X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcExpr.lhs;h=32f687fab65f2ec440a932c3030c168fd92ba2a3;hb=9003a18c4efa4548ae80709aef9963f7b544ded3;hp=2e984fec3bfc8ec26447e53b0755e1d7c8ae66a8;hpb=9e93335020e64a811dbbb223e1727c76933a93ae;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcExpr.lhs b/ghc/compiler/typecheck/TcExpr.lhs index 2e984fe..32f687f 100644 --- a/ghc/compiler/typecheck/TcExpr.lhs +++ b/ghc/compiler/typecheck/TcExpr.lhs @@ -4,60 +4,62 @@ \section[TcExpr]{Typecheck an expression} \begin{code} -module TcExpr ( tcApp, tcExpr, tcMonoExpr, tcPolyExpr, tcId ) where +module TcExpr ( tcExpr, tcMonoExpr, tcId ) where #include "HsVersions.h" import HsSyn ( HsExpr(..), HsLit(..), ArithSeqInfo(..), - HsMatchContext(..), HsDoContext(..), mkMonoBind + HsMatchContext(..), HsDoContext(..), + mkMonoBind ) import RnHsSyn ( RenamedHsExpr, RenamedRecordBinds ) -import TcHsSyn ( TcExpr, TcRecordBinds, mkHsLet ) +import TcHsSyn ( TcExpr, TcRecordBinds, simpleHsLitTy, mkHsDictApp, mkHsTyApp ) import TcMonad +import TcUnify ( tcSubExp, tcGen, (<$>), + unifyTauTy, unifyFunTy, unifyListTy, unifyPArrTy, + unifyTupleTy ) import BasicTypes ( RecFlag(..), isMarkedStrict ) import Inst ( InstOrigin(..), LIE, mkLIE, emptyLIE, unitLIE, plusLIE, plusLIEs, newOverloadedLit, newMethod, newIPDict, - newDicts, - instToId, tcInstId + newDicts, newMethodWithGivenTy, + instToId, tcInstCall, tcInstDataCon ) import TcBinds ( tcBindsAndThen ) import TcEnv ( tcLookupClass, tcLookupGlobalId, tcLookupGlobal_maybe, - tcLookupTyCon, tcLookupDataCon, tcLookupId, - tcExtendGlobalTyVars + tcLookupTyCon, tcLookupDataCon, tcLookupId ) import TcMatches ( tcMatchesCase, tcMatchLambda, tcStmts ) -import TcMonoType ( tcHsSigType, UserTypeCtxt(..), checkSigTyVars, sigCtxt ) -import TcPat ( badFieldCon, simpleHsLitTy ) -import TcSimplify ( tcSimplifyCheck, tcSimplifyIPs ) -import TcMType ( tcInstTyVars, tcInstType, - newTyVarTy, newTyVarTys, zonkTcType, - unifyTauTy, unifyFunTy, unifyListTy, unifyTupleTy - ) -import TcType ( tcSplitFunTys, tcSplitTyConApp, - isQualifiedTy, - mkFunTy, mkAppTy, mkTyConTy, +import TcMonoType ( tcHsSigType, UserTypeCtxt(..) ) +import TcPat ( badFieldCon ) +import TcSimplify ( tcSimplifyIPs ) +import TcMType ( tcInstTyVars, tcInstType, newHoleTyVarTy, zapToType, + newTyVarTy, newTyVarTys, zonkTcType, readHoleResult ) +import TcType ( TcType, TcSigmaType, TcRhoType, TyVarDetails(VanillaTv), + tcSplitFunTys, tcSplitTyConApp, mkTyVarTys, + isSigmaTy, mkFunTy, mkAppTy, mkTyConTy, mkFunTys, mkTyConApp, mkClassPred, tcFunArgTy, - isTauTy, tyVarsOfType, tyVarsOfTypes, + tyVarsOfTypes, isLinearPred, liftedTypeKind, openTypeKind, mkArrowKind, tcSplitSigmaTy, tcTyConAppTyCon, tidyOpenType ) import FieldLabel ( FieldLabel, fieldLabelName, fieldLabelType, fieldLabelTyCon ) -import Id ( idType, recordSelectorFieldLabel, isRecordSelector ) +import Id ( idType, recordSelectorFieldLabel, isRecordSelector, isDataConWrapId_maybe ) import DataCon ( dataConFieldLabels, dataConSig, dataConStrictMarks ) import Name ( Name ) -import TyCon ( TyCon, tyConTyVars, isAlgTyCon, tyConDataCons ) +import TyCon ( TyCon, tyConTyVars, tyConTheta, isAlgTyCon, tyConDataCons ) import Subst ( mkTopTyVarSubst, substTheta, substTy ) -import VarSet ( elemVarSet ) -import TysWiredIn ( boolTy, mkListTy, listTyCon ) +import VarSet ( emptyVarSet, elemVarSet ) +import TysWiredIn ( boolTy, mkListTy, mkPArrTy, listTyCon, parrTyCon ) import PrelNames ( cCallableClassName, cReturnableClassName, enumFromName, enumFromThenName, enumFromToName, enumFromThenToName, + enumFromToPName, enumFromThenToPName, thenMName, failMName, returnMName, ioTyConName ) import Outputable @@ -75,112 +77,77 @@ import HscTypes ( TyThing(..) ) %************************************************************************ \begin{code} -tcExpr :: RenamedHsExpr -- Expession to type check - -> TcType -- Expected type (could be a polytpye) - -> TcM (TcExpr, LIE) - -tcExpr expr ty | isQualifiedTy ty = -- Polymorphic case - tcPolyExpr expr ty `thenTc` \ (expr', lie, _, _, _) -> - returnTc (expr', lie) - - | otherwise = -- Monomorphic case - tcMonoExpr expr ty +tcExpr :: RenamedHsExpr -- Expession to type check + -> TcSigmaType -- Expected type (could be a polytpye) + -> TcM (TcExpr, LIE) -- Generalised expr with expected type, and LIE + +tcExpr expr expected_ty + = traceTc (text "tcExpr" <+> (ppr expected_ty $$ ppr expr)) `thenNF_Tc_` + tc_expr' expr expected_ty + +tc_expr' expr expected_ty + | not (isSigmaTy expected_ty) -- Monomorphic case + = tcMonoExpr expr expected_ty + + | otherwise + = tcGen expected_ty emptyVarSet ( + tcMonoExpr expr + ) `thenTc` \ (gen_fn, expr', lie) -> + returnTc (gen_fn <$> expr', lie) \end{code} %************************************************************************ %* * -\subsection{@tcPolyExpr@ typchecks an application} +\subsection{The TAUT rules for variables} %* * %************************************************************************ \begin{code} --- tcPolyExpr is like tcMonoExpr, except that the expected type --- can be a polymorphic one. -tcPolyExpr :: RenamedHsExpr - -> TcType -- Expected type - -> TcM (TcExpr, LIE, -- Generalised expr with expected type, and LIE - TcExpr, TcTauType, LIE) -- Same thing, but instantiated; tau-type returned - -tcPolyExpr arg expected_arg_ty - = -- Ha! The argument type of the function is a for-all type, - -- An example of rank-2 polymorphism. - - -- To ensure that the forall'd type variables don't get unified with each - -- other or any other types, we make fresh copy of the alleged type - tcInstType expected_arg_ty `thenNF_Tc` \ (sig_tyvars, sig_theta, sig_tau) -> - let - free_tvs = tyVarsOfType expected_arg_ty - in - -- Type-check the arg and unify with expected type - tcMonoExpr arg sig_tau `thenTc` \ (arg', lie_arg) -> - - -- Check that the sig_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. - - tcExtendGlobalTyVars free_tvs $ - tcAddErrCtxtM (sigCtxt sig_msg sig_tyvars sig_theta sig_tau) $ - - newDicts SignatureOrigin sig_theta `thenNF_Tc` \ sig_dicts -> - tcSimplifyCheck - (text "the type signature of an expression") - sig_tyvars - sig_dicts lie_arg `thenTc` \ (free_insts, inst_binds) -> - - checkSigTyVars sig_tyvars free_tvs `thenTc` \ zonked_sig_tyvars -> +tcMonoExpr :: RenamedHsExpr -- Expession to type check + -> TcRhoType -- Expected type (could be a type variable) + -- Definitely no foralls at the top + -- Can be a 'hole'. + -> TcM (TcExpr, LIE) - let - -- This HsLet 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. - generalised_arg = TyLam zonked_sig_tyvars $ - DictLam (map instToId sig_dicts) $ - mkHsLet inst_binds $ - arg' - in - returnTc ( generalised_arg, free_insts, - arg', sig_tau, lie_arg ) - where - sig_msg = ptext SLIT("When checking an expression type signature") +tcMonoExpr (HsVar name) res_ty + = tcId name `thenNF_Tc` \ (expr', lie1, id_ty) -> + tcSubExp res_ty id_ty `thenTc` \ (co_fn, lie2) -> + returnTc (co_fn <$> expr', lie1 `plusLIE` lie2) + +tcMonoExpr (HsIPVar ip) res_ty + = -- Implicit parameters must have a *tau-type* not a + -- type scheme. We enforce this by creating a fresh + -- type