X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcExpr.lhs;h=f44b7572d35cb06733dcad1b218191c488501261;hb=cb51a09231da94d729bcd62177cbdec1a888a180;hp=6cfd4452b0b8cb37cb292bf95f1ac7f248d46944;hpb=c86e9006fbdc9cb229080dd6a64ce462e9e460af;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcExpr.lhs b/ghc/compiler/typecheck/TcExpr.lhs index 6cfd445..f44b757 100644 --- a/ghc/compiler/typecheck/TcExpr.lhs +++ b/ghc/compiler/typecheck/TcExpr.lhs @@ -4,7 +4,7 @@ \section[TcExpr]{Typecheck an expression} \begin{code} -module TcExpr ( tcExpr, tcExpr_id, tcMonoExpr ) where +module TcExpr ( tcCheckSigma, tcCheckRho, tcInferRho, tcMonoExpr ) where #include "HsVersions.h" @@ -21,8 +21,8 @@ import HsSyn ( HsExpr(..), HsLit(..), ArithSeqInfo(..), recBindFields ) import RnHsSyn ( RenamedHsExpr, RenamedRecordBinds ) import TcHsSyn ( TcExpr, TcRecordBinds, hsLitType, mkHsDictApp, mkHsTyApp, mkHsLet, (<$>) ) import TcRnMonad -import TcUnify ( tcSubExp, tcGen, - unifyTauTy, unifyFunTy, unifyListTy, unifyPArrTy, unifyTupleTy ) +import TcUnify ( Expected(..), newHole, zapExpectedType, zapExpectedTo, tcSubExp, tcGen, + unifyFunTy, zapToListTy, zapToPArrTy, zapToTupleTy ) import BasicTypes ( isMarkedStrict ) import Inst ( InstOrigin(..), newOverloadedLit, newMethodFromName, newIPDict, @@ -36,8 +36,7 @@ import TcEnv ( tcLookupClass, tcLookupGlobal_maybe, tcLookupIdLvl, import TcMatches ( tcMatchesCase, tcMatchLambda, tcDoStmts, tcThingWithSig ) import TcMonoType ( tcHsSigType, UserTypeCtxt(..) ) import TcPat ( badFieldCon ) -import TcMType ( tcInstTyVars, tcInstType, newHoleTyVarTy, zapToType, - newTyVarTy, newTyVarTys, zonkTcType, readHoleResult ) +import TcMType ( tcInstTyVars, tcInstType, newTyVarTy, newTyVarTys, zonkTcType ) import TcType ( TcType, TcSigmaType, TcRhoType, TyVarDetails(VanillaTv), tcSplitFunTys, tcSplitTyConApp, mkTyVarTys, isSigmaTy, mkFunTy, mkFunTys, @@ -76,26 +75,45 @@ import FastString %************************************************************************ \begin{code} -tcExpr :: RenamedHsExpr -- Expession to type check - -> TcSigmaType -- Expected type (could be a polytpye) - -> TcM TcExpr -- Generalised expr with expected type +-- tcCheckSigma does type *checking*; it's passed the expected type of the result +tcCheckSigma :: RenamedHsExpr -- Expession to type check + -> TcSigmaType -- Expected type (could be a polytpye) + -> TcM TcExpr -- Generalised expr with expected type -tcExpr expr expected_ty +tcCheckSigma expr expected_ty = traceTc (text "tcExpr" <+> (ppr expected_ty $$ ppr expr)) `thenM_` 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 +tc_expr' expr sigma_ty + | isSigmaTy sigma_ty + = tcGen sigma_ty emptyVarSet ( + \ rho_ty -> tcCheckRho expr rho_ty ) `thenM` \ (gen_fn, expr') -> returnM (gen_fn <$> 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. + +\begin{code} +tcCheckRho :: RenamedHsExpr -> TcRhoType -> TcM TcExpr +tcCheckRho expr rho_ty = tcMonoExpr expr (Check rho_ty) + +tcInferRho :: RenamedHsExpr -> TcM (TcExpr, TcRhoType) +tcInferRho (HsVar name) = tcId name +tcInferRho expr = newHole `thenM` \ hole -> + tcMonoExpr expr (Infer