X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcExpr.lhs;h=a044f43ef2f80e00aa7e8f3fde330de1b59b5b5a;hb=28a464a75e14cece5db40f2765a29348273ff2d2;hp=4cdf5b5c7f29cdf152f9396c1f4bed98ec7da000;hpb=b04828749b71a57e4132f91156eb94d50b4308c5;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcExpr.lhs b/ghc/compiler/typecheck/TcExpr.lhs index 4cdf5b5..a044f43 100644 --- a/ghc/compiler/typecheck/TcExpr.lhs +++ b/ghc/compiler/typecheck/TcExpr.lhs @@ -4,9 +4,8 @@ \section[TcExpr]{Typecheck an expression} \begin{code} -module TcExpr ( tcCheckSigma, tcCheckRho, tcInferRho, - tcMonoExpr, tcExpr, tcSyntaxOp - ) where +module TcExpr ( tcPolyExpr, tcPolyExprNC, + tcMonoExpr, tcInferRho, tcSyntaxOp ) where #include "HsVersions.h" @@ -21,57 +20,62 @@ import HsSyn ( nlHsApp ) import qualified DsMeta #endif -import HsSyn ( HsExpr(..), LHsExpr, HsLit(..), ArithSeqInfo(..), recBindFields, - HsMatchContext(..), HsRecordBinds, mkHsApp ) -import TcHsSyn ( hsLitType, (<$>) ) +import HsSyn ( HsExpr(..), LHsExpr, ArithSeqInfo(..), recBindFields, + HsMatchContext(..), HsRecordBinds, + mkHsCoerce, mkHsApp, mkHsDictApp, mkHsTyApp ) +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 ( tcBindsAndThen ) +import TcUnify ( tcInfer, tcSubExp, tcFunResTy, 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 TcArrows ( tcProc ) -import TcMatches ( tcMatchesCase, tcMatchLambda, tcDoStmts, tcThingWithSig, TcMatchCtxt(..) ) +import TcMatches ( tcMatchesCase, tcMatchLambda, tcDoStmts, TcMatchCtxt(..) ) import TcHsType ( tcHsSigType, UserTypeCtxt(..) ) -import TcPat ( badFieldCon, refineTyVars ) -import TcMType ( tcInstTyVars, tcInstType, newTyFlexiVarTy, zonkTcType ) -import TcType ( Type, TcTyVar, TcType, TcSigmaType, TcRhoType, - tcSplitFunTys, tcSplitTyConApp, mkTyVarTys, - isSigmaTy, mkFunTy, mkTyConApp, tyVarsOfTypes, isLinearPred, - tcSplitSigmaTy, tidyOpenType +import TcPat ( tcOverloadedLit, badFieldCon ) +import TcMType ( tcInstTyVars, newFlexiTyVarTy, newBoxyTyVars, readFilledBox, + tcInstBoxyTyVar, tcInstTyVar ) +import TcType ( TcType, TcSigmaType, TcRhoType, + BoxySigmaType, BoxyRhoType, ThetaType, + mkTyVarTys, mkFunTys, tcMultiSplitSigmaTy, tcSplitFunTysN, + isSigmaTy, mkFunTy, mkTyConApp, isLinearPred, + exactTyVarsOfType, exactTyVarsOfTypes, mkTyVarTy, + zipTopTvSubst, zipOpenTvSubst, substTys, substTyVar, lookupTyVar ) -import Kind ( openTypeKind, liftedTypeKind, argTypeKind ) +import Kind ( argTypeKind ) -import Id ( idType, recordSelectorFieldLabel, isRecordSelector ) -import DataCon ( DataCon, dataConFieldLabels, dataConStrictMarks, - dataConWrapId ) +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, FieldLabel, tyConTyVars, tyConStupidTheta, - tyConDataCons, tyConFields ) -import Type ( zipTopTvSubst, substTheta, substTy ) -import Var ( tyVarKind ) -import VarSet ( emptyVarSet, elemVarSet ) +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, negateName ) -import ListSetOps ( minusList ) import DynFlags import StaticFlags ( opt_NoMethodSharing ) import HscTypes ( TyThing(..) ) -import SrcLoc ( Located(..), unLoc, getLoc ) +import SrcLoc ( Located(..), unLoc, noLoc, getLoc ) import Util +import ListSetOps ( assocMaybe ) +import Maybes ( catMaybes ) import Outputable import FastString #ifdef DEBUG -import TyCon ( isAlgTyCon ) +import TyCon ( tyConArity ) #endif \end{code} @@ -82,101 +86,122 @@ import TyCon ( isAlgTyCon ) %************************************************************************ \begin{code} --- 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 $$ ppr expr)) `thenM_` - tc_expr' expr expected_ty - -tc_expr' expr sigma_ty - | isSigmaTy sigma_ty - = tcGen sigma_ty emptyVarSet ( - \ rho_ty -> tcCheckRho expr rho_ty - ) `thenM` \ (gen_fn, expr') -> - returnM (L (getLoc expr') (gen_fn <$> unLoc expr')) - -tc_expr' expr rho_ty -- Monomorphic case - = tcCheckRho expr rho_ty -\end{code} - -Typecheck expression which in most cases will be an Id. -The expression can return a higher-ranked type, such as - (forall a. a->a) -> Int -so we must create a hole to pass in as the expected tyvar. +tcPolyExpr, tcPolyExprNC + :: LHsExpr Name -- Expession to type check + -> BoxySigmaType -- Expected type (could be a polytpye) + -> TcM (LHsExpr TcId) -- Generalised expr with expected type + +-- tcPolyExpr is a convenient place (frequent but not too frequent) place +-- to add context