variable as its type. (Because res_ty may not + -- be a tau-type.) + newTyVarTy openTypeKind `thenNF_Tc` \ ip_ty -> + newIPDict (IPOcc ip) ip ip_ty `thenNF_Tc` \ (ip', inst) -> + tcSubExp res_ty ip_ty `thenTc` \ (co_fn, lie) -> + returnNF_Tc (co_fn <$> HsIPVar ip', lie `plusLIE` unitLIE inst) \end{code} + %************************************************************************ %* * -\subsection{The TAUT rules for variables} +\subsection{Expressions type signatures} %* * %************************************************************************ \begin{code} -tcMonoExpr :: RenamedHsExpr -- Expession to type check - -> TcTauType -- Expected type (could be a type variable) - -> TcM (TcExpr, LIE) - -tcMonoExpr (HsVar name) res_ty - = tcId name `thenNF_Tc` \ (expr', lie, id_ty) -> - unifyTauTy res_ty id_ty `thenTc_` +tcMonoExpr in_expr@(ExprWithTySig expr poly_ty) res_ty + = tcHsSigType ExprSigCtxt poly_ty `thenTc` \ sig_tc_ty -> + tcExpr expr sig_tc_ty `thenTc` \ (expr', lie1) -> - -- Check that the result type doesn't have any nested for-alls. - -- For example, a "build" on its own is no good; it must be - -- applied to something. - checkTc (isTauTy id_ty) - (lurkingRank2Err name id_ty) `thenTc_` + -- Must instantiate the outer for-alls of sig_tc_ty + -- else we risk instantiating a ? res_ty to a forall-type + -- which breaks the invariant that tcMonoExpr only returns phi-types + tcAddErrCtxt (exprSigCtxt in_expr) $ + tcInstCall SignatureOrigin sig_tc_ty `thenNF_Tc` \ (inst_fn, lie2, inst_sig_ty) -> + tcSubExp res_ty inst_sig_ty `thenTc` \ (co_fn, lie3) -> - returnTc (expr', lie) + returnTc (co_fn <$> inst_fn expr', lie1 `plusLIE` lie2 `plusLIE` lie3) \end{code} -\begin{code} -tcMonoExpr (HsIPVar name) res_ty - = newIPDict (IPOcc name) name res_ty `thenNF_Tc` \ ip -> - returnNF_Tc (HsIPVar (instToId ip), unitLIE ip) -\end{code} %************************************************************************ %* * @@ -200,17 +167,8 @@ tcMonoExpr (HsLam match) res_ty = tcMatchLambda match res_ty `thenTc` \ (match',lie) -> returnTc (HsLam match', lie) -tcMonoExpr (HsApp e1 e2) res_ty = accum e1 [e2] - where - accum (HsApp e1 e2) args = accum e1 (e2:args) - accum fun args - = tcApp fun args res_ty `thenTc` \ (fun', args', lie) -> - returnTc (foldl HsApp fun' args', lie) - --- equivalent to (op e1) e2: -tcMonoExpr (OpApp arg1 op fix arg2) res_ty - = tcApp op [arg1,arg2] res_ty `thenTc` \ (op', [arg1', arg2'], lie) -> - returnTc (OpApp arg1' op' fix arg2', lie) +tcMonoExpr (HsApp e1 e2) res_ty + = tcApp e1 [e2] res_ty \end{code} Note that the operators in sections are expected to be binary, and @@ -224,30 +182,36 @@ a type error will occur if they aren't. -- or just -- op e -tcMonoExpr in_expr@(SectionL arg op) res_ty - = tcApp op [arg] res_ty `thenTc` \ (op', [arg'], lie) -> - - -- Check that res_ty is a function type - -- Without this check we barf in the desugarer on - -- f op = (3 `op`) - -- because it tries to desugar to - -- f op = \r -> 3 op r - -- so (3 `op`) had better be a function! - tcAddErrCtxt (sectionLAppCtxt in_expr) $ - unifyFunTy res_ty `thenTc_` - - returnTc (SectionL arg' op', lie) +tcMonoExpr in_expr@(SectionL arg1 op) res_ty + = tcExpr_id op `thenTc` \ (op', lie1, op_ty) -> + split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) -> + tcArg op (arg1, arg1_ty, 1) `thenTc` \ (arg1',lie2) -> + tcAddErrCtxt (exprCtxt in_expr) $ + tcSubExp res_ty (mkFunTy arg2_ty op_res_ty) `thenTc` \ (co_fn, lie3) -> + returnTc (co_fn <$> SectionL arg1' op', lie1 `plusLIE` lie2 `plusLIE` lie3) -- Right sections, equivalent