X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;ds=sidebyside;f=ghc%2Fcompiler%2Ftypecheck%2FTcExpr.lhs;h=65c328c7667aab61797a9e60da19ef0ab76acfb4;hb=ca49225cd41123ab6ce229040a93cc4b993b190a;hp=15b67291bdaab4944394da158b4b624e430e7e34;hpb=10521d8418fd3a1cf32882718b5bd28992db36fd;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcExpr.lhs b/ghc/compiler/typecheck/TcExpr.lhs index 15b6729..a26a106 100644 --- a/ghc/compiler/typecheck/TcExpr.lhs +++ b/ghc/compiler/typecheck/TcExpr.lhs @@ -1,165 +1,193 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1995 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % -\section[TcExpr]{TcExpr} +\section[TcExpr]{Typecheck an expression} \begin{code} +module TcExpr ( tcCheckSigma, tcCheckRho, tcInferRho, + tcMonoExpr, tcExpr, tcSyntaxOp + ) where + #include "HsVersions.h" -module TcExpr ( - tcExpr -#ifdef DPH - , tcExprs +#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 - ) where -import TcMonad -- typechecking monad machinery -import TcMonadFns ( newPolyTyVarTy, newOpenTyVarTy, - newDict, newMethod, newOverloadedLit, - applyTcSubstAndCollectTyVars, - mkIdsWithPolyTyVarTys +import HsSyn ( HsExpr(..), LHsExpr, HsLit(..), ArithSeqInfo(..), recBindFields, + HsMatchContext(..), HsRecordBinds, mkHsApp ) +import TcHsSyn ( hsLitType, (<$>) ) +import TcRnMonad +import TcUnify ( Expected(..), tcInfer, zapExpectedType, zapExpectedTo, + tcSubExp, tcGen, tcSub, + unifyFunTys, zapToListTy, zapToTyConApp ) +import BasicTypes ( isMarkedStrict ) +import Inst ( tcOverloadedLit, newMethodFromName, newIPDict, + newDicts, newMethodWithGivenTy, tcInstStupidTheta, tcInstCall ) +import TcBinds ( tcLocalBinds ) +import TcEnv ( tcLookup, tcLookupId, + tcLookupDataCon, tcLookupGlobalId ) -import AbsSyn -- the stuff being typechecked - - -import AbsPrel ( intPrimTy, charPrimTy, doublePrimTy, - floatPrimTy, addrPrimTy, addrTy, - boolTy, charTy, stringTy, mkFunTy, mkListTy, - mkTupleTy, mkPrimIoTy -#ifdef DPH - ,mkProcessorTy, mkPodTy,toPodId, - processorClass,pidClass -#endif {- Data Parallel Haskell -} +import TcArrows ( tcProc ) +import TcMatches ( tcMatchesCase, tcMatchLambda, tcDoStmts, tcThingWithSig, TcMatchCtxt(..) ) +import TcHsType ( tcHsSigType, UserTypeCtxt(..) ) +import TcPat ( badFieldCon, refineTyVars ) +import TcMType ( tcInstTyVars, tcInstType, newTyFlexiVarTy, zonkTcType ) +import TcType ( TcTyVar, TcType, TcSigmaType, TcRhoType, + tcSplitFunTys, mkTyVarTys, + isSigmaTy, mkFunTy, mkTyConApp, tyVarsOfTypes, isLinearPred, + tcSplitSigmaTy, tidyOpenType ) -import AbsUniType -import E -import CE ( lookupCE ) - -import Errors -import GenSpecEtc ( checkSigTyVars ) -import Id ( mkInstId, getIdUniType, Id ) -import Inst -import LIE ( nullLIE, unitLIE, plusLIE, unMkLIE, mkLIE, LIE ) -import ListSetOps ( unionLists ) -import Maybes ( Maybe(..) ) -import TVE ( nullTVE, TVE(..) ) -import Spec ( specId, specTy ) -import TcBinds ( tcLocalBindsAndThen ) -import TcMatches ( tcMatchesCase, tcMatch ) -import TcPolyType ( tcPolyType ) -import TcQuals ( tcQuals ) -import TcSimplify ( tcSimplifyAndCheck, tcSimplifyRank2 ) -#ifdef DPH -import TcParQuals -#endif {- Data Parallel Haskell -} -import Unify ( unifyTauTy, unifyTauTyList, unifyTauTyLists ) -import UniqFM ( emptyUFM ) -- profiling, pragmas only -import Unique -- *Key stuff +import Kind ( openTypeKind, liftedTypeKind, argTypeKind ) + +import Id ( idType, recordSelectorFieldLabel, isRecordSelector, isNaughtyRecordSelector ) +import DataCon ( DataCon, dataConFieldLabels, dataConStrictMarks, + dataConWrapId, isVanillaDataCon, dataConTyVars, dataConOrigArgTys ) +import Name ( Name ) +import TyCon ( FieldLabel, tyConStupidTheta, tyConDataCons ) +import Type ( substTheta, substTy ) +import Var ( tyVarKind ) +import VarSet ( emptyVarSet, elemVarSet ) +import TysWiredIn ( boolTy, parrTyCon, tupleTyCon ) +import PrelNames ( enumFromName, enumFromThenName, + enumFromToName, enumFromThenToName, + enumFromToPName, enumFromThenToPName, negateName + ) +import DynFlags +import StaticFlags ( opt_NoMethodSharing ) +import HscTypes ( TyThing(..) ) +import SrcLoc ( Located(..), unLoc, getLoc ) import Util +import ListSetOps ( assocMaybe ) +import Maybes ( catMaybes ) +import Outputable +import FastString -tcExpr :: E -> RenamedExpr -> TcM (TypecheckedExpr, LIE, UniType) +#ifdef DEBUG +import TyCon ( tyConArity ) +#endif \end{code} %************************************************************************ %* * -\subsection{The TAUT rules for variables} +\subsection{Main wrappers} %* * %************************************************************************ \begin{code} -tcExpr e (Var name) - = specId (lookupE_Value e name) `thenNF_Tc` \ stuff@(expr, lie, ty) -> +-- tcCheckSigma does type *checking*; it's passed the expected type of the result +tcCheckSigma :: LHsExpr Name -- Expession to type check + -> TcSigmaType -- Expected type (could be a polytpye) + -> TcM (LHsExpr TcId) -- Generalised expr with expected type + +tcCheckSigma expr expected_ty + = -- traceTc (text "tcExpr" <+> (ppr expected_ty $$ ppr expr)) `thenM_` + tc_expr' expr expected_ty + +tc_expr' expr sigma_ty + | isSigmaTy sigma_ty + = tcGen sigma_ty emptyVarSet ( + \ rho_ty -> tcCheckRho expr rho_ty + ) `thenM` \ (gen_fn, expr') -> + returnM (L (getLoc expr') (gen_fn <$> unLoc expr')) + +tc_expr' expr rho_ty -- Monomorphic case + = tcCheckRho expr rho_ty +\end{code} - -- Check that there's no lurking rank-2 polymorphism - -- isTauTy is over-paranoid, because we don't expect - -- any submerged polymorphism other than rank-2 polymorphism +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 hole to pass in as the expected tyvar. - getSrcLocTc `thenNF_Tc` \ loc -> - checkTc (not (isTauTy ty)) (lurkingRank2Err name ty loc) `thenTc_` - - returnTc stuff +\begin{code} +tcCheckRho :: LHsExpr Name -> TcRhoType -> TcM (LHsExpr TcId) +tcCheckRho expr rho_ty = tcMonoExpr expr (Check rho_ty) + +tcInferRho :: LHsExpr Name -> TcM (LHsExpr TcId, TcRhoType) +tcInferRho (L loc (HsVar name)) = setSrcSpan loc $ do + { (e,_,ty) <- tcId (OccurrenceOf name) name + ; return (L loc e, ty) } +tcInferRho expr = tcInfer (tcMonoExpr expr) + +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 = do { (expr', _, id_ty) <- tcId orig op + ; co_fn <- tcSub ty id_ty + ; returnM (co_fn <$> expr') } +tcSyntaxOp