%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcPat]{Typechecking patterns}
\begin{code}
-#include "HsVersions.h"
-
-module TcPat ( tcPat ) where
+module TcPat ( tcPat, tcMonoPatBndr, tcSubPat,
+ badFieldCon, polyPatSig
+ ) where
-IMP_Ubiq(){-uitous-}
+#include "HsVersions.h"
-import HsSyn ( InPat(..), OutPat(..), HsExpr(..), HsLit(..),
- Match, HsBinds, HsType, Fixity,
- ArithSeqInfo, Stmt, DoOrListComp, Fake )
-import RnHsSyn ( SYN_IE(RenamedPat) )
-import TcHsSyn ( SYN_IE(TcPat), TcIdOcc(..) )
+import HsSyn ( Pat(..), LPat, HsConDetails(..), HsLit(..), HsOverLit(..), HsExpr(..) )
+import HsUtils
+import TcHsSyn ( TcId, hsLitType,
+ mkCoercion, idCoercion, isIdCoercion,
+ (<$>), PatCoFn )
-import TcMonad
-import Inst ( Inst, OverloadedLit(..), InstOrigin(..),
- emptyLIE, plusLIE, plusLIEs, SYN_IE(LIE),
- newMethod, newOverloadedLit
+import TcRnMonad
+import Inst ( InstOrigin(..),
+ newMethodFromName, newOverloadedLit, newDicts,
+ instToId, tcInstDataCon, tcSyntaxName
)
-import Name ( Name {- instance Outputable -} )
-import TcEnv ( tcLookupGlobalValue, tcLookupGlobalValueByKey,
- tcLookupLocalValueOK )
-import SpecEnv ( SpecEnv )
-import TcType ( SYN_IE(TcType), TcMaybe, newTyVarTy, newTyVarTys, tcInstId )
-import Unify ( unifyTauTy, unifyTauTyList, unifyTauTyLists )
-
-import Bag ( Bag )
+import Id ( idType, mkLocalId, mkSysLocal )
+import Name ( Name )
+import FieldLabel ( fieldLabelName )
+import TcEnv ( tcLookupClass, tcLookupLocatedDataCon, tcLookupId )
+import TcMType ( newTyVarTy, arityErr )
+import TcType ( TcType, TcTyVar, TcSigmaType, mkClassPred )
+import Kind ( argTypeKind, liftedTypeKind )
+import TcUnify ( tcSubOff, Expected(..), readExpectedType, zapExpectedType,
+ unifyTauTy, zapToListTy, zapToPArrTy, zapToTupleTy )
+import TcHsType ( tcHsSigType, UserTypeCtxt(..) )
+
+import TysWiredIn ( stringTy )
import CmdLineOpts ( opt_IrrefutableTuples )
-import Id ( GenId, idType )
-import Kind ( Kind, mkBoxedTypeKind, mkTypeKind )
-import Maybes ( maybeToBool )
-import PprType ( GenType, GenTyVar )
---import PprStyle--ToDo:rm
-import Pretty
-import Type ( splitFunTy, splitRhoTy, splitSigmaTy, mkTyVarTys,
- getFunTy_maybe, maybeAppDataTyCon,
- SYN_IE(Type), GenType
- )
-import TyVar ( GenTyVar )
-import TysPrim ( charPrimTy, intPrimTy, floatPrimTy,
- doublePrimTy, addrPrimTy
- )
-import TysWiredIn ( charTy, stringTy, mkListTy, mkTupleTy, addrTy )
-import Unique ( Unique, eqClassOpKey, geClassOpKey, minusClassOpKey )
-import Util ( assertPanic, panic )
+import DataCon ( DataCon, dataConFieldLabels, dataConSourceArity )
+import PrelNames ( eqStringName, eqName, geName, negateName, minusName,
+ integralClassName )
+import BasicTypes ( isBoxed )
+import SrcLoc ( Located(..), noLoc, unLoc )
+import Bag
+import Outputable
+import FastString
\end{code}
+
+%************************************************************************
+%* *
+\subsection{Variable patterns}
+%* *
+%************************************************************************
+
\begin{code}
-tcPat :: RenamedPat -> TcM s (TcPat s, LIE s, TcType s)
+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 argTypeKind `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}
+
%************************************************************************
%* *
-\subsection{Variables, wildcards, lazy pats, as-pats}
+\subsection{Typechecking patterns}
%* *
%************************************************************************
\begin{code}
-tcPat (VarPatIn name)
- = tcLookupLocalValueOK ("tcPat1:"{-++ppShow 80 (ppr PprDebug name)-}) 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
+ -> LPat Name
+
+ -> 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 (LPat TcId,
+ 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.