to \ x -> x op expr, or -- \ x -> op x expr -tcMonoExpr in_expr@(SectionR op expr) res_ty - = tcExpr_id op `thenTc` \ (op', lie1, op_ty) -> - tcAddErrCtxt (sectionRAppCtxt in_expr) $ - split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) -> - tcMonoExpr expr arg2_ty `thenTc` \ (expr',lie2) -> - unifyTauTy res_ty (mkFunTy arg1_ty op_res_ty) `thenTc_` - returnTc (SectionR op' expr', lie1 `plusLIE` lie2) +tcMonoExpr in_expr@(SectionR op arg2) res_ty + = tcExpr_id op `thenTc` \ (op', lie1, op_ty) -> + split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) -> + tcArg op (arg2, arg2_ty, 2) `thenTc` \ (arg2',lie2) -> + tcAddErrCtxt (exprCtxt in_expr) $ + tcSubExp res_ty (mkFunTy arg1_ty op_res_ty) `thenTc` \ (co_fn, lie3) -> + returnTc (co_fn <$> SectionR op' arg2', lie1 `plusLIE` lie2 `plusLIE` lie3) + +-- equivalent to (op e1) e2: + +tcMonoExpr in_expr@(OpApp arg1 op fix arg2) res_ty + = tcExpr_id op `thenTc` \ (op', lie1, op_ty) -> + split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) -> + tcArg op (arg1, arg1_ty, 1) `thenTc` \ (arg1',lie2a) -> + tcArg op (arg2, arg2_ty, 2) `thenTc` \ (arg2',lie2b) -> + tcAddErrCtxt (exprCtxt in_expr) $ + tcSubExp res_ty op_res_ty `thenTc` \ (co_fn, lie3) -> + returnTc (OpApp arg1' op' fix arg2', + lie1 `plusLIE` lie2a `plusLIE` lie2b `plusLIE` lie3) \end{code} The interesting thing about @ccall@ is that it is just a template @@ -354,8 +318,11 @@ tcMonoExpr (HsIf pred b1 b2 src_loc) res_ty tcAddErrCtxt (predCtxt pred) ( tcMonoExpr pred boolTy ) `thenTc` \ (pred',lie1) -> - tcMonoExpr b1 res_ty `thenTc` \ (b1',lie2) -> - tcMonoExpr b2 res_ty `thenTc` \ (b2',lie3) -> + zapToType res_ty `thenTc` \ res_ty' -> + -- C.f. the call to zapToType in TcMatches.tcMatches + + tcMonoExpr b1 res_ty' `thenTc` \ (b1',lie2) -> + tcMonoExpr b2 res_ty' `thenTc` \ (b2',lie3) -> returnTc (HsIf pred' b1' b2' src_loc, plusLIE lie1 (plusLIE lie2 lie3)) \end{code} @@ -374,6 +341,15 @@ tcMonoExpr in_expr@(ExplicitList _ exprs) res_ty -- Non-empty list = tcAddErrCtxt (listCtxt expr) $ tcMonoExpr expr elt_ty +tcMonoExpr in_expr@(ExplicitPArr _ exprs) res_ty -- maybe empty + = unifyPArrTy res_ty `thenTc` \ elt_ty -> + mapAndUnzipTc (tc_elt elt_ty) exprs `thenTc` \ (exprs', lies) -> + returnTc (ExplicitPArr elt_ty exprs', plusLIEs lies) + where + tc_elt elt_ty expr + = tcAddErrCtxt (parrCtxt expr) $ + tcMonoExpr expr elt_ty + tcMonoExpr (ExplicitTuple exprs boxity) res_ty = unifyTupleTy boxity (length exprs) res_ty `thenTc` \ arg_tys -> mapAndUnzipTc (\ (expr, arg_ty) -> tcMonoExpr expr arg_ty) @@ -468,15 +444,16 @@ tcMonoExpr 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) - (Just (AnId sel_id) : _) = maybe_sel_ids - (_, _, tau) = tcSplitSigmaTy (idType sel_id) -- Selectors can be overloaded - -- when the data type has a context - data_ty = tcFunArgTy tau -- Must succeed since sel_id is a selector - tycon = tcTyConAppTyCon data_ty - data_cons = tyConDataCons tycon - (con_tyvars, _, _, _, _, _) = dataConSig (head data_cons) + (Just (AnId sel_id) : _) = maybe_sel_ids + + (_, _, tau) = tcSplitSigmaTy (idType sel_id) -- Selectors can be overloaded + -- when the data type has a context + data_ty = tcFunArgTy tau -- Must succeed since sel_id is a selector + tycon = tcTyConAppTyCon data_ty + data_cons = tyConDataCons tycon + tycon_tyvars = tyConTyVars tycon -- The data cons use the same type vars in - tcInstTyVars con_tyvars `thenNF_Tc` \ (_, result_inst_tys, _) -> + tcInstTyVars VanillaTv tycon_tyvars `thenNF_Tc` \ (_, result_inst_tys, inst_env) -> -- STEP 2 -- Check that at least one