hole) `thenM` \ expr' -> + readMutVar hole `thenM` \ rho_ty -> + returnM (expr', rho_ty) \end{code} + %************************************************************************ %* * \subsection{The TAUT rules for variables} @@ -104,7 +122,7 @@ tc_expr' expr expected_ty \begin{code} tcMonoExpr :: RenamedHsExpr -- Expession to type check - -> TcRhoType -- Expected type (could be a type variable) + -> Expected TcRhoType -- Expected type (could be a type variable) -- Definitely no foralls at the top -- Can be a 'hole'. -> TcM TcExpr @@ -137,7 +155,7 @@ tcMonoExpr (HsIPVar ip) res_ty tcMonoExpr in_expr@(ExprWithTySig expr poly_ty) res_ty = addErrCtxt (exprSigCtxt in_expr) $ tcHsSigType ExprSigCtxt poly_ty `thenM` \ sig_tc_ty -> - tcThingWithSig sig_tc_ty (tcMonoExpr expr) res_ty `thenM` \ (co_fn, expr') -> + tcThingWithSig sig_tc_ty (tcCheckRho expr) res_ty `thenM` \ (co_fn, expr') -> returnM (co_fn <$> expr') tcMonoExpr (HsType ty) res_ty @@ -158,7 +176,8 @@ tcMonoExpr (HsType ty) res_ty \begin{code} tcMonoExpr (HsLit lit) res_ty = tcLit lit res_ty -tcMonoExpr (HsOverLit lit) res_ty = newOverloadedLit (LiteralOrigin lit) lit res_ty +tcMonoExpr (HsOverLit lit) res_ty = zapExpectedType res_ty `thenM` \ res_ty' -> + newOverloadedLit (LiteralOrigin lit) lit res_ty' tcMonoExpr (HsPar expr) res_ty = tcMonoExpr expr res_ty `thenM` \ expr' -> returnM (HsPar expr') tcMonoExpr (HsSCC lbl expr) res_ty = tcMonoExpr expr res_ty `thenM` \ expr' -> @@ -190,7 +209,7 @@ a type error will occur if they aren't. -- op e tcMonoExpr in_expr@(SectionL arg1 op) res_ty - = tcExpr_id op `thenM` \ (op', op_ty) -> + = tcInferRho op `thenM` \ (op', op_ty) -> split_fun_ty op_ty 2 {- two args -} `thenM` \ ([arg1_ty, arg2_ty], op_res_ty) -> tcArg op (arg1, arg1_ty, 1) `thenM` \ arg1' -> addErrCtxt (exprCtxt in_expr) $ @@ -201,7 +220,7 @@ tcMonoExpr in_expr@(SectionL arg1 op) res_ty -- \ x -> op x expr tcMonoExpr in_expr@(SectionR op arg2) res_ty - = tcExpr_id op `thenM` \ (op', op_ty) -> + = tcInferRho op `thenM` \ (op', op_ty) -> split_fun_ty op_ty 2 {- two args -} `thenM` \ ([arg1_ty, arg2_ty], op_res_ty) -> tcArg op (arg2, arg2_ty, 2) `thenM` \ arg2' -> addErrCtxt (exprCtxt in_expr) $ @@ -211,7 +230,7 @@ tcMonoExpr in_expr@(SectionR op arg2) res_ty -- equivalent to (op e1) e2: tcMonoExpr in_expr@(OpApp arg1 op fix arg2) res_ty - = tcExpr_id op `thenM` \ (op', op_ty) -> + = tcInferRho op `thenM` \ (op', op_ty) -> split_fun_ty op_ty 2 {- 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' -> @@ -237,19 +256,11 @@ tcMonoExpr in_expr@(HsCase scrut matches src_loc) res_ty -- case (map f) of -- (x:xs) -> ... -- will report that map is applied to too few arguments - -- - -- Not only that, but it's better to check the matches on their - -- own, so that we get the expected results for scoped type variables. - -- f x = case x of - -- (p::a, q::b) -> (q,p) - -- The above should work: the match (p,q) -> (q,p) is polymorphic as - -- claimed by the pattern signatures. But if we typechecked the - -- match with x in scope and x's type as the expected type, we'd be hosed. tcMatchesCase matches res_ty `thenM` \ (scrut_ty, matches') -> addErrCtxt (caseScrutCtxt scrut) ( - tcMonoExpr scrut scrut_ty + tcCheckRho scrut scrut_ty ) `thenM` \ scrut' -> returnM (HsCase scrut' matches' src_loc) @@ -257,41 +268,43 @@ tcMonoExpr in_expr@(HsCase scrut matches src_loc) res_ty tcMonoExpr (HsIf pred b1 b2 src_loc) res_ty = addSrcLoc src_loc $ addErrCtxt (predCtxt pred) ( - tcMonoExpr pred boolTy ) `thenM` \ pred' -> + tcCheckRho pred boolTy ) `thenM` \ pred' -> - zapToType res_ty `thenM` \ res_ty' -> + zapExpectedType res_ty `thenM` \ res_ty' -> -- C.f. the call to zapToType in TcMatches.tcMatches - tcMonoExpr b1 res_ty' `thenM` \ b1' -> - tcMonoExpr b2 res_ty' `thenM` \ b2' -> + tcCheckRho b1 res_ty' `thenM` \ b1' -> + tcCheckRho b2 res_ty' `thenM` \ b2' -> returnM (HsIf pred' b1' b2' src_loc) tcMonoExpr (HsDo do_or_lc stmts method_names _ src_loc) res_ty - = addSrcLoc src_loc $ - tcDoStmts do_or_lc stmts method_names res_ty `thenM` \ (binds, stmts', methods') -> - returnM (mkHsLet binds (HsDo do_or_lc stmts' methods' res_ty src_loc)) + = addSrcLoc src_loc $ + zapExpectedType res_ty `thenM` \ res_ty' -> + -- All comprehensions yield a monotype + tcDoStmts do_or_lc stmts method_names res_ty' `thenM` \ (binds, stmts', methods') -> + returnM (mkHsLet binds (HsDo do_or_lc stmts' methods' res_ty' src_loc)) tcMonoExpr in_expr@(ExplicitList _ exprs) res_ty -- Non-empty list - = unifyListTy res_ty `thenM` \ elt_ty -> + = 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) $ - tcMonoExpr expr elt_ty + tcCheckRho expr elt_ty tcMonoExpr in_expr@(ExplicitPArr _ exprs) res_ty -- maybe empty - = unifyPArrTy res_ty `thenM` \ elt_ty -> + = zapToPArrTy res_ty `thenM` \ elt_ty -> mappM (tc_elt elt_ty) exprs `thenM` \ exprs' -> returnM (ExplicitPArr elt_ty exprs') where tc_elt elt_ty expr = addErrCtxt (parrCtxt expr) $ - tcMonoExpr expr elt_ty + tcCheckRho expr elt_ty tcMonoExpr (ExplicitTuple exprs boxity) res_ty - = unifyTupleTy boxity (length exprs) res_ty `thenM` \ arg_tys -> - tcMonoExprs exprs arg_tys `thenM` \ exprs' -> + = zapToTupleTy boxity (length exprs) res_ty `thenM` \ arg_tys -> + tcCheckRhos exprs arg_tys `thenM` \ exprs' -> returnM (ExplicitTuple exprs' boxity) \end{code} @@ -339,7 +352,7 @@ tcMonoExpr e0@(HsCCall lbl args may_gc is_casm ignored_fake_result_ty) res_ty | otherwise = [1..length args] in newTyVarTys (length tv_idxs) openTypeKind `thenM` \ arg_tys -> - tcMonoExprs args arg_tys `thenM` \ args' -> + tcCheckRhos args arg_tys `thenM` \ args' -> -- The argument types can be unlifted or lifted; the result -- type must, however, be lifted since it's an argument to the IO @@ -348,7 +361,7 @@ tcMonoExpr e0@(HsCCall lbl args may_gc is_casm ignored_fake_result_ty) res_ty let io_result_ty = mkTyConApp ioTyCon [result_ty] in - unifyTauTy res_ty io_result_ty `thenM_` + zapExpectedTo res_ty io_result_ty `thenM_` -- Construct the extra insts, which encode the -- constraints on the argument and result types. @@ -374,11 +387,11 @@ tcMonoExpr expr@(RecordCon con_name rbinds) res_ty (tycon, ty_args) = tcSplitTyConApp record_ty in ASSERT( isAlgTyCon tycon ) - unifyTauTy res_ty record_ty `thenM_` + 