+ [Inst]) -- Dicts or methods [see below] bound by the pattern
+ -- from existential constructor patterns
+tcPat tc_bndr (L span pat) exp_ty
+ = addSrcSpan span $
+ do { (pat', tvs, ids, lie) <- tc_pat tc_bndr pat exp_ty
+ ; return (L span pat', tvs, ids, lie) }
\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_`
+tc_pat tc_bndr pat@(TypePat ty) pat_ty
+ = failWithTc (badTypePat pat)
+
+tc_pat tc_bndr (VarPat name) pat_ty
+ = tc_bndr name pat_ty `thenM` \ (co_fn, bndr_id) ->
+ returnM (co_fn <$> VarPat bndr_id,
+ emptyBag, unitBag (name, bndr_id), [])
+
+tc_pat tc_bndr (LazyPat pat) pat_ty
+ = tcPat tc_bndr pat pat_ty `thenM` \ (pat', tvs, ids, lie_avail) ->
+ returnM (LazyPat pat', tvs, ids, lie_avail)
+
+tc_pat tc_bndr pat_in@(AsPat (L nm_loc name) pat) pat_ty
+ = addSrcSpan nm_loc (tc_bndr name pat_ty) `thenM` \ (co_fn, bndr_id) ->
+ tcPat tc_bndr pat (Check (idType bndr_id)) `thenM` \ (pat', tvs, ids, lie_avail) ->
+ -- NB: if we have:
+ -- \ (y@(x::forall a. a->a)) = e
+ -- we'll fail. The as-pattern infers a monotype for 'y', which then
+ -- fails to unify with the polymorphic type for 'x'. This could be
+ -- fixed, but only with a bit more work.
+ returnM (co_fn <$> (AsPat (L nm_loc bndr_id) pat'),
+ tvs, (name, bndr_id) `consBag` ids, lie_avail)
+
+tc_pat tc_bndr (WildPat _) pat_ty
+ = zapExpectedType pat_ty argTypeKind `thenM` \ pat_ty' ->
+ -- We might have an incoming 'hole' type variable; no annotation
+ -- so zap it to a type. Rather like tcMonoPatBndr.
+ -- Note argTypeKind, so that
+ -- f _ = 3
+ -- is rejected when f applied to an unboxed tuple
+ -- However, this means that
+ -- (case g x of _ -> ...)
+ -- is rejected g returns an unboxed tuple, which is perhpas
+ -- annoying. I suppose we could pass the context into tc_pat...