orig other ty = pprPanic "tcSyntaxOp" (ppr other) \end{code} + + %************************************************************************ %* * -\subsection{Literals} +\subsection{The TAUT rules for variables}TcExpr %* * %************************************************************************ -Overloaded literals. - \begin{code} -tcExpr e (Lit lit@(IntLit i)) - = getSrcLocTc `thenNF_Tc` \ loc -> - newPolyTyVarTy `thenNF_Tc` \ ty -> - let - from_int = lookupE_ClassOpByKey e numClassKey SLIT("fromInt") - from_integer = lookupE_ClassOpByKey e numClassKey SLIT("fromInteger") - in - newOverloadedLit (LiteralOrigin lit loc) - (OverloadedIntegral i from_int from_integer) - ty - `thenNF_Tc` \ over_lit -> - - returnTc (Var (mkInstId over_lit), unitLIE over_lit, ty) - -tcExpr e (Lit lit@(FracLit f)) - = getSrcLocTc `thenNF_Tc` \ loc -> - newPolyTyVarTy `thenNF_Tc` \ ty -> - let - from_rational = lookupE_ClassOpByKey e fractionalClassKey SLIT("fromRational") - in - newOverloadedLit (LiteralOrigin lit loc) - (OverloadedFractional f from_rational) - ty - `thenNF_Tc` \ over_lit -> - - returnTc (Var (mkInstId over_lit), unitLIE over_lit, ty) - -tcExpr e (Lit lit@(LitLitLitIn s)) - = getSrcLocTc `thenNF_Tc` \ loc -> - let - -- Get the callable class. Rather turgid and a HACK (ToDo). - ce = getE_CE e - cCallableClass = lookupCE ce (PreludeClass cCallableClassKey bottom) - bottom = panic "tcExpr:LitLitLit" - in - newPolyTyVarTy `thenNF_Tc` \ ty -> - - newDict (LitLitOrigin loc (_UNPK_ s)) cCallableClass ty `thenNF_Tc` \ dict -> - - returnTc (Lit (LitLitLit s ty), mkLIE [dict], ty) +tcMonoExpr :: LHsExpr Name -- Expession to type check + -> Expected TcRhoType -- Expected type (could be a type variable) + -- Definitely no foralls at the top + -- Can be a 'hole'. + -> TcM (LHsExpr TcId) + +tcMonoExpr (L loc expr) res_ty + = setSrcSpan loc (do { expr' <- tcExpr expr res_ty + ; return (L loc expr') }) + +tcExpr :: HsExpr Name -> Expected TcRhoType -> TcM (HsExpr TcId) +tcExpr (HsVar name) res_ty + = do { (expr', _, id_ty) <- tcId (OccurrenceOf name) name + ; co_fn <- tcSubExp res_ty id_ty + ; returnM (co_fn <$> expr') } + +tcExpr (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.) + newTyFlexiVarTy argTypeKind `thenM` \ ip_ty -> + -- argTypeKind: it can't be an unboxed tuple + newIPDict (IPOccOrigin ip) ip ip_ty `thenM` \ (ip', inst) -> + extendLIE inst `thenM_` + tcSubExp res_ty ip_ty `thenM` \ co_fn -> + returnM (co_fn <$> HsIPVar ip') \end{code} -Primitive literals: - -\begin{code} -tcExpr e (Lit (CharPrimLit c)) - = returnTc (Lit (CharPrimLit c), nullLIE, charPrimTy) - -tcExpr e (Lit (StringPrimLit s)) - = returnTc (Lit (StringPrimLit s), nullLIE, addrPrimTy) - -tcExpr e (Lit (IntPrimLit i)) - = returnTc (Lit (IntPrimLit i), nullLIE, intPrimTy) - -tcExpr e (Lit (FloatPrimLit f)) - = returnTc (Lit (FloatPrimLit f), nullLIE, floatPrimTy) -tcExpr e (Lit (DoublePrimLit d)) - = returnTc (Lit (DoublePrimLit d), nullLIE, doublePrimTy) -\end{code} - -Unoverloaded literals: +%************************************************************************ +%* * +\subsection{Expressions type signatures} +%* * +%************************************************************************ \begin{code} -tcExpr e (Lit (CharLit c)) - = returnTc (Lit (CharLit c), nullLIE, charTy) - -tcExpr e (Lit (StringLit str)) - = returnTc (Lit (StringLit str), nullLIE, stringTy) +tcExpr in_expr@(ExprWithTySig expr poly_ty) res_ty + = addErrCtxt (exprCtxt in_expr) $ + tcHsSigType ExprSigCtxt poly_ty `thenM` \ sig_tc_ty -> + tcThingWithSig sig_tc_ty (tcCheckRho expr) res_ty `thenM` \ (co_fn, expr') -> + returnM (co_fn <$> ExprWithTySigOut expr' poly_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} @@ -167,531 +195,928 @@ tcExpr e (Lit (StringLit str)) %************************************************************************ \begin{code} -tcExpr e (Lam match) - = tcMatch e match `thenTc` \ (match',lie,ty) -> - returnTc (Lam match',lie,ty) - -tcExpr e (App e1 e2) = accum e1 [e2] - where - accum (App e1 e2) args = accum e1 (e2:args) - accum fun args = tcApp (foldl App) e fun args - --- equivalent to (op e1) e2: -tcExpr e (OpApp e1 op e2) - = tcApp (\fun [arg1,arg2] -> OpApp arg1 fun arg2) e op [e1,e2] +tcExpr (HsPar expr) res_ty = tcMonoExpr expr res_ty `thenM` \ expr' -> + returnM (HsPar expr') +tcExpr (HsSCC lbl expr) res_ty = tcMonoExpr expr res_ty `thenM` \ expr' -> + returnM (HsSCC lbl expr') +tcExpr (HsCoreAnn lbl expr) res_ty = tcMonoExpr expr res_ty `thenM` \ expr' -> -- hdaume: core annotation + returnM (HsCoreAnn lbl expr') + +tcExpr (HsLit lit) res_ty = tcLit lit res_ty + +tcExpr (HsOverLit lit) res_ty + = zapExpectedType res_ty liftedTypeKind `thenM` \ res_ty' -> + -- Overloaded literals must have liftedTypeKind, because + -- we're instantiating an overloaded function here, + -- whereas res_ty might be openTypeKind. This was a bug in 6.2.2 + tcOverloadedLit (LiteralOrigin lit) lit res_ty' `thenM` \ lit' -> + returnM (HsOverLit lit') + +tcExpr (NegApp expr neg_expr) res_ty + = do { res_ty' <- zapExpectedType res_ty liftedTypeKind + ; neg_expr' <- tcSyntaxOp (OccurrenceOf negateName) neg_expr + (mkFunTy res_ty' res_ty') + ; expr' <- tcCheckRho expr res_ty' + ; return (NegApp expr' neg_expr') } + +tcExpr (HsLam match) res_ty + = tcMatchLambda match res_ty `thenM` \ match' -> + returnM (HsLam match') + +tcExpr (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} --- equivalent to --- \ x -> e op x, +-- Left sections, equivalent to +-- \ x -> e op x, -- or --- \ x -> op e x, +-- \ x -> op e x, -- or just -- op e -tcExpr e (SectionL expr op) - = tcApp (\ fun [arg] -> SectionL arg fun) e op [expr] +tcExpr in_expr@(SectionL arg1 op) res_ty + = tcInferRho op `thenM` \ (op', op_ty) -> + unifyInfixTy op in_expr op_ty `thenM` \ ([arg1_ty, arg2_ty], op_res_ty) -> + tcArg op (arg1, arg1_ty, 1) `thenM` \ arg1' -> + addErrCtxt (exprCtxt in_expr) $ + tcSubExp res_ty (mkFunTy arg2_ty op_res_ty) `thenM` \ co_fn -> + returnM (co_fn <$> SectionL arg1' op') --- equivalent to \ x -> x op expr, or +-- Right sections, equivalent to \ x -> x op expr, or -- \ x -> op x expr -tcExpr e (SectionR op expr) - = tcExpr e op `thenTc` \ (op', lie1, op_ty) -> - tcExpr e expr `thenTc` \ (expr',lie2, expr_ty) -> - newOpenTyVarTy `thenNF_Tc` \ ty1 -> - newOpenTyVarTy `thenNF_Tc` \ ty2 -> - let - result_ty = mkFunTy ty1 ty2 - in - unifyTauTy op_ty (mkFunTy ty1 (mkFunTy expr_ty ty2)) - (SectionRAppCtxt op expr) `thenTc_` - - returnTc (SectionR op' expr', plusLIE lie1 lie2, result_ty) -\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} -tcExpr e (CCall lbl args may_gc is_asm ignored_fake_result_ty) - = getSrcLocTc `thenNF_Tc` \ src_loc -> - let - -- Get the callable and returnable classes. Rather turgid (ToDo). - ce = getE_CE e - cCallableClass = lookupCE ce (PreludeClass cCallableClassKey bottom) - cReturnableClass = lookupCE ce (PreludeClass cReturnableClassKey bottom) - bottom = panic "tcExpr:CCall" +tcExpr in_expr@(SectionR op arg2) res_ty + = tcInferRho op `thenM` \ (op', op_ty) -> + unifyInfixTy op in_expr op_ty `thenM` \ ([arg1_ty, arg2_ty], op_res_ty) -> + tcArg op (arg2, arg2_ty, 2) `thenM` \ arg2' -> + addErrCtxt (exprCtxt in_expr) $ + tcSubExp res_ty (mkFunTy arg1_ty op_res_ty) `thenM` \ co_fn -> + returnM (co_fn <$> SectionR op' arg2') - new_arg_dict (arg, arg_ty) = newDict (CCallOrigin src_loc (_UNPK_ lbl) (Just arg)) - cCallableClass arg_ty +-- equivalent to (op e1) e2: - result_origin = CCallOrigin src_loc (_UNPK_ lbl) Nothing {- Not an arg -} - in - - -- Arguments - tcExprs e args `thenTc` \ (args', args_lie, arg_tys) -> - - -- The argument types can be unboxed or boxed; the result - -- type must, however, be boxed since it's an argument to the PrimIO - -- type constructor. - newPolyTyVarTy `thenNF_Tc` \ result_ty -> - - -- Construct the extra insts, which encode the - -- constraints on the argument and result types. - mapNF_Tc new_arg_dict (args `zip` arg_tys) `thenNF_Tc` \ arg_dicts -> - newDict result_origin cReturnableClass result_ty `thenNF_Tc` \ res_dict -> - - returnTc (CCall lbl args' may_gc is_asm result_ty, - args_lie `plusLIE` mkLIE (res_dict : arg_dicts), - mkPrimIoTy result_ty) +tcExpr in_expr@(OpApp arg1 op fix arg2) res_ty + = tcInferRho op `thenM` \ (op', op_ty) -> + unifyInfixTy op in_expr op_ty `thenM` \ ([arg1_ty, arg2_ty], op_res_ty) -> + tcArg op (arg1, arg1_ty, 1) `thenM` \ arg1' -> + tcArg op (arg2, arg2_ty, 2) `thenM` \ arg2' -> + addErrCtxt (exprCtxt in_expr) $ + tcSubExp res_ty op_res_ty `thenM` \ co_fn -> + returnM (co_fn <$> OpApp arg1' op' fix arg2') \end{code} \begin{code} -tcExpr e (SCC label expr) - = tcExpr e expr `thenTc` \ (expr', lie, expr_ty) -> - -- No unification. Give SCC the type of expr - returnTc (SCC label expr', lie, expr_ty) - -tcExpr e (Let binds expr) - = tcLocalBindsAndThen e - Let -- The combiner - binds -- Bindings to check - (\ e -> tcExpr e expr) -- Typechecker for the expression +tcExpr (HsLet binds expr) res_ty + = do { (binds', expr') <- tcLocalBinds binds $ + tcMonoExpr expr res_ty + ; return (HsLet binds' expr') } + +tcExpr in_expr@(HsCase scrut matches) exp_ty + = -- 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 + addErrCtxt (caseScrutCtxt scrut) + (tcInferRho scrut) `thenM` \ (scrut', scrut_ty) -> + + addErrCtxt (caseCtxt in_expr) $ + tcMatchesCase match_ctxt scrut_ty matches exp_ty `thenM` \ matches' -> + returnM (HsCase scrut' matches') + where + match_ctxt = MC { mc_what = CaseAlt, + mc_body = tcMonoExpr } -tcExpr e (Case expr matches) - = tcExpr e expr `thenTc` \ (expr',lie1,expr_ty) -> - tcMatchesCase e matches `thenTc` \ (matches',lie2,match_ty) -> - newOpenTyVarTy `thenNF_Tc` \ result_ty -> +tcExpr (HsIf pred b1 b2) res_ty + = addErrCtxt (predCtxt pred) + (tcCheckRho pred boolTy) `thenM` \ pred' -> - unifyTauTy (mkFunTy expr_ty result_ty) match_ty - (CaseCtxt expr matches) `thenTc_` + zapExpectedType res_ty openTypeKind `thenM` \ res_ty' -> + -- C.f. the call to zapToType in TcMatches.tcMatches - returnTc (Case expr' matches', plusLIE lie1 lie2, result_ty) + tcCheckRho b1 res_ty' `thenM` \ b1' -> + tcCheckRho b2 res_ty' `thenM` \ b2' -> + returnM (HsIf pred' b1' b2') -tcExpr e (If pred b1 b2) - = tcExpr e pred `thenTc` \ (pred',lie1,predTy) -> +tcExpr (HsDo do_or_lc stmts body _) res_ty + = tcDoStmts do_or_lc stmts body res_ty - unifyTauTy predTy boolTy (PredCtxt pred) `thenTc_` +tcExpr in_expr@(ExplicitList _ exprs) res_ty -- Non-empty list + = zapToListTy res_ty `thenM` \ elt_ty -> + mappM (tc_elt elt_ty) exprs `thenM` \ exprs' -> + returnM (ExplicitList elt_ty exprs') + where + tc_elt elt_ty expr + = addErrCtxt (listCtxt expr) $ + tcCheckRho expr elt_ty + +tcExpr in_expr@(ExplicitPArr _ exprs) res_ty -- maybe empty + = do { [elt_ty] <- zapToTyConApp parrTyCon res_ty + ; exprs' <- mappM (tc_elt elt_ty) exprs + ; return (ExplicitPArr elt_ty exprs') } + where + tc_elt elt_ty expr + = addErrCtxt (parrCtxt expr) (tcCheckRho expr elt_ty) - tcExpr e b1 `thenTc` \ (b1',lie2,result_ty) -> - tcExpr e b2 `thenTc` \ (b2',lie3,b2Ty) -> +tcExpr (ExplicitTuple exprs boxity) res_ty + = do { arg_tys <- zapToTyConApp (tupleTyCon boxity (length exprs)) res_ty + ; exprs' <- tcCheckRhos exprs arg_tys + ; return (ExplicitTuple exprs' boxity) } - unifyTauTy result_ty b2Ty (BranchCtxt b1 b2) `thenTc_` +tcExpr (HsProc pat cmd) res_ty + = tcProc pat cmd res_ty `thenM` \ (pat', cmd') -> + returnM (HsProc pat' cmd') - returnTc (If pred' b1' b2', plusLIE lie1 (plusLIE lie2 lie3), result_ty) +tcExpr e@(HsArrApp _ _ _ _ _) _ + = failWithTc (vcat [ptext SLIT("The arrow command"), nest 2 (ppr e), + ptext SLIT("was found where an expression was expected")]) -tcExpr e (ListComp expr quals) - = mkIdsWithPolyTyVarTys binders `thenNF_Tc` \ lve -> - -- Binders of a list comprehension must be boxed. - let - new_e = growE_LVE e lve - in - tcQuals new_e quals `thenTc` \ (quals',lie1) -> - tcExpr new_e expr `thenTc` \ (expr', lie2, ty) -> - returnTc (ListComp expr' quals', plusLIE lie1 lie2, mkListTy ty) - where - binders = collectQualBinders quals +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} -tcExpr e (ExplicitList []) - = newPolyTyVarTy `thenNF_Tc` \ tyvar_ty -> - returnTc (ExplicitListOut tyvar_ty [], nullLIE, mkListTy tyvar_ty) - - -tcExpr e (ExplicitList exprs) -- Non-empty list - = tcExprs e exprs `thenTc` \ (exprs', lie, tys@(elt_ty:_)) -> - unifyTauTyList tys (ListCtxt exprs) `thenTc_` - returnTc (ExplicitListOut elt_ty exprs', lie, mkListTy elt_ty) - -tcExpr e (ExplicitTuple exprs) - = tcExprs e exprs `thenTc` \ (exprs', lie, tys) -> - returnTc (ExplicitTuple exprs', lie, mkTupleTy (length tys) tys) +%************************************************************************ +%* * + Record construction and update +%* * +%************************************************************************ -tcExpr e (ArithSeqIn seq@(From expr)) - = getSrcLocTc `thenNF_Tc` \ loc -> - tcExpr e expr `thenTc` \ (expr', lie, ty) -> +\begin{code} +tcExpr expr@(RecordCon (L loc con_name) _ rbinds) res_ty + = addErrCtxt (recordConCtxt expr) $ + do { (con_expr, _, con_tau) <- setSrcSpan loc $ + tcId (OccurrenceOf con_name) con_name + ; data_con <- tcLookupDataCon con_name + + ; let (arg_tys, record_ty) = tcSplitFunTys con_tau + flds_w_tys = zipEqual "tcExpr RecordCon" (dataConFieldLabels data_con) arg_tys + + -- Make the result type line up + ; zapExpectedTo res_ty record_ty + + -- Typecheck the record bindings + ; rbinds' <- tcRecordBinds data_con flds_w_tys rbinds + + -- Check for missing fields + ; checkMissingFields data_con rbinds + + ; 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: +-- +-- data T a b = MkT1 { fa :: a, fb :: b } +-- | MkT2 { fa :: a, fc :: Int -> Int } +-- | MkT3 { fd :: a } +-- +-- upd :: T a b -> c -> T a c +-- upd t x = t { fb = x} +-- +-- The type signature on upd is correct (i.e. the result should not be (T a b)) +-- because upd should be equivalent to: +-- +-- upd t x = case t of +-- MkT1 p q -> MkT1 p x +-- MkT2 a b -> MkT2 p b +-- MkT3 d -> error ... +-- +-- So we need to give a completely fresh type to the result record, +-- and then constrain it by the fields that are *not* updated ("p" above). +-- +-- Note that because MkT3 doesn't contain all the fields being updated, +-- 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. + + +tcExpr expr@(RecordUpd record_expr rbinds _ _) res_ty + = addErrCtxt (recordUpdCtxt expr) $ + + -- STEP 0 + -- Check that the field names are really field names + ASSERT( notNull rbinds ) + let + field_names = map fst rbinds + in + mappM (tcLookupGlobalId.unLoc) field_names `thenM` \ sel_ids -> + -- The renamer has already checked that they + -- are all in scope let - enum_from_id = lookupE_ClassOpByKey e enumClassKey SLIT("enumFrom") + 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 - newMethod (ArithSeqOrigin seq loc) - enum_from_id [ty] `thenNF_Tc` \ enum_from -> - - returnTc (ArithSeqOut (Var (mkInstId enum_from)) (From expr'), - plusLIE (unitLIE enum_from) lie, - mkListTy ty) - -tcExpr e (ArithSeqIn seq@(FromThen expr1 expr2)) - = getSrcLocTc `thenNF_Tc` \ loc -> - tcExpr e expr1 `thenTc` \ (expr1',lie1,ty1) -> - tcExpr e expr2 `thenTc` \ (expr2',lie2,ty2) -> - - unifyTauTyList [ty1, ty2] (ArithSeqCtxt (ArithSeqIn seq)) `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 - enum_from_then_id = lookupE_ClassOpByKey e enumClassKey SLIT("enumFromThen") + -- It's OK to use the non-tc splitters here (for a selector) + 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 - newMethod (ArithSeqOrigin seq loc) - enum_from_then_id [ty1] `thenNF_Tc` \ enum_from_then -> - returnTc (ArithSeqOut (Var (mkInstId enum_from_then)) - (FromThen expr1' expr2'), - (unitLIE enum_from_then) `plusLIE` lie1 `plusLIE` lie2, - mkListTy ty1) + -- 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 (not (null relevant_cons)) + (badFieldsUpd rbinds) `thenM_` + + -- 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 + -- which type arguments must be the same in updatee and result. + -- + -- WARNING: this code assumes that all data_cons in a common tycon + -- have FieldLabels abstracted over the same tyvars. + let + -- A constructor is only relevant to this process if + -- it contains *all* the fields that are being updated + con1 = head relevant_cons -- A representative constructor + con1_tyvars = dataConTyVars con1 + con1_fld_tys = dataConFieldLabels con1 `zip` dataConOrigArgTys con1 + common_tyvars = tyVarsOfTypes [ty | (fld,ty) <- con1_fld_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 = newTyFlexiVarTy (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 -> -tcExpr e (ArithSeqIn seq@(FromTo expr1 expr2)) - = getSrcLocTc `thenNF_Tc` \ loc -> - tcExpr e expr1 `thenTc` \ (expr1',lie1,ty1) -> - tcExpr e expr2 `thenTc` \ (expr2',lie2,ty2) -> + -- 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 + inst_fld_tys = [(fld, substTy inst_env ty) | (fld, ty) <- con1_fld_tys] + in + zapExpectedTo res_ty result_record_ty `thenM_` + tcRecordBinds con1 inst_fld_tys rbinds `thenM` \ rbinds' -> - unifyTauTyList [ty1,ty2] (ArithSeqCtxt (ArithSeqIn seq)) `thenTc_` + -- STEP 5 + -- Typecheck the expression to be updated let - enum_from_to_id = lookupE_ClassOpByKey e enumClassKey SLIT("enumFromTo") + 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 - newMethod (ArithSeqOrigin seq loc) - enum_from_to_id [ty1] `thenNF_Tc` \ enum_from_to -> - returnTc (ArithSeqOut (Var (mkInstId enum_from_to)) - (FromTo expr1' expr2'), - (unitLIE enum_from_to) `plusLIE` lie1 `plusLIE` lie2, - mkListTy ty1) - -tcExpr e (ArithSeqIn seq@(FromThenTo expr1 expr2 expr3)) - = getSrcLocTc `thenNF_Tc` \ loc -> - tcExpr e expr1 `thenTc` \ (expr1',lie1,ty1) -> - tcExpr e expr2 `thenTc` \ (expr2',lie2,ty2) -> - tcExpr e expr3 `thenTc` \ (expr3',lie3,ty3) -> - - unifyTauTyList [ty1,ty2,ty3] (ArithSeqCtxt (ArithSeqIn seq)) `thenTc_` + tcCheckRho 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 pattern matching over the data cons. + -- + -- 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 - enum_from_then_to_id = lookupE_ClassOpByKey e enumClassKey SLIT("enumFromThenTo") + theta' = substTheta inst_env (tyConStupidTheta tycon) in - newMethod (ArithSeqOrigin seq loc) - enum_from_then_to_id [ty1] `thenNF_Tc` \ enum_from_then_to -> + newDicts RecordUpdOrigin theta' `thenM` \ dicts -> + extendLIEs dicts `thenM_` - returnTc (ArithSeqOut (Var (mkInstId enum_from_then_to)) - (FromThenTo expr1' expr2' expr3'), - (unitLIE enum_from_then_to) `plusLIE` lie1 `plusLIE` lie2 `plusLIE` lie3, - mkListTy ty1) + -- Phew! + returnM (RecordUpd record_expr' rbinds' record_ty result_record_ty) \end{code} + %************************************************************************ %* * -\subsection{Expressions type signatures} + Arithmetic sequences e.g. [a,b..] + and their parallel-array counterparts e.g. [: a,b.. :] + %* * %************************************************************************ \begin{code} -tcExpr e (ExprWithTySig expr poly_ty) - = tcExpr e expr `thenTc` \ (texpr, lie, tau_ty) -> - babyTcMtoTcM (tcPolyType (getE_CE e) (getE_TCE e) nullTVE poly_ty) `thenTc` \ sigma_sig -> - - -- Check the tau-type part - specTy SignatureOrigin sigma_sig `thenNF_Tc` \ (sig_tyvars, sig_dicts, sig_tau) -> - unifyTauTy tau_ty sig_tau (ExprSigCtxt expr sig_tau) `thenTc_` - - -- Check the type variables of the signature - applyTcSubstAndCollectTyVars (tvOfE e) `thenNF_Tc` \ env_tyvars -> - checkSigTyVars env_tyvars sig_tyvars sig_tau tau_ty (ExprSigCtxt expr sig_tau) - `thenTc` \ sig_tyvars' -> - - -- Check overloading constraints - tcSimplifyAndCheck - False {- Not top level -} - env_tyvars sig_tyvars' - sig_dicts (unMkLIE lie) - (ExprSigCtxt expr sigma_sig) `thenTc_` - - -- If everything is ok, return the stuff unchanged, except for - -- the effect of any substutions etc. We simply discard the - -- result of the tcSimplifyAndCheck, except for any default - -- resolution it may have done, which is recorded in the - -- substitution. - returnTc (texpr, lie, tau_ty) +tcExpr (ArithSeq _ seq@(From expr)) res_ty + = zapToListTy res_ty `thenM` \ elt_ty -> + tcCheckRho expr elt_ty `thenM` \ expr' -> + + newMethodFromName (ArithSeqOrigin seq) + elt_ty enumFromName `thenM` \ enum_from -> + + returnM (ArithSeq (HsVar enum_from) (From expr')) + +tcExpr in_expr@(ArithSeq _ seq@(FromThen expr1 expr2)) res_ty + = addErrCtxt (arithSeqCtxt in_expr) $ + zapToListTy res_ty `thenM` \ elt_ty -> + tcCheckRho expr1 elt_ty `thenM` \ expr1' -> + tcCheckRho expr2 elt_ty `thenM` \ expr2' -> + newMethodFromName (ArithSeqOrigin seq) + elt_ty enumFromThenName `thenM` \ enum_from_then -> + + returnM (ArithSeq (HsVar enum_from_then) (FromThen expr1' expr2')) + + +tcExpr in_expr@(ArithSeq _ seq@(FromTo expr1 expr2)) res_ty + = addErrCtxt (arithSeqCtxt in_expr) $ + zapToListTy res_ty `thenM` \ elt_ty -> + tcCheckRho expr1 elt_ty `thenM` \ expr1' -> + tcCheckRho expr2 elt_ty `thenM` \ expr2' -> + newMethodFromName (ArithSeqOrigin seq) + elt_ty enumFromToName `thenM` \ enum_from_to -> + + returnM (ArithSeq (HsVar enum_from_to) (FromTo expr1' expr2')) + +tcExpr in_expr@(ArithSeq _ seq@(FromThenTo expr1 expr2 expr3)) res_ty + = addErrCtxt (arithSeqCtxt in_expr) $ + zapToListTy res_ty `thenM` \ elt_ty -> + tcCheckRho expr1 elt_ty `thenM` \ expr1' -> + tcCheckRho expr2 elt_ty `thenM` \ expr2' -> + tcCheckRho expr3 elt_ty `thenM` \ expr3' -> + newMethodFromName (ArithSeqOrigin seq) + elt_ty enumFromThenToName `thenM` \ eft -> + + returnM (ArithSeq (HsVar eft) (FromThenTo expr1' expr2' expr3')) + +tcExpr in_expr@(PArrSeq _ seq@(FromTo expr1 expr2)) res_ty + = addErrCtxt (parrSeqCtxt in_expr) $ + zapToTyConApp parrTyCon res_ty `thenM` \ [elt_ty] -> + tcCheckRho expr1 elt_ty `thenM` \ expr1' -> + tcCheckRho expr2 elt_ty `thenM` \ expr2' -> + newMethodFromName (PArrSeqOrigin seq) + elt_ty enumFromToPName `thenM` \ enum_from_to -> + + returnM (PArrSeq (HsVar enum_from_to) (FromTo expr1' expr2')) + +tcExpr in_expr@(PArrSeq _ seq@(FromThenTo expr1 expr2 expr3)) res_ty + = addErrCtxt (parrSeqCtxt in_expr) $ + zapToTyConApp parrTyCon res_ty `thenM` \ [elt_ty] -> + tcCheckRho expr1 elt_ty `thenM` \ expr1' -> + tcCheckRho expr2 elt_ty `thenM` \ expr2' -> + tcCheckRho expr3 elt_ty `thenM` \ expr3' -> + newMethodFromName (PArrSeqOrigin seq) + elt_ty enumFromThenToPName `thenM` \ eft -> + + returnM (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{Data Parallel Expressions (DPH only)} + Template Haskell %* * %************************************************************************ -Constraints enforced by the Static semantics for ParallelZF -$exp_1$ = << $exp_2$ | quals >> +\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} -\begin{enumerate} -\item The type of the expression $exp_1$ is <<$exp_2$>> -\item The type of $exp_2$ must be in the class {\tt Processor} -\end{enumerate} + +%************************************************************************ +%* * + Catch-all +%* * +%************************************************************************ \begin{code} -#ifdef DPH -tcExpr e (ParallelZF expr quals) - = let binders = collectParQualBinders quals in - mkIdsWithPolyTyVarTys binders `thenNF_Tc` (\ lve -> - let e' = growE_LVE e lve in - tcParQuals e' quals `thenTc` (\ (quals',lie1) -> - tcExpr e' expr `thenTc` (\ (expr', lie2,ty) -> - getSrcLocTc `thenNF_Tc` (\ src_loc -> - if (isProcessorTy ty) then - returnTc (ParallelZF expr' quals', - plusLIE lie1 lie2 , - mkPodTy ty) - else - failTc (podCompLhsError ty src_loc) - )))) -#endif {- Data Parallel Haskell -} +tcExpr other _ = pprPanic "tcMonoExpr" (ppr other) \end{code} -Constraints enforced by the Static semantics for Explicit Pods -exp = << $exp_1$ ... $exp_n$>> (where $n >= 0$) -\begin{enumerate} -\item The type of the all the expressions in the Pod must be the same. -\item The type of an expression in a POD must be in class {\tt Processor} -\end{enumerate} +%************************************************************************ +%* * +\subsection{@tcApp@ typchecks an application} +%* * +%************************************************************************ \begin{code} -#ifdef DPH -tcExpr e (ExplicitPodIn exprs) - = panic "Ignoring explicit PODs for the time being" -{- - = tcExprs e exprs `thenTc` (\ (exprs',lie,tys) -> - newPolyTyVarTy `thenNF_Tc` (\ elt_ty -> - newDict processorClass elt_ty `thenNF_Tc` (\ procDict -> - let - procLie = mkLIEFromDicts procDict - in - unifyTauTyList (elt_ty:tys) (PodCtxt exprs) `thenTc_` - - returnTc ((App - (DictApp - (TyApp (Var toPodId) [elt_ty]) - procDict) - (ExplicitListOut elt_ty exprs')), - plusLIE procLie lie, - mkPodTy elt_ty) - ))) -} -#endif {- Data Parallel Haskell -} + +tcApp :: LHsExpr Name -> [LHsExpr Name] -- Function and args + -> Expected TcRhoType -- Expected result type of application + -> TcM (HsExpr TcId) -- Translated fun and args + +tcApp (L _ (HsApp e1 e2)) args res_ty + = tcApp e1 (e2:args) res_ty -- Accumulate the arguments + +tcApp fun args res_ty + = do { let n_args = length args + ; (fun', fun_tvs, fun_tau) <- tcFun fun -- Type-check the function + + -- Extract its argument types + ; (expected_arg_tys, actual_res_ty) + <- do { traceTc (text "tcApp" <+> (ppr fun $$ ppr fun_tau)) + ; let msg = sep [ptext