X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcPat.lhs;h=0561b78cf7a88e23a88377183f604c0c751b85a8;hb=4bca2e7f766e3a265e77cbce4884f889d6d28299;hp=71a8e4994928186d3cf9a43de06598b2f478b60e;hpb=904f158f9fe208b8154029dff655a6eab4b2828e;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/TcPat.lhs b/ghc/compiler/typecheck/TcPat.lhs index 71a8e49..0561b78 100644 --- a/ghc/compiler/typecheck/TcPat.lhs +++ b/ghc/compiler/typecheck/TcPat.lhs @@ -4,48 +4,43 @@ \section[TcPat]{Typechecking patterns} \begin{code} -module TcPat ( tcPat, tcPatBndr_NoSigs, badFieldCon, polyPatSig ) where +module TcPat ( tcPat, tcMonoPatBndr, tcSubPat, + badFieldCon, polyPatSig + ) where #include "HsVersions.h" -import {-# SOURCE #-} TcExpr( tcExpr ) - -import HsSyn ( InPat(..), OutPat(..), HsLit(..), HsExpr(..), Sig(..) ) +import HsSyn ( InPat(..), OutPat(..), HsLit(..), HsOverLit(..), HsExpr(..) ) import RnHsSyn ( RenamedPat ) -import TcHsSyn ( TcPat, TcId ) +import TcHsSyn ( TcPat, TcId, simpleHsLitTy ) import TcMonad -import Inst ( Inst, OverloadedLit(..), InstOrigin(..), - emptyLIE, plusLIE, LIE, - newMethod, newOverloadedLit, - newDicts, instToIdBndr +import Inst ( InstOrigin(..), + emptyLIE, plusLIE, LIE, mkLIE, unitLIE, instToId, isEmptyLIE, + newMethod, newMethodFromName, newOverloadedLit, newDicts, + tcInstDataCon, tcSyntaxName ) -import Name ( Name, getOccName, getSrcLoc ) +import Id ( mkLocalId, mkSysLocal ) +import Name ( Name ) import FieldLabel ( fieldLabelName ) -import TcEnv ( tcLookupValue, - tcLookupValueByKey, newLocalId, badCon - ) -import TcType ( TcType, TcTyVar, tcInstTyVars ) -import TcMonoType ( tcHsType ) -import TcUnify ( unifyTauTy, unifyListTy, - unifyTupleTy, unifyUnboxedTupleTy - ) - -import Bag ( Bag ) +import TcEnv ( tcLookupClass, tcLookupDataCon, tcLookupGlobalId, tcLookupId ) +import TcMType ( newTyVarTy, zapToType ) +import TcType ( TcType, TcTyVar, TcSigmaType, + mkClassPred, liftedTypeKind ) +import TcUnify ( tcSubOff, TcHoleType, + unifyTauTy, unifyListTy, unifyPArrTy, unifyTupleTy, + mkCoercion, idCoercion, isIdCoercion, + (<$>), PatCoFn ) +import TcMonoType ( tcHsSigType, UserTypeCtxt(..) ) + +import TysWiredIn ( stringTy ) import CmdLineOpts ( opt_IrrefutableTuples ) -import DataCon ( DataCon, dataConSig, dataConFieldLabels, dataConSourceArity ) -import Id ( Id, idType, isDataConId_maybe ) -import Type ( Type, isTauTy, mkTyConApp ) -import Subst ( substTy, substTheta ) -import TysPrim ( charPrimTy, intPrimTy, floatPrimTy, - doublePrimTy, addrPrimTy - ) -import TysWiredIn ( charTy, stringTy, intTy ) -import SrcLoc ( SrcLoc ) -import Unique ( eqClassOpKey, geClassOpKey, minusClassOpKey ) +import DataCon ( dataConFieldLabels, dataConSourceArity ) +import PrelNames ( eqStringName, eqName, geName, minusName, cCallableClassName ) +import BasicTypes ( isBoxed ) import Bag -import Util ( zipEqual ) import Outputable +import FastString \end{code} @@ -56,14 +51,34 @@ import Outputable %************************************************************************ \begin{code} --- This is the right function to pass to tcPat when there are no signatures -tcPatBndr_NoSigs binder_name pat_ty - = -- Need to make a new, monomorphic, Id - -- The binder_name is already being used for the polymorphic Id - newLocalId (getOccName binder_name) pat_ty loc `thenNF_Tc` \ bndr_id -> - returnTc bndr_id - where - loc = getSrcLoc binder_name +type BinderChecker = Name -> TcSigmaType -> TcM (PatCoFn, LIE, 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 + = zapToType pat_ty `thenNF_Tc` \ 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. + + returnTc (idCoercion, emptyLIE, mkLocalId binder_name pat_ty') \end{code} @@ -74,18 +89,14 @@ tcPatBndr_NoSigs binder_name pat_ty %************************************************************************ \begin{code} -tcPat :: (Name -> TcType -> TcM s 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 + -> TcHoleType -- 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 - -> TcM s (TcPat, + -> TcM (TcPat, LIE, -- Required by n+k and literal pats Bag TcTyVar, -- TyVars bound by the pattern -- These are just the existentially-bound ones. @@ -107,51 +118,45 @@ tcPat :: (Name -> TcType -> TcM s TcId) -- How to construct a suitable (monomorp %************************************************************************ \begin{code} +tcPat tc_bndr pat@(TypePatIn 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) + = tc_bndr name pat_ty `thenTc` \ (co_fn, lie_req, bndr_id) -> + returnTc (co_fn <$> VarPat bndr_id, lie_req, + 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, + = tc_bndr name pat_ty `thenTc` \ (co_fn, lie_req1, bndr_id) -> + tcPat tc_bndr pat pat_ty `thenTc` \ (pat', lie_req2, tvs, ids, lie_avail) -> + returnTc (co_fn <$> (AsPat bndr_id pat'), lie_req1 `plusLIE` lie_req2, 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 (NegPatIn pat) pat_ty - = tcPat tc_bndr (negate_lit pat) pat_ty - where - negate_lit (LitPatIn (HsInt i)) = LitPatIn (HsInt (-i)) - negate_lit (LitPatIn (HsIntPrim i)) = LitPatIn (HsIntPrim (-i)) - negate_lit (LitPatIn (HsFrac f)) = LitPatIn (HsFrac (-f)) - negate_lit (LitPatIn (HsFloatPrim f)) = LitPatIn (HsFloatPrim (-f)) - negate_lit (LitPatIn (HsDoublePrim f)) = LitPatIn (HsDoublePrim (-f)) - negate_lit _ = panic "TcPat:negate_pat" + = zapToType pat_ty `thenNF_Tc` \ pat_ty' -> + -- We might have an incoming 'hole' type variable; no annotation + -- so zap it to a type. Rather like tcMonoPatBndr. + 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 - = tcHsType 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 pat_in@(SigPatIn pat sig) pat_ty + = tcAddErrCtxt (patCtxt pat_in) $ + tcHsSigType PatSigCtxt sig `thenTc` \ sig_ty -> + tcSubPat sig_ty pat_ty `thenTc` \ (co_fn, lie_sig) -> + tcPat tc_bndr pat sig_ty `thenTc` \ (pat', lie_req, tvs, ids, lie_avail) -> + returnTc (co_fn <$> pat', lie_req `plusLIE` lie_sig, tvs, ids, lie_avail) \end{code} + %************************************************************************ %* * -\subsection{Explicit lists and tuples} +\subsection{Explicit lists, parallel arrays, and tuples} %* * %************************************************************************ @@ -162,18 +167,21 @@ tcPat tc_bndr pat_in@(ListPatIn pats) pat_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@(TuplePatIn pats boxed) pat_ty - = tcAddErrCtxt (patCtxt pat_in) $ +tcPat tc_bndr pat_in@(PArrPatIn pats) pat_ty + = tcAddErrCtxt (patCtxt pat_in) $ + unifyPArrTy pat_ty `thenTc` \ elem_ty -> + tcPats tc_bndr pats (repeat