+ returnM (WildPat pat_ty', emptyBag, emptyBag, [])
+
+tc_pat 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)
+
+tc_pat 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 <$> unLoc pat', 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}
+tc_pat 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)
+
+tc_pat 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)
- -- Make sure we record that the tuples can only contain boxed types
- newTyVarTys arity mkBoxedTypeKind `thenNF_Tc` \ tyvar_tys ->
+tc_pat tc_bndr pat_in@(TuplePat pats boxity) pat_ty
+ = addErrCtxt (patCtxt pat_in) $
- tcAddErrCtxt (patCtxt pat_in) $
- unifyTauTyLists tyvar_tys tys `thenTc_`
+ 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
- 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 (noLoc unmangled_result)
+ | otherwise = unmangled_result
in
- returnTc (possibly_mangled_result, lie, mkTupleTy arity tys)
+ returnM (possibly_mangled_result, 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) ->
-
- tcAddErrCtxt (patCtxt pat_in) $
- matchConArgTys name tys `thenTc` \ (con_id, data_ty) ->
+tc_pat tc_bndr pat_in@(ConPatIn con_name arg_pats) pat_ty
+ = addErrCtxt (patCtxt pat_in) $
- returnTc (ConPat con_id data_ty pats',
- lie,
- data_ty)
+ -- Check that it's a constructor, and instantiate it
+ tcLookupLocatedDataCon con_name `thenM` \ data_con ->
+ tcInstDataCon (PatOrigin pat_in) data_con `thenM` \ (_, ex_dicts1, arg_tys, con_res_ty, ex_tvs) ->
-tcPat pat_in@(ConOpPatIn pat1 op _ pat2) -- in binary-op form...
- = tcPat pat1 `thenTc` \ (pat1', lie1, ty1) ->
- tcPat pat2 `thenTc` \ (pat2', lie2, ty2) ->
+ -- 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 ->
- tcAddErrCtxt (patCtxt pat_in) $
- matchConArgTys op [ty1,ty2] `thenTc` \ (con_id, data_ty) ->
+ -- Check the argument patterns
+ tcConStuff tc_bndr data_con arg_pats arg_tys `thenM` \ (arg_pats', arg_tvs, arg_ids, ex_dicts2) ->
- returnTc (ConOpPat pat1' con_id pat2' data_ty,
- lie1 `plusLIE` lie2,
- data_ty)
+ 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{Records}
+\subsection{Literals}
%* *
%************************************************************************
\begin{code}
-tcPat pat_in@(RecPatIn name rpats)
- = tcLookupGlobalValue name `thenNF_Tc` \ con_id ->
- tcInstId con_id `thenNF_Tc` \ (_, _, con_tau) ->
+tc_pat tc_bndr pat@(LitPat lit@(HsString _)) pat_ty
+ = zapExpectedType pat_ty liftedTypeKind `thenM` \ pat_ty' ->
+ unifyTauTy pat_ty' stringTy `thenM_`
+ tcLookupId eqStringName `thenM` \ eq_id ->
+ returnM (NPatOut lit stringTy (nlHsVar eq_id `HsApp` nlHsLit lit),
+ emptyBag, emptyBag, [])
+
+tc_pat tc_bndr (LitPat simple_lit) pat_ty
+ = zapExpectedType pat_ty argTypeKind `thenM` \ pat_ty' ->
+ unifyTauTy pat_ty' (hsLitType simple_lit) `thenM_`
+ returnM (LitPat simple_lit, emptyBag, emptyBag, [])
+
+tc_pat tc_bndr pat@(NPatIn over_lit mb_neg) pat_ty
+ = zapExpectedType pat_ty liftedTypeKind `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, noLoc (HsVar neg)) `thenM` \ (_, neg_expr) ->
+ returnM (mkHsApp neg_expr pos_lit_expr)
+ ) `thenM` \ lit_expr ->
+
let
- -- Ignore the con_theta; overloaded constructors only
- -- behave differently when called, not when used for
- -- matching.
