X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcPat.lhs;h=133db82eb7881f69bd81eb82ac6e044a84e714e2;hb=16e4ce4c0c02650082f2e11982017c903c549ad5;hp=2ed45be2eb40740fd7973a697d53f5d24f4acbba;hpb=4e342297f796001e7107d8c348bb023168954bc7;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcPat.lhs b/ghc/compiler/typecheck/TcPat.lhs index 2ed45be..133db82 100644 --- a/ghc/compiler/typecheck/TcPat.lhs +++ b/ghc/compiler/typecheck/TcPat.lhs @@ -4,41 +4,43 @@ \section[TcPat]{Typechecking patterns} \begin{code} -module TcPat ( tcPat, tcMonoPatBndr, simpleHsLitTy, badFieldCon, polyPatSig ) where +module TcPat ( tcPat, tcMonoPatBndr, tcSubPat, + badFieldCon, polyPatSig + ) where #include "HsVersions.h" -import HsSyn ( InPat(..), OutPat(..), HsLit(..), HsOverLit(..), HsExpr(..) ) +import HsSyn ( Pat(..), HsConDetails(..), HsLit(..), HsOverLit(..), HsExpr(..) ) import RnHsSyn ( RenamedPat ) -import TcHsSyn ( TcPat, TcId ) +import TcHsSyn ( TcPat, TcId, hsLitType, + mkCoercion, idCoercion, isIdCoercion, + (<$>), PatCoFn ) -import TcMonad +import TcRnMonad import Inst ( InstOrigin(..), - emptyLIE, plusLIE, LIE, mkLIE, unitLIE, instToId, - newMethod, newOverloadedLit, newDicts, newClassDicts + newMethodFromName, newOverloadedLit, newDicts, + instToId, tcInstDataCon, tcSyntaxName ) -import Id ( mkVanillaId ) +import Id ( idType, mkLocalId, mkSysLocal ) import Name ( Name ) import FieldLabel ( fieldLabelName ) -import TcEnv ( tcLookupClass, tcLookupDataCon, tcLookupGlobalId ) -import TcType ( TcType, TcTyVar, tcInstTyVars, newTyVarTy ) -import TcMonoType ( tcHsSigType ) -import TcUnify ( unifyTauTy, unifyListTy, unifyTupleTy ) - +import TcEnv ( tcLookupClass, tcLookupDataCon, tcLookupId ) +import TcMType ( newTyVarTy, arityErr ) +import TcType ( TcType, TcTyVar, TcSigmaType, + mkClassPred, liftedTypeKind ) +import TcUnify ( tcSubOff, Expected(..), readExpectedType, zapExpectedType, + unifyTauTy, zapToListTy, zapToPArrTy, zapToTupleTy ) +import TcMonoType ( tcHsSigType, UserTypeCtxt(..) ) + +import TysWiredIn ( stringTy ) import CmdLineOpts ( opt_IrrefutableTuples ) -import DataCon ( dataConSig, dataConFieldLabels, - dataConSourceArity - ) -import Type ( isTauTy, mkTyConApp, mkClassPred, liftedTypeKind ) -import Subst ( substTy, substClasses ) -import TysPrim ( charPrimTy, intPrimTy, floatPrimTy, - doublePrimTy, addrPrimTy - ) -import TysWiredIn ( charTy, stringTy, intTy, integerTy ) -import PrelNames ( eqStringName, eqName, geName, cCallableClassName ) +import DataCon ( DataCon, dataConFieldLabels, dataConSourceArity ) +import PrelNames ( eqStringName, eqName, geName, negateName, minusName, + integralClassName, cCallableClassName ) import BasicTypes ( isBoxed ) import Bag import Outputable +import FastString \end{code} @@ -49,10 +51,34 @@ import Outputable %************************************************************************ \begin{code} --- This is the right function to pass to tcPat when --- we're looking at a lambda-bound pattern, --- so there's no polymorphic guy to worry about -tcMonoPatBndr binder_name pat_ty = returnTc (mkVanillaId binder_name pat_ty) +type BinderChecker = Name -> Expected TcSigmaType -> TcM (PatCoFn, TcId) + -- How to construct a suitable (monomorphic) + -- Id for variables found in the pattern + -- The TcSigmaType is the expected type + -- from the pattern context + +-- The Id may have a sigma type (e.g. f (x::forall a. a->a)) +-- so we want to *create* it during pattern type checking. +-- We