%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcPat]{Typechecking patterns}
\begin{code}
-module TcPat ( tcPat ) where
+module TcPat ( tcPat, tcMonoPatBndr, tcSubPat,
+ badFieldCon, polyPatSig
+ ) where
#include "HsVersions.h"
-import HsSyn ( InPat(..), OutPat(..), HsLit(..), HsExpr(..) )
+import HsSyn ( InPat(..), OutPat(..), HsLit(..), HsOverLit(..), HsExpr(..) )
import RnHsSyn ( RenamedPat )
-import TcHsSyn ( TcPat )
+import TcHsSyn ( TcPat, TcId, simpleHsLitTy )
import TcMonad
-import Inst ( Inst, OverloadedLit(..), InstOrigin(..),
- emptyLIE, plusLIE, plusLIEs, LIE,
- newMethod, newOverloadedLit
+import Inst ( InstOrigin(..),
+ emptyLIE, plusLIE, LIE, mkLIE, unitLIE, instToId, isEmptyLIE,
+ newMethod, newMethodFromName, newOverloadedLit, newDicts, tcInstDataCon
)
-import Name ( Name {- instance Outputable -} )
-import TcEnv ( TcIdOcc(..), tcLookupGlobalValue, tcLookupGlobalValueByKey,
- tcLookupLocalValueOK, tcInstId
- )
-import TcType ( TcType, TcMaybe, newTyVarTy, newTyVarTys )
-import Unify ( unifyTauTy, unifyTauTyList, unifyTauTyLists )
-
-import Bag ( Bag )
+import Id ( mkLocalId, mkSysLocal )
+import Name ( Name )
+import FieldLabel ( fieldLabelName )
+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 Id ( GenId, idType, Id )
-import Kind ( Kind, mkBoxedTypeKind, mkTypeKind )
-import PprType ( GenType, GenTyVar )
-import Type ( splitFunTys, splitRhoTy,
- splitFunTy_maybe,
- Type, GenType
- )
-import TyVar ( GenTyVar )
-import TysPrim ( charPrimTy, intPrimTy, floatPrimTy,
- doublePrimTy, addrPrimTy
- )
-import TysWiredIn ( charTy, stringTy, mkListTy, mkTupleTy )
-import Unique ( Unique, eqClassOpKey, geClassOpKey, minusClassOpKey )
-import Util ( assertPanic, panic )
+import DataCon ( dataConFieldLabels, dataConSourceArity )
+import PrelNames ( eqStringName, eqName, geName, cCallableClassName )
+import BasicTypes ( isBoxed )
+import Bag
import Outputable
\end{code}
+
+%************************************************************************
+%* *
+\subsection{Variable patterns}
+%* *
+%************************************************************************
+
\begin{code}
-tcPat :: RenamedPat -> TcM s (TcPat s, LIE s, TcType s)
+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}
+
%************************************************************************
%* *
-\subsection{Variables, wildcards, lazy pats, as-pats}
+\subsection{Typechecking patterns}
%* *
%************************************************************************
\begin{code}
-tcPat (VarPatIn name)
- = tcLookupLocalValueOK "tcPat1:" name `thenNF_Tc` \ id ->
- returnTc (VarPat (TcId id), emptyLIE, idType id)
-
-tcPat (LazyPatIn pat)
- = tcPat pat `thenTc` \ (pat', lie, ty) ->
- returnTc (LazyPat pat', lie, ty)
-
-tcPat pat_in@(AsPatIn name pat)
- = tcLookupLocalValueOK "tcPat2" name `thenNF_Tc` \ id ->
- tcPat pat `thenTc` \ (pat', lie, ty) ->
- tcAddErrCtxt (patCtxt pat_in) $
- unifyTauTy (idType id) ty `thenTc_`
- returnTc (AsPat (TcId id) pat', lie, ty)
-
-tcPat WildPatIn
- = newTyVarTy mkTypeKind `thenNF_Tc` \ tyvar_ty ->
- returnTc (WildPat tyvar_ty, emptyLIE, tyvar_ty)
-
-tcPat (NegPatIn pat)
- = tcPat (negate_lit pat)
- where
- negate_lit (LitPatIn (HsInt i)) = LitPatIn (HsInt (-i))
- negate_lit (LitPatIn (HsFrac f)) = LitPatIn (HsFrac (-f))
- negate_lit _ = panic "TcPat:negate_pat"
-
-tcPat (ParPatIn parend_pat)
- = tcPat parend_pat
+tcPat :: BinderChecker
+ -> RenamedPat
+
+ -> 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.
