (hsLitType lit) res_ty + ; return (HsLit lit) } + +tcExpr (HsPar expr) res_ty = do { expr' <- tcMonoExpr expr res_ty + ; return (HsPar expr') } + +tcExpr (HsSCC lbl expr) res_ty = do { expr' <- tcMonoExpr expr res_ty + ; returnM (HsSCC lbl expr') } + +tcExpr (HsCoreAnn lbl expr) res_ty -- hdaume: core annotation + = do { expr' <- tcMonoExpr expr res_ty + ; return (HsCoreAnn lbl expr') } + +tcExpr (HsOverLit lit) res_ty + = do { lit' <- tcOverloadedLit (LiteralOrigin lit) lit res_ty + ; return (HsOverLit lit') } + +tcExpr (NegApp expr neg_expr) res_ty + = do { neg_expr' <- tcSyntaxOp (OccurrenceOf negateName) neg_expr + (mkFunTy res_ty res_ty) + ; expr' <- tcMonoExpr expr res_ty + ; return (NegApp expr' neg_expr') } + +tcExpr (HsIPVar ip) res_ty + = do { -- Implicit parameters must have a *tau-type* not a + -- type scheme. We enforce this by creating a fresh + -- type variable as its type. (Because res_ty may not + -- be a tau-type.) + ip_ty <- newFlexiTyVarTy argTypeKind -- argTypeKind: it can't be an unboxed tuple + ; co_fn <- tcSubExp ip_ty res_ty + ; (ip', inst) <- newIPDict (IPOccOrigin ip) ip ip_ty + ; extendLIE inst + ; return (mkHsCoerce co_fn (HsIPVar ip')) } + +tcExpr (HsApp e1 e2) res_ty + = go e1 [e2] + where + go :: LHsExpr Name -> [LHsExpr Name] -> TcM (HsExpr TcId) + go (L _ (HsApp e1 e2)) args = go e1 (e2:args) + go lfun@(L loc fun) args + = do { (fun', args') <- addErrCtxt (callCtxt lfun args) $ + tcApp fun (length args) (tcArgs lfun args) res_ty + ; return (unLoc (foldl mkHsApp (L loc fun') args')) } + +tcExpr (HsLam match) res_ty + = do { (co_fn, match') <- tcMatchLambda match res_ty + ; return (mkHsCoerce co_fn (HsLam match')) } + +tcExpr in_expr@(ExprWithTySig expr sig_ty) res_ty + = do { sig_tc_ty <- tcHsSigType ExprSigCtxt sig_ty + ; expr' <- tcPolyExpr expr sig_tc_ty + ; co_fn <- tcSubExp sig_tc_ty res_ty + ; return (mkHsCoerce co_fn (ExprWithTySigOut expr' sig_ty)) } + +tcExpr (HsType ty) res_ty + = failWithTc (text "Can't handle type argument:" <+> ppr ty) + -- This is the syntax for type applications that I was planning + -- but there are difficulties (e.g. what order for type args) + -- so it's not enabled yet. + -- Can't eliminate it altogether from the parser, because the + -- same parser parses *patterns*. \end{code} %************************************************************************ %* * -\subsection{Other expression forms} + Infix operators and sections %* * %************************************************************************ \begin{code} -tcMonoExpr (HsLit lit) res_ty = tcLit lit res_ty -tcMonoExpr (HsOverLit lit) res_ty = newOverloadedLit (LiteralOrigin lit) lit res_ty -tcMonoExpr (HsPar expr) res_ty = tcMonoExpr expr res_ty +tcExpr in_expr@(OpApp arg1 lop@(L loc op) fix arg2) res_ty + = do { (op', [arg1', arg2']) <- tcApp op 2 (tcArgs lop [arg1,arg2]) res_ty + ; return (OpApp arg1' (L loc op') fix arg2') } -tcMonoExpr (NegApp expr neg_name) res_ty - = tcMonoExpr (HsApp (HsVar neg_name) expr) res_ty - -tcMonoExpr (HsLam match) res_ty - = tcMatchLambda match res_ty `thenTc` \ (match',lie) -> - returnTc (HsLam match', lie) - -tcMonoExpr (HsApp e1 e2) res_ty - = tcApp e1 [e2] res_ty -\end{code} - -Note that the operators in sections are expected to be binary, and -a type error will occur if they aren't. - -\begin{code} -- Left sections, equivalent to -- \ x -> e op x, -- or -- \ x -> op e x, -- or just -- op e +-- +-- We treat it as similar to the latter, so we don't +-- actually require the function to take two arguments +-- at all. For example, (x `not`) means (not x); +-- you get postfix operators! Not really Haskell 98 +-- I suppose, but it's less work and kind of useful. -tcMonoExpr in_expr@(SectionL arg1 op) res_ty - = tcExpr_id op `thenTc` \ (op', lie1, op_ty) -> - split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) -> - tcArg op (arg1, arg1_ty, 1) `thenTc` \ (arg1',lie2) -> - tcAddErrCtxt (exprCtxt in_expr) $ - tcSub res_ty (mkFunTy arg2_ty op_res_ty) `thenTc` \ (co_fn, lie3) -> - returnTc (co_fn <$> SectionL arg1' op', lie1 `plusLIE` lie2 `plusLIE` lie3) +tcExpr in_expr@(SectionL arg1 lop@(L loc op)) res_ty + = do { (op', [arg1']) <- tcApp op 1 (tcArgs lop [arg1]) res_ty + ; return (SectionL arg1' (L loc op')) } --- Right sections, equivalent to \ x -> x op expr, or +-- Right sections, equivalent to \ x -> x `op` expr, or -- \ x -> op x expr - -tcMonoExpr in_expr@(SectionR op arg2) res_ty - = tcExpr_id op `thenTc` \ (op', lie1, op_ty) -> - split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) -> - tcArg op (arg2, arg2_ty, 2) `thenTc` \ (arg2',lie2) -> - tcAddErrCtxt (exprCtxt in_expr) $ - tcSub res_ty (mkFunTy arg1_ty op_res_ty) `thenTc` \ (co_fn, lie3) -> - returnTc (co_fn <$> SectionR op' arg2', lie1 `plusLIE` lie2 `plusLIE` lie3) - --- equivalent to (op e1) e2: - -tcMonoExpr in_expr@(OpApp arg1 op fix arg2) res_ty - = tcExpr_id op `thenTc` \ (op', lie1, op_ty) -> - split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) -> - tcArg op (arg1, arg1_ty, 1) `thenTc` \ (arg1',lie2a) -> - tcArg op (arg2, arg2_ty, 2) `thenTc` \ (arg2',lie2b) -> - tcAddErrCtxt (exprCtxt in_expr) $ - tcSub res_ty op_res_ty `thenTc` \ (co_fn, lie3) -> - returnTc (OpApp arg1' op' fix arg2', - lie1 `plusLIE` lie2a `plusLIE` lie2b `plusLIE` lie3) + +tcExpr in_expr@(SectionR lop@(L loc op) arg2) res_ty + = do { (co_fn, (op', arg2')) <- subFunTys doc 1 res_ty $ \ [arg1_ty'] res_ty' -> + tcApp op 2 (tc_args arg1_ty') res_ty' + ; return (mkHsCoerce co_fn (SectionR (L loc op') arg2')) } + where + doc = ptext SLIT("The section") <+> quotes (ppr in_expr) + <+> ptext SLIT("takes one argument") + tc_args arg1_ty' [arg1_ty, arg2_ty] + = do { boxyUnify arg1_ty' arg1_ty + ; tcArg lop (arg2, arg2_ty, 2) } \end{code} -The interesting thing about @ccall@ is that it is just a template -which we instantiate by filling in details about the types of its -argument and result (ie minimal typechecking is performed). So, the -basic story is that we allocate a load of type variables (to hold the -arg/result types); unify them with the args/result; and store them for -later use. - \begin{code} -tcMonoExpr e0@(HsCCall lbl args may_gc is_casm ignored_fake_result_ty) res_ty - - = getDOptsTc `thenNF_Tc` \ dflags -> - - checkTc (not (is_casm && dopt_HscLang dflags /= HscC)) - (vcat [text "_casm_ is only supported when compiling via C (-fvia-C).", - text "Either compile with -fvia-C, or, better, rewrite your code", - text "to use the foreign function interface. _casm_s are deprecated", - text "and support for them may one day disappear."]) - `thenTc_` +tcExpr (HsLet binds expr) res_ty + = do { (binds', expr') <- tcLocalBinds binds $ + tcMonoExpr expr res_ty + ; return (HsLet binds' expr') } + +tcExpr (HsCase scrut matches) exp_ty + = do { -- We used to typecheck the case alternatives first. + -- The case patterns tend to give good type info to use + -- when typechecking the scrutinee. For example + -- case (map f) of + -- (x:xs) -> ... + -- will report that map is applied to too few arguments + -- + -- But now, in the GADT world, we need to typecheck the scrutinee + -- first, to get type info that may be refined in the case alternatives + (scrut', scrut_ty) <- addErrCtxt (caseScrutCtxt scrut) + (tcInferRho scrut) + + ; traceTc (text "HsCase" <+> ppr scrut_ty) + ; matches' <- tcMatchesCase match_ctxt scrut_ty matches exp_ty + ; return (HsCase scrut' matches') } + where + match_ctxt = MC { mc_what = CaseAlt, + mc_body = tcPolyExpr } + +tcExpr (HsIf pred b1 b2) res_ty + = do { pred' <- addErrCtxt (predCtxt pred) $ + tcMonoExpr pred boolTy + ; b1' <- tcMonoExpr b1 res_ty + ; b2' <- tcMonoExpr b2 res_ty + ; return (HsIf pred' b1' b2') } + +tcExpr (HsDo do_or_lc stmts body _) res_ty + = tcDoStmts do_or_lc stmts body res_ty + +tcExpr in_expr@(ExplicitList _ exprs) res_ty -- Non-empty list + = do { elt_ty <- boxySplitListTy res_ty + ; exprs' <- mappM (tc_elt elt_ty) exprs + ; return (ExplicitList elt_ty exprs') } + where + tc_elt