elem_ty) `thenTc` \ (pats', lie_req, tvs, ids, lie_avail) -> + returnTc (PArrPat elem_ty pats', lie_req, tvs, ids, lie_avail) - (if boxed - then unifyTupleTy arity pat_ty - else unifyUnboxedTupleTy arity pat_ty) `thenTc` \ arg_tys -> +tcPat tc_bndr pat_in@(TuplePatIn pats boxity) pat_ty + = tcAddErrCtxt (patCtxt pat_in) $ - tcPats tc_bndr pats arg_tys `thenTc` \ (pats', lie_req, tvs, ids, lie_avail) -> + unifyTupleTy boxity arity pat_ty `thenTc` \ arg_tys -> + tcPats tc_bndr pats arg_tys `thenTc` \ (pats', lie_req, tvs, ids, lie_avail) -> -- possibly do the "make all tuple-pats irrefutable" test: let - unmangled_result = TuplePat pats' boxed + unmangled_result = TuplePat pats' boxity -- Under flag control turn a pattern (x,y,z) into ~(x,y,z) -- so that we can experiment with lazy tuple-matching. @@ -181,14 +189,15 @@ tcPat tc_bndr pat_in@(TuplePatIn pats boxed) pat_ty -- it was easy to do. possibly_mangled_result - | opt_IrrefutableTuples && boxed = LazyPat unmangled_result - | otherwise = unmangled_result + | opt_IrrefutableTuples && isBoxed boxity = LazyPat unmangled_result + | otherwise = unmangled_result in returnTc (possibly_mangled_result, lie_req, tvs, ids, lie_avail) where arity = length pats \end{code} + %************************************************************************ %* * \subsection{Other constructors} @@ -216,18 +225,23 @@ 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) -> + tcConstructor pat name `thenTc` \ (data_con, lie_req1, ex_tvs, ex_dicts, lie_avail1, arg_tys, con_res_ty) -> + + -- Check overall type matches (c.f. tcConPat) + tcSubPat con_res_ty pat_ty `thenTc` \ (co_fn, lie_req2) -> let - field_tys = zipEqual "tcPat" - (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). + field_tys = zip (map fieldLabelName (dataConFieldLabels data_con)) + arg_tys in -- Check the fields - tc_fields field_tys rpats `thenTc` \ (rpats', lie_req, tvs, ids, lie_avail2) -> + tc_fields field_tys rpats `thenTc` \ (rpats', lie_req3, tvs, ids, lie_avail2) -> - returnTc (RecPat data_con pat_ty ex_tvs dicts rpats', - lie_req, + returnTc (RecPat data_con pat_ty ex_tvs ex_dicts rpats', + lie_req1 `plusLIE` lie_req2 `plusLIE` lie_req3, listToBag ex_tvs `unionBags` tvs, ids, lie_avail1 `plusLIE` lie_avail2) @@ -237,90 +251,112 @@ tcPat tc_bndr pat@(RecPatIn name rpats) pat_ty = returnTc ([], emptyLIE, emptyBag, emptyBag, emptyLIE) tc_fields field_tys ((field_label, rhs_pat, pun_flag) : rpats) - | null matching_fields - = addErrTc (badFieldCon name field_label) `thenNF_Tc_` - tc_fields field_tys rpats - - | otherwise - = ASSERT( null extras ) - tc_fields field_tys rpats `thenTc` \ (rpats', lie_req1, tvs1, ids1, lie_avail1) -> - - tcLookupValue field_label `thenNF_Tc` \ sel_id -> - tcPat tc_bndr rhs_pat rhs_ty `thenTc` \ (rhs_pat', lie_req2, tvs2, ids2, lie_avail2) -> + = 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) + + -- 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) - where - matching_fields = [ty | (f,ty) <- field_tys, f == field_label] - (rhs_ty : extras) = matching_fields \end{code} %************************************************************************ %* * -\subsection{Non-overloaded literals} +\subsection{Literals} %* * %************************************************************************ \begin{code} -tcPat tc_bndr (LitPatIn lit@(HsChar _)) pat_ty = tcSimpleLitPat lit charTy pat_ty -tcPat tc_bndr (LitPatIn lit@(HsIntPrim _)) pat_ty = tcSimpleLitPat lit intPrimTy pat_ty -tcPat tc_bndr (LitPatIn lit@(HsCharPrim _)) pat_ty = tcSimpleLitPat lit charPrimTy pat_ty -tcPat tc_bndr (LitPatIn lit@(HsStringPrim _)) pat_ty = tcSimpleLitPat lit addrPrimTy pat_ty -tcPat tc_bndr (LitPatIn lit@(HsFloatPrim _)) pat_ty = tcSimpleLitPat lit floatPrimTy pat_ty -tcPat tc_bndr (LitPatIn lit@(HsDoublePrim _)) pat_ty = tcSimpleLitPat lit doublePrimTy pat_ty - -tcPat tc_bndr (LitPatIn lit@(HsLitLit s)) pat_ty = tcSimpleLitPat lit intTy pat_ty - -- This one looks weird! +tcPat tc_bndr (LitPatIn lit@(HsLitLit s _)) pat_ty + -- cf tcExpr on LitLits + = tcLookupClass cCallableClassName `thenNF_Tc` \ cCallableClass -> + newDicts (LitLitOrigin (unpackFS 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 mb_neg) pat_ty + = newOverloadedLit origin over_lit pat_ty `thenNF_Tc` \ (pos_lit_expr, lie1) -> + newMethodFromName origin pat_ty eqName `thenNF_Tc` \ eq -> + (case mb_neg of + Nothing -> returnNF_Tc (pos_lit_expr, emptyLIE) -- Positive literal + Just neg -> -- Negative literal + -- The 'negate' is re-mappable syntax + tcLookupId neg `thenNF_Tc` \ neg_sel_id -> + newMethod origin neg_sel_id [pat_ty] `thenNF_Tc` \ neg -> + returnNF_Tc (HsApp (HsVar (instToId neg)) pos_lit_expr, unitLIE neg) + ) `thenNF_Tc` \ (lit_expr, lie2) -> + + returnTc (NPat lit' pat_ty (HsApp (HsVar (instToId eq)) lit_expr), + lie1 `plusLIE` lie2 `plusLIE` unitLIE eq, + emptyBag, emptyBag, emptyLIE) + where + origin = PatOrigin pat + + -- 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 \end{code} %************************************************************************ %* * -\subsection{Overloaded patterns: int literals and \tr{n+k} patterns} +\subsection{n+k patterns} %* * %************************************************************************ \begin{code} -tcPat tc_bndr pat@(LitPatIn lit@(HsString str)) pat_ty - = unifyTauTy pat_ty stringTy `thenTc_` - tcLookupValueByKey eqClassOpKey `thenNF_Tc` \ sel_id -> - newMethod (PatOrigin pat) sel_id [stringTy] `thenNF_Tc` \ (lie, eq_id) -> - let - comp_op = HsApp (HsVar eq_id) (HsLitOut lit stringTy) - in - returnTc (NPat lit stringTy comp_op, lie, emptyBag, emptyBag, emptyLIE) - - -tcPat tc_bndr pat@(LitPatIn lit@(HsInt i)) pat_ty - = tcOverloadedLitPat pat lit (OverloadedIntegral i) pat_ty - -tcPat tc_bndr pat@(LitPatIn lit@(HsFrac f)) pat_ty - = tcOverloadedLitPat pat lit (OverloadedFractional f) pat_ty - - -tcPat tc_bndr pat@(NPlusKPatIn name lit@(HsInt i)) pat_ty - = tc_bndr name pat_ty `thenTc` \ bndr_id -> - tcLookupValueByKey geClassOpKey `thenNF_Tc` \ ge_sel_id -> - tcLookupValueByKey minusClassOpKey `thenNF_Tc` \ minus_sel_id -> - - newOverloadedLit origin - (OverloadedIntegral i) pat_ty `thenNF_Tc` \ (over_lit_expr, lie1) -> - - newMethod origin ge_sel_id [pat_ty] `thenNF_Tc` \ (lie2, ge_id) -> - newMethod origin minus_sel_id [pat_ty] `thenNF_Tc` \ (lie3, minus_id) -> - - returnTc (NPlusKPat bndr_id lit pat_ty - (SectionR (HsVar ge_id) over_lit_expr) - (SectionR (HsVar minus_id) over_lit_expr), - lie1 `plusLIE` lie2 `plusLIE` lie3, +tcPat tc_bndr pat@(NPlusKPatIn name