+
+ -> 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
+ -- patterns are brought into scope before we begin.
+ Bag (Name, TcId), -- Ids bound by the pattern, along with the Name under
+ -- 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
+ -- from existential constructor patterns
\end{code}
+
%************************************************************************
%* *
-\subsection{Explicit lists and tuples}
+\subsection{Variables, wildcards, lazy pats, as-pats}
%* *
%************************************************************************
\begin{code}
-tcPat pat_in@(ListPatIn pats)
- = tcPats pats `thenTc` \ (pats', lie, tys) ->
- newTyVarTy mkBoxedTypeKind `thenNF_Tc` \ tyvar_ty ->
- tcAddErrCtxt (patCtxt pat_in) $
- unifyTauTyList (tyvar_ty:tys) `thenTc_`
+tcPat tc_bndr pat@(TypePatIn ty) pat_ty
+ = failWithTc (badTypePat pat)
+
+tcPat tc_bndr (VarPatIn name) pat_ty
+ = tc_bndr name pat_ty `thenTc` \ (co_fn, lie_req, bndr_id) ->
+ returnTc (co_fn <$> VarPat bndr_id, lie_req,
+ emptyBag, unitBag (name, bndr_id), emptyLIE)
+
+tcPat tc_bndr (LazyPatIn pat) pat_ty
+ = tcPat tc_bndr pat pat_ty `thenTc` \ (pat', lie_req, tvs, ids, lie_avail) ->
+ returnTc (LazyPat pat', lie_req, tvs, ids, lie_avail)
+
+tcPat tc_bndr pat_in@(AsPatIn name pat) pat_ty
+ = tc_bndr name pat_ty `thenTc` \ (co_fn, lie_req1, bndr_id) ->
+ tcPat tc_bndr pat pat_ty `thenTc` \ (pat', lie_req2, tvs, ids, lie_avail) ->
+ returnTc (co_fn <$> (AsPat bndr_id pat'), lie_req1 `plusLIE` lie_req2,
+ tvs, (name, bndr_id) `consBag` ids, lie_avail)
+
+tcPat tc_bndr WildPatIn pat_ty
+ = 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 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}
- returnTc (ListPat tyvar_ty pats', lie, mkListTy tyvar_ty)
-tcPat pat_in@(TuplePatIn pats)
- = let
- arity = length pats
- in
- tcPats pats `thenTc` \ (pats', lie, tys) ->
+%************************************************************************
+%* *
+\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@(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)
- -- Make sure we record that the tuples can only contain boxed types
- newTyVarTys arity mkBoxedTypeKind `thenNF_Tc` \ tyvar_tys ->
+tcPat tc_bndr pat_in@(TuplePatIn pats boxity) pat_ty
+ = tcAddErrCtxt (patCtxt pat_in) $
- tcAddErrCtxt (patCtxt pat_in) $
- unifyTauTyLists tyvar_tys tys `thenTc_`
+ 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'
+ 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.