elt_ty expr = tcPolyExpr expr elt_ty + +tcExpr in_expr@(ExplicitPArr _ exprs) res_ty -- maybe empty + = do { [elt_ty] <- boxySplitTyConApp parrTyCon res_ty + ; exprs' <- mappM (tc_elt elt_ty) exprs + ; ifM (null exprs) (zapToMonotype elt_ty) + -- If there are no expressions in the comprehension + -- we must still fill in the box + -- (Not needed for [] and () becuase they happen + -- to parse as data constructors.) + ; return (ExplicitPArr elt_ty exprs') } + where + tc_elt elt_ty expr = tcPolyExpr expr elt_ty - -- Get the callable and returnable classes. - tcLookupClass cCallableClassName `thenNF_Tc` \ cCallableClass -> - tcLookupClass cReturnableClassName `thenNF_Tc` \ cReturnableClass -> - tcLookupTyCon ioTyConName `thenNF_Tc` \ ioTyCon -> - let - new_arg_dict (arg, arg_ty) - = newDicts (CCallOrigin (_UNPK_ lbl) (Just arg)) - [mkClassPred cCallableClass [arg_ty]] `thenNF_Tc` \ arg_dicts -> - returnNF_Tc arg_dicts -- Actually a singleton bag +tcExpr (ExplicitTuple exprs boxity) res_ty + = do { arg_tys <- boxySplitTyConApp (tupleTyCon boxity (length exprs)) res_ty + ; exprs' <- tcPolyExprs exprs arg_tys + ; return (ExplicitTuple exprs' boxity) } - result_origin = CCallOrigin (_UNPK_ lbl) Nothing {- Not an arg -} - in +tcExpr (HsProc pat cmd) res_ty + = do { (pat', cmd') <- tcProc pat cmd res_ty + ; return (HsProc pat' cmd') } - -- Arguments - let tv_idxs | null args = [] - | otherwise = [1..length args] - in - newTyVarTys (length tv_idxs) openTypeKind `thenNF_Tc` \ arg_tys -> - tcMonoExprs args arg_tys `thenTc` \ (args', args_lie) -> +tcExpr e@(HsArrApp _ _ _ _ _) _ + = failWithTc (vcat [ptext SLIT("The arrow command"), nest 2 (ppr e), + ptext SLIT("was found where an expression was expected")]) - -- The argument types can be unlifted or lifted; the result - -- type must, however, be lifted since it's an argument to the IO - -- type constructor. - newTyVarTy liftedTypeKind `thenNF_Tc` \ result_ty -> - let - io_result_ty = mkTyConApp ioTyCon [result_ty] - in - unifyTauTy res_ty io_result_ty `thenTc_` - - -- Construct the extra insts, which encode the - -- constraints on the argument and result types. - mapNF_Tc new_arg_dict (zipEqual "tcMonoExpr:CCall" args arg_tys) `thenNF_Tc` \ ccarg_dicts_s -> - newDicts result_origin [mkClassPred cReturnableClass [result_ty]] `thenNF_Tc` \ ccres_dict -> - returnTc (HsCCall lbl args' may_gc is_casm io_result_ty, - mkLIE (ccres_dict ++ concat ccarg_dicts_s) `plusLIE` args_lie) +tcExpr e@(HsArrForm _ _ _) _ + = failWithTc (vcat [ptext SLIT("The arrow command"), nest 2 (ppr e), + ptext SLIT("was found where an expression was expected")]) \end{code} -\begin{code} -tcMonoExpr (HsSCC lbl expr) res_ty - = tcMonoExpr expr res_ty `thenTc` \ (expr', lie) -> - returnTc (HsSCC lbl expr', lie) - -tcMonoExpr (HsLet binds expr) res_ty - = tcBindsAndThen - combiner - binds -- Bindings to check - tc_expr `thenTc` \ (expr', lie) -> - returnTc (expr', lie) - where - tc_expr = tcMonoExpr expr res_ty `thenTc` \ (expr', lie) -> - returnTc (expr', lie) - combiner is_rec bind expr = HsLet (mkMonoBind bind [] is_rec) expr - -tcMonoExpr in_expr@(HsCase scrut matches src_loc) res_ty - = tcAddSrcLoc src_loc $ - tcAddErrCtxt (caseCtxt in_expr) $ - - -- Typecheck the case alternatives first. - -- The case patterns tend to give good type info to use - -- when typechecking the scrutinee. For example - -- case (map f) of - -- (x:xs) -> ... - -- will report that map is applied to too few arguments - -- - -- Not only that, but it's better to check the matches on their - -- own, so that we get the expected results for scoped type variables. - -- f x = case x of - -- (p::a, q::b) -> (q,p) - -- The above should work: the match (p,q) -> (q,p) is polymorphic as - -- claimed by the pattern signatures. But if we typechecked the - -- match with x in scope and x's type as the expected type, we'd be hosed. - - tcMatchesCase matches res_ty `thenTc` \ (scrut_ty, matches', lie2) -> - - tcAddErrCtxt (caseScrutCtxt scrut) ( - tcMonoExpr scrut scrut_ty - ) `thenTc` \ (scrut',lie1) -> - - returnTc (HsCase scrut' matches' src_loc, plusLIE lie1 lie2) - -tcMonoExpr (HsIf pred b1 b2 src_loc) res_ty - = tcAddSrcLoc src_loc $ - tcAddErrCtxt (predCtxt pred) ( - tcMonoExpr pred boolTy ) `thenTc` \ (pred',lie1) -> - - tcMonoExpr b1 res_ty `thenTc` \ (b1',lie2) -> - tcMonoExpr b2 res_ty `thenTc` \ (b2',lie3) -> - returnTc (HsIf pred' b1' b2' src_loc, plusLIE lie1 (plusLIE lie2 lie3)) -\end{code} +%************************************************************************ +%* * + Record construction and update +%* * +%************************************************************************ \begin{code} -tcMonoExpr expr@(HsDo do_or_lc stmts src_loc) res_ty - = tcDoStmts do_or_lc stmts src_loc res_ty -\end{code} +tcExpr expr@(RecordCon (L loc con_name) _ rbinds) res_ty + = do { data_con <- tcLookupDataCon con_name -\begin{code} -tcMonoExpr in_expr@(ExplicitList _ exprs) res_ty -- Non-empty list - = unifyListTy res_ty `thenTc` \ elt_ty -> - mapAndUnzipTc (tc_elt elt_ty) exprs `thenTc` \ (exprs', lies) -> - returnTc (ExplicitList elt_ty exprs', plusLIEs lies) - where - tc_elt elt_ty expr - = tcAddErrCtxt (listCtxt expr) $ - tcMonoExpr expr elt_ty - -tcMonoExpr in_expr@(ExplicitPArr _ exprs) res_ty -- maybe empty - = unifyPArrTy res_ty `thenTc` \ elt_ty -> - mapAndUnzipTc (tc_elt elt_ty) exprs `thenTc` \ (exprs', lies) -> - returnTc (ExplicitPArr elt_ty exprs', plusLIEs lies) - where - tc_elt elt_ty expr - = tcAddErrCtxt (parrCtxt expr) $ - tcMonoExpr expr elt_ty - -tcMonoExpr (ExplicitTuple exprs boxity) res_ty - = unifyTupleTy boxity (length exprs) res_ty `thenTc` \ arg_tys -> - mapAndUnzipTc (\ (expr, arg_ty) -> tcMonoExpr expr arg_ty) - (exprs `zip` arg_tys) -- we know they're of equal length. - `thenTc` \ (exprs', lies) -> - returnTc (ExplicitTuple exprs' boxity, plusLIEs lies) - -tcMonoExpr expr@(RecordCon con_name rbinds) res_ty - = tcAddErrCtxt (recordConCtxt expr) $ - tcId con_name `thenNF_Tc` \ (con_expr, con_lie, con_tau) -> - let - (_, record_ty) = tcSplitFunTys con_tau - (tycon, ty_args) = tcSplitTyConApp record_ty - in - ASSERT( isAlgTyCon tycon ) - unifyTauTy res_ty record_ty `thenTc_` + -- Check for missing fields + ; checkMissingFields data_con rbinds - -- Check that the record bindings match the constructor - -- con_name is syntactically constrained to be a data constructor - tcLookupDataCon con_name `thenTc` \ data_con -> - let - bad_fields = badFields rbinds data_con - in - if not (null bad_fields) then - mapNF_Tc (addErrTc . badFieldCon con_name) bad_fields `thenNF_Tc_` - failTc -- Fail now, because tcRecordBinds will crash on a bad field - else + ; let arity = dataConSourceArity data_con + check_fields arg_tys + = do { rbinds' <- tcRecordBinds data_con arg_tys rbinds + ; mapM unBox arg_tys + ; return rbinds' } + -- The unBox ensures that all the boxes in arg_tys are indeed + -- filled, which is the invariant expected by tcIdApp - -- Typecheck the record bindings - tcRecordBinds tycon ty_args rbinds `thenTc` \ (rbinds', rbinds_lie) -> - - let - (missing_s_fields, missing_fields) = missingFields rbinds data_con - in - checkTcM (null missing_s_fields) - (mapNF_Tc (addErrTc . missingStrictFieldCon con_name) missing_s_fields `thenNF_Tc_` - returnNF_Tc ()) `thenNF_Tc_` - doptsTc Opt_WarnMissingFields `thenNF_Tc` \ warn -> - checkTcM (not (warn && not (null missing_fields))) - (mapNF_Tc ((warnTc True) . missingFieldCon con_name) missing_fields `thenNF_Tc_` - returnNF_Tc ()) `thenNF_Tc_` + ; (con_expr, rbinds') <- tcIdApp con_name arity check_fields res_ty - returnTc (RecordConOut data_con con_expr rbinds', con_lie `plusLIE` rbinds_lie) + ; returnM (RecordCon (L loc (dataConWrapId data_con)) con_expr rbinds') } -- The main complication with RecordUpd is that we need to explicitly -- handle the *non-updated* fields. Consider: @@ -411,56 +381,54 @@ tcMonoExpr expr@(RecordCon con_name rbinds) res_ty -- its RHS is simply an error, so it doesn't