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 -> + tcLookupDataCon con_name `thenM` \ data_con -> let bad_fields = badFields rbinds data_con in @@ -466,7 +479,7 @@ tcMonoExpr expr@(RecordUpd record_expr rbinds) res_ty let result_record_ty = mkTyConApp tycon result_inst_tys in - unifyTauTy res_ty result_record_ty `thenM_` + zapExpectedTo res_ty result_record_ty `thenM_` tcRecordBinds tycon result_inst_tys rbinds `thenM` \ rbinds' -> -- STEP 4 @@ -498,7 +511,7 @@ tcMonoExpr expr@(RecordUpd record_expr rbinds) res_ty let record_ty = mkTyConApp tycon inst_tys in - tcMonoExpr record_expr record_ty `thenM` \ record_expr' -> + tcCheckRho record_expr record_ty `thenM` \ record_expr' -> -- STEP 6 -- Figure out the LIE we need. We have to generate some @@ -528,8 +541,8 @@ tcMonoExpr expr@(RecordUpd record_expr rbinds) res_ty \begin{code} tcMonoExpr (ArithSeqIn seq@(From expr)) res_ty - = unifyListTy res_ty `thenM` \ elt_ty -> - tcMonoExpr expr elt_ty `thenM` \ expr' -> + = zapToListTy res_ty `thenM` \ elt_ty -> + tcCheckRho expr elt_ty `thenM` \ expr' -> newMethodFromName (ArithSeqOrigin seq) elt_ty enumFromName `thenM` \ enum_from -> @@ -538,9 +551,9 @@ tcMonoExpr (ArithSeqIn seq@(From expr)) res_ty tcMonoExpr in_expr@(ArithSeqIn seq@(FromThen expr1 expr2)) res_ty = addErrCtxt (arithSeqCtxt in_expr) $ - unifyListTy res_ty `thenM` \ elt_ty -> - tcMonoExpr expr1 elt_ty `thenM` \ expr1' -> - tcMonoExpr expr2 elt_ty `thenM` \ expr2' -> + 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 -> @@ -549,9 +562,9 @@ tcMonoExpr in_expr@(ArithSeqIn seq@(FromThen expr1 expr2)) res_ty tcMonoExpr in_expr@(ArithSeqIn seq@(FromTo expr1 expr2)) res_ty = addErrCtxt (arithSeqCtxt in_expr) $ - unifyListTy res_ty `thenM` \ elt_ty -> - tcMonoExpr expr1 elt_ty `thenM` \ expr1' -> - tcMonoExpr expr2 elt_ty `thenM` \ expr2' -> + 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 -> @@ -559,10 +572,10 @@ tcMonoExpr in_expr@(ArithSeqIn seq@(FromTo expr1 expr2)) res_ty tcMonoExpr in_expr@(ArithSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty = addErrCtxt (arithSeqCtxt in_expr) $ - unifyListTy res_ty `thenM` \ elt_ty -> - tcMonoExpr expr1 elt_ty `thenM` \ expr1' -> - tcMonoExpr expr2 elt_ty `thenM` \ expr2' -> - tcMonoExpr expr3 elt_ty `thenM` \ expr3' -> + 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 -> @@ -570,9 +583,9 @@ tcMonoExpr in_expr@(ArithSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty tcMonoExpr in_expr@(PArrSeqIn seq@(FromTo expr1 expr2)) res_ty = addErrCtxt (parrSeqCtxt in_expr) $ - unifyPArrTy res_ty `thenM` \ elt_ty -> - tcMonoExpr expr1 elt_ty `thenM` \ expr1' -> - tcMonoExpr expr2 elt_ty `thenM` \ expr2' -> + zapToPArrTy 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 -> @@ -580,10 +593,10 @@ tcMonoExpr in_expr@(PArrSeqIn seq@(FromTo expr1 expr2)) res_ty tcMonoExpr in_expr@(PArrSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty = addErrCtxt (parrSeqCtxt in_expr) $ - unifyPArrTy res_ty `thenM` \ elt_ty -> - tcMonoExpr expr1 elt_ty `thenM` \ expr1' -> - tcMonoExpr expr2 elt_ty `thenM` \ expr2' -> - tcMonoExpr expr3 elt_ty `thenM` \ expr3' -> + zapToPArrTy 