- (_, record_ty) = splitFunTy con_tau
+ -- 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 pat_ty'
+ (HsIntegral i _, Just _) -> HsInteger (-i) pat_ty'
+ (HsFractional f _, Nothing) -> HsRat f pat_ty'
+ (HsFractional f _, Just _) -> HsRat (-f) pat_ty'
in
- -- Con is syntactically constrained to be a data constructor
- ASSERT( maybeToBool (maybeAppDataTyCon record_ty) )
-
- mapAndUnzipTc (do_bind record_ty) rpats `thenTc` \ (rpats', lies) ->
-
- returnTc (RecPat con_id record_ty rpats',
- plusLIEs lies,
- record_ty)
-
+ returnM (NPatOut lit' pat_ty' (HsApp (nlHsVar eq) lit_expr),
+ emptyBag, emptyBag, [])
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 (getFunTy_maybe tau) )
- let
- -- Selector must have type RecordType -> FieldType
- Just (record_ty, field_ty) = getFunTy_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)
+ origin = PatOrigin pat
\end{code}
%************************************************************************
%* *
-\subsection{Non-overloaded literals}
+\subsection{n+k patterns}
%* *
%************************************************************************
\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)
+tc_pat tc_bndr pat@(NPlusKPatIn (L nm_loc name) lit@(HsIntegral i _) minus_name) pat_ty
+ = addSrcSpan nm_loc (tc_bndr name pat_ty) `thenM` \ (co_fn, bndr_id) ->
+ let
+ pat_ty' = idType bndr_id
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)
+ 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, noLoc (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 (L nm_loc bndr_id) i
+ (SectionR (nlHsVar ge) over_lit_expr)
+ (SectionR minus_expr over_lit_expr),
+ emptyBag, unitBag (name, bndr_id), [])
+ where
+ origin = PatOrigin pat
\end{code}
+
%************************************************************************
%* *
-\subsection{Overloaded patterns: int literals and \tr{n+k} patterns}
+\subsection{Lists of patterns}
%* *
%************************************************************************
+Helper functions
+
\begin{code}
-tcPat (LitPatIn lit@(HsInt i))
- = newTyVarTy mkBoxedTypeKind `thenNF_Tc` \ tyvar_ty ->
- newOverloadedLit origin
- (OverloadedIntegral i) tyvar_ty `thenNF_Tc` \ (lie1, over_lit_id) ->
-
- 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)
- (HsVar over_lit_id)),
- lie1 `plusLIE` lie2,
- tyvar_ty)
- where
- origin = LiteralOrigin lit
+tcPats :: BinderChecker -- How to deal with variables
+ -> [LPat Name] -> [TcType] -- Excess 'expected types' discarded
+ -> TcM ([LPat TcId],
+ Bag TcTyVar,
+ Bag (Name, TcId), -- Ids bound by the pattern
+ [Inst]) -- Dicts bound by the pattern
+
+tcPats tc_bndr [] tys = returnM ([], emptyBag, emptyBag, [])
+
+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) ->
+
+ returnM (pat':pats',
+ tvs1 `unionBags` tvs2, ids1 `unionBags` ids2,
+ lie_avail1 ++ lie_avail2)
+\end{code}
-tcPat (LitPatIn lit@(HsFrac f))
- = newTyVarTy mkBoxedTypeKind `thenNF_Tc` \ tyvar_ty ->
- newOverloadedLit origin
- (OverloadedFractional f) tyvar_ty `thenNF_Tc` \ (lie1, over_lit_id) ->
- tcLookupGlobalValueByKey eqClassOpKey `thenNF_Tc` \ eq_sel_id ->
- newMethod origin (RealId eq_sel_id) [tyvar_ty] `thenNF_Tc` \ (lie2, eq_id) ->
+%************************************************************************
+%* *
+\subsection{Constructor arguments}
+%* *
+%************************************************************************
- returnTc (NPat lit tyvar_ty (HsApp (HsVar eq_id)
- (HsVar over_lit_id)),
- lie1 `plusLIE` lie2,
- tyvar_ty)
- where
- origin = LiteralOrigin lit
+\begin{code}
+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_`
-tcPat (LitPatIn lit@(HsLitLit s))
- = error "tcPat: can't handle ``literal-literal'' patterns"
+ -- Check arguments
+ tcPats tc_bndr arg_pats arg_tys `thenM` \ (arg_pats', tvs, ids, lie_avail) ->
-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 ->
+ returnM (PrefixCon arg_pats', tvs, ids, lie_avail)
+ where
+ con_arity = dataConSourceArity data_con
+ no_of_args = length arg_pats
- newOverloadedLit origin
- (OverloadedIntegral i) local_ty `thenNF_Tc` \ (lie1, over_lit_id) ->
+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_`
- 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) ->
+ -- 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 (NPlusKPat (TcId local) lit local_ty
- (SectionR (HsVar ge_id) (HsVar over_lit_id))
- (SectionR (HsVar minus_id) (HsVar over_lit_id)),
- lie1 `plusLIE` lie2 `plusLIE` lie3,
- local_ty)
+ returnM (InfixCon p1' p2',
+ tvs1 `unionBags` tvs2, ids1 `unionBags` ids2,
+ lie_avail1 ++ lie_avail2)
where
- origin = LiteralOrigin lit -- Not very good!