impose any type constraints -- -- All this is done in STEP 4 below. +-- +-- Note about GADTs +-- ~~~~~~~~~~~~~~~~ +-- For record update we require that every constructor involved in the +-- update (i.e. that has all the specified fields) is "vanilla". I +-- don't know how to do the update otherwise. -tcMonoExpr expr@(RecordUpd record_expr rbinds) res_ty - = tcAddErrCtxt (recordUpdCtxt expr) $ - -- STEP 0 +tcExpr expr@(RecordUpd record_expr rbinds _ _) res_ty + = -- STEP 0 -- Check that the field names are really field names - ASSERT( not (null rbinds) ) + ASSERT( notNull rbinds ) let - field_names = [field_name | (field_name, _, _) <- rbinds] + field_names = map fst rbinds in - mapNF_Tc tcLookupGlobal_maybe field_names `thenNF_Tc` \ maybe_sel_ids -> + mappM (tcLookupGlobalId.unLoc) field_names `thenM` \ sel_ids -> + -- The renamer has already checked that they + -- are all in scope let - bad_guys = [ addErrTc (notSelector field_name) - | (field_name, maybe_sel_id) <- field_names `zip` maybe_sel_ids, - case maybe_sel_id of - Just (AnId sel_id) -> not (isRecordSelector sel_id) - other -> True + bad_guys = [ setSrcSpan loc $ addErrTc (notSelector field_name) + | (L loc field_name, sel_id) <- field_names `zip` sel_ids, + not (isRecordSelector sel_id) -- Excludes class ops ] in - checkTcM (null bad_guys) (listNF_Tc bad_guys `thenNF_Tc_` failTc) `thenTc_` + checkM (null bad_guys) (sequenceM bad_guys `thenM_` failM) `thenM_` -- STEP 1 -- Figure out the tycon and data cons from the first field name let -- It's OK to use the non-tc splitters here (for a selector) - (Just (AnId sel_id) : _) = maybe_sel_ids - (_, _, tau) = tcSplitSigmaTy (idType sel_id) -- Selectors can be overloaded - -- when the data type has a context - data_ty = tcFunArgTy tau -- Must succeed since sel_id is a selector - tycon = tcTyConAppTyCon data_ty - data_cons = tyConDataCons tycon - (con_tyvars, _, _, _, _, _) = dataConSig (head data_cons) + upd_field_lbls = recBindFields rbinds + sel_id : _ = sel_ids + (tycon, _) = recordSelectorFieldLabel sel_id -- We've failed already if + data_cons = tyConDataCons tycon -- it's not a field label + relevant_cons = filter is_relevant data_cons + is_relevant con = all (`elem` dataConFieldLabels con) upd_field_lbls in - tcInstTyVars con_tyvars `thenNF_Tc` \ (_, result_inst_tys, _) -> -- STEP 2 -- Check that at least one constructor has all the named fields -- i.e. has an empty set of bad fields returned by badFields - checkTc (any (null . badFields rbinds) data_cons) - (badFieldsUpd rbinds) `thenTc_` + checkTc (not (null relevant_cons)) + (badFieldsUpd rbinds) `thenM_` - -- STEP 3 - -- Typecheck the update bindings. - -- (Do this after checking for bad fields in case there's a field that - -- doesn't match the constructor.) - let - result_record_ty = mkTyConApp tycon result_inst_tys - in - unifyTauTy res_ty result_record_ty `thenTc_` - tcRecordBinds tycon result_inst_tys rbinds `thenTc` \ (rbinds', rbinds_lie) -> + -- Check that all relevant data cons are vanilla. Doing record updates on + -- GADTs and/or existentials is more than my tiny brain can cope with today + checkTc (all isVanillaDataCon relevant_cons) + (nonVanillaUpd tycon) `thenM_` -- STEP 4 -- Use the un-updated fields to find a vector of booleans saying @@ -469,257 +437,437 @@ tcMonoExpr expr@(RecordUpd record_expr rbinds) res_ty -- WARNING: this code assumes that all data_cons in a common tycon -- have FieldLabels abstracted over the same tyvars. let - upd_field_lbls = [recordSelectorFieldLabel sel_id | (sel_id, _, _) <- rbinds'] - con_field_lbls_s = map dataConFieldLabels data_cons - -- A constructor is only relevant to this process if - -- it contains all the fields that are being updated - relevant_field_lbls_s = filter is_relevant con_field_lbls_s - is_relevant con_field_lbls = all (`elem` con_field_lbls) upd_field_lbls - - non_upd_field_lbls = concat relevant_field_lbls_s `minusList` upd_field_lbls - common_tyvars = tyVarsOfTypes (map fieldLabelType non_upd_field_lbls) + -- it contains *all* the fields that are being updated + con1 = head relevant_cons -- A representative constructor + con1_tyvars = dataConTyVars con1 + con1_flds = dataConFieldLabels con1 + con1_arg_tys = dataConOrigArgTys con1 + common_tyvars = exactTyVarsOfTypes [ty | (fld,ty) <- con1_flds `zip` con1_arg_tys + , not (fld `elem` upd_field_lbls) ] + + is_common_tv tv = tv `elemVarSet` common_tyvars + + mk_inst_ty tv result_inst_ty + | is_common_tv tv = returnM result_inst_ty -- Same as result type + | otherwise = newFlexiTyVarTy (tyVarKind tv) -- Fresh type, of correct kind + in + tcInstTyVars con1_tyvars `thenM` \ (_, result_inst_tys, inst_env) -> + zipWithM mk_inst_ty con1_tyvars result_inst_tys `thenM` \ inst_tys -> - mk_inst_ty (tyvar, result_inst_ty) - | tyvar `elemVarSet` common_tyvars = returnNF_Tc result_inst_ty -- Same as result type - | otherwise = newTyVarTy liftedTypeKind -- Fresh type + -- STEP 3 + -- Typecheck the update bindings. + -- (Do this after checking for bad fields in case there's a field that + -- doesn't match the constructor.) + let + result_record_ty = mkTyConApp tycon result_inst_tys + con1_arg_tys' = map (substTy inst_env) con1_arg_tys in - mapNF_Tc mk_inst_ty (zip con_tyvars result_inst_tys) `thenNF_Tc` \ inst_tys -> + tcSubExp result_record_ty res_ty `thenM` \ co_fn -> + tcRecordBinds con1 con1_arg_tys' rbinds `thenM` \ rbinds' -> -- STEP 5 -- Typecheck the expression to be updated let - record_ty = mkTyConApp tycon inst_tys + record_ty = ASSERT( length inst_tys == tyConArity tycon ) + mkTyConApp tycon inst_tys + -- This is one place where the isVanilla check is important + -- So that inst_tys matches the tycon in - tcMonoExpr record_expr record_ty `thenTc` \ (record_expr', record_lie) -> + tcMonoExpr record_expr record_ty `thenM` \ record_expr' -> -- STEP 6 -- Figure out the LIE we need. We have to generate some -- dictionaries for the data type context, since we are going to - -- do some construction. + -- do pattern matching over the data cons. -- - -- What dictionaries do we need? For the moment we assume that all - -- data constructors have the same context, and grab it from the first - -- constructor. If they have varying contexts then we'd have to - -- union the ones that could participate in the update. + -- What dictionaries do we need? + -- We just take the context of the first data constructor + -- This isn't right, but I just can't bear to union up all the relevant ones let - (tyvars, theta, _, _, _, _) = dataConSig (head data_cons) - inst_env = mkTopTyVarSubst tyvars result_inst_tys - theta' = substTheta inst_env theta + theta' = substTheta inst_env (tyConStupidTheta tycon) in - newDicts RecordUpdOrigin theta' `thenNF_Tc` \ dicts -> + newDicts RecordUpdOrigin theta' `thenM` \ dicts -> + extendLIEs dicts `thenM_` -- Phew! - returnTc (RecordUpdOut record_expr' record_ty result_record_ty (map instToId dicts) rbinds', - mkLIE dicts `plusLIE` record_lie `plusLIE` rbinds_lie) - -tcMonoExpr (ArithSeqIn seq@(From expr)) res_ty - = unifyListTy res_ty `thenTc` \ elt_ty -> - tcMonoExpr expr elt_ty `thenTc` \ (expr', lie1) -> - - tcLookupGlobalId enumFromName `thenNF_Tc` \ sel_id -> - newMethod (ArithSeqOrigin seq) - sel_id [elt_ty] `thenNF_Tc` \ enum_from -> - - returnTc (ArithSeqOut (HsVar (instToId enum_from)) (From expr'), - lie1 `plusLIE` unitLIE enum_from) - -tcMonoExpr in_expr@(ArithSeqIn seq@(FromThen expr1 expr2)) res_ty - = tcAddErrCtxt (arithSeqCtxt in_expr) $ - unifyListTy res_ty `thenTc` \ elt_ty -> - tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) -> - tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) -> - tcLookupGlobalId enumFromThenName `thenNF_Tc` \ sel_id -> - newMethod (ArithSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ enum_from_then -> - - returnTc (ArithSeqOut (HsVar (instToId enum_from_then)) - (FromThen expr1' expr2'), - lie1 `plusLIE` lie2 `plusLIE` unitLIE enum_from_then) - -tcMonoExpr in_expr@(ArithSeqIn seq@(FromTo