information. +-- The NC version does not do so, usually because the caller wants +-- to do so himself. + +tcPolyExpr expr res_ty + = addErrCtxt (exprCtxt (unLoc expr)) $ + tcPolyExprNC expr res_ty + +tcPolyExprNC expr res_ty + | isSigmaTy res_ty + = do { (gen_fn, expr') <- tcGen res_ty emptyVarSet (tcPolyExprNC expr) + -- Note the recursive call to tcPolyExpr, because the + -- type may have multiple layers of for-alls + ; return (L (getLoc expr') (mkHsCoerce gen_fn (unLoc expr'))) } + + | otherwise + = tcMonoExpr expr res_ty + +--------------- +tcPolyExprs :: [LHsExpr Name] -> [TcType] -> TcM [LHsExpr TcId] +tcPolyExprs [] [] = returnM [] +tcPolyExprs (expr:exprs) (ty:tys) + = do { expr' <- tcPolyExpr expr ty + ; exprs' <- tcPolyExprs exprs tys + ; returnM (expr':exprs') } +tcPolyExprs exprs tys = pprPanic "tcPolyExprs" (ppr exprs $$ 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) -\begin{code} -tcCheckRho :: LHsExpr Name -> TcRhoType -> TcM (LHsExpr TcId) -tcCheckRho expr rho_ty = tcMonoExpr expr (Check rho_ty) +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 (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 <$> expr') } -tcSyntaxOp orig other ty = pprPanic "tcSyntaxOp" (ppr other) +tcInferRho expr = tcInfer (tcMonoExpr expr) \end{code} %************************************************************************ %* * -\subsection{The TAUT rules for variables}TcExpr + tcExpr: the main expression typechecker %* * %************************************************************************ \begin{code} -tcMonoExpr :: LHsExpr Name -- Expession to type check - -> Expected TcRhoType -- Expected type (could be a type variable) - -- Definitely no foralls at the top - -- Can be a 'hole'. - -> TcM (LHsExpr TcId) +tcExpr :: HsExpr Name -> BoxyRhoType -> TcM (HsExpr TcId) +tcExpr (HsVar name) res_ty = tcId (OccurrenceOf name) name res_ty -tcMonoExpr (L loc expr) res_ty - = setSrcSpan loc (do { expr' <- tcExpr expr res_ty - ; return (L loc expr') }) +tcExpr (HsLit lit) res_ty = do { boxyUnify (hsLitType lit) res_ty + ; return (HsLit lit) } -tcExpr :: HsExpr Name -> Expected TcRhoType -> TcM (HsExpr TcId) -tcExpr (HsVar name) res_ty - = do { (expr', _, id_ty) <- tcId (OccurrenceOf name) name - ; co_fn <- tcSubExp res_ty id_ty - ; returnM (co_fn <$> expr') } +tcExpr (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 - = -- 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} + = 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')) } -%************************************************************************ -%* * -\subsection{Expressions type signatures} -%* * -%************************************************************************ +tcExpr (HsLam match) res_ty + = do { (co_fn, match') <- tcMatchLambda match res_ty + ; return (mkHsCoerce co_fn (HsLam match')) } -\begin{code} -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 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) @@ -190,153 +215,110 @@ tcExpr (HsType ty) res_ty %************************************************************************ %* * -\subsection{Other expression forms} + Infix operators and sections %* * %************************************************************************ \begin{code} -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 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') } -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} -- 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. -tcExpr in_expr@(SectionL arg1 op) res_ty - = tcInferRho op `thenM` \ (op', op_ty) -> - unifyFunTys 2 op_ty {- two args -} `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') +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 - -tcExpr in_expr@(SectionR op arg2) res_ty - = tcInferRho op `thenM` \ (op', op_ty) -> - unifyFunTys 2 op_ty {- two args -} `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') - --- equivalent to (op e1) e2: - -tcExpr in_expr@(OpApp arg1 op fix arg2) res_ty - = tcInferRho op `thenM` \ (op', op_ty) -> - unifyFunTys 2 op_ty {- two args -} `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') + +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} \begin{code} -tcExpr (HsLet binds (L loc expr)) res_ty - = tcBindsAndThen - glue - binds -- Bindings to check - (setSrcSpan loc $ tcExpr expr res_ty) - where - glue bind expr = HsLet [bind] (L loc 