constructor has all the named fields @@ -514,35 +491,31 @@ tcMonoExpr expr@(RecordUpd record_expr rbinds) res_ty mk_inst_ty (tyvar, result_inst_ty) | tyvar `elemVarSet` common_tyvars = returnNF_Tc result_inst_ty -- Same as result type - | otherwise = newTyVarTy liftedTypeKind -- Fresh type + | otherwise = newTyVarTy liftedTypeKind -- Fresh type in - mapNF_Tc mk_inst_ty (zip con_tyvars result_inst_tys) `thenNF_Tc` \ inst_tys -> + mapNF_Tc mk_inst_ty (zip tycon_tyvars result_inst_tys) `thenNF_Tc` \ inst_tys -> -- STEP 5 -- Typecheck the expression to be updated let record_ty = mkTyConApp tycon inst_tys in - tcMonoExpr record_expr record_ty `thenTc` \ (record_expr', record_lie) -> + tcMonoExpr record_expr record_ty `thenTc` \ (record_expr', record_lie) -> -- STEP 6 -- Figure out the LIE we need. We have to generate some -- dictionaries for the data type context, since we are going to - -- do some construction. + -- do pattern matching over the data cons. -- - -- What dictionaries do we need? For the moment we assume that all - -- data constructors have the same context, and grab it from the first - -- constructor. If they have varying contexts then we'd have to - -- union the ones that could participate in the update. + -- What dictionaries do we need? + -- We just take the context of the type constructor let - (tyvars, theta, _, _, _, _) = dataConSig (head data_cons) - inst_env = mkTopTyVarSubst tyvars result_inst_tys - theta' = substTheta inst_env theta + theta' = substTheta inst_env (tyConTheta tycon) in newDicts RecordUpdOrigin theta' `thenNF_Tc` \ dicts -> -- Phew! - returnTc (RecordUpdOut record_expr' record_ty result_record_ty (map instToId dicts) rbinds', + returnTc (RecordUpdOut record_expr' record_ty result_record_ty rbinds', mkLIE dicts `plusLIE` record_lie `plusLIE` rbinds_lie) tcMonoExpr (ArithSeqIn seq@(From expr)) res_ty @@ -592,64 +565,63 @@ tcMonoExpr in_expr@(ArithSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty returnTc (ArithSeqOut (HsVar (instToId eft)) (FromThenTo expr1' expr2' expr3'), lie1 `plusLIE` lie2 `plusLIE` lie3 `plusLIE` unitLIE eft) + +tcMonoExpr in_expr@(PArrSeqIn seq@(FromTo expr1 expr2)) res_ty + = tcAddErrCtxt (parrSeqCtxt in_expr) $ + unifyPArrTy res_ty `thenTc` \ elt_ty -> + tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) -> + tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) -> + tcLookupGlobalId enumFromToPName `thenNF_Tc` \ sel_id -> + newMethod (PArrSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ enum_from_to -> + + returnTc (PArrSeqOut (HsVar (instToId enum_from_to)) + (FromTo expr1' expr2'), + lie1 `plusLIE` lie2 `plusLIE` unitLIE enum_from_to) + +tcMonoExpr in_expr@(PArrSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty + = tcAddErrCtxt (parrSeqCtxt in_expr) $ + unifyPArrTy res_ty `thenTc` \ elt_ty -> + tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) -> + tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) -> + tcMonoExpr expr3 elt_ty `thenTc` \ (expr3',lie3) -> + tcLookupGlobalId enumFromThenToPName `thenNF_Tc` \ sel_id -> + newMethod (PArrSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ eft -> + + returnTc (PArrSeqOut (HsVar (instToId eft)) + (FromThenTo expr1' expr2' expr3'), + lie1 `plusLIE` lie2 `plusLIE` lie3 `plusLIE` unitLIE eft) + +tcMonoExpr (PArrSeqIn _) _ + = panic "TcExpr.tcMonoExpr: Infinite parallel array!" + -- the parser shouldn't have generated it and the renamer shouldn't have + -- let it through \end{code} %************************************************************************ %* * -\subsection{Expressions