SLIT("The function") <+> quotes (ppr fun), + ptext SLIT("is applied to") + <+> speakN n_args <+> ptext SLIT("arguments")] + ; unifyFunTys msg n_args fun_tau } + + ; case res_ty of + Check _ -> do -- Connect to result type first + -- See Note [Push result type in] + { co_fn <- tcResult fun args res_ty actual_res_ty + ; the_app' <- tcArgs fun fun' args expected_arg_tys + ; traceTc (text "tcApp: check" <+> vcat [ppr fun <+> ppr args, + ppr the_app', ppr actual_res_ty]) + ; returnM (co_fn <$> the_app') } + + Infer _ -> do -- Type check args first, then + -- refine result type, then do tcResult + { the_app' <- tcArgs fun fun' args expected_arg_tys + ; subst <- refineTyVars fun_tvs + ; let actual_res_ty' = substTy subst actual_res_ty + ; co_fn <- tcResult fun args res_ty actual_res_ty' + ; traceTc (text "tcApp: infer" <+> vcat [ppr fun <+> ppr args, ppr the_app', + ppr actual_res_ty, ppr actual_res_ty']) + ; returnM (co_fn <$> the_app') } + } + +-- 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) + +-- 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.] + +---------------- +tcFun :: LHsExpr Name -> TcM (LHsExpr TcId, [TcTyVar], TcRhoType) +-- Instantiate the function, returning the type variables used +-- If the function isn't simple, infer its type, and return no +-- type variables +tcFun (L loc (HsVar f)) = setSrcSpan loc $ do + { (fun', tvs, fun_tau) <- tcId (OccurrenceOf f) f + ; return (L loc fun', tvs, fun_tau) } +tcFun fun = do { (fun', fun_tau) <- tcInfer (tcMonoExpr fun) + ; return (fun', [], fun_tau) } + +---------------- +tcArgs :: LHsExpr Name -- The function (for error messages) + -> LHsExpr TcId -- The function (to build into result) + -> [LHsExpr Name] -> [TcSigmaType] -- Actual arguments and expected arg types + -> TcM (HsExpr TcId) -- Resulting application + +tcArgs fun fun' args expected_arg_tys + = do { args' <- mappM (tcArg fun) (zip3 args expected_arg_tys [1..]) + ; return (unLoc (foldl mkHsApp fun' args')) } + +tcArg :: LHsExpr Name -- The function (for error messages) + -> (LHsExpr Name, TcSigmaType, Int) -- Actual argument and expected arg type + -> TcM (LHsExpr TcId) -- Resulting argument +tcArg fun (arg, ty, arg_no) = addErrCtxt (funAppCtxt fun arg arg_no) + (tcCheckSigma arg ty) + +---------------- +tcResult fun args res_ty actual_res_ty + = addErrCtxtM (checkArgsCtxt fun args res_ty actual_res_ty) + (tcSubExp res_ty actual_res_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. +-- The ~(Check...) is because in the Infer case the tcSubExp +-- definitely won't fail, so we can be certain we're in the Check branch +checkArgsCtxt fun args (Infer _) actual_res_ty tidy_env + = return (tidy_env, ptext SLIT("Urk infer")) + +checkArgsCtxt fun args (Check 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 args + | len_exp_args > len_act_args = wrongArgsCtxt "too many" fun args + | otherwise = appCtxt fun args + in + returnM (env2, message) + +---------------- +unifyInfixTy :: LHsExpr Name -> HsExpr Name -> TcType + -> TcM ([TcType], TcType) +-- This wrapper just prepares the error message for unifyFunTys +unifyInfixTy op expr op_ty + = unifyFunTys msg 2 op_ty + where + msg = sep [herald <+> quotes (ppr expr), + ptext SLIT("requires") <+> quotes (ppr op) + <+> ptext SLIT("to take two arguments")] + herald = case expr of + OpApp _ _ _ _ -> ptext SLIT("The infix expression") + other -> ptext SLIT("The operator section") \end{code} + +%************************************************************************ +%* * +\subsection{@tcId@ typchecks an identifier occurrence} +%* * +%************************************************************************ + +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)} + +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 +something like + f :: Num a => a -> a + f = /\a (d:Num a) -> let m = (+) a d in \ (x:a) -> m x x +If you specify -fno-method-sharing, the dictionary application +isn't shared, so we get + f :: Num a => a -> a + f = /\a (d:Num a) (x:a) -> (+) a d x x +This gets a bit less sharing, but + a) it's better for RULEs involving overloaded functions + b) perhaps fewer separated lambdas + \begin{code} -#ifdef DPH -tcExpr e (ExplicitProcessor exprs expr) - = tcPidExprs e exprs `thenTc` (\ (exprs',lie1,tys) -> - tcExpr e expr `thenTc` (\ (expr',lie2,ty) -> - returnTc (ExplicitProcessor exprs' expr', - plusLIE lie1 lie2, - mkProcessorTy tys ty) - )) -#endif {- Data Parallel Haskell -} +tcId :: InstOrigin -> Name -> TcM (HsExpr TcId, [TcTyVar], TcRhoType) + -- Return the type variables at which the function + -- is instantiated, as well as the translated variable and its type + +tcId orig id_name -- Look up the Id and instantiate its type + = tcLookup id_name `thenM` \ thing -> + case thing of { + AGlobal (ADataCon con) -- Similar, but instantiate the stupid theta too + -> do { (expr, tvs, tau) <- instantiate (dataConWrapId con) + ; tcInstStupidTheta con (mkTyVarTys tvs) + -- Remember to chuck in the constraints from the "silly context" + ; return (expr, tvs, tau) } + + ; AGlobal (AnId id) | isNaughtyRecordSelector id + -> failWithTc (naughtyRecordSel id) + ; AGlobal (AnId id) -> instantiate id + -- A global cannot possibly be ill-staged + -- nor does it need the 'lifting' treatment + + ; ATcId id th_level -> tc_local_id id th_level + + ; other -> failWithTc (ppr other <+> ptext SLIT("used where a value identifer was expected")) + } + where + +#ifndef GHCI + tc_local_id id th_bind_lvl -- Non-TH case + = instantiate id + +#else /* GHCI and TH is on */ + tc_local_id id th_bind_lvl -- TH case + = -- Check for cross-stage lifting + getStage `thenM` \ use_stage -> + case use_stage of + Brack use_lvl ps_var lie_var + | use_lvl > th_bind_lvl + -> if isExternalName id_name then + -- 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. + keepAliveTc id_name `thenM_` + instantiate id + + else -- Nested identifiers, such as 'x' in + -- E.g. \x -> [| h x |] + -- We must behave as if the reference to x was + -- h $(lift x) + -- We use 'x' itself as the splice proxy, used by + -- the desugarer to stitch it all back together. + -- If 'x' occurs many times we may get many identical + -- bindings of the same splice proxy, but that doesn't + -- matter, although it's a mite untidy. + let + id_ty = idType id + in + checkTc (isTauTy id_ty) (polySpliceErr