-- it was easy to do.
possibly_mangled_result
- = if opt_IrrefutableTuples
- then LazyPat unmangled_result
- else unmangled_result
-
- -- ToDo: IrrefutableEverything
+ | opt_IrrefutableTuples && isBoxed boxity = LazyPat unmangled_result
+ | otherwise = unmangled_result
in
- returnTc (possibly_mangled_result, lie, mkTupleTy arity tys)
+ returnTc (possibly_mangled_result, lie_req, tvs, ids, lie_avail)
+ where
+ arity = length pats
\end{code}
+
%************************************************************************
%* *
\subsection{Other constructors}
%* *
-%************************************************************************
-Constructor patterns are a little fun:
-\begin{itemize}
-\item
-typecheck the arguments
-\item
-look up the constructor
-\item
-specialise its type (ignore the translation this produces)
-\item
-check that the context produced by this specialisation is empty
-\item
-get the arguments out of the function type produced from specialising
-\item
-unify them with the types of the patterns
-\item
-back substitute with the type of the result of the constructor
-\end{itemize}
-
-ToDo: exploit new representation of constructors to make this more
-efficient?
+%************************************************************************
\begin{code}
-tcPat pat_in@(ConPatIn name pats)
- = tcPats pats `thenTc` \ (pats', lie, tys) ->
+tcPat tc_bndr pat@(ConPatIn name arg_pats) pat_ty
+ = tcConPat tc_bndr pat name arg_pats pat_ty
- tcAddErrCtxt (patCtxt pat_in) $
- matchConArgTys name tys `thenTc` \ (con_id, data_ty) ->
-
- returnTc (ConPat con_id data_ty pats',
- lie,
- data_ty)
-
-tcPat pat_in@(ConOpPatIn pat1 op _ pat2) -- in binary-op form...
- = tcPat pat1 `thenTc` \ (pat1', lie1, ty1) ->
- tcPat pat2 `thenTc` \ (pat2', lie2, ty2) ->
-
- tcAddErrCtxt (patCtxt pat_in) $
- matchConArgTys op [ty1,ty2] `thenTc` \ (con_id, data_ty) ->
-
- returnTc (ConOpPat pat1' con_id pat2' data_ty,
- lie1 `plusLIE` lie2,
- data_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 pat_in@(RecPatIn name rpats)
- = tcLookupGlobalValue name `thenNF_Tc` \ con_id ->
- tcInstId con_id `thenNF_Tc` \ (_, _, con_tau) ->
+tcPat tc_bndr pat@(RecPatIn name rpats) pat_ty
+ = tcAddErrCtxt (patCtxt pat) $
+
+ -- Check the constructor itself
+ 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
- -- Ignore the con_theta; overloaded constructors only
- -- behave differently when called, not when used for
- -- matching.
- (_, record_ty) = splitFunTys con_tau
+ -- 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
- -- Con is syntactically constrained to be a data constructor
- ASSERT( maybeToBool (splitAlgTyConApp_maybe record_ty) )
- mapAndUnzipTc (do_bind record_ty) rpats `thenTc` \ (rpats', lies) ->
+ -- Check the fields
+ tc_fields field_tys rpats `thenTc` \ (rpats', lie_req3, tvs, ids, lie_avail2) ->
- returnTc (RecPat con_id record_ty rpats',
- plusLIEs lies,
- record_ty)
+ 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)
where
- do_bind expected_record_ty (field_label, rhs_pat, pun_flag)
- = tcLookupGlobalValue field_label `thenNF_Tc` \ sel_id ->
- tcInstId sel_id `thenNF_Tc` \ (_, _, tau) ->
-
- -- Record selectors all have type