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') +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 = tcMonoExpr } + mc_body = tcPolyExpr } tcExpr (HsIf pred b1 b2) res_ty - = addErrCtxt (predCtxt pred) - (tcCheckRho pred boolTy) `thenM` \ pred' -> - - zapExpectedType res_ty openTypeKind `thenM` \ res_ty' -> - -- C.f. the call to zapToType in TcMatches.tcMatches - - tcCheckRho b1 res_ty' `thenM` \ b1' -> - tcCheckRho b2 res_ty' `thenM` \ b2' -> - returnM (HsIf pred' b1' b2') + = 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 - = zapToListTy res_ty `thenM` \ elt_ty -> - mappM (tc_elt elt_ty) exprs `thenM` \ exprs' -> - returnM (ExplicitList elt_ty exprs') + = do { elt_ty <- boxySplitListTy res_ty + ; exprs' <- mappM (tc_elt elt_ty) exprs + ; return (ExplicitList elt_ty exprs') } where - tc_elt elt_ty expr - = addErrCtxt (listCtxt expr) $ - tcCheckRho expr elt_ty + tc_elt elt_ty expr = tcPolyExpr 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 + = 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 - = addErrCtxt (parrCtxt expr) (tcCheckRho expr elt_ty) + tc_elt elt_ty expr = tcPolyExpr expr elt_ty tcExpr (ExplicitTuple exprs boxity) res_ty - = do { arg_tys <- zapToTyConApp (tupleTyCon boxity (length exprs)) res_ty - ; exprs' <- tcCheckRhos exprs arg_tys + = do { arg_tys <- boxySplitTyConApp (tupleTyCon boxity (length exprs)) res_ty + ; exprs' <- tcPolyExprs exprs arg_tys ; return (ExplicitTuple exprs' boxity) } tcExpr (HsProc pat cmd) res_ty - = tcProc pat cmd res_ty `thenM` \ (pat', cmd') -> - returnM (HsProc pat' cmd') + = do { (pat', cmd') <- tcProc pat cmd res_ty + ; return (HsProc pat' cmd') } tcExpr e@(HsArrApp _ _ _ _ _) _ = failWithTc (vcat [ptext SLIT("The arrow command"), nest 2 (ppr e), @@ -354,34 +336,23 @@ tcExpr e@(HsArrForm _ _ _) _ %************************************************************************ \begin{code} -tcExpr expr@(RecordCon con@(L loc con_name) _ rbinds) res_ty - = addErrCtxt (recordConCtxt expr) $ - addLocM (tcId (OccurrenceOf con_name)) con `thenM` \ (con_expr, _, con_tau) -> - let - (_, record_ty) = tcSplitFunTys con_tau - (tycon, ty_args) = tcSplitTyConApp record_ty - in - ASSERT( isAlgTyCon tycon ) - zapExpectedTo res_ty record_ty `thenM_` - - -- Check that the record bindings match the constructor - -- con_name is syntactically constrained to be a data constructor - tcLookupDataCon con_name `thenM` \ data_con -> - let - bad_fields = badFields rbinds data_con - in - if notNull bad_fields then - mappM (addErrTc . badFieldCon data_con) bad_fields `thenM_` - failM -- Fail now, because tcRecordBinds will crash on a bad field - else +tcExpr expr@(RecordCon (L loc con_name) _ rbinds) res_ty + = do { data_con <- tcLookupDataCon con_name - -- Typecheck the record bindings - tcRecordBinds tycon ty_args rbinds `thenM` \ rbinds' -> - -- Check for missing fields - checkMissingFields data_con rbinds `thenM_` + ; checkMissingFields data_con rbinds + + ; 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 - returnM (RecordCon (L loc (dataConWrapId data_con)) con_expr rbinds') + ; (con_expr, rbinds') <- tcIdApp con_name arity check_fields res_ty + + ; 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: @@ -408,11 +379,16 @@ tcExpr expr@(RecordCon con@(L loc 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. -tcExpr expr@(RecordUpd record_expr rbinds _ _) res_ty - = addErrCtxt (recordUpdCtxt expr) $ - -- STEP 0 +tcExpr expr@(RecordUpd record_expr rbinds _ _) res_ty + = -- STEP 0 -- Check that the field names are really field names ASSERT( notNull rbinds ) let @@ -433,28 +409,24 @@ tcExpr expr@(RecordUpd record_expr rbinds _ _) res_ty -- 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) - sel_id : _ = sel_ids - (tycon, _) = recordSelectorFieldLabel sel_id -- We've failed already if - data_cons = tyConDataCons tycon -- it's not a field label - tycon_tyvars = tyConTyVars tycon -- The data cons use the same type vars + 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 tycon_tyvars `thenM` \ (_, result_inst_tys, inst_env) -> -- 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) + 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 - zapExpectedTo res_ty result_record_ty `thenM_` - tcRecordBinds tycon result_inst_tys rbinds `thenM` \ rbinds' -> + -- 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 @@ -463,31 +435,44 @@ tcExpr 