don't want to make Ids first with a type-variable type +-- and then unify... becuase we can't unify a sigma type with a type variable. + +tcMonoPatBndr :: BinderChecker + -- This is the right function to pass to tcPat when + -- we're looking at a lambda-bound pattern, + -- so there's no polymorphic guy to worry about + +tcMonoPatBndr binder_name pat_ty + = zapExpectedType pat_ty `thenM` \ pat_ty' -> + -- If there are *no constraints* on the pattern type, we + -- revert to good old H-M typechecking, making + -- the type of the binder into an *ordinary* + -- type variable. We find out if there are no constraints + -- by seeing if we are given an "open hole" as our info. + -- What we are trying to avoid here is giving a binder + -- a type that is a 'hole'. The only place holes should + -- appear is as an argument to tcPat and tcExpr/tcMonoExpr. + + returnM (idCoercion, mkLocalId binder_name pat_ty') \end{code} @@ -63,19 +89,14 @@ tcMonoPatBndr binder_name pat_ty = returnTc (mkVanillaId binder_name pat_ty) %************************************************************************ \begin{code} -tcPat :: (Name -> TcType -> TcM TcId) -- How to construct a suitable (monomorphic) - -- Id for variables found in the pattern - -- The TcType is the expected type, see note below +tcPat :: BinderChecker -> RenamedPat - -> TcType -- Expected type derived from the context - -- In the case of a function with a rank-2 signature, - -- this type might be a forall type. - -- INVARIANT: if it is, the foralls will always be visible, - -- not hidden inside a mutable type variable + -> Expected TcSigmaType -- Expected type derived from the context + -- In the case of a function with a rank-2 signature, + -- this type might be a forall type. -> TcM (TcPat, - LIE, -- Required by n+k and literal pats Bag TcTyVar, -- TyVars bound by the pattern -- These are just the existentially-bound ones. -- Any tyvars bound by *type signatures* in the @@ -84,7 +105,7 @@ tcPat :: (Name -> TcType -> TcM TcId) -- How to construct a suitable (monomorphi -- which it occurs in the pattern -- The two aren't the same because we conjure up a new -- local name for each variable. - LIE) -- Dicts or methods [see below] bound by the pattern + [Inst]) -- Dicts or methods [see below] bound by the pattern -- from existential constructor patterns \end{code} @@ -96,59 +117,74 @@ tcPat :: (Name -> TcType -> TcM TcId) -- How to construct a suitable (monomorphi %************************************************************************ \begin{code} -tcPat tc_bndr pat@(TypePatIn ty) pat_ty +tcPat tc_bndr pat@(TypePat ty) pat_ty = failWithTc (badTypePat pat) -tcPat tc_bndr (VarPatIn name) pat_ty - = tc_bndr name pat_ty `thenTc` \ bndr_id -> - returnTc (VarPat bndr_id, emptyLIE, emptyBag, unitBag (name, bndr_id), emptyLIE) - -tcPat tc_bndr (LazyPatIn pat) pat_ty - = tcPat tc_bndr pat pat_ty `thenTc` \ (pat', lie_req, tvs, ids, lie_avail) -> - returnTc (LazyPat pat', lie_req, tvs, ids, lie_avail) - -tcPat tc_bndr pat_in@(AsPatIn name pat) pat_ty - = tc_bndr name pat_ty `thenTc` \ bndr_id -> - tcPat tc_bndr pat pat_ty `thenTc` \ (pat', lie_req, tvs, ids, lie_avail) -> - tcAddErrCtxt (patCtxt pat_in) $ - returnTc (AsPat bndr_id pat', lie_req, +tcPat tc_bndr (VarPat name) pat_ty + = tc_bndr name pat_ty `thenM` \ (co_fn, bndr_id) -> + returnM (co_fn <$> VarPat bndr_id, + emptyBag, unitBag (name, bndr_id), []) + +tcPat tc_bndr (LazyPat pat) pat_ty + = tcPat tc_bndr pat pat_ty `thenM` \ (pat', tvs, ids, lie_avail) -> + returnM (LazyPat pat', tvs, ids, lie_avail) + +tcPat tc_bndr pat_in@(AsPat name pat) pat_ty + = tc_bndr name pat_ty `thenM` \ (co_fn, bndr_id) -> + tcPat tc_bndr pat (Check (idType bndr_id)) `thenM` \ (pat', tvs, ids, lie_avail) -> + -- NB: if we have: + -- \ (y@(x::forall a. a->a)) = e + -- we'll fail. The as-pattern infers a monotype for 'y', which then + -- fails to unify with the polymorphic type for 'x'. This could be + -- fixed, but only with a bit more work. + returnM (co_fn <$> (AsPat bndr_id pat'), tvs, (name, bndr_id) `consBag` ids, lie_avail) -tcPat tc_bndr WildPatIn pat_ty - = returnTc (WildPat pat_ty, emptyLIE, emptyBag, emptyBag, emptyLIE) - -tcPat tc_bndr (ParPatIn parend_pat) pat_ty - = tcPat tc_bndr parend_pat pat_ty - -tcPat tc_bndr (SigPatIn pat sig) pat_ty - = tcHsSigType sig `thenTc` \ sig_ty -> - - -- Check that the signature isn't a polymorphic one, which - -- we don't permit (at present, anyway) - checkTc (isTauTy sig_ty) (polyPatSig sig_ty) `thenTc_` - - unifyTauTy pat_ty sig_ty `thenTc_` - tcPat tc_bndr pat sig_ty +tcPat tc_bndr (WildPat _) pat_ty + = zapExpectedType pat_ty `thenM` \ pat_ty' -> + -- We might have an incoming 'hole' type variable; no annotation + -- so zap it to a type. Rather like tcMonoPatBndr. + returnM (WildPat pat_ty', emptyBag, emptyBag, []) + +tcPat tc_bndr (ParPat parend_pat) pat_ty +-- Leave the parens in, so that warnings from the +-- desugarer have parens in them + = tcPat tc_bndr parend_pat pat_ty `thenM` \ (pat', tvs, ids, lie_avail) -> + returnM (ParPat pat', tvs, ids, lie_avail) + +tcPat tc_bndr pat_in@(SigPatIn pat sig) pat_ty + = addErrCtxt (patCtxt pat_in) $ + tcHsSigType PatSigCtxt sig `thenM` \ sig_ty -> + tcSubPat sig_ty pat_ty `thenM` \ co_fn -> + tcPat tc_bndr pat (Check sig_ty) `thenM` \ (pat', tvs, ids, lie_avail) -> + returnM (co_fn <$> pat', tvs, ids, lie_avail) \end{code} + %************************************************************************ %* * -\subsection{Explicit lists and tuples} +\subsection{Explicit lists, parallel arrays, and tuples} %* * %************************************************************************ \begin{code} -tcPat tc_bndr pat_in@(ListPatIn pats) pat_ty - = tcAddErrCtxt (patCtxt pat_in) $ - unifyListTy pat_ty `thenTc` \ elem_ty -> - tcPats tc_bndr pats (repeat elem_ty) `thenTc` \ (pats', lie_req, tvs, ids, lie_avail) -> - returnTc (ListPat elem_ty pats', lie_req, tvs, ids, lie_avail) +tcPat tc_bndr pat_in@(ListPat pats _) pat_ty + = addErrCtxt (patCtxt pat_in) $ + zapToListTy pat_ty `thenM` \ elem_ty -> + tcPats tc_bndr pats (repeat elem_ty) `thenM` \ (pats', tvs, ids, lie_avail) -> + returnM (ListPat pats' elem_ty, tvs, ids, lie_avail) + +tcPat tc_bndr pat_in@(PArrPat pats _) pat_ty + = addErrCtxt (patCtxt pat_in) $ + zapToPArrTy pat_ty `thenM` \ elem_ty -> + tcPats tc_bndr pats (repeat elem_ty) `thenM` \ (pats', tvs, ids, lie_avail) -> + returnM (PArrPat pats' elem_ty, tvs, ids, lie_avail) -tcPat tc_bndr pat_in@(TuplePatIn pats boxity) pat_ty - = tcAddErrCtxt (patCtxt pat_in) $ +tcPat tc_bndr pat_in@(TuplePat pats boxity) pat_ty + = addErrCtxt (patCtxt pat_in) $ - unifyTupleTy boxity arity pat_ty `thenTc` \ arg_tys -> - tcPats tc_bndr pats arg_tys `thenTc` \ (pats', lie_req, tvs, ids, lie_avail) -> + zapToTupleTy boxity arity pat_ty `thenM` \ arg_tys -> + tcPats tc_bndr pats arg_tys `thenM` \ (pats', tvs, ids, lie_avail) -> -- possibly do the "make all tuple-pats