id) `thenM_` + -- If x is polymorphic, its occurrence sites might + -- have different instantiations, so we can't use plain + -- 'x' as the splice proxy name. I don't know how to + -- solve this, and it's probably unimportant, so I'm + -- just going to flag an error for now + + setLIEVar lie_var ( + newMethodFromName orig id_ty DsMeta.liftName `thenM` \ lift -> + -- Put the 'lift' constraint into the right LIE + + -- Update the pending splices + readMutVar ps_var `thenM` \ ps -> + writeMutVar ps_var ((id_name, nlHsApp (nlHsVar lift) (nlHsVar id)) : ps) `thenM_` + + returnM (HsVar id, [], id_ty)) + + other -> + checkWellStaged (quotes (ppr id)) th_bind_lvl use_stage `thenM_` + instantiate id +#endif /* GHCI */ + + instantiate :: TcId -> TcM (HsExpr TcId, [TcTyVar], TcRhoType) + instantiate fun_id = loop (HsVar fun_id) [] (idType fun_id) + + loop (HsVar fun_id) tvs fun_ty + | want_method_inst fun_ty + = tcInstType fun_ty `thenM` \ (tyvars, theta, tau) -> + newMethodWithGivenTy orig fun_id + (mkTyVarTys tyvars) theta tau `thenM` \ meth_id -> + loop (HsVar meth_id) (tvs ++ tyvars) tau + + loop fun tvs fun_ty + | isSigmaTy fun_ty + = tcInstCall orig fun_ty `thenM` \ (inst_fn, new_tvs, tau) -> + loop (inst_fn <$> fun) (tvs ++ new_tvs) tau + + | otherwise + = returnM (fun, tvs, fun_ty) + + -- Hack Alert (want_method_inst)! + -- 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 fun_ty + | opt_NoMethodSharing = False + | otherwise = case tcSplitSigmaTy fun_ty of + (_,[],_) -> False -- Not overloaded + (_,theta,_) -> not (any isLinearPred theta) \end{code} %************************************************************************ %* * -\subsection{@tcExprs@ typechecks a {\em list} of expressions} +\subsection{Record bindings} %* * %************************************************************************ -ToDo: Possibly find a version of a listTc TcM which would pass the -appropriate functions for the LIE. +Game plan for record bindings +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +1. Find the TyCon for the bindings, from the first field label. + +2. Instantiate its tyvars and unify (T a1 .. an) with expected_ty. + +For each binding field = value + +3. Instantiate the field type (from the field label) using the type + envt from step 2. + +4 Type check the value using tcArg, passing the field type as + the expected argument type. + +This extends OK when the field types are universally quantified. + \begin{code} -tcExprs :: E -> [RenamedExpr] -> TcM ([TypecheckedExpr],LIE,[TauType]) +tcRecordBinds + :: DataCon + -> [(FieldLabel,TcType)] -- Expected type for each field + -> HsRecordBinds Name + -> TcM (HsRecordBinds TcId) + +tcRecordBinds data_con flds_w_tys rbinds + = do { mb_binds <- mappM do_bind rbinds + ; return (catMaybes mb_binds) } + where + do_bind (L loc field_lbl, rhs) + | Just field_ty <- assocMaybe flds_w_tys field_lbl + = addErrCtxt (fieldCtxt field_lbl) $ + do { rhs' <- tcCheckSigma 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)) + + where + missing_s_fields + = [ fl | (fl, str) <- field_info, + isMarkedStrict str, + not (fl `elem` field_names_used) + ] + missing_ns_fields + = [ fl | (fl, str) <- field_info, + not (isMarkedStrict str), + not (fl `elem` field_names_used) + ] + + field_names_used = recBindFields rbinds + field_labels = dataConFieldLabels data_con + + field_info = zipEqual "missingFields" + field_labels + field_strs + + field_strs = dataConStrictMarks data_con +\end{code} + +%************************************************************************ +%* * +\subsection{@tcCheckRhos@ typechecks a {\em list} of expressions} +%* * +%************************************************************************ -tcExprs e [] = returnTc ([], nullLIE, []) -tcExprs e (expr:exprs) - = tcExpr e expr `thenTc` \ (expr', lie1, ty) -> - tcExprs e exprs `thenTc` \ (exprs', lie2, tys) -> - returnTc (expr':exprs', plusLIE lie1 lie2, ty:tys) +\begin{code} +tcCheckRhos :: [LHsExpr Name] -> [TcType] -> TcM [LHsExpr TcId] + +tcCheckRhos [] [] = returnM [] +tcCheckRhos (expr:exprs) (ty:tys) + = tcCheckRho expr ty `thenM` \ expr' -> + tcCheckRhos exprs tys `thenM` \ exprs' -> + returnM (expr':exprs') +tcCheckRhos exprs tys = pprPanic "tcCheckRhos" (ppr exprs $$ ppr tys) \end{code} %************************************************************************ %* * -\subsection{@tcApp@ typchecks an application} +\subsection{Literals} %* * %************************************************************************ +Overloaded literals. + \begin{code} -tcApp :: (TypecheckedExpr -> [TypecheckedExpr] -> TypecheckedExpr) -- Result builder - -> E - -> RenamedExpr - -> [RenamedExpr] - -> TcM (TypecheckedExpr, LIE, UniType) - -tcApp build_result_expression e orig_fun arg_exprs - = tcExpr' e orig_fun (length arg_exprs) - `thenTc` \ (fun', lie_fun, fun_ty) -> - unify_fun 1 fun' lie_fun arg_exprs fun_ty - where - -- Used only in the error message - maybe_fun_id = case orig_fun of - Var name -> Just (lookupE_Value e name) - other -> Nothing - - unify_args :: Int -- Current argument number - -> TypecheckedExpr -- Current rebuilt expression - -> LIE -- Corresponding LIE - -> [RenamedExpr] -- Remaining args - -> [TauType] -- Remaining arg types - -> TauType -- result type - -> TcM (TypecheckedExpr, LIE, UniType) - - unify_args arg_no fun lie (arg:args) (arg_ty:arg_tys) fun_res_ty - = tcExpr e arg `thenTc` \ (arg', lie_arg, actual_arg_ty) -> - - -- These applyTcSubstToTy's are just to improve the error message... - applyTcSubstToTy actual_arg_ty `thenNF_Tc` \ actual_arg_ty' -> - applyTcSubstToTy arg_ty `thenNF_Tc` \ arg_ty' -> - let - err_ctxt = FunAppCtxt orig_fun maybe_fun_id arg arg_ty' actual_arg_ty' arg_no - in - matchArgTy e arg_ty' arg' lie_arg actual_arg_ty' err_ctxt - `thenTc` \ (arg'', lie_arg') -> - - unify_args (arg_no+1) (App fun arg'') (lie `plusLIE` lie_arg') args arg_tys fun_res_ty - - unify_args arg_no fun lie [] arg_tys fun_res_ty - = -- We've run out of actual arguments. Check that none of - -- arg_tys has a for-all at the top. For example, "build" on - -- its own is no good; it must be applied to something. - let - result_ty = glueTyArgs arg_tys fun_res_ty - in - getSrcLocTc `thenNF_Tc` \ loc -> - checkTc (not (isTauTy result_ty)) - (underAppliedTyErr result_ty loc) `thenTc_` - returnTc (fun, lie, result_ty) - - -- When we run out of arg_tys we go back to unify_fun in the hope - -- that our unification work may have shown up some more arguments - unify_args arg_no fun lie args [] fun_res_ty - = unify_fun arg_no fun lie args fun_res_ty - - - unify_fun :: Int -- Current argument number - -> TypecheckedExpr -- Current rebuilt expression - -> LIE -- Corresponding LIE - -> [RenamedExpr] -- Remaining args - -> TauType -- Remaining function type - -> TcM (TypecheckedExpr, LIE, UniType) - - unify_fun arg_no fun lie args fun_ty - = -- Find out as much as possible about the function - applyTcSubstToTy fun_ty `thenNF_Tc` \ fun_ty' -> - - -- Now see whether it has any arguments - case (splitTyArgs fun_ty') of - - ([], _) -> -- Function has no arguments left - - newOpenTyVarTy `thenNF_Tc` \ result_ty -> - tcExprs e args `thenTc` \ (args', lie_args, arg_tys) -> - - -- At this point, a unification error must mean the function is - -- being applied to too many arguments. - unifyTauTy fun_ty' (glueTyArgs arg_tys result_ty) - (TooManyArgsCtxt orig_fun) `thenTc_` - - returnTc (build_result_expression fun args', - lie `plusLIE` lie_args, - result_ty) - - (fun_arg_tys, fun_res_ty) -> -- Function has non-empty list of argument types - - unify_args arg_no fun lie args fun_arg_tys fun_res_ty +tcLit :: HsLit -> Expected TcRhoType -> TcM (HsExpr TcId) +tcLit lit res_ty + = zapExpectedTo res_ty (hsLitType lit) `thenM_` + returnM (HsLit lit) \end{code} + +%************************************************************************ +%* * +\subsection{Errors and contexts} +%* * +%************************************************************************ + +Boring and alphabetical: \begin{code} -matchArgTy :: E - -> UniType -- Expected argument type - -> TypecheckedExpr -- Type checked argument - -> LIE -- Actual argument LIE - -> UniType -- Actual argument type - -> UnifyErrContext - -> TcM (TypecheckedExpr, -- The incoming type checked arg, - -- possibly wrapped in a big lambda - LIE) -- Possibly reduced somewhat - -matchArgTy e expected_arg_ty arg_expr actual_arg_lie actual_arg_ty err_ctxt - | isForAllTy expected_arg_ty - = -- Ha! The argument type of the function is a for-all type, - -- An example of rank-2 polymorphism. - - -- This applyTcSubstToTy is just to improve the error message.. - - applyTcSubstToTy actual_arg_ty `thenNF_Tc` \ actual_arg_ty' -> - - -- Instantiate the argument type - -- ToDo: give this a real origin - specTy UnknownOrigin expected_arg_ty `thenNF_Tc` \ (arg_tyvars, arg_lie, arg_tau) -> - - if not (null arg_lie) then - -- Paranoia check - panic "Non-null overloading in tcApp" - else - -- Assert: arg_lie = [] - - unifyTauTy arg_tau actual_arg_ty' err_ctxt `thenTc_` - - -- Check that the arg_tyvars havn't been constrained - -- The interesting bit here is that we must include the free variables - -- of the expected arg ty. Here's an example: - -- runST (newVar True) - -- Here, if we don't make a check, we'll get a type (ST s (MutVar s Bool)) - -- for (newVar True), with s fresh. Then we unify with the runST's arg type - -- forall s'. ST s' a. That unifies s' with s, and a with MutVar s Bool. - -- So now s' isn't unconstrained because it's linked to a. - -- Conclusion: include the free vars of the expected arg type in the - -- list of "free vars" for the signature check. - applyTcSubstAndCollectTyVars - (tvOfE e `unionLists` - extractTyVarsFromTy expected_arg_ty) `thenNF_Tc` \ free_tyvars -> - checkSigTyVars free_tyvars arg_tyvars arg_tau actual_arg_ty rank2_err_ctxt - `thenTc` \ arg_tyvars' -> - - -- Check that there's no overloading involved - -- Even if there isn't, there may be some Insts which mention the arg_tyvars, - -- but which, on simplification, don't actually need a dictionary involving - -- the tyvar. So we have to do a proper simplification right here. - let insts = unMkLIE actual_arg_lie - in - applyTcSubstToInsts insts `thenNF_Tc` \ insts' -> +arithSeqCtxt expr + = hang (ptext SLIT("In an arithmetic sequence:")) 4 (ppr expr) - tcSimplifyRank2 arg_tyvars' insts' rank2_err_ctxt `thenTc` \ (free_insts, inst_binds) -> +parrSeqCtxt expr + = hang (ptext SLIT("In a parallel array sequence:")) 4 (ppr expr) - -- This Let binds any Insts which came out of the simplification. - -- It's a bit out of place here, but using AbsBind involves inventing - -- a couple of new names which seems worse. - returnTc (TyLam arg_tyvars' (Let (mk_binds inst_binds) arg_expr), mkLIE free_insts) +caseCtxt expr + = hang (ptext SLIT("In the case expression:")) 4 (ppr expr) - | otherwise - = -- The ordinary, non-rank-2 polymorphic case - unifyTauTy expected_arg_ty actual_arg_ty err_ctxt `thenTc_` - returnTc (arg_expr, actual_arg_lie) +caseScrutCtxt expr + = hang (ptext SLIT("In the scrutinee of a case expression:")) 4 (ppr expr) - where - rank2_err_ctxt = Rank2ArgCtxt arg_expr expected_arg_ty +exprCtxt expr + = hang (ptext SLIT("In the expression:")) 4 (ppr expr) - mk_binds [] = EmptyBinds - mk_binds ((inst,rhs):inst_binds) = (SingleBind (NonRecBind (VarMonoBind (mkInstId inst) rhs))) - `ThenBinds` - mk_binds inst_binds -\end{code} +fieldCtxt field_name + = ptext SLIT("In the") <+> quotes (ppr field_name) <+> ptext SLIT("field of a record") -This version only does not check for 2nd order if it is applied. +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)) -\begin{code} -tcExpr' :: E -> RenamedExpr -> Int -> TcM (TypecheckedExpr,LIE,UniType) +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) -tcExpr' e v@(Var name) n - | n > 0 = specId (lookupE_Value e name) `thenNF_Tc` \ (expr, lie, ty) -> - returnTc (expr, lie, ty) -tcExpr' e exp n = tcExpr e exp +predCtxt expr + = hang (ptext SLIT("In the predicate expression:")) 4 (ppr expr) + +appCtxt fun args + = ptext SLIT("In the application") <+> quotes (ppr the_app) + where + the_app = foldl mkHsApp fun args -- Used in error messages + +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 (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")] + +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 + +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 mkHsApp fun args -- Used in error messages + +#ifdef GHCI +polySpliceErr :: Id -> SDoc +polySpliceErr id + = ptext SLIT("Can't splice the polymorphic local variable") <+> quotes (ppr id) +#endif \end{code}