expr1 expr2)) res_ty - = tcAddErrCtxt (arithSeqCtxt in_expr) $ - unifyListTy res_ty `thenTc` \ elt_ty -> - tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) -> - tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) -> - tcLookupGlobalId enumFromToName `thenNF_Tc` \ sel_id -> - newMethod (ArithSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ enum_from_to -> - - returnTc (ArithSeqOut (HsVar (instToId enum_from_to)) - (FromTo expr1' expr2'), - lie1 `plusLIE` lie2 `plusLIE` unitLIE enum_from_to) - -tcMonoExpr in_expr@(ArithSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty - = tcAddErrCtxt (arithSeqCtxt in_expr) $ - unifyListTy res_ty `thenTc` \ elt_ty -> - tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) -> - tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) -> - tcMonoExpr expr3 elt_ty `thenTc` \ (expr3',lie3) -> - tcLookupGlobalId enumFromThenToName `thenNF_Tc` \ sel_id -> - newMethod (ArithSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ eft -> - - returnTc (ArithSeqOut (HsVar (instToId eft)) - (FromThenTo expr1' expr2' expr3'), - lie1 `plusLIE` lie2 `plusLIE` lie3 `plusLIE` unitLIE eft) - -tcMonoExpr in_expr@(PArrSeqIn seq@(FromTo expr1 expr2)) res_ty - = tcAddErrCtxt (parrSeqCtxt in_expr) $ - unifyPArrTy res_ty `thenTc` \ elt_ty -> - tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) -> - tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) -> - tcLookupGlobalId enumFromToPName `thenNF_Tc` \ sel_id -> - newMethod (PArrSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ enum_from_to -> - - returnTc (PArrSeqOut (HsVar (instToId enum_from_to)) - (FromTo expr1' expr2'), - lie1 `plusLIE` lie2 `plusLIE` unitLIE enum_from_to) - -tcMonoExpr in_expr@(PArrSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty - = tcAddErrCtxt (parrSeqCtxt in_expr) $ - unifyPArrTy res_ty `thenTc` \ elt_ty -> - tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) -> - tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) -> - tcMonoExpr expr3 elt_ty `thenTc` \ (expr3',lie3) -> - tcLookupGlobalId enumFromThenToPName `thenNF_Tc` \ sel_id -> - newMethod (PArrSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ eft -> - - returnTc (PArrSeqOut (HsVar (instToId eft)) - (FromThenTo expr1' expr2' expr3'), - lie1 `plusLIE` lie2 `plusLIE` lie3 `plusLIE` unitLIE eft) - -tcMonoExpr (PArrSeqIn _) _ - = panic "TcExpr.tcMonoExpr: Infinite parallel array!" - -- the parser shouldn't have generated it and the renamer shouldn't have - -- let it through + returnM (mkHsCoerce co_fn (RecordUpd record_expr' rbinds' record_ty result_record_ty)) \end{code} + %************************************************************************ %* * -\subsection{Implicit Parameter bindings} + Arithmetic sequences e.g. [a,b..] + and their parallel-array counterparts e.g. [: a,b.. :] + %* * %************************************************************************ \begin{code} -tcMonoExpr (HsWith expr binds) res_ty - = tcMonoExpr expr res_ty `thenTc` \ (expr', expr_lie) -> - mapAndUnzip3Tc tcIPBind binds `thenTc` \ (avail_ips, binds', bind_lies) -> - - -- If the binding binds ?x = E, we must now - -- discharge any ?x constraints in expr_lie - tcSimplifyIPs avail_ips expr_lie `thenTc` \ (expr_lie', dict_binds) -> - let - expr'' = HsLet (mkMonoBind dict_binds [] Recursive) expr' - in - returnTc (HsWith expr'' binds', expr_lie' `plusLIE` plusLIEs bind_lies) - -tcIPBind (ip, expr) - = newTyVarTy openTypeKind `thenTc` \ ty -> - tcGetSrcLoc `thenTc` \ loc -> - newIPDict (IPBind ip) ip ty `thenNF_Tc` \ (ip', ip_inst) -> - tcMonoExpr expr ty `thenTc` \ (expr', lie) -> - returnTc (ip_inst, (ip', expr'), lie) +tcExpr (ArithSeq _ seq@(From expr)) res_ty + = do { elt_ty <- boxySplitListTy res_ty + ; expr' <- tcPolyExpr expr elt_ty + ; enum_from <- newMethodFromName (ArithSeqOrigin seq) + elt_ty enumFromName + ; return (ArithSeq (HsVar enum_from) (From expr')) } + +tcExpr in_expr@(ArithSeq _ seq@(FromThen expr1 expr2)) res_ty + = do { elt_ty <- boxySplitListTy res_ty + ; expr1' <- tcPolyExpr expr1 elt_ty + ; expr2' <- tcPolyExpr expr2 elt_ty + ; enum_from_then <- newMethodFromName (ArithSeqOrigin seq) + elt_ty enumFromThenName + ; return (ArithSeq (HsVar enum_from_then) (FromThen expr1' expr2')) } + + +tcExpr in_expr@(ArithSeq _ seq@(FromTo expr1 expr2)) res_ty + = do { elt_ty <- boxySplitListTy res_ty + ; expr1' <- tcPolyExpr expr1 elt_ty + ; expr2' <- tcPolyExpr expr2 elt_ty + ; enum_from_to <- newMethodFromName (ArithSeqOrigin seq) + elt_ty enumFromToName + ; return (ArithSeq (HsVar enum_from_to) (FromTo expr1' expr2')) } + +tcExpr in_expr@(ArithSeq _ seq@(FromThenTo expr1 expr2 expr3)) res_ty + = do { elt_ty <- boxySplitListTy res_ty + ; expr1' <- tcPolyExpr expr1 elt_ty + ; expr2' <- tcPolyExpr expr2 elt_ty + ; expr3' <- tcPolyExpr expr3 elt_ty + ; eft <- newMethodFromName (ArithSeqOrigin seq) + elt_ty enumFromThenToName + ; return (ArithSeq (HsVar eft) (FromThenTo expr1' expr2' expr3')) } + +tcExpr in_expr@(PArrSeq _ seq@(FromTo expr1 expr2)) res_ty + = do { [elt_ty] <- boxySplitTyConApp parrTyCon res_ty + ; expr1' <- tcPolyExpr expr1 elt_ty + ; expr2' <- tcPolyExpr expr2 elt_ty + ; enum_from_to <- newMethodFromName (PArrSeqOrigin seq) + elt_ty enumFromToPName + ; return (PArrSeq (HsVar enum_from_to) (FromTo expr1' expr2')) } + +tcExpr in_expr@(PArrSeq _ seq@(FromThenTo expr1 expr2 expr3)) res_ty + = do { [elt_ty] <- boxySplitTyConApp parrTyCon res_ty + ; expr1' <- tcPolyExpr expr1 elt_ty + ; expr2' <- tcPolyExpr expr2 elt_ty + ; expr3' <- tcPolyExpr expr3 elt_ty + ; eft <- newMethodFromName (PArrSeqOrigin seq) + elt_ty enumFromThenToPName + ; return (PArrSeq (HsVar eft) (FromThenTo expr1' expr2' expr3')) } + +tcExpr (PArrSeq _ _) _ + = panic "TcExpr.tcMonoExpr: Infinite parallel array!" + -- the parser shouldn't have generated it and the renamer shouldn't have + -- let it through \end{code} + %************************************************************************ %* * -\subsection{@tcApp@ typchecks an application} + Template Haskell %* * %************************************************************************ \begin{code} +#ifdef GHCI /* Only if bootstrapped */ + -- Rename excludes these cases otherwise +tcExpr (HsSpliceE splice) res_ty = tcSpliceExpr splice res_ty +tcExpr (HsBracket brack) res_ty = do { e <- tcBracket brack res_ty + ; return (unLoc e) } +#endif /* GHCI */ +\end{code} -tcApp :: RenamedHsExpr -> [RenamedHsExpr] -- Function and args - -> TcType -- Expected result type of application - -> TcM (TcExpr, LIE) -- Translated fun and args -tcApp (HsApp e1 e2) args res_ty - = tcApp e1 (e2:args) res_ty -- Accumulate the arguments +%************************************************************************ +%* * + Catch-all +%* * +%************************************************************************ -tcApp fun args res_ty - = -- First type-check the function - tcExpr_id fun `thenTc` \ (fun', lie_fun, fun_ty) -> +\begin{code} +tcExpr other _ = pprPanic "tcMonoExpr" (ppr other) +\end{code} - tcAddErrCtxt (wrongArgsCtxt "too many" fun args) ( - split_fun_ty fun_ty (length args) - ) `thenTc` \ (expected_arg_tys, actual_result_ty) -> - -- Now typecheck the args - mapAndUnzipTc (tcArg fun) - (zip3 args expected_arg_tys [1..]) `thenTc` \ (args', lie_args_s) -> +%************************************************************************ +%* * + Applications +%* * +%************************************************************************ - -- Unify with expected result after type-checking the args - -- so that the info from args percolates to actual_result_ty. - -- This is when we might detect a too-few args situation. - -- (One can think of cases when the opposite order would give - -- a better error message.) - tcAddErrCtxtM (checkArgsCtxt fun args res_ty actual_result_ty) - (tcSub res_ty actual_result_ty) `thenTc` \ (co_fn, lie_res) -> +\begin{code} +--------------------------- +tcApp :: HsExpr Name -- Function + -> Arity -- Number of args