+ con_arity = dataConSourceArity data_con
+ [ty1, ty2] = arg_tys
-tcPat (NPlusKPatIn pat other) = panic "TcPat:NPlusKPat: not an HsInt literal"
+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)
+
+ 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).
+
+ tc_fields field_tys []
+ = returnM ([], emptyBag, emptyBag, [])
+
+ tc_fields field_tys ((L lbl_loc field_label, rhs_pat) : rpats)
+ = tc_fields field_tys rpats `thenM` \ (rpats', 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 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 )
+ addSrcSpan lbl_loc (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 ((L lbl_loc sel_id, rhs_pat') : rpats',
+ tvs1 `unionBags` tvs2,
+ ids1 `unionBags` ids2,
+ lie_avail1 ++ lie_avail2)
\end{code}
+
%************************************************************************
%* *
-\subsection{Lists of patterns}
+\subsection{Subsumption}
%* *
%************************************************************************
-\begin{code}
-tcPats :: [RenamedPat] -> TcM s ([TcPat s], LIE s, [TcType s])
-
-tcPats [] = returnTc ([], emptyLIE, [])
-
-tcPats (pat:pats)
- = tcPat pat `thenTc` \ (pat', lie, ty) ->
- tcPats pats `thenTc` \ (pats', lie', tys) ->
-
- returnTc (pat':pats', plusLIE lie lie', ty:tys)
-\end{code}
-
-@matchConArgTys@ grabs the signature of the data constructor, and
-unifies the actual args against the expected ones.
+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}
-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.
- let
- (con_args, con_result) = splitFunTy con_tau
- con_arity = length con_args
- no_of_args = length arg_tys
- in
- checkTc (con_arity == no_of_args)
- (arityErr "Constructor" con_id con_arity no_of_args) `thenTc_`
-
- unifyTauTyLists con_args arg_tys `thenTc_`
- returnTc (con_id, con_result)
+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] (noLoc (co_fn <$> HsVar arg_id))
+ pat_co_fn p = SigPatOut (noLoc p) exp_ty' the_fn
+ in
+ returnM (mkCoercion pat_co_fn)
\end{code}
-% =================================================
+%************************************************************************
+%* *
+\subsection{Errors and contexts}
+%* *
+%************************************************************************
-Errors and contexts
-~~~~~~~~~~~~~~~~~~~
\begin{code}
-patCtxt pat sty = ppHang (ppPStr SLIT("In the pattern:")) 4 (ppr sty pat)
+patCtxt pat = hang (ptext SLIT("When checking the pattern:"))
+ 4 (ppr pat)
-recordLabel field_label sty
- = ppHang (ppBesides [ppPStr SLIT("When matching record field"), ppr sty field_label])
- 4 (ppBesides [ppPStr SLIT("with its immediately enclosing constructor")])
+badFieldCon :: DataCon -> 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 sty
- = ppHang (ppPStr SLIT("In the record field pattern"))
- 4 (ppSep [ppr sty field_label, ppChar '=', ppr sty 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}
+
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