- -- forall a1..an. T a1 .. an -> tau
- ASSERT( maybeToBool (splitFunTy_maybe tau) )
- let
- -- Selector must have type RecordType -> FieldType
- Just (record_ty, field_ty) = splitFunTy_maybe tau
- in
- tcAddErrCtxt (recordLabel field_label) (
- unifyTauTy expected_record_ty record_ty
- ) `thenTc_`
- tcPat rhs_pat `thenTc` \ (rhs_pat', lie, rhs_ty) ->
- tcAddErrCtxt (recordRhs field_label rhs_pat) (
- unifyTauTy field_ty rhs_ty
- ) `thenTc_`
- returnTc ((sel_id, rhs_pat', pun_flag), lie)
+ 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)
+
+ -- 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)
\end{code}
%************************************************************************
%* *
-\subsection{Non-overloaded literals}
+\subsection{Literals}
%* *
%************************************************************************
\begin{code}
-tcPat (LitPatIn lit@(HsChar str))
- = returnTc (LitPat lit charTy, emptyLIE, charTy)
-
-tcPat (LitPatIn lit@(HsString str))
- = tcLookupGlobalValueByKey eqClassOpKey `thenNF_Tc` \ sel_id ->
- newMethod (LiteralOrigin lit)
- (RealId 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, stringTy)
-
-tcPat (LitPatIn lit@(HsIntPrim _))
- = returnTc (LitPat lit intPrimTy, emptyLIE, intPrimTy)
-tcPat (LitPatIn lit@(HsCharPrim _))
- = returnTc (LitPat lit charPrimTy, emptyLIE, charPrimTy)
-tcPat (LitPatIn lit@(HsStringPrim _))
- = returnTc (LitPat lit addrPrimTy, emptyLIE, addrPrimTy)
-tcPat (LitPatIn lit@(HsFloatPrim _))
- = returnTc (LitPat lit floatPrimTy, emptyLIE, floatPrimTy)
-tcPat (LitPatIn lit@(HsDoublePrim _))
- = returnTc (LitPat lit doublePrimTy, emptyLIE, doublePrimTy)
+tcPat tc_bndr (LitPatIn 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 origin over_lit pat_ty `thenNF_Tc` \ (over_lit_expr, lie1) ->
+ newMethodFromName origin pat_ty eqName `thenNF_Tc` \ eq ->
+
+ returnTc (NPat lit' pat_ty (HsApp (HsVar (instToId eq)) over_lit_expr),
+ lie1 `plusLIE` unitLIE eq,
+ emptyBag, emptyBag, emptyLIE)
+ where
+ origin = PatOrigin pat
+ lit' = case over_lit of
+ HsIntegral i _ -> HsInteger i
+ HsFractional f _ -> HsRat f pat_ty
\end{code}
%************************************************************************
%* *
-\subsection{Overloaded patterns: int literals and \tr{n+k} patterns}
+\subsection{n+k patterns}
%* *
%************************************************************************
\begin{code}
-tcPat (LitPatIn lit@(HsInt i))
- = newTyVarTy mkBoxedTypeKind `thenNF_Tc` \ tyvar_ty ->
- newOverloadedLit origin
- (OverloadedIntegral i) tyvar_ty `thenNF_Tc` \ (over_lit_expr, lie1) ->
-
- tcLookupGlobalValueByKey eqClassOpKey `thenNF_Tc` \ eq_sel_id ->
- newMethod origin (RealId eq_sel_id) [tyvar_ty] `thenNF_Tc` \ (lie2, eq_id) ->
-
- returnTc (NPat lit tyvar_ty (HsApp (HsVar eq_id)
- over_lit_expr),
- lie1 `plusLIE` lie2,
- tyvar_ty)
- where
- origin = LiteralOrigin lit
-
-tcPat (LitPatIn lit@(HsFrac f))
- = newTyVarTy mkBoxedTypeKind `thenNF_Tc` \ tyvar_ty ->
- newOverloadedLit origin
- (OverloadedFractional f) tyvar_ty `thenNF_Tc` \ (over_lit_expr, lie1) ->
-
- tcLookupGlobalValueByKey eqClassOpKey `thenNF_Tc` \ eq_sel_id ->
- newMethod origin (RealId eq_sel_id) [tyvar_ty] `thenNF_Tc` \ (lie2, eq_id) ->