lit@(HsIntegral i _) minus_name) pat_ty + = tc_bndr name pat_ty `thenTc` \ (co_fn, lie1, bndr_id) -> + newOverloadedLit origin lit pat_ty `thenNF_Tc` \ (over_lit_expr, lie2) -> + newMethodFromName origin pat_ty geName `thenNF_Tc` \ ge -> + + -- The '-' part is re-mappable syntax + tcSyntaxName origin pat_ty minusName minus_name `thenTc` \ (minus_expr, minus_lie, _) -> + + returnTc (NPlusKPat bndr_id i pat_ty + (SectionR (HsVar (instToId ge)) over_lit_expr) + (SectionR minus_expr over_lit_expr), + lie1 `plusLIE` lie2 `plusLIE` minus_lie `plusLIE` unitLIE ge, emptyBag, unitBag (name, bndr_id), emptyLIE) where origin = PatOrigin pat - -tcPat tc_bndr (NPlusKPatIn pat other) pat_ty - = panic "TcPat:NPlusKPat: not an HsInt literal" \end{code} %************************************************************************ @@ -332,9 +368,9 @@ tcPat tc_bndr (NPlusKPatIn pat other) pat_ty Helper functions \begin{code} -tcPats :: (Name -> TcType -> TcM s TcId) -- How to deal with variables +tcPats :: BinderChecker -- How to deal with variables -> [RenamedPat] -> [TcType] -- Excess 'expected types' discarded - -> TcM s ([TcPat], + -> TcM ([TcPat], LIE, -- Required by n+k and literal pats Bag TcTyVar, Bag (Name, TcId), -- Ids bound by the pattern @@ -353,56 +389,14 @@ tcPats tc_bndr (ty:tys) (pat:pats) ------------------------------------------------------ \begin{code} -tcSimpleLitPat lit lit_ty pat_ty - = unifyTauTy pat_ty lit_ty `thenTc_` - returnTc (LitPat lit lit_ty, emptyLIE, emptyBag, emptyBag, emptyLIE) - - -tcOverloadedLitPat pat lit over_lit pat_ty - = newOverloadedLit (PatOrigin pat) over_lit pat_ty `thenNF_Tc` \ (over_lit_expr, lie1) -> - tcLookupValueByKey eqClassOpKey `thenNF_Tc` \ eq_sel_id -> - newMethod origin eq_sel_id [pat_ty] `thenNF_Tc` \ (lie2, eq_id) -> - - returnTc (NPat lit pat_ty (HsApp (HsVar eq_id) - over_lit_expr), - lie1 `plusLIE` lie2, - emptyBag, emptyBag, emptyLIE) - where - origin = PatOrigin pat -\end{code} - ------------------------------------------------------- -\begin{code} -tcConstructor pat con_name pat_ty +tcConstructor pat con_name = -- Check that it's a constructor - tcLookupValue con_name `thenNF_Tc` \ con_id -> - case isDataConId_maybe con_id of { - Nothing -> failWithTc (badCon con_id); - Just data_con -> + tcLookupDataCon con_name `thenNF_Tc` \ data_con -> -- Instantiate it - let - (tvs, theta, 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' = substTheta tenv ex_theta - arg_tys' = map (substTy tenv) arg_tys - - 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 - newDicts (PatOrigin pat) ex_theta' `thenNF_Tc` \ (lie_avail, dicts) -> - - -- Check overall type matches - unifyTauTy pat_ty result_ty `thenTc_` + tcInstDataCon (PatOrigin pat) data_con `thenNF_Tc` \ (_, ex_dicts, arg_tys, result_ty, lie_req, ex_lie, ex_tvs) -> - returnTc (data_con, ex_tvs', dicts, lie_avail, arg_tys') - } + returnTc (data_con, lie_req, ex_tvs, ex_dicts, ex_lie, arg_tys, result_ty) \end{code} ------------------------------------------------------ @@ -411,7 +405,12 @@ tcConPat tc_bndr pat con_name arg_pats pat_ty = tcAddErrCtxt (patCtxt pat) $ -- Check the constructor itself - tcConstructor pat con_name pat_ty `thenTc` \ (data_con, ex_tvs', dicts, lie_avail1, arg_tys') -> + tcConstructor pat con_name `thenTc` \ (data_con, lie_req1, ex_tvs, ex_dicts, lie_avail1, arg_tys, con_res_ty) -> + + -- 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 `thenTc` \ (co_fn, lie_req2) -> -- Check correct arity let @@ -422,11 +421,11 @@ tcConPat tc_bndr pat con_name arg_pats pat_ty (arityErr "Constructor" data_con con_arity no_of_args) `thenTc_` -- Check arguments - tcPats tc_bndr arg_pats arg_tys' `thenTc` \ (arg_pats', lie_req, tvs, ids, lie_avail2) -> + tcPats tc_bndr arg_pats arg_tys `thenTc` \ (arg_pats', lie_req3, tvs, ids, lie_avail2) -> - returnTc (ConPat data_con pat_ty ex_tvs' dicts arg_pats', - lie_req, - listToBag ex_tvs' `unionBags` tvs, + returnTc (co_fn <$> ConPat data_con pat_ty ex_tvs ex_dicts arg_pats', + lie_req1 `plusLIE` lie_req2 `plusLIE` lie_req3, + listToBag ex_tvs `unionBags` tvs, ids, lie_avail1 `plusLIE` lie_avail2) \end{code} @@ -434,21 +433,55 @@ tcConPat tc_bndr pat con_name arg_pats pat_ty %************************************************************************ %* * -\subsection{Errors and contexts} +\subsection{Subsumption} %* * %************************************************************************ +Example: + f :: (forall a. a->a) -> Int -> Int + f (g::Int->Int) y = g y +This is ok: the type signature allows fewer callers than +the (more general) signature f :: (Int->Int) -> Int -> Int +I.e. (forall a. a->a) <= Int -> Int +We end up translating this to: + f = \g' :: (forall a. a->a). let g = g' Int in g' y + +tcSubPat does the work + sig_ty is the signature on the pattern itself + (Int->Int in the example) + expected_ty is the type passed inwards from the context + (forall a. a->a in the example) + \begin{code} -patCtxt pat = hang (ptext SLIT("In the pattern:")) - 4 (ppr pat) +tcSubPat :: TcSigmaType -> TcHoleType -> TcM (PatCoFn, LIE) + +tcSubPat sig_ty exp_ty + = tcSubOff sig_ty exp_ty `thenTc` \ (co_fn, lie) -> + -- co_fn is a coercion on *expressions*, and we + -- need to make a coercion on *patterns* + if isIdCoercion co_fn then + ASSERT( isEmptyLIE lie ) + returnNF_Tc (idCoercion, emptyLIE) + else + tcGetUnique `thenNF_Tc` \ uniq -> + let + arg_id = mkSysLocal FSLIT("sub") uniq exp_ty + the_fn = DictLam [arg_id] (co_fn <$> HsVar arg_id) + pat_co_fn p = SigPat p exp_ty the_fn + in + returnNF_Tc (mkCoercion pat_co_fn, lie) +\end{code} -recordLabel field_label - = hang (hcat [ptext SLIT("When matching record field"), ppr field_label]) - 4 (hcat [ptext SLIT("with its immediately enclosing constructor")]) -recordRhs field_label pat - = hang (ptext SLIT("In the record field pattern")) - 4 (sep [ppr field_label, char '=', ppr pat]) +%************************************************************************ +%* * +\subsection{Errors and contexts} +%* * +%************************************************************************ + +\begin{code} +patCtxt pat = hang (ptext SLIT("When checking the pattern:")) + 4 (ppr pat) badFieldCon :: Name -> Name -> SDoc badFieldCon con field @@ -457,7 +490,9 @@ badFieldCon con field polyPatSig :: TcType -> SDoc polyPatSig sig_ty - = hang (ptext SLIT("Polymorphic type signature in pattern")) + = hang (ptext SLIT("Illegal polymorphic type signature in pattern:")) 4 (ppr sig_ty) + +badTypePat pat = ptext SLIT("Illegal type pattern") <+> ppr pat \end{code}