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 -> @@ -611,15 +624,15 @@ tcMonoExpr (HsBracket brack loc) res_ty = addSrcLoc loc (tcBracket brack res_ty) tcMonoExpr (HsReify (Reify flavour name)) res_ty = addErrCtxt (ptext SLIT("At the reification of") <+> ppr name) $ - tcMetaTy tycon_name `thenM` \ reify_ty -> - unifyTauTy res_ty reify_ty `thenM_` + tcMetaTy tycon_name `thenM` \ reify_ty -> + zapExpectedTo res_ty reify_ty `thenM_` returnM (HsReify (ReifyOut flavour name)) where tycon_name = case flavour of - ReifyDecl -> DsMeta.declTyConName - ReifyType -> DsMeta.typeTyConName + ReifyDecl -> DsMeta.decQTyConName + ReifyType -> DsMeta.typeQTyConName ReifyFixity -> pprPanic "tcMonoExpr: cant do reifyFixity yet" (ppr name) -#endif GHCI +#endif /* GHCI */ \end{code} @@ -643,7 +656,7 @@ tcMonoExpr other _ = pprPanic "tcMonoExpr" (ppr other) \begin{code} tcApp :: RenamedHsExpr -> [RenamedHsExpr] -- Function and args - -> TcType -- Expected result type of application + -> Expected TcRhoType -- Expected result type of application -> TcM TcExpr -- Translated fun and args tcApp (HsApp e1 e2) args res_ty @@ -651,32 +664,50 @@ tcApp (HsApp e1 e2) args res_ty tcApp fun args res_ty = -- First type-check the function - tcExpr_id fun `thenM` \ (fun', fun_ty) -> + tcInferRho fun `thenM` \ (fun', fun_ty) -> addErrCtxt (wrongArgsCtxt "too many" fun args) ( traceTc (text "tcApp" <+> (ppr fun $$ ppr fun_ty)) `thenM_` split_fun_ty fun_ty (length args) ) `thenM` \ (expected_arg_tys, actual_result_ty) -> - -- Now typecheck the args - mappM (tcArg fun) - (zip3 args expected_arg_tys [1..]) `thenM` \ args' -> - - -- Unify with expected result after type-checking the args - -- so that the info from args percolates to actual_result_ty. + -- 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_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.) + -- [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.] + addErrCtxtM (checkArgsCtxt fun args res_ty actual_result_ty) - (tcSubExp res_ty actual_result_ty) `thenM` \ co_fn -> + (tcSubExp res_ty actual_result_ty) `thenM` \ co_fn -> + + -- Now typecheck the args + mappM (tcArg fun) + (zip3 args expected_arg_tys [1..]) `thenM` \ args' -> returnM (co_fn <$> foldl HsApp fun' args') -- If an error happens we try to figure out whether the -- function has been given too many or too few arguments, --- and say so -checkArgsCtxt fun args expected_res_ty actual_res_ty tidy_env +-- 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 ~(Check expected_res_ty) actual_res_ty tidy_env = zonkTcType expected_res_ty `thenM` \ exp_ty' -> zonkTcType actual_res_ty `thenM` \ act_ty' -> let @@ -695,7 +726,7 @@ checkArgsCtxt fun args expected_res_ty actual_res_ty tidy_env returnM (env2, message) -split_fun_ty :: TcType -- The type of the function +split_fun_ty :: TcRhoType -- The type of the function -> Int -- Number of arguments -> TcM ([TcType], -- Function argument types TcType) -- Function result types @@ -717,7 +748,7 @@ tcArg :: RenamedHsExpr -- The function (for error messages) tcArg the_fun (arg, expected_arg_ty, arg_no) = addErrCtxt (funAppCtxt the_fun