-
- returnTc (NPat lit tyvar_ty (HsApp (HsVar eq_id)
- over_lit_expr),
- lie1 `plusLIE` lie2,
- tyvar_ty)
- where
- origin = LiteralOrigin lit
-
-tcPat (LitPatIn lit@(HsLitLit s))
- = error "tcPat: can't handle ``literal-literal'' patterns"
-
-tcPat (NPlusKPatIn name lit@(HsInt i))
- = tcLookupLocalValueOK "tcPat1:n+k" name `thenNF_Tc` \ local ->
- let
- local_ty = idType local
- in
- tcLookupGlobalValueByKey geClassOpKey `thenNF_Tc` \ ge_sel_id ->
- tcLookupGlobalValueByKey minusClassOpKey `thenNF_Tc` \ minus_sel_id ->
-
- newOverloadedLit origin
- (OverloadedIntegral i) local_ty `thenNF_Tc` \ (over_lit_expr, lie1) ->
-
- newMethod origin (RealId ge_sel_id) [local_ty] `thenNF_Tc` \ (lie2, ge_id) ->
- newMethod origin (RealId minus_sel_id) [local_ty] `thenNF_Tc` \ (lie3, minus_id) ->
-
- returnTc (NPlusKPat (TcId local) lit local_ty
- (SectionR (HsVar ge_id) over_lit_expr)
- (SectionR (HsVar minus_id) over_lit_expr),
- lie1 `plusLIE` lie2 `plusLIE` lie3,
- local_ty)
+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
+ tcLookupId minus_name `thenNF_Tc` \ minus_sel_id ->
+ 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` lie2 `plusLIE` mkLIE [ge,minus],
+ emptyBag, unitBag (name, bndr_id), emptyLIE)
where
- origin = LiteralOrigin lit -- Not very good!
-
-tcPat (NPlusKPatIn pat other) = panic "TcPat:NPlusKPat: not an HsInt literal"
+ origin = PatOrigin pat
\end{code}
%************************************************************************
%* *
%************************************************************************
-\begin{code}
-tcPats :: [RenamedPat] -> TcM s ([TcPat s], LIE s, [TcType s])
+Helper functions
-tcPats [] = returnTc ([], emptyLIE, [])
+\begin{code}
+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
+
+tcPats tc_bndr [] tys = returnTc ([], emptyLIE, emptyBag, emptyBag, emptyLIE)
+
+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) ->
+
+ returnTc (pat':pats', lie_req1 `plusLIE` lie_req2,
+ tvs1 `unionBags` tvs2, ids1 `unionBags` ids2,
+ lie_avail1 `plusLIE` lie_avail2)
+\end{code}
-tcPats (pat:pats)
- = tcPat pat `thenTc` \ (pat', lie, ty) ->
- tcPats pats `thenTc` \ (pats', lie', tys) ->
+------------------------------------------------------
+\begin{code}
+tcConstructor pat con_name
+ = -- Check that it's a constructor
+ tcLookupDataCon con_name `thenNF_Tc` \ data_con ->
- returnTc (pat':pats', plusLIE lie lie', ty:tys)
-\end{code}
+ -- Instantiate it
+ tcInstDataCon (PatOrigin pat) data_con `thenNF_Tc` \ (_, ex_dicts, arg_tys, result_ty, lie_req, ex_lie, ex_tvs) ->
-@matchConArgTys@ grabs the signature of the data constructor, and
-unifies the actual args against the expected ones.
+ returnTc (data_con, lie_req, ex_tvs, ex_dicts, ex_lie, arg_tys, result_ty)
+\end{code}
+------------------------------------------------------
\begin{code}
-matchConArgTys :: Name -> [TcType s] -> TcM s (Id, TcType s)
-
-matchConArgTys con arg_tys
- = tcLookupGlobalValue con `thenNF_Tc` \ con_id ->
- tcInstId con_id `thenNF_Tc` \ (_, _, con_tau) ->
- -- Ignore the con_theta; overloaded constructors only
- -- behave differently when called, not when used for
- -- matching.