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 = recBindFields 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 + -- 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) ] - non_upd_field_lbls = concat relevant_field_lbls_s `minusList` upd_field_lbls - common_tyvars = tyVarsOfTypes [ty | (fld,ty,_) <- tyConFields tycon, - fld `elem` non_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 + | otherwise = newFlexiTyVarTy (tyVarKind tv) -- Fresh type, of correct kind in - zipWithM mk_inst_ty tycon_tyvars result_inst_tys `thenM` \ inst_tys -> + tcInstTyVars con1_tyvars `thenM` \ (_, result_inst_tys, inst_env) -> + zipWithM mk_inst_ty con1_tyvars result_inst_tys `thenM` \ inst_tys -> + + -- 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 + 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 - tcCheckRho record_expr record_ty `thenM` \ record_expr' -> + tcMonoExpr record_expr record_ty `thenM` \ record_expr' -> -- STEP 6 -- Figure out the LIE we need. We have to generate some @@ -495,7 +480,8 @@ tcExpr expr@(RecordUpd record_expr rbinds _ _) res_ty -- do pattern matching over the data cons. -- -- What dictionaries do we need? - -- We just take the context of the type constructor + -- 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 theta' = substTheta inst_env (tyConStupidTheta tycon) in @@ -503,7 +489,7 @@ tcExpr expr@(RecordUpd record_expr rbinds _ _) res_ty extendLIEs dicts `thenM_` -- Phew! - returnM (RecordUpd record_expr' rbinds' record_ty result_record_ty) + returnM (mkHsCoerce co_fn (RecordUpd record_expr' rbinds' record_ty result_record_ty)) \end{code} @@ -517,66 +503,54 @@ tcExpr expr@(RecordUpd record_expr rbinds _ _) res_ty \begin{code} 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')) + = 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 - = 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')) + = 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 - = 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')) + = 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 - = 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')) + = 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 - = 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')) + = 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 - = 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')) + = 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!" @@ -614,48 +588,159 @@ tcExpr other _ = pprPanic "tcMonoExpr" (ppr other) %************************************************************************ %* * -\subsection{@tcApp@ typchecks an application} + Applications %* * %************************************************************************ \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 <- tcFunResTy fun_name 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} -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 { (fun', fun_tvs, fun_tau) <- tcFun fun -- Type-check the function - - -- Extract its argument types - ; (expected_arg_tys, actual_res_ty) - <- addErrCtxt (wrongArgsCtxt "too many" fun args) $ do - { traceTc (text "tcApp" <+> (ppr fun $$ ppr fun_tau)) - ; unifyFunTys (length 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 [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 <- tcFunResTy fun_name 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] -- @@ -680,81 +765,105 @@ tcApp fun args res_ty -- 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 +--------------------------- +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) -tcArgs fun fun' args expected_arg_tys - = do { args' <- mappM (tcArg fun) (zip3 args expected_arg_tys [1..]) - ; return (unLoc (foldl mkHsApp fun' args')) } +--------------------------- +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) -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'' + go fun [] = return fun - len_act_args = length act_args - len_exp_args = length exp_args + 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 } - 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) + -- 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} +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 -%************************************************************************ -%* * -\subsection{@tcId@ typchecks an identifier occurrence} -%* * -%************************************************************************ + 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. -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)} +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. + +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 @@ -770,121 +879,112 @@ This gets a bit less sharing, but b) perhaps fewer separated lambdas \begin{code} -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) -> 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 +tcArgs :: LHsExpr Name -- The function (for error messages) + -> [LHsExpr Name] -> [TcSigmaType] -- Actual arguments and expected arg types + -> TcM [LHsExpr TcId] -- Resulting args -#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)) +tcArgs fun args expected_arg_tys + = mapM (tcArg fun) (zip3 args expected_arg_tys [1..]) - other -> - checkWellStaged (quotes (ppr id)) th_bind_lvl use_stage `thenM_` - instantiate id -#endif /* GHCI */ +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 +\end{code} + + +%************************************************************************ +%* * +\subsection{@tcId@ typchecks an identifier occurrence} +%* * +%************************************************************************ - instantiate :: TcId -> TcM (HsExpr TcId, [TcTyVar], TcRhoType) - instantiate fun_id = loop (HsVar fun_id) [] (idType fun_id) +\begin{code} +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 - 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 +#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 - 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 + other -> failWithTc (ppr other <+> ptext SLIT("used where a value identifer was expected")) + } - | otherwise - = returnM (fun, tvs, fun_ty) +#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) - -- 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) + ; return id } } +#endif /* GHCI */ \end{code} + %************************************************************************ %* * \subsection{Record bindings} @@ -910,39 +1010,26 @@ 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 + :: DataCon + -> [TcType] -- Expected type for each field -> HsRecordBinds Name -> TcM (HsRecordBinds TcId) -tcRecordBinds tycon ty_args rbinds - = mappM do_bind rbinds +tcRecordBinds data_con arg_tys rbinds + = do { mb_binds <- mappM do_bind rbinds + ; return (catMaybes mb_binds) } where - tenv = zipTopTvSubst (tyConTyVars tycon) ty_args - + 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) $ - let - field_ty = tyConFieldType tycon field_lbl - field_ty' = substTy tenv field_ty - in - tcCheckSigma rhs field_ty' `thenM` \ rhs' -> - tcLookupId field_lbl `thenM` \ sel_id -> - ASSERT( isRecordSelector sel_id ) - returnM (L loc sel_id, rhs') - -tyConFieldType :: TyCon -> FieldLabel -> Type -tyConFieldType tycon field_lbl - = case [ty | (f,ty,_) <- tyConFields tycon, f == field_lbl] of - (ty:other) -> ASSERT( null other) ty - -- This lookup and assertion will surely succeed, because - -- we check that the fields are indeed record selectors - -- before calling tcRecordBinds - -badFields rbinds data_con - = filter (not . (`elem` field_names)) (recBindFields rbinds) - where - field_names = dataConFieldLabels data_con + 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 @@ -986,54 +1073,12 @@ checkMissingFields data_con rbinds %************************************************************************ %* * -\subsection{@tcCheckRhos@ typechecks a {\em list} of expressions} -%* * -%************************************************************************ - -\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') -\end{code} - - -%************************************************************************ -%* * -\subsection{Literals} -%* * -%************************************************************************ - -Overloaded literals. - -\begin{code} -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} -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) @@ -1048,26 +1093,21 @@ funAppCtxt fun arg arg_no quotes (ppr fun) <> text ", namely"]) 4 (quotes (ppr arg)) -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) -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")] @@ -1088,13 +1128,8 @@ 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 +callCtxt fun args + = ptext SLIT("In the call") <+> parens (ppr (foldl mkHsApp fun args)) #ifdef GHCI polySpliceErr :: Id -> SDoc