type signatures} +\subsection{Implicit Parameter bindings} %* * %************************************************************************ \begin{code} -tcMonoExpr in_expr@(ExprWithTySig expr poly_ty) res_ty - = tcHsSigType ExprSigCtxt poly_ty `thenTc` \ sig_tc_ty -> - - tcAddErrCtxt (exprSigCtxt in_expr) $ - if not (isQualifiedTy sig_tc_ty) then - -- Easy case - unifyTauTy sig_tc_ty res_ty `thenTc_` - tcMonoExpr expr sig_tc_ty - - else -- Signature is polymorphic - tcPolyExpr expr sig_tc_ty `thenTc` \ (_, _, expr, expr_ty, lie) -> - - -- Now match the signature type with res_ty. - -- We must not do this earlier, because res_ty might well - -- mention variables free in the environment, and we'd get - -- bogus complaints about not being able to for-all the - -- sig_tyvars - unifyTauTy res_ty expr_ty `thenTc_` - - -- If everything is ok, return the stuff unchanged, except for - -- the effect of any substutions etc. We simply discard the - -- result of the tcSimplifyCheck (inside tcPolyExpr), except for any default - -- resolution it may have done, which is recorded in the - -- substitution. - returnTc (expr, lie) -\end{code} - -Implicit Parameter bindings. - -\begin{code} tcMonoExpr (HsWith expr binds) res_ty = tcMonoExpr expr res_ty `thenTc` \ (expr', expr_lie) -> - mapAndUnzipTc tcIPBind binds `thenTc` \ (pairs, bind_lies) -> + mapAndUnzip3Tc tcIPBind binds `thenTc` \ (avail_ips, binds', bind_lies) -> -- If the binding binds ?x = E, we must now -- discharge any ?x constraints in expr_lie - tcSimplifyIPs (map fst pairs) expr_lie `thenTc` \ (expr_lie', dict_binds) -> + tcSimplifyIPs avail_ips expr_lie `thenTc` \ (expr_lie', dict_binds) -> let - binds' = [(instToId ip, rhs) | (ip,rhs) <- pairs] expr'' = HsLet (mkMonoBind dict_binds [] Recursive) expr' in returnTc (HsWith expr'' binds', expr_lie' `plusLIE` plusLIEs bind_lies) -tcIPBind (name, expr) +tcIPBind (ip, expr) = newTyVarTy openTypeKind `thenTc` \ ty -> tcGetSrcLoc `thenTc` \ loc -> - newIPDict (IPBind name) name ty `thenNF_Tc` \ ip -> + newIPDict (IPBind ip) ip ty `thenNF_Tc` \ (ip', ip_inst) -> tcMonoExpr expr ty `thenTc` \ (expr', lie) -> - returnTc ((ip, expr'), lie) + returnTc (ip_inst, (ip', expr'), lie) \end{code} %************************************************************************ @@ -662,33 +634,34 @@ tcIPBind (name, expr) tcApp :: RenamedHsExpr -> [RenamedHsExpr] -- Function and args -> TcType -- Expected result type of application - -> TcM (TcExpr, [TcExpr], -- Translated fun and args - LIE) + -> TcM (TcExpr, LIE) -- Translated fun and args + +tcApp (HsApp e1 e2) args res_ty + = tcApp e1 (e2:args) res_ty -- Accumulate the arguments tcApp fun args res_ty = -- First type-check the function tcExpr_id fun `thenTc` \ (fun', lie_fun, fun_ty) -> tcAddErrCtxt (wrongArgsCtxt "too many" fun args) ( + traceTc (text "tcApp" <+> (ppr fun $$ ppr fun_ty)) `thenNF_Tc_` split_fun_ty fun_ty (length args) ) `thenTc` \ (expected_arg_tys, actual_result_ty) -> - -- Unify with expected result before type-checking the args - -- This is when we might detect a too-few args situation - tcAddErrCtxtM (checkArgsCtxt fun args res_ty actual_result_ty) ( - unifyTauTy res_ty actual_result_ty - ) `thenTc_` - -- Now typecheck the args mapAndUnzipTc (tcArg fun) (zip3 args expected_arg_tys [1..]) `thenTc` \ (args', lie_args_s) -> - -- Check that the result type doesn't have any nested for-alls. - -- For example, a "build" on its own is no good; it must be applied to something. - checkTc (isTauTy actual_result_ty) - (lurkingRank2Err fun actual_result_ty) `thenTc_` + -- Unify