+tcConPat tc_bndr pat con_name arg_pats pat_ty
+ = tcAddErrCtxt (patCtxt pat) $
+
+ -- Check the constructor itself
+ 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
- (con_args, con_result) = splitFunTys con_tau
- con_arity = length con_args
- no_of_args = length arg_tys
+ con_arity = dataConSourceArity data_con
+ no_of_args = length arg_pats
in
checkTc (con_arity == no_of_args)
- (arityErr "Constructor" con_id con_arity no_of_args) `thenTc_`
+ (arityErr "Constructor" data_con con_arity no_of_args) `thenTc_`
+
+ -- Check arguments
+ tcPats tc_bndr arg_pats arg_tys `thenTc` \ (arg_pats', lie_req3, tvs, ids, lie_avail2) ->
- unifyTauTyLists con_args arg_tys `thenTc_`
- returnTc (con_id, con_result)
+ returnTc (co_fn <$> ConPat data_con pat_ty ex_tvs ex_dicts arg_pats',
+ lie_req1 `plusLIE` lie_req2 `plusLIE` lie_req3,
+ listToBag ex_tvs `unionBags` tvs,
+ ids,
+ lie_avail1 `plusLIE` lie_avail2)
\end{code}
-% =================================================
+%************************************************************************
+%* *
+\subsection{Subsumption}
+%* *
+%************************************************************************
+
+Example:
+ f :: (forall a. a->a) -> Int -> Int
+ f (g::Int->Int) y = g y
+This is ok: the type signature allows fewer callers than
+the (more general) signature f :: (Int->Int) -> Int -> Int
+I.e. (forall a. a->a) <= Int -> Int
+We end up translating this to:
+ f = \g' :: (forall a. a->a). let g = g' Int in g' y
+
+tcSubPat does the work
+ sig_ty is the signature on the pattern itself
+ (Int->Int in the example)
+ expected_ty is the type passed inwards from the context
+ (forall a. a->a in the example)
-Errors and contexts
-~~~~~~~~~~~~~~~~~~~
\begin{code}
-patCtxt pat = hang (ptext SLIT("In the pattern:"))
+tcSubPat :: TcSigmaType -> TcHoleType -> TcM (PatCoFn, LIE)
+
+tcSubPat sig_ty exp_ty
+ = tcSubOff sig_ty exp_ty `thenTc` \ (co_fn, lie) ->
+ -- co_fn is a coercion on *expressions*, and we
+ -- need to make a coercion on *patterns*
+ if isIdCoercion co_fn then
+ ASSERT( isEmptyLIE lie )
+ returnNF_Tc (idCoercion, emptyLIE)
+ else
+ tcGetUnique `thenNF_Tc` \ uniq ->
+ let
+ arg_id = mkSysLocal FSLIT("sub") uniq exp_ty
+ the_fn = DictLam [arg_id] (co_fn <$> HsVar arg_id)
+ pat_co_fn p = SigPat p exp_ty the_fn
+ in
+ returnNF_Tc (mkCoercion pat_co_fn, lie)
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{Errors and contexts}
+%* *
+%************************************************************************
+
+\begin{code}
+patCtxt pat = hang (ptext SLIT("When checking the pattern:"))
4 (ppr pat)
-recordLabel field_label
- = hang (hcat [ptext SLIT("When matching record field"), ppr field_label])
- 4 (hcat [ptext SLIT("with its immediately enclosing constructor")])
+badFieldCon :: Name -> Name -> SDoc
+badFieldCon con field
+ = hsep [ptext SLIT("Constructor") <+> quotes (ppr con),
+ ptext SLIT("does not have field"), quotes (ppr field)]
-recordRhs field_label pat
- = hang (ptext SLIT("In the record field pattern"))
- 4 (sep [ppr field_label, char '=', ppr pat])
+polyPatSig :: TcType -> SDoc
+polyPatSig sig_ty
+ = hang (ptext SLIT("Illegal polymorphic type signature in pattern:"))
+ 4 (ppr sig_ty)
+
+badTypePat pat = ptext SLIT("Illegal type pattern") <+> ppr pat
\end{code}
+
projects / ghc-hetmet.git / blobdiff