reqd + -> ([BoxySigmaType] -> TcM arg_results) -- Argument type-checker + -> BoxyRhoType -- Result type + -> TcM (HsExpr TcId, arg_results) + +-- (tcFun fun n_args arg_checker res_ty) +-- The argument type checker, arg_checker, will be passed exactly n_args types + +tcApp (HsVar fun_name) n_args arg_checker res_ty + = tcIdApp fun_name n_args arg_checker res_ty + +tcApp fun n_args arg_checker res_ty -- The vanilla case (rula APP) + = do { arg_boxes <- newBoxyTyVars (replicate n_args argTypeKind) + ; fun' <- tcExpr fun (mkFunTys (mkTyVarTys arg_boxes) res_ty) + ; arg_tys' <- mapM readFilledBox arg_boxes + ; args' <- arg_checker arg_tys' + ; return (fun', args') } + +--------------------------- +tcIdApp :: Name -- Function + -> Arity -- Number of args reqd + -> ([BoxySigmaType] -> TcM arg_results) -- Argument type-checker + -- The arg-checker guarantees to fill all boxes in the arg types + -> BoxyRhoType -- Result type + -> TcM (HsExpr TcId, arg_results) + +-- Call (f e1 ... en) :: res_ty +-- Type f :: forall a b c. theta => fa_1 -> ... -> fa_k -> fres +-- (where k <= n; fres has the rest) +-- NB: if k < n then the function doesn't have enough args, and +-- presumably fres is a type variable that we are going to +-- instantiate with a function type +-- +-- Then fres <= bx_(k+1) -> ... -> bx_n -> res_ty + +tcIdApp fun_name n_args arg_checker res_ty + = do { fun_id <- lookupFun (OccurrenceOf fun_name) fun_name + + -- Split up the function type + ; let (tv_theta_prs, rho) = tcMultiSplitSigmaTy (idType fun_id) + (fun_arg_tys, fun_res_ty) = tcSplitFunTysN rho n_args + + qtvs = concatMap fst tv_theta_prs -- Quantified tyvars + arg_qtvs = exactTyVarsOfTypes fun_arg_tys + res_qtvs = exactTyVarsOfType fun_res_ty + -- NB: exactTyVarsOfType. See Note [Silly type synonyms in smart-app] + tau_qtvs = arg_qtvs `unionVarSet` res_qtvs + k = length fun_arg_tys -- k <= n_args + n_missing_args = n_args - k -- Always >= 0 + + -- Match the result type of the function with the + -- result type of the context, to get an inital substitution + ; extra_arg_boxes <- newBoxyTyVars (replicate n_missing_args argTypeKind) + ; let extra_arg_tys' = mkTyVarTys extra_arg_boxes + res_ty' = mkFunTys extra_arg_tys' res_ty + subst = boxySubMatchType arg_qtvs fun_res_ty res_ty' + -- Only bind arg_qtvs, since only they will be + -- *definitely* be filled in by arg_checker + -- E.g. error :: forall a. String -> a + -- (error "foo") :: bx5 + -- Don't make subst [a |-> bx5] + -- because then the result subsumption becomes + -- bx5 ~ bx5 + -- and the unifer doesn't expect the + -- same box on both sides + inst_qtv tv | Just boxy_ty <- lookupTyVar subst tv = return boxy_ty + | tv `elemVarSet` tau_qtvs = do { tv' <- tcInstBoxyTyVar tv + ; return (mkTyVarTy tv') } + | otherwise = do { tv' <- tcInstTyVar tv + ; return (mkTyVarTy tv') } + -- The 'otherwise' case handles type variables that are + -- mentioned only in the constraints, not in argument or + -- result types. We'll make them tau-types + + ; qtys' <- mapM inst_qtv qtvs + ; let arg_subst = zipOpenTvSubst qtvs qtys' + fun_arg_tys' = substTys arg_subst fun_arg_tys + + -- Typecheck the arguments! + -- Doing so will fill arg_qtvs and extra_arg_tys' + ; args' <- arg_checker (fun_arg_tys' ++ extra_arg_tys') + + ; let strip qtv qty' | qtv `elemVarSet` arg_qtvs = stripBoxyType qty' + | otherwise = return qty' + ; qtys'' <- zipWithM strip qtvs qtys' + ; extra_arg_tys'' <- mapM readFilledBox extra_arg_boxes + + -- Result subsumption + ; let res_subst = zipOpenTvSubst qtvs qtys'' + fun_res_ty'' = substTy res_subst fun_res_ty + res_ty'' = mkFunTys extra_arg_tys'' res_ty + ; co_fn <- addErrCtxtM (checkFunResCtxt fun_name res_ty fun_res_ty'') $ + tcSubExp fun_res_ty'' res_ty'' + + -- And pack up the results + -- By applying the coercion just to the *function* we can make + -- tcFun work nicely for OpApp and Sections too + ; fun' <- instFun fun_id qtvs qtys'' tv_theta_prs + ; co_fn' <- wrapFunResCoercion fun_arg_tys' co_fn + ; return (mkHsCoerce co_fn' fun', args') } +\end{code} - returnTc (co_fn <$> foldl HsApp fun' args', - lie_res `plusLIE` lie_fun `plusLIE` plusLIEs lie_args_s) +Note [Silly type synonyms in smart-app] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +When we call sripBoxyType, all of the boxes should be filled +in. But we need to be careful about type synonyms: + type T a = Int + f :: T a -> Int + ...(f x)... +In the call (f x) we'll typecheck x, expecting it to have type +(T box). Usually that would fill in the box, but in this case not; +because 'a' is discarded by the silly type synonym T. So we must +use exactTyVarsOfType to figure out which type variables are free +in the argument type. +\begin{code} +-- tcId is a specialisation of tcIdApp when there are no arguments +-- tcId f ty = do { (res, _) <- tcIdApp f [] (\[] -> return ()) ty +-- ; return res } + +tcId :: InstOrigin + -> Name -- Function + -> BoxyRhoType -- Result type + -> TcM (HsExpr TcId) +tcId orig fun_name res_ty + = do { traceTc (text "tcId" <+> ppr fun_name <+> ppr res_ty) + ; fun_id <- lookupFun orig fun_name + + -- Split up the function type + ; let (tv_theta_prs, fun_tau) = tcMultiSplitSigmaTy (idType fun_id) + qtvs = concatMap fst tv_theta_prs -- Quantified tyvars + tau_qtvs = exactTyVarsOfType fun_tau -- Mentiond in the tau part + inst_qtv tv | tv `elemVarSet` tau_qtvs = do { tv' <- tcInstBoxyTyVar tv + ; return (mkTyVarTy tv') } + | otherwise = do { tv' <- tcInstTyVar tv + ; return (mkTyVarTy tv') } + + -- Do the subsumption check wrt the result type + ; qtv_tys <- mapM inst_qtv qtvs + ; let res_subst = zipTopTvSubst qtvs qtv_tys + fun_tau' = substTy res_subst fun_tau + + ; co_fn <- addErrCtxtM (checkFunResCtxt fun_name res_ty fun_tau') $ + tcSubExp fun_tau' res_ty + + -- And pack up the results + ; fun' <- instFun fun_id qtvs qtv_tys tv_theta_prs + ; return (mkHsCoerce co_fn fun') } + +-- Note [Push result type in] +-- +-- Unify with expected result before (was: after) type-checking the args +-- so that the info from res_ty (was: args) percolates to args (was actual_res_ty). +-- This is when we might detect a too-few args situation. +-- (One can think of cases when the opposite order would give +-- a better error message.) +-- [March 2003: I'm experimenting with putting this first. Here's an +-- example where it actually makes a real difference +-- class C t a b | t a -> b +-- instance C Char a Bool +-- +-- data P t a = forall b. (C t a b) => MkP b +-- data Q t = MkQ (forall a. P t a) --- If an error happens we try to figure out whether the --- function has been given too many or too few arguments, --- and say so -checkArgsCtxt fun args expected_res_ty actual_res_ty tidy_env - = zonkTcType expected_res_ty `thenNF_Tc` \ exp_ty' -> - zonkTcType actual_res_ty `thenNF_Tc` \ act_ty' -> - let - (env1, exp_ty'') = tidyOpenType tidy_env exp_ty' - (env2, act_ty'') = tidyOpenType env1 act_ty' - (exp_args, _) = tcSplitFunTys exp_ty'' - (act_args, _) = tcSplitFunTys act_ty'' +-- f1, f2 :: Q Char; +-- f1 = MkQ (MkP True) +-- f2 = MkQ (MkP True :: forall a. P Char a) +-- +-- With the change, f1 will type-check, because the 'Char' info from +-- the signature is propagated into MkQ's argument. With the check +-- in the other order, the extra signature in f2 is reqd.] + +--------------------------- +tcSyntaxOp :: InstOrigin -> HsExpr Name -> TcType -> TcM (HsExpr TcId) +-- Typecheck a syntax operator, checking that it has the specified type +-- The operator is always a variable at this stage (i.e. renamer output) +tcSyntaxOp orig (HsVar op) ty = tcId orig op ty +tcSyntaxOp orig other ty = pprPanic "tcSyntaxOp" (ppr other) + +--------------------------- +instFun :: TcId + -> [TyVar] -> [TcType] -- Quantified type variables and + -- their instantiating types + -> [([TyVar], ThetaType)] -- Stuff to instantiate + -> TcM (HsExpr TcId) +instFun fun_id qtvs qtv_tys [] + = return (HsVar fun_id) -- Common short cut + +instFun fun_id qtvs qtv_tys tv_theta_prs + = do { let subst = zipOpenTvSubst qtvs qtv_tys + ty_theta_prs' = map subst_pr tv_theta_prs + subst_pr (tvs, theta) = (map (substTyVar subst) tvs, + substTheta subst theta) + + -- The ty_theta_prs' is always non-empty + ((tys1',theta1') : further_prs') = ty_theta_prs' + + -- First, chuck in the constraints from + -- the "stupid theta" of a data constructor (sigh) + ; case isDataConId_maybe fun_id of + Just con -> tcInstStupidTheta con tys1' + Nothing -> return () + + ; if want_method_inst theta1' + then do { meth_id <- newMethodWithGivenTy orig fun_id tys1' + -- See Note [Multiple instantiation] + ; go (HsVar meth_id) further_prs' } + else go (HsVar fun_id) ty_theta_prs' + } + where + orig = OccurrenceOf (idName fun_id) - len_act_args = length act_args - len_exp_args = length exp_args + go fun [] = return fun - message | len_exp_args < len_act_args = wrongArgsCtxt "too few" fun args - | len_exp_args > len_act_args = wrongArgsCtxt "too many" fun args - | otherwise = appCtxt fun args - in - returnNF_Tc (env2, message) + go fun ((tys, theta) : prs) + = do { dicts <- newDicts orig theta + ; extendLIEs dicts + ; let the_app = unLoc $ mkHsDictApp (mkHsTyApp (noLoc fun) tys) + (map instToId dicts) + ; go the_app prs } + -- Hack Alert (want_method_inst)! + -- See Note [No method sharing] + -- If f :: (%x :: T) => Int -> Int + -- Then if we have two separate calls, (f 3, f 4), we cannot + -- make a method constraint that then gets shared, thus: + -- let m = f %x in (m 3, m 4) + -- because that loses the linearity of the constraint. + -- The simplest thing to do is never to construct a method constraint + -- in the first place that has a linear implicit parameter in it. + want_method_inst theta = not (null theta) -- Overloaded + && not (any isLinearPred theta) -- Not linear + && not opt_NoMethodSharing + -- See Note [No method sharing] below +\end{code} -split_fun_ty :: TcType -- The type of the function - -> Int -- Number of arguments - -> TcM ([TcType], -- Function argument types - TcType) -- Function result types +Note [Multiple instantiation] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +We are careful never to make a MethodInst that has, as its meth_id, another MethodInst. +For example, consider + f :: forall a. Eq a => forall b. Ord b => a -> b +At a call to f, at say [Int, Bool], it's tempting to translate the call to -split_fun_ty fun_ty 0 - = returnTc ([], fun_ty) + f_m1 + where + f_m1 :: forall b. Ord b => Int -> b + f_m1 = f Int dEqInt -split_fun_ty fun_ty n - = -- Expect the function to have type A->B - unifyFunTy fun_ty `thenTc` \ (arg_ty, res_ty) -> - split_fun_ty res_ty (n-1) `thenTc` \ (arg_tys, final_res_ty) -> - returnTc (arg_ty:arg_tys, final_res_ty) -\end{code} + f_m2 :: Int -> Bool + f_m2 = f_m1 Bool dOrdBool -\begin{code} -tcArg :: RenamedHsExpr -- The function (for error messages) - -> (RenamedHsExpr, TcSigmaType, Int) -- Actual argument and expected arg type - -> TcM (TcExpr, LIE) -- Resulting argument and LIE +But notice that f_m2 has f_m1 as its meth_id. Now the danger is that if we do +a tcSimplCheck with a Given f_mx :: f Int dEqInt, we may make a binding + f_m1 = f_mx +But it's entirely possible that f_m2 will continue to float out, because it +mentions no type variables. Result, f_m1 isn't in scope. -tcArg the_fun (arg, expected_arg_ty, arg_no) - = tcAddErrCtxt (funAppCtxt the_fun arg arg_no) $ - tcExpr arg expected_arg_ty -\end{code} +Here's a concrete example that does this (test tc200): + class C a where + f :: Eq b => b -> a -> Int + baz :: Eq a => Int -> a -> Int -%************************************************************************ -%* * -\subsection{@tcId@ typchecks an identifier occurrence} -%* * -%************************************************************************ + instance C Int where + baz = f -tcId instantiates an occurrence of an Id. -The instantiate_it loop runs round instantiating the Id. -It has to be a loop because we are now prepared to entertain -types like - f:: forall a. Eq a => forall b. Baz b => tau -We want to instantiate this to - f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)} +Current solution: only do the "method sharing" thing for the first type/dict +application, not for the iterated ones. A horribly subtle point. +Note [No method sharing] +~~~~~~~~~~~~~~~~~~~~~~~~ The -fno-method-sharing flag controls what happens so far as the LIE is concerned. The default case is that for an overloaded function we generate a "method" Id, and add the Method Inst to the LIE. So you get @@ -735,132 +883,167 @@ This gets a bit less sharing, but b) perhaps fewer separated lambdas \begin{code} -tcId :: Name -> NF_TcM (TcExpr, LIE, TcType) -tcId name -- Look up the Id and instantiate its type - = tcLookupId name `thenNF_Tc` \ id -> - loop (OccurrenceOf id) (HsVar id) emptyLIE (idType id) - where - loop orig (HsVar fun_id) lie fun_ty - | want_method_inst fun_ty - = tcInstType fun_ty `thenNF_Tc` \ (tyvars, theta, tau) -> - newMethodWithGivenTy orig fun_id - (mkTyVarTys tyvars) theta tau `thenNF_Tc` \ meth -> - loop orig (HsVar (instToId meth)) - (unitLIE meth `plusLIE` lie) tau - - loop orig fun lie fun_ty - | isSigmaTy fun_ty - = tcInstCall orig fun_ty `thenNF_Tc` \ (inst_fn, inst_lie, tau) -> - loop orig (inst_fn fun) (inst_lie `plusLIE` lie) tau - - | otherwise - = returnNF_Tc (fun, lie, fun_ty) - - want_method_inst fun_ty - | opt_NoMethodSharing = False - | otherwise = case tcSplitSigmaTy fun_ty of - (_,[],_) -> False -- Not overloaded - (_,theta,_) -> not (any isLinearPred theta) - -- This is a slight hack. - -- If f :: (%x :: T) => Int -> Int - -- Then if we have two separate calls, (f 3, f 4), we cannot - -- make a method constraint that then gets shared, thus: - -- let m = f %x in (m 3, m 4) - -- because that loses the linearity of the constraint. - -- The simplest thing to do is never to construct a method constraint - -- in the first place that has a linear implicit parameter in it. -\end{code} +tcArgs :: LHsExpr Name -- The function (for error messages) + -> [LHsExpr Name] -> [TcSigmaType] -- Actual arguments and expected arg types + -> TcM [LHsExpr TcId] -- Resulting args -Typecheck expression which in most cases will be an Id. -The expression can return a higher-ranked type, such as - (forall a. a->a) -> Int -so we must create a HoleTyVarTy to pass in as the expected tyvar. +tcArgs fun args expected_arg_tys + = mapM (tcArg fun) (zip3 args expected_arg_tys [1..]) -\begin{code} -tcExpr_id :: RenamedHsExpr -> TcM (TcExpr, LIE, TcType) -tcExpr_id (HsVar name) = tcId name -tcExpr_id expr = newHoleTyVarTy `thenNF_Tc` \ id_ty -> - tcMonoExpr expr id_ty `thenTc` \ (expr', lie_id) -> - returnTc (expr', lie_id, id_ty) +tcArg :: LHsExpr Name -- The function (for error messages) + -> (LHsExpr Name, BoxySigmaType, Int) -- Actual argument and expected arg type + -> TcM (LHsExpr TcId) -- Resulting argument +tcArg fun (arg, ty, arg_no) = addErrCtxt (funAppCtxt fun arg arg_no) $ + tcPolyExprNC arg ty + + +---------------- +-- If an error happens we try to figure out whether the +-- function has been given too many or too few arguments, +-- and say so. +checkFunResCtxt fun expected_res_ty actual_res_ty tidy_env + = zonkTcType expected_res_ty `thenM` \ exp_ty' -> + zonkTcType actual_res_ty `thenM` \ act_ty' -> + let + (env1, exp_ty'') = tidyOpenType tidy_env exp_ty' + (env2, act_ty'') = tidyOpenType env1 act_ty' + (exp_args, _) = tcSplitFunTys exp_ty'' + (act_args, _) = tcSplitFunTys act_ty'' + + len_act_args = length act_args + len_exp_args = length exp_args + + message | len_exp_args < len_act_args = wrongArgsCtxt "too few" fun + | len_exp_args > len_act_args = wrongArgsCtxt "too many" fun + | otherwise = empty + in + returnM (env2, message) \end{code} %************************************************************************ %* * -\subsection{@tcDoStmts@ typechecks a {\em list} of do statements} +\subsection{@tcId@ typchecks an identifier occurrence} %* * %************************************************************************ \begin{code} --- I don't like this lumping together of do expression and list/array --- comprehensions; creating the monad instances is entirely pointless in the --- latter case; I'll leave the list case as it is for the moment, but handle --- arrays extra (would be better to handle arrays and lists together, though) --- -=chak --- -tcDoStmts PArrComp stmts src_loc res_ty - = - ASSERT( not (null stmts) ) - tcAddSrcLoc src_loc $ - - unifyPArrTy res_ty `thenTc` \elt_ty -> - let tc_ty = mkTyConTy parrTyCon - m_ty = (mkPArrTy, elt_ty) - in - tcStmts (DoCtxt PArrComp) m_ty stmts `thenTc` \(stmts', stmts_lie) -> - returnTc (HsDoOut PArrComp stmts' - undefined undefined undefined -- don't touch! - res_ty src_loc, - stmts_lie) - -tcDoStmts do_or_lc stmts src_loc res_ty - = -- get the Monad and MonadZero classes - -- create type consisting of a fresh monad tyvar - ASSERT( not (null stmts) ) - tcAddSrcLoc src_loc $ - - -- If it's a comprehension we're dealing with, - -- force it to be a list comprehension. - -- (as of Haskell 98, monad comprehensions are no more.) - -- Similarily, array comprehensions must involve parallel arrays types - -- -=chak - (case do_or_lc of - ListComp -> unifyListTy res_ty `thenTc` \ elt_ty -> - returnNF_Tc (mkTyConTy listTyCon, (mkListTy, elt_ty)) - - PArrComp -> panic "TcExpr.tcDoStmts: How did we get here?!?" - - _ -> newTyVarTy (mkArrowKind liftedTypeKind liftedTypeKind) `thenNF_Tc` \ m_ty -> - newTyVarTy liftedTypeKind `thenNF_Tc` \ elt_ty -> - unifyTauTy res_ty (mkAppTy m_ty elt_ty) `thenTc_` - returnNF_Tc (m_ty, (mkAppTy m_ty, elt_ty)) - ) `thenNF_Tc` \ (tc_ty, m_ty) -> - - tcStmts (DoCtxt do_or_lc) m_ty stmts `thenTc` \ (stmts', stmts_lie) -> - - -- Build the then and zero methods in case we need them - -- It's important that "then" and "return" appear just once in the final LIE, - -- not only for typechecker efficiency, but also because otherwise during - -- simplification we end up with silly stuff like - -- then = case d of (t,r) -> t - -- then = then - -- where the second "then" sees that it already exists in the "available" stuff. - -- - tcLookupGlobalId returnMName `thenNF_Tc` \ return_sel_id -> - tcLookupGlobalId thenMName `thenNF_Tc` \ then_sel_id -> - tcLookupGlobalId failMName `thenNF_Tc` \ fail_sel_id -> - newMethod DoOrigin return_sel_id [tc_ty] `thenNF_Tc` \ return_inst -> - newMethod DoOrigin then_sel_id [tc_ty] `thenNF_Tc` \ then_inst -> - newMethod DoOrigin fail_sel_id [tc_ty] `thenNF_Tc` \ fail_inst -> - let - monad_lie = mkLIE [return_inst, then_inst, fail_inst] - in - returnTc (HsDoOut do_or_lc stmts' - (instToId return_inst) (instToId then_inst) (instToId fail_inst) - res_ty src_loc, - stmts_lie `plusLIE` monad_lie) +lookupFun :: InstOrigin -> Name -> TcM TcId +lookupFun orig id_name + = do { thing <- tcLookup id_name + ; case thing of + AGlobal (ADataCon con) -> return (dataConWrapId con) + + AGlobal (AnId id) + | isNaughtyRecordSelector id -> failWithTc (naughtyRecordSel id) + | otherwise -> return id + -- A global cannot possibly be ill-staged + -- nor does it need the 'lifting' treatment + +#ifndef GHCI + ATcId id th_level _ -> return id -- Non-TH case +#else + ATcId id th_level _ -> do { use_stage <- getStage -- TH case + ; thLocalId orig id_name id th_level use_stage } +#endif + + other -> failWithTc (ppr other <+> ptext SLIT("used where a value identifer was expected")) + } + +#ifdef GHCI /* GHCI and TH is on */ +-------------------------------------- +-- thLocalId : Check for cross-stage lifting +thLocalId orig id_name id th_bind_lvl (Brack use_lvl ps_var lie_var) + | use_lvl > th_bind_lvl + = thBrackId orig id_name id ps_var lie_var +thLocalId orig id_name id th_bind_lvl use_stage + = do { checkWellStaged (quotes (ppr id)) th_bind_lvl use_stage + ; return id } + +-------------------------------------- +thBrackId orig id_name id ps_var lie_var + | isExternalName id_name + = -- Top-level identifiers in this module, + -- (which have External Names) + -- are just like the imported case: + -- no need for the 'lifting' treatment + -- E.g. this is fine: + -- f x = x + -- g y = [| f 3 |] + -- But we do need to put f into the keep-alive + -- set, because after desugaring the code will + -- only mention f's *name*, not f itself. + do { keepAliveTc id_name; return id } + + | otherwise + = -- Nested identifiers, such as 'x' in + -- E.g. \x -> [| h x |] + -- We must behave as if the reference to x was + -- h $(lift x) + -- We use 'x' itself as the splice proxy, used by + -- the desugarer to stitch it all back together. + -- If 'x' occurs many times we may get many identical + -- bindings of the same splice proxy, but that doesn't + -- matter, although it's a mite untidy. + do { let id_ty = idType id + ; checkTc (isTauTy id_ty) (polySpliceErr id) + -- If x is polymorphic, its occurrence sites might + -- have different instantiations, so we can't use plain + -- 'x' as the splice proxy name. I don't know how to + -- solve this, and it's probably unimportant, so I'm + -- just going to flag an error for now + + ; id_ty' <- zapToMonotype id_ty + -- The id_ty might have an OpenTypeKind, but we + -- can't instantiate the Lift class at that kind, + -- so we zap it to a LiftedTypeKind monotype + -- C.f. the call in TcPat.newLitInst + + ; setLIEVar lie_var $ do + { lift <- newMethodFromName orig id_ty' DsMeta.liftName + -- Put the 'lift' constraint into the right LIE + + -- Update the pending splices + ; ps <- readMutVar ps_var + ; writeMutVar ps_var ((id_name, nlHsApp (nlHsVar lift) (nlHsVar id)) : ps) + + ; return id } } +#endif /* GHCI */ \end{code} +Note [Multiple instantiation] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +We are careful never to make a MethodInst that has, as its meth_id, another MethodInst. +For example, consider + f :: forall a. Eq a => forall b. Ord b => a -> b +At a call to f, at say [Int, Bool], it's tempting to translate the call to + + f_m1 + where + f_m1 :: forall b. Ord b => Int -> b + f_m1 = f Int dEqInt + + f_m2 :: Int -> Bool + f_m2 = f_m1 Bool dOrdBool + +But notice that f_m2 has f_m1 as its meth_id. Now the danger is that if we do +a tcSimplCheck with a Given f_mx :: f Int dEqInt, we may make a binding + f_m1 = f_mx +But it's entirely possible that f_m2 will continue to float out, because it +mentions no type variables. Result, f_m1 isn't in scope. + +Here's a concrete example that does this (test tc200): + + class C a where + f :: Eq b => b -> a -> Int + baz :: Eq a => Int -> a -> Int + + instance C Int where + baz = f + +Current solution: only do the "method sharing" thing for the first type/dict +application, not for the iterated ones. A horribly subtle point. + %************************************************************************ %* * @@ -887,189 +1070,135 @@ This extends OK when the field types are universally quantified. \begin{code} tcRecordBinds - :: TyCon -- Type constructor for the record - -> [TcType] -- Args of this type constructor - -> RenamedRecordBinds - -> TcM (TcRecordBinds, LIE) - -tcRecordBinds tycon ty_args rbinds - = mapAndUnzipTc do_bind rbinds `thenTc` \ (rbinds', lies) -> - returnTc (rbinds', plusLIEs lies) - where - tenv = mkTopTyVarSubst (tyConTyVars tycon) ty_args - - do_bind (field_lbl_name, rhs, pun_flag) - = tcLookupGlobalId field_lbl_name `thenNF_Tc` \ sel_id -> - let - field_lbl = recordSelectorFieldLabel sel_id - field_ty = substTy tenv (fieldLabelType field_lbl) - in - ASSERT( isRecordSelector sel_id ) - -- This lookup and assertion will surely succeed, because - -- we check that the fields are indeed record selectors - -- before calling tcRecordBinds - ASSERT2( fieldLabelTyCon field_lbl == tycon, ppr field_lbl ) - -- The caller of tcRecordBinds has already checked - -- that all the fields come from the same type - - tcExpr rhs field_ty `thenTc` \ (rhs', lie) -> - - returnTc ((sel_id, rhs', pun_flag), lie) - -badFields rbinds data_con - = [field_name | (field_name, _, _) <- rbinds, - not (field_name `elem` field_names) - ] + :: DataCon + -> [TcType] -- Expected type for each field + -> HsRecordBinds Name + -> TcM (HsRecordBinds TcId) + +tcRecordBinds data_con arg_tys rbinds + = do { mb_binds <- mappM do_bind rbinds + ; return (catMaybes mb_binds) } where - field_names = map fieldLabelName (dataConFieldLabels data_con) + flds_w_tys = zipEqual "tcRecordBinds" (dataConFieldLabels data_con) arg_tys + do_bind (L loc field_lbl, rhs) + | Just field_ty <- assocMaybe flds_w_tys field_lbl + = addErrCtxt (fieldCtxt field_lbl) $ + do { rhs' <- tcPolyExprNC rhs field_ty + ; sel_id <- tcLookupId field_lbl + ; ASSERT( isRecordSelector sel_id ) + return (Just (L loc sel_id, rhs')) } + | otherwise + = do { addErrTc (badFieldCon data_con field_lbl) + ; return Nothing } + +checkMissingFields :: DataCon -> HsRecordBinds Name -> TcM () +checkMissingFields data_con rbinds + | null field_labels -- Not declared as a record; + -- But C{} is still valid if no strict fields + = if any isMarkedStrict field_strs then + -- Illegal if any arg is strict + addErrTc (missingStrictFields data_con []) + else + returnM () + + | otherwise -- A record + = checkM (null missing_s_fields) + (addErrTc (missingStrictFields data_con missing_s_fields)) `thenM_` + + doptM Opt_WarnMissingFields `thenM` \ warn -> + checkM (not (warn && notNull missing_ns_fields)) + (warnTc True (missingFields data_con missing_ns_fields)) -missingFields rbinds data_con - | null field_labels = ([], []) -- Not declared as a record; - -- But C{} is still valid - | otherwise - = (missing_strict_fields, other_missing_fields) where - missing_strict_fields + missing_s_fields = [ fl | (fl, str) <- field_info, isMarkedStrict str, - not (fieldLabelName fl `elem` field_names_used) + not (fl `elem` field_names_used) ] - other_missing_fields + missing_ns_fields = [ fl | (fl, str) <- field_info, not (isMarkedStrict str), - not (fieldLabelName fl `elem` field_names_used) + not (fl `elem` field_names_used) ] - field_names_used = [ field_name | (field_name, _, _) <- rbinds ] + field_names_used = recBindFields rbinds field_labels = dataConFieldLabels data_con field_info = zipEqual "missingFields" field_labels - (dropList ex_theta (dataConStrictMarks data_con)) - -- The 'drop' is because dataConStrictMarks - -- includes the existential dictionaries - (_, _, _, ex_theta, _, _) = dataConSig data_con -\end{code} - -%************************************************************************ -%* * -\subsection{@tcMonoExprs@ typechecks a {\em list} of expressions} -%* * -%************************************************************************ - -\begin{code} -tcMonoExprs :: [RenamedHsExpr] -> [TcType] -> TcM ([TcExpr], LIE) - -tcMonoExprs [] [] = returnTc ([], emptyLIE) -tcMonoExprs (expr:exprs) (ty:tys) - = tcMonoExpr expr ty `thenTc` \ (expr', lie1) -> - tcMonoExprs exprs tys `thenTc` \ (exprs', lie2) -> - returnTc (expr':exprs', lie1 `plusLIE` lie2) -\end{code} - - -%************************************************************************ -%* * -\subsection{Literals} -%* * -%************************************************************************ + field_strs -Overloaded literals. - -\begin{code} -tcLit :: HsLit -> TcType -> TcM (TcExpr, LIE) -tcLit (HsLitLit s _) res_ty - = tcLookupClass cCallableClassName `thenNF_Tc` \ cCallableClass -> - newDicts (LitLitOrigin (_UNPK_ s)) - [mkClassPred cCallableClass [res_ty]] `thenNF_Tc` \ dicts -> - returnTc (HsLit (HsLitLit s res_ty), mkLIE dicts) - -tcLit lit res_ty - = unifyTauTy res_ty (simpleHsLitTy lit) `thenTc_` - returnTc (HsLit lit, emptyLIE) + field_strs = dataConStrictMarks data_con \end{code} - %************************************************************************ %* * \subsection{Errors and contexts} %* * %************************************************************************ -Mini-utils: - Boring and alphabetical: \begin{code} -arithSeqCtxt expr - = hang (ptext SLIT("In an arithmetic sequence:")) 4 (ppr expr) - -parrSeqCtxt expr - = hang (ptext SLIT("In a parallel array sequence:")) 4 (ppr expr) - -caseCtxt expr - = hang (ptext SLIT("In the case expression:")) 4 (ppr expr) - caseScrutCtxt expr = hang (ptext SLIT("In the scrutinee of a case expression:")) 4 (ppr expr) -exprSigCtxt expr - = hang (ptext SLIT("When checking the type signature of the expression:")) - 4 (ppr expr) - -listCtxt expr - = hang (ptext SLIT("In the list element:")) 4 (ppr expr) - -parrCtxt expr - = hang (ptext SLIT("In the parallel array element:")) 4 (ppr expr) - -predCtxt expr - = hang (ptext SLIT("In the predicate expression:")) 4 (ppr expr) - exprCtxt expr = hang (ptext SLIT("In the expression:")) 4 (ppr expr) +fieldCtxt field_name + = ptext SLIT("In the") <+> quotes (ppr field_name) <+> ptext SLIT("field of a record") + funAppCtxt fun arg arg_no = hang (hsep [ ptext SLIT("In the"), speakNth arg_no, ptext SLIT("argument of"), quotes (ppr fun) <> text ", namely"]) 4 (quotes (ppr arg)) -wrongArgsCtxt too_many_or_few fun args - = hang (ptext SLIT("Probable cause:") <+> quotes (ppr fun) - <+> ptext SLIT("is applied to") <+> text too_many_or_few - <+> ptext SLIT("arguments in the call")) - 4 (parens (ppr the_app)) - where - the_app = foldl HsApp fun args -- Used in error messages - -appCtxt fun args - = ptext SLIT("In the application") <+> quotes (ppr the_app) - where - the_app = foldl HsApp fun args -- Used in error messages - -lurkingRank2Err fun fun_ty - = hang (hsep [ptext SLIT("Illegal use of"), quotes (ppr fun)]) - 4 (vcat [ptext SLIT("It is applied to too few arguments"), - ptext SLIT("so that the result type has for-alls in it:") <+> ppr fun_ty]) +predCtxt expr + = hang (ptext SLIT("In the predicate expression:")) 4 (ppr expr) +nonVanillaUpd tycon + = vcat [ptext SLIT("Record update for the non-Haskell-98 data type") <+> quotes (ppr tycon) + <+> ptext SLIT("is not (yet) supported"), + ptext SLIT("Use pattern-matching instead")] badFieldsUpd rbinds = hang (ptext SLIT("No constructor has all these fields:")) - 4 (pprQuotedList fields) - where - fields = [field | (field, _, _) <- rbinds] + 4 (pprQuotedList (recBindFields rbinds)) -recordUpdCtxt expr = ptext SLIT("In the record update:") <+> ppr expr -recordConCtxt expr = ptext SLIT("In the record construction:") <+> ppr expr +naughtyRecordSel sel_id + = ptext SLIT("Cannot use record selector") <+> quotes (ppr sel_id) <+> + ptext SLIT("as a function due to escaped type variables") $$ + ptext SLIT("Probably fix: use pattern-matching syntax instead") notSelector field = hsep [quotes (ppr field), ptext SLIT("is not a record selector")] -missingStrictFieldCon :: Name -> FieldLabel -> SDoc -missingStrictFieldCon con field - = hsep [ptext SLIT("Constructor") <+> quotes (ppr con), - ptext SLIT("does not have the required strict field"), quotes (ppr field)] - -missingFieldCon :: Name -> FieldLabel -> SDoc -missingFieldCon con field - = hsep [ptext SLIT("Field") <+> quotes (ppr field), - ptext SLIT("is not initialised")] +missingStrictFields :: DataCon -> [FieldLabel] -> SDoc +missingStrictFields con fields + = header <> rest + where + rest | null fields = empty -- Happens for non-record constructors + -- with strict fields + | otherwise = colon <+> pprWithCommas ppr fields + + header = ptext SLIT("Constructor") <+> quotes (ppr con) <+> + ptext SLIT("does not have the required strict field(s)") + +missingFields :: DataCon -> [FieldLabel] -> SDoc +missingFields con fields + = ptext SLIT("Fields of") <+> quotes (ppr con) <+> ptext SLIT("not initialised:") + <+> pprWithCommas ppr fields + +callCtxt fun args + = ptext SLIT("In the call") <+> parens (ppr (foldl mkHsApp fun args)) + +wrongArgsCtxt too_many_or_few fun + = ptext SLIT("Probable cause:") <+> quotes (ppr fun) + <+> ptext SLIT("is applied to") <+> text too_many_or_few + <+> ptext SLIT("arguments") + +#ifdef GHCI +polySpliceErr :: Id -> SDoc +polySpliceErr id + = ptext SLIT("Can't splice the polymorphic local variable") <+> quotes (ppr id) +#endif \end{code}