irrefutable" test: let @@ -163,11 +199,12 @@ tcPat tc_bndr pat_in@(TuplePatIn pats boxity) pat_ty | opt_IrrefutableTuples && isBoxed boxity = LazyPat unmangled_result | otherwise = unmangled_result in - returnTc (possibly_mangled_result, lie_req, tvs, ids, lie_avail) + returnM (possibly_mangled_result, tvs, ids, lie_avail) where arity = length pats \end{code} + %************************************************************************ %* * \subsection{Other constructors} @@ -176,80 +213,28 @@ tcPat tc_bndr pat_in@(TuplePatIn pats boxity) pat_ty %************************************************************************ \begin{code} -tcPat tc_bndr pat@(ConPatIn name arg_pats) pat_ty - = tcConPat tc_bndr pat name arg_pats pat_ty - -tcPat tc_bndr pat@(ConOpPatIn pat1 op _ pat2) pat_ty - = tcConPat tc_bndr pat op [pat1, pat2] pat_ty -\end{code} - - -%************************************************************************ -%* * -\subsection{Records} -%* * -%************************************************************************ - -\begin{code} -tcPat tc_bndr pat@(RecPatIn name rpats) pat_ty - = tcAddErrCtxt (patCtxt pat) $ - - -- Check the constructor itself - tcConstructor pat name pat_ty `thenTc` \ (data_con, ex_tvs, dicts, lie_avail1, arg_tys) -> - let - -- Don't use zipEqual! If the constructor isn't really a record, then - -- dataConFieldLabels will be empty (and each field in the pattern - -- will generate an error below). - field_tys = zip (map fieldLabelName (dataConFieldLabels data_con)) - arg_tys - in +tcPat tc_bndr pat_in@(ConPatIn con_name arg_pats) pat_ty + = addErrCtxt (patCtxt pat_in) $ - -- Check the fields - tc_fields field_tys rpats `thenTc` \ (rpats', lie_req, tvs, ids, lie_avail2) -> + -- Check that it's a constructor, and instantiate it + tcLookupDataCon con_name `thenM` \ data_con -> + tcInstDataCon (PatOrigin pat_in) data_con `thenM` \ (_, ex_dicts1, arg_tys, con_res_ty, ex_tvs) -> - returnTc (RecPat data_con pat_ty ex_tvs dicts rpats', - lie_req, - listToBag ex_tvs `unionBags` tvs, - ids, - lie_avail1 `plusLIE` lie_avail2) + -- Check overall type matches. + -- The pat_ty might be a for-all type, in which + -- case we must instantiate to match + tcSubPat con_res_ty pat_ty `thenM` \ co_fn -> - where - tc_fields field_tys [] - = returnTc ([], emptyLIE, emptyBag, emptyBag, emptyLIE) - - tc_fields field_tys ((field_label, rhs_pat, pun_flag) : rpats) - = tc_fields field_tys rpats `thenTc` \ (rpats', lie_req1, tvs1, ids1, lie_avail1) -> - - (case [ty | (f,ty) <- field_tys, f == field_label] of - - -- No matching field; chances are this field label comes from some - -- other record type (or maybe none). As well as reporting an - -- error we still want to typecheck the pattern, principally to - -- make sure that all the variables it binds are put into the - -- environment, else the type checker crashes later: - -- f (R { foo = (a,b) }) = a+b - -- If foo isn't one of R's fields, we don't want to crash when - -- typechecking the "a+b". - [] -> addErrTc (badFieldCon name field_label) `thenNF_Tc_` - newTyVarTy liftedTypeKind `thenNF_Tc_` - returnTc (error "Bogus selector Id", pat_ty) + -- Check the argument patterns + tcConStuff tc_bndr data_con arg_pats arg_tys `thenM` \ (arg_pats', arg_tvs, arg_ids, ex_dicts2) -> - -- The normal case, when the field comes from the right constructor - (pat_ty : extras) -> - ASSERT( null extras ) - tcLookupGlobalId field_label `thenNF_Tc` \ sel_id -> - returnTc (sel_id, pat_ty) - ) `thenTc` \ (sel_id, pat_ty) -> - - tcPat tc_bndr rhs_pat pat_ty `thenTc` \ (rhs_pat', lie_req2, tvs2, ids2, lie_avail2) -> - - returnTc ((sel_id, rhs_pat', pun_flag) : rpats', - lie_req1 `plusLIE` lie_req2, - tvs1 `unionBags` tvs2, - ids1 `unionBags` ids2, - lie_avail1 `plusLIE` lie_avail2) + returnM (co_fn <$> ConPatOut data_con arg_pats' con_res_ty ex_tvs (map instToId ex_dicts1), + listToBag ex_tvs `unionBags` arg_tvs, + arg_ids, + ex_dicts1 ++ ex_dicts2) \end{code} + %************************************************************************ %* * \subsection{Literals} @@ -257,36 +242,53 @@ tcPat tc_bndr pat@(RecPatIn name rpats) pat_ty %************************************************************************ \begin{code} -tcPat tc_bndr (LitPatIn lit@(HsLitLit s _)) pat_ty +tcPat tc_bndr (LitPat lit@(HsLitLit s _)) pat_ty -- cf tcExpr on LitLits - = tcLookupClass cCallableClassName `thenNF_Tc` \ cCallableClass -> - newDicts (LitLitOrigin (_UNPK_ s)) - [mkClassPred cCallableClass [pat_ty]] `thenNF_Tc` \ dicts -> - returnTc (LitPat (HsLitLit s pat_ty) pat_ty, mkLIE dicts, emptyBag, emptyBag, emptyLIE) - -tcPat tc_bndr pat@(LitPatIn lit@(HsString _)) pat_ty - = unifyTauTy pat_ty stringTy `thenTc_` - tcLookupGlobalId eqStringName `thenNF_Tc` \ eq_id -> - returnTc (NPat lit stringTy (HsVar eq_id `HsApp` HsLit lit), - emptyLIE, emptyBag, emptyBag, emptyLIE) - -tcPat tc_bndr (LitPatIn simple_lit) pat_ty - = unifyTauTy pat_ty (simpleHsLitTy simple_lit) `thenTc_` - returnTc (LitPat simple_lit pat_ty, emptyLIE, emptyBag, emptyBag, emptyLIE) - -tcPat tc_bndr pat@(NPatIn over_lit) pat_ty - = newOverloadedLit (PatOrigin pat) over_lit pat_ty `thenNF_Tc` \ (over_lit_expr, lie1) -> - tcLookupGlobalId eqName `thenNF_Tc` \ eq_sel_id -> - newMethod origin eq_sel_id [pat_ty] `thenNF_Tc` \ eq -> - - returnTc (NPat lit' pat_ty (HsApp (HsVar (instToId eq)) over_lit_expr), - lie1 `plusLIE` unitLIE eq, - emptyBag, emptyBag, emptyLIE) + = zapExpectedType pat_ty `thenM` \ pat_ty' -> + tcLookupClass cCallableClassName `thenM` \ cCallableClass -> + newDicts (LitLitOrigin (unpackFS s)) + [mkClassPred cCallableClass [pat_ty']] `thenM` \ dicts -> + extendLIEs dicts `thenM_` + returnM (LitPat (HsLitLit s pat_ty'), emptyBag, emptyBag, []) + +tcPat tc_bndr pat@(LitPat lit@(HsString _)) pat_ty + = zapExpectedType pat_ty `thenM` \ pat_ty' -> + unifyTauTy pat_ty' stringTy `thenM_` + tcLookupId eqStringName `thenM` \ eq_id -> + returnM (NPatOut lit stringTy (HsVar eq_id `HsApp` HsLit lit), + emptyBag, emptyBag, []) + +tcPat tc_bndr (LitPat simple_lit) pat_ty + = zapExpectedType pat_ty `thenM` \ pat_ty' -> + unifyTauTy pat_ty' (hsLitType simple_lit) `thenM_` + returnM (LitPat simple_lit, emptyBag, emptyBag, []) + +tcPat tc_bndr pat@(NPatIn over_lit mb_neg) pat_ty + = zapExpectedType pat_ty `thenM` \ pat_ty' -> + newOverloadedLit origin over_lit pat_ty' `thenM` \ pos_lit_expr -> + newMethodFromName origin pat_ty' eqName `thenM` \ eq -> + (case mb_neg of + Nothing -> returnM pos_lit_expr -- Positive literal + Just neg -> -- Negative literal + -- The 'negate' is re-mappable syntax + tcSyntaxName origin pat_ty' (negateName, HsVar neg) `thenM` \ (_, neg_expr) -> + returnM (HsApp neg_expr pos_lit_expr) + ) `thenM` \ lit_expr -> + + let + -- The literal in an NPatIn is always positive... + -- But in NPat, the literal is used to find identical patterns + -- so we must negate the literal when necessary! + lit' = case (over_lit, mb_neg) of + (HsIntegral