arg arg_no) $ - tcExpr arg expected_arg_ty + tcCheckSigma arg expected_arg_ty \end{code} @@ -750,7 +781,7 @@ This gets a bit less sharing, but b) perhaps fewer separated lambdas \begin{code} -tcId :: Name -> TcM (TcExpr, TcType) +tcId :: Name -> TcM (TcExpr, TcRhoType) tcId name -- Look up the Id and instantiate its type = -- First check whether it's a DataCon -- Reason: we must not forget to chuck in the @@ -846,7 +877,8 @@ tcId name -- Look up the Id and instantiate its type -- 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 + -- the type of dataConWrapId (see note on "stupid context" in DataCon.lhs + -- It's dual to TcPat.tcConstructor inst_data_con data_con = tcInstDataCon orig data_con `thenM` \ (ty_args, ex_dicts, arg_tys, result_ty, _) -> extendLIEs ex_dicts `thenM_` @@ -855,21 +887,6 @@ tcId name -- Look up the Id and instantiate its type 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, TcType) -tcExpr_id (HsVar name) = tcId name -tcExpr_id expr = newHoleTyVarTy `thenM` \ id_ty -> - tcMonoExpr expr id_ty `thenM` \ expr' -> - readHoleResult id_ty `thenM` \ id_ty' -> - returnM (expr', id_ty') -\end{code} - - %************************************************************************ %* * \subsection{Record bindings} @@ -920,7 +937,7 @@ tcRecordBinds tycon ty_args rbinds -- The caller of tcRecordBinds has already checked -- that all the fields come from the same type - tcExpr rhs field_ty `thenM` \ rhs' -> + tcCheckSigma rhs field_ty `thenM` \ rhs' -> returnM (sel_id, rhs') @@ -974,17 +991,17 @@ checkMissingFields data_con rbinds %************************************************************************ %* * -\subsection{@tcMonoExprs@ typechecks a {\em list} of expressions} +\subsection{@tcCheckRhos@ typechecks a {\em list} of expressions} %* * %************************************************************************ \begin{code} -tcMonoExprs :: [RenamedHsExpr] -> [TcType] -> TcM [TcExpr] +tcCheckRhos :: [RenamedHsExpr] -> [TcType] -> TcM [TcExpr] -tcMonoExprs [] [] = returnM [] -tcMonoExprs (expr:exprs) (ty:tys) - = tcMonoExpr expr ty `thenM` \ expr' -> - tcMonoExprs exprs tys `thenM` \ exprs' -> +tcCheckRhos [] [] = returnM [] +tcCheckRhos (expr:exprs) (ty:tys) + = tcCheckRho expr ty `thenM` \ expr' -> + tcCheckRhos exprs tys `thenM` \ exprs' -> returnM (expr':exprs') \end{code} @@ -998,16 +1015,17 @@ tcMonoExprs (expr:exprs) (ty:tys) Overloaded literals. \begin{code} -tcLit :: HsLit -> TcType -> TcM TcExpr +tcLit :: HsLit -> Expected TcRhoType -> TcM TcExpr tcLit (HsLitLit s _) res_ty - = tcLookupClass cCallableClassName `thenM` \ cCallableClass -> + = zapExpectedType res_ty `thenM` \ res_ty' -> + tcLookupClass cCallableClassName `thenM` \ cCallableClass -> newDicts (LitLitOrigin (unpackFS s)) - [mkClassPred cCallableClass [res_ty]] `thenM` \ dicts -> + [mkClassPred cCallableClass [res_ty']] `thenM` \ dicts -> extendLIEs dicts `thenM_` - returnM (HsLit (HsLitLit s res_ty)) + returnM (HsLit (HsLitLit s res_ty')) tcLit lit res_ty - = unifyTauTy res_ty (hsLitType lit) `thenM_` + = zapExpectedTo res_ty (hsLitType lit) `thenM_` returnM (HsLit lit) \end{code}