with expected result after type-checking the args + -- so that the info from args percolates to actual_result_ty. + -- This is when we might detect a too-few args situation. + -- (One can think of cases when the opposite order would give + -- a better error message.) + tcAddErrCtxtM (checkArgsCtxt fun args res_ty actual_result_ty) + (tcSubExp res_ty actual_result_ty) `thenTc` \ (co_fn, lie_res) -> - returnTc (fun', args', lie_fun `plusLIE` plusLIEs lie_args_s) + returnTc (co_fn <$> foldl HsApp fun' args', + lie_res `plusLIE` lie_fun `plusLIE` plusLIEs lie_args_s) -- If an error happens we try to figure out whether the @@ -714,9 +687,9 @@ checkArgsCtxt fun args expected_res_ty actual_res_ty tidy_env split_fun_ty :: TcType -- The type of the function - -> Int -- Number of arguments + -> Int -- Number of arguments -> TcM ([TcType], -- Function argument types - TcType) -- Function result types + TcType) -- Function result types split_fun_ty fun_ty 0 = returnTc ([], fun_ty) @@ -729,9 +702,9 @@ split_fun_ty fun_ty n \end{code} \begin{code} -tcArg :: RenamedHsExpr -- The function (for error messages) - -> (RenamedHsExpr, TcType, Int) -- Actual argument and expected arg type - -> TcM (TcExpr, LIE) -- Resulting argument and LIE +tcArg :: RenamedHsExpr -- The function (for error messages) + -> (RenamedHsExpr, TcSigmaType, Int) -- Actual argument and expected arg type + -> TcM (TcExpr, LIE) -- Resulting argument and LIE tcArg the_fun (arg, expected_arg_ty, arg_no) = tcAddErrCtxt (funAppCtxt the_fun arg arg_no) $ @@ -745,21 +718,90 @@ tcArg the_fun (arg, expected_arg_ty, arg_no) %* * %************************************************************************ +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} tcId :: Name -> NF_TcM (TcExpr, LIE, TcType) tcId name -- Look up the Id and instantiate its type = tcLookupId name `thenNF_Tc` \ id -> - tcInstId id + case isDataConWrapId_maybe id of + Nothing -> loop (HsVar id) emptyLIE (idType id) + Just data_con -> inst_data_con id data_con + where + orig = OccurrenceOf name + + loop (HsVar fun_id) lie fun_ty + | want_method_inst fun_ty + = tcInstType VanillaTv fun_ty `thenNF_Tc` \ (tyvars, theta, tau) -> + newMethodWithGivenTy orig fun_id + (mkTyVarTys tyvars) theta tau `thenNF_Tc` \ meth -> + loop (HsVar (instToId meth)) + (unitLIE meth `plusLIE` lie) tau + + loop fun lie fun_ty + | isSigmaTy fun_ty + = tcInstCall orig fun_ty `thenNF_Tc` \ (inst_fn, inst_lie, tau) -> + loop (inst_fn fun) (inst_lie `plusLIE` lie) tau + + | otherwise + = returnNF_Tc (fun, lie, fun_ty) + + want_method_inst fun_ty + | opt_NoMethodSharing = False + | otherwise = case tcSplitSigmaTy fun_ty of + (_,[],_) -> False -- Not overloaded + (_,theta,_) -> not (any isLinearPred theta) + -- This is a slight hack. + -- If f :: (%x :: T) => Int -> Int + -- Then if we have two separate calls, (f 3, f 4), we cannot + -- make a method constraint that then gets shared, thus: + -- let m = f %x in (m 3, m 4) + -- because that loses the linearity of the constraint. + -- The simplest thing to do is never to construct a method constraint + -- in the first place that has a linear implicit parameter in it. + + -- We treat data constructors differently, because we have to generate + -- constraints for their silly theta, which no longer appears in + -- the type of dataConWrapId. It's dual to TcPat.tcConstructor + inst_data_con id data_con + = tcInstDataCon orig data_con `thenNF_Tc` \ (ty_args, ex_dicts, arg_tys, result_ty, stupid_lie, ex_lie, _) -> + returnNF_Tc (mkHsDictApp (mkHsTyApp (HsVar