i _, Nothing) -> HsInteger i + (HsIntegral i _, Just _) -> HsInteger (-i) + (HsFractional f _, Nothing) -> HsRat f pat_ty' + (HsFractional f _, Just _) -> HsRat (-f) pat_ty' + in + returnM (NPatOut lit' pat_ty' (HsApp (HsVar eq) lit_expr), + emptyBag, emptyBag, []) where origin = PatOrigin pat - lit' = case over_lit of - HsIntegral i _ -> HsInteger i - HsFractional f _ -> HsRat f pat_ty \end{code} %************************************************************************ @@ -296,23 +298,32 @@ tcPat tc_bndr pat@(NPatIn over_lit) pat_ty %************************************************************************ \begin{code} -tcPat tc_bndr pat@(NPlusKPatIn name lit@(HsIntegral i _) minus) pat_ty - = tc_bndr name pat_ty `thenTc` \ bndr_id -> - tcLookupGlobalId minus `thenNF_Tc` \ minus_sel_id -> - tcLookupGlobalId geName `thenNF_Tc` \ ge_sel_id -> - newOverloadedLit origin lit pat_ty `thenNF_Tc` \ (over_lit_expr, lie1) -> - newMethod origin ge_sel_id [pat_ty] `thenNF_Tc` \ ge -> - newMethod origin minus_sel_id [pat_ty] `thenNF_Tc` \ minus -> - - returnTc (NPlusKPat bndr_id i pat_ty - (SectionR (HsVar (instToId ge)) over_lit_expr) - (SectionR (HsVar (instToId minus)) over_lit_expr), - lie1 `plusLIE` mkLIE [ge,minus], - emptyBag, unitBag (name, bndr_id), emptyLIE) +tcPat tc_bndr pat@(NPlusKPatIn name lit@(HsIntegral i _) minus_name) pat_ty + = tc_bndr name pat_ty `thenM` \ (co_fn, bndr_id) -> + let + pat_ty' = idType bndr_id + in + newOverloadedLit origin lit pat_ty' `thenM` \ over_lit_expr -> + newMethodFromName origin pat_ty' geName `thenM` \ ge -> + + -- The '-' part is re-mappable syntax + tcSyntaxName origin pat_ty' (minusName, HsVar minus_name) `thenM` \ (_, minus_expr) -> + + -- The Report says that n+k patterns must be in Integral + -- We may not want this when using re-mappable syntax, though (ToDo?) + tcLookupClass integralClassName `thenM` \ icls -> + newDicts origin [mkClassPred icls [pat_ty']] `thenM` \ dicts -> + extendLIEs dicts `thenM_` + + returnM (NPlusKPatOut bndr_id i + (SectionR (HsVar ge) over_lit_expr) + (SectionR minus_expr over_lit_expr), + emptyBag, unitBag (name, bndr_id), []) where origin = PatOrigin pat \end{code} + %************************************************************************ %* * \subsection{Lists of patterns} @@ -322,94 +333,147 @@ tcPat tc_bndr pat@(NPlusKPatIn name lit@(HsIntegral i _) minus) pat_ty Helper functions \begin{code} -tcPats :: (Name -> TcType -> TcM TcId) -- How to deal with variables - -> [RenamedPat] -> [TcType] -- Excess 'expected types' discarded +tcPats :: BinderChecker -- How to deal with variables + -> [RenamedPat] -> [TcType] -- Excess 'expected types' discarded -> TcM ([TcPat], - LIE, -- Required by n+k and literal pats Bag TcTyVar, Bag (Name, TcId), -- Ids bound by the pattern - LIE) -- Dicts bound by the pattern + [Inst]) -- Dicts bound by the pattern -tcPats tc_bndr [] tys = returnTc ([], emptyLIE, emptyBag, emptyBag, emptyLIE) +tcPats tc_bndr [] tys = returnM ([], emptyBag, emptyBag, []) -tcPats tc_bndr (ty:tys) (pat:pats) - = tcPat tc_bndr ty pat `thenTc` \ (pat', lie_req1, tvs1, ids1, lie_avail1) -> - tcPats tc_bndr tys pats `thenTc` \ (pats', lie_req2, tvs2, ids2, lie_avail2) -> +tcPats tc_bndr (pat:pats) (ty:tys) + = tcPat tc_bndr pat (Check ty) `thenM` \ (pat', tvs1, ids1, lie_avail1) -> + tcPats tc_bndr pats tys `thenM` \ (pats', tvs2, ids2, lie_avail2) -> - returnTc (pat':pats', lie_req1 `plusLIE` lie_req2, + returnM (pat':pats', tvs1 `unionBags` tvs2, ids1 `unionBags` ids2, - lie_avail1 `plusLIE` lie_avail2) + lie_avail1 ++ lie_avail2) \end{code} ------------------------------------------------------- -\begin{code} -simpleHsLitTy :: HsLit -> TcType -simpleHsLitTy (HsCharPrim c) = charPrimTy -simpleHsLitTy (HsStringPrim s) = addrPrimTy -simpleHsLitTy (HsInt i) = intTy -simpleHsLitTy (HsInteger i) = integerTy -simpleHsLitTy (HsIntPrim i) = intPrimTy -simpleHsLitTy (HsFloatPrim f) = floatPrimTy -simpleHsLitTy (HsDoublePrim d) = doublePrimTy -simpleHsLitTy (HsChar c) = charTy -simpleHsLitTy (HsString str) = stringTy -\end{code} +%************************************************************************ +%* * +\subsection{Constructor arguments} +%* * +%************************************************************************ ------------------------------------------------------- \begin{code} -tcConstructor pat con_name pat_ty - = -- Check that it's a constructor - tcLookupDataCon con_name `thenNF_Tc` \ data_con -> +tcConStuff tc_bndr data_con (PrefixCon arg_pats) arg_tys + = -- Check correct arity + checkTc (con_arity == no_of_args) + (arityErr "Constructor" data_con con_arity no_of_args) `thenM_` - -- Instantiate it - let - (tvs, _, ex_tvs, ex_theta, arg_tys, tycon) = dataConSig data_con - -- Ignore the theta; overloaded constructors only - -- behave differently when called, not when used for - -- matching. - in - tcInstTyVars (ex_tvs ++ tvs) `thenNF_Tc` \ (all_tvs', ty_args', tenv) -> - let - ex_theta' = substClasses tenv ex_theta - arg_tys' = map (substTy tenv) arg_tys + -- Check arguments + tcPats tc_bndr arg_pats arg_tys `thenM` \ (arg_pats', tvs, ids, lie_avail) -> - n_ex_tvs = length ex_tvs - ex_tvs' = take n_ex_tvs all_tvs' - result_ty = mkTyConApp tycon (drop n_ex_tvs ty_args') - in - newClassDicts (PatOrigin pat) ex_theta' `thenNF_Tc` \ dicts -> + returnM (PrefixCon arg_pats', tvs, ids, lie_avail) + where + con_arity = dataConSourceArity data_con + no_of_args = length arg_pats + +tcConStuff tc_bndr data_con (InfixCon p1 p2) arg_tys + = -- Check correct arity + checkTc (con_arity == 2) + (arityErr "Constructor" data_con con_arity 2) `thenM_` - -- Check overall type matches - unifyTauTy pat_ty result_ty `thenTc_` + -- Check arguments + tcPat tc_bndr p1 (Check ty1) `thenM` \ (p1', tvs1, ids1, lie_avail1) -> + tcPat tc_bndr p2 (Check ty2) `thenM` \ (p2', tvs2, ids2, lie_avail2) -> - returnTc (data_con, ex_tvs', map instToId dicts, mkLIE dicts, arg_tys') -\end{code} + returnM (InfixCon p1' p2', + tvs1 `unionBags` tvs2, ids1 `unionBags` ids2, + lie_avail1 ++ lie_avail2) + where + con_arity = dataConSourceArity data_con + [ty1, ty2] = arg_tys ------------------------------------------------------- -\begin{code} -tcConPat tc_bndr pat con_name arg_pats pat_ty - = tcAddErrCtxt (patCtxt pat) $ +tcConStuff tc_bndr data_con (RecCon rpats) arg_tys + = -- Check the fields + tc_fields field_tys rpats `thenM` \ (rpats', tvs, ids, lie_avail) -> + returnM (RecCon rpats', tvs, ids, lie_avail) - -- Check the constructor itself - tcConstructor pat con_name pat_ty `thenTc` \ (data_con, ex_tvs', dicts, lie_avail1, arg_tys') -> + where + field_tys = zip (map fieldLabelName (dataConFieldLabels data_con)) arg_tys + -- Don't use zipEqual! If the constructor isn't really a record, then + -- dataConFieldLabels will be empty (and each field in the pattern + -- will generate an error below). - -- Check correct arity - let - con_arity = dataConSourceArity data_con - no_of_args = length arg_pats - in - checkTc (con_arity == no_of_args) - (arityErr "Constructor" data_con con_arity no_of_args) `thenTc_` + tc_fields field_tys [] + = returnM ([], emptyBag, emptyBag, []) - -- Check arguments - tcPats tc_bndr arg_pats arg_tys' `thenTc` \ (arg_pats', lie_req, tvs, ids, lie_avail2) -> + tc_fields field_tys ((field_label, rhs_pat) : rpats) + = tc_fields field_tys rpats `thenM` \ (rpats', tvs1, ids1, lie_avail1) -> - returnTc (ConPat data_con pat_ty ex_tvs' dicts arg_pats', - lie_req, - listToBag ex_tvs' `unionBags` tvs, - ids, - lie_avail1 `plusLIE` lie_avail2) + (case [ty | (f,ty) <- field_tys, f == field_label] of + + -- No matching field; chances are this field label comes from some + -- other record type (or maybe none). As well as reporting an + -- error we still want to typecheck the pattern, principally to + -- make sure that all the variables it binds are put into the + -- environment, else the type checker crashes later: + -- f (R { foo = (a,b) }) = a+b + -- If foo isn't one of R's fields, we don't want to crash when + -- typechecking the "a+b". + [] -> addErrTc (badFieldCon data_con field_label) `thenM_` + newTyVarTy liftedTypeKind `thenM` \ bogus_ty -> + returnM (error "Bogus selector Id", bogus_ty) + + -- The normal case, when the field comes from the right constructor + (pat_ty : extras) -> + ASSERT( null extras ) + tcLookupId field_label `thenM` \ sel_id -> + returnM (sel_id, pat_ty) + ) `thenM` \ (sel_id, pat_ty) -> + + tcPat tc_bndr rhs_pat (Check pat_ty) `thenM` \ (rhs_pat', tvs2, ids2, lie_avail2) -> + + returnM ((sel_id, rhs_pat') : rpats', + tvs1 `unionBags` tvs2, + ids1 `unionBags` ids2, + lie_avail1 ++ lie_avail2) +\end{code} + + +%************************************************************************ +%* * +\subsection{Subsumption} +%* * +%************************************************************************ + +Example: + f :: (forall a. a->a) -> Int -> Int + f (g::Int->Int) y = g y +This is ok: the type signature allows fewer callers than +the (more general) signature f :: (Int->Int) -> Int -> Int +I.e. (forall a. a->a) <= Int -> Int +We end up translating this to: + f = \g' :: (forall a. a->a). let g = g' Int in g' y + +tcSubPat does the work + sig_ty is the signature on the pattern itself + (Int->Int in the example) + expected_ty is the type passed inwards from the context + (forall a. a->a in the example) + +\begin{code} +tcSubPat :: TcSigmaType -> Expected TcSigmaType -> TcM PatCoFn + +tcSubPat sig_ty exp_ty + = tcSubOff sig_ty exp_ty `thenM` \ co_fn -> + -- co_fn is a coercion on *expressions*, and we + -- need to make a coercion on *patterns* + if isIdCoercion co_fn then + returnM idCoercion + else + newUnique `thenM` \ uniq -> + readExpectedType exp_ty `thenM` \ exp_ty' -> + let + arg_id = mkSysLocal FSLIT("sub") uniq exp_ty' + the_fn = DictLam [arg_id] (co_fn <$> HsVar arg_id) + pat_co_fn p = SigPatOut p exp_ty' the_fn + in + returnM (mkCoercion pat_co_fn) \end{code} @@ -420,10 +484,10 @@ tcConPat tc_bndr pat con_name arg_pats pat_ty %************************************************************************ \begin{code} -patCtxt pat = hang (ptext SLIT("In the pattern:")) +patCtxt pat = hang (ptext SLIT("When checking the pattern:")) 4 (ppr pat) -badFieldCon :: Name -> Name -> SDoc +badFieldCon :: DataCon -> Name -> SDoc badFieldCon con field = hsep [ptext SLIT("Constructor") <+> quotes (ppr con), ptext SLIT("does not have field"), quotes (ppr field)]