id) ty_args) ex_dicts, + stupid_lie `plusLIE` ex_lie, + mkFunTys arg_tys result_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 HoleTyVarTy to pass in as the expected tyvar. \begin{code} tcExpr_id :: RenamedHsExpr -> TcM (TcExpr, LIE, TcType) tcExpr_id (HsVar name) = tcId name -tcExpr_id expr = newTyVarTy openTypeKind `thenNF_Tc` \ id_ty -> - tcMonoExpr expr id_ty `thenTc` \ (expr', lie_id) -> - returnTc (expr', lie_id, id_ty) +tcExpr_id expr = newHoleTyVarTy `thenNF_Tc` \ id_ty -> + tcMonoExpr expr id_ty `thenTc` \ (expr', lie_id) -> + readHoleResult id_ty `thenTc` \ id_ty' -> + returnTc (expr', lie_id, id_ty') \end{code} @@ -770,6 +812,27 @@ tcExpr_id expr = newTyVarTy openTypeKind `thenNF_Tc` \ id_ty -> %************************************************************************ \begin{code} +-- I don't like this lumping together of do expression and list/array +-- comprehensions; creating the monad instances is entirely pointless in the +-- latter case; I'll leave the list case as it is for the moment, but handle +-- arrays extra (would be better to handle arrays and lists together, though) +-- -=chak +-- +tcDoStmts PArrComp stmts src_loc res_ty + = + ASSERT( not (null stmts) ) + tcAddSrcLoc src_loc $ + + unifyPArrTy res_ty `thenTc` \elt_ty -> + let tc_ty = mkTyConTy parrTyCon + m_ty = (mkPArrTy, elt_ty) + in + tcStmts (DoCtxt PArrComp) m_ty stmts `thenTc` \(stmts', stmts_lie) -> + returnTc (HsDoOut PArrComp stmts' + undefined undefined undefined -- don't touch! + res_ty src_loc, + stmts_lie) + tcDoStmts do_or_lc stmts src_loc res_ty = -- get the Monad and MonadZero classes -- create type consisting of a fresh monad tyvar @@ -779,10 +842,14 @@ tcDoStmts do_or_lc stmts src_loc res_ty -- If it's a comprehension we're dealing with, -- force it to be a list comprehension. -- (as of Haskell 98, monad comprehensions are no more.) + -- Similarily, array comprehensions must involve parallel arrays types + -- -=chak (case do_or_lc of ListComp -> unifyListTy res_ty `thenTc` \ elt_ty -> returnNF_Tc (mkTyConTy listTyCon, (mkListTy, elt_ty)) + PArrComp -> panic "TcExpr.tcDoStmts: How did we get here?!?" + _ -> newTyVarTy (mkArrowKind liftedTypeKind liftedTypeKind) `thenNF_Tc` \ m_ty -> newTyVarTy liftedTypeKind `thenNF_Tc` \ elt_ty -> unifyTauTy res_ty (mkAppTy m_ty elt_ty) `thenTc_` @@ -865,7 +932,7 @@ tcRecordBinds tycon ty_args rbinds -- The caller of tcRecordBinds has already checked -- that all the fields come from the same type - tcPolyExpr rhs field_ty `thenTc` \ (rhs', lie, _, _, _) -> + tcExpr rhs field_ty `thenTc` \ (rhs', lie) -> returnTc ((sel_id, rhs', pun_flag), lie) @@ -956,6 +1023,9 @@ Boring and alphabetical: 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) @@ -963,20 +1033,20 @@ caseScrutCtxt expr = hang (ptext SLIT("In the scrutinee of a case expression:")) 4 (ppr expr) exprSigCtxt expr - = hang (ptext SLIT("In an expression with a type signature:")) + = hang (ptext SLIT("When checking the type signature of the expression:")) 4 (ppr expr) listCtxt expr = hang (ptext SLIT("In the list element:")) 4 (ppr expr) +parrCtxt expr + = hang (ptext SLIT("In the parallel array element:")) 4 (ppr expr) + predCtxt expr = hang (ptext SLIT("In the predicate expression:")) 4 (ppr expr) -sectionRAppCtxt expr - = hang (ptext SLIT("In the right section:")) 4 (ppr expr) - -sectionLAppCtxt expr - = hang (ptext SLIT("In the left section:")) 4 (ppr expr) +exprCtxt expr + = hang (ptext SLIT("In the expression:")) 4 (ppr expr) funAppCtxt fun arg arg_no = hang (hsep [ ptext SLIT("In the"), speakNth arg_no, ptext SLIT("argument of"),