\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, newClassDicts
+import Inst ( InstOrigin(..),
+ emptyLIE, plusLIE, LIE, mkLIE, unitLIE, instToId, isEmptyLIE,
+ newMethod, newMethodFromName, newOverloadedLit, newDicts, tcInstDataCon
)
-import Name ( Name, getOccName, getSrcLoc )
+import Id ( mkLocalId, mkSysLocal )
+import Name ( Name )
import FieldLabel ( fieldLabelName )
-import TcEnv ( tcLookupValue, tcLookupClassByKey,
- tcLookupValueByKey, newLocalId, badCon
- )
-import TcType ( TcType, TcTyVar, tcInstTyVars, newTyVarTy )
-import TcMonoType ( tcHsSigType )
-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, isDataConWrapId_maybe )
-import Type ( Type, isTauTy, mkTyConApp, mkClassPred, boxedTypeKind )
-import PprType ( {- instance Outputable Type -} )
-import Subst ( substTy, substClasses )
-import TysPrim ( charPrimTy, intPrimTy, floatPrimTy,
- doublePrimTy, addrPrimTy
- )
-import TysWiredIn ( charTy, stringTy, intTy )
-import SrcLoc ( SrcLoc )
-import Unique ( eqClassOpKey, geClassOpKey, minusClassOpKey,
- cCallableClassKey
- )
+import DataCon ( dataConFieldLabels, dataConSourceArity )
+import PrelNames ( eqStringName, eqName, geName, cCallableClassName )
+import BasicTypes ( isBoxed )
import Bag
-import Util ( zipEqual )
import Outputable
\end{code}
%************************************************************************
\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}
%************************************************************************
\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.
%************************************************************************
\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
- = 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 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}
%* *
%************************************************************************
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.
-- 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}
= 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)
-- 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 boxedTypeKind `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 )
- tcLookupValue field_label `thenNF_Tc` \ sel_id ->
+ tcLookupGlobalId field_label `thenNF_Tc` \ sel_id ->
returnTc (sel_id, pat_ty)
) `thenTc` \ (sel_id, pat_ty) ->
%************************************************************************
%* *
-\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
+tcPat tc_bndr (LitPatIn lit@(HsLitLit s _)) pat_ty
-- cf tcExpr on LitLits
- = tcLookupClassByKey cCallableClassKey `thenNF_Tc` \ cCallableClass ->
+ = tcLookupClass cCallableClassName `thenNF_Tc` \ cCallableClass ->
newDicts (LitLitOrigin (_UNPK_ s))
- [mkClassPred cCallableClass [pat_ty]] `thenNF_Tc` \ (dicts, _) ->
- returnTc (LitPat lit pat_ty, dicts, emptyBag, emptyBag, emptyLIE)
+ [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 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
+ 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 = PatOrigin pat
-
-tcPat tc_bndr (NPlusKPatIn pat other) pat_ty
- = panic "TcPat:NPlusKPat: not an HsInt literal"
\end{code}
%************************************************************************
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
------------------------------------------------------
\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 isDataConWrapId_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' = substClasses tenv ex_theta
- arg_tys' = map (substTy tenv) arg_tys
+ tcInstDataCon (PatOrigin pat) data_con `thenNF_Tc` \ (_, ex_dicts, arg_tys, result_ty, lie_req, ex_lie, ex_tvs) ->
- 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` \ (lie_avail, dicts) ->
-
- -- Check overall type matches
- unifyTauTy pat_ty result_ty `thenTc_`
-
- 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}
------------------------------------------------------
= 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
(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 <$> ConPat data_con pat_ty ex_tvs ex_dicts arg_pats',
+ lie_req1 `plusLIE` lie_req2 `plusLIE` lie_req3,
+ listToBag ex_tvs `unionBags` tvs,
ids,
lie_avail1 `plusLIE` lie_avail2)
\end{code}
%************************************************************************
%* *
-\subsection{Errors and contexts}
+\subsection{Subsumption}
%* *
%************************************************************************
+Example:
+ f :: (forall a. a->a) -> Int -> Int
+ f (g::Int->Int) y = g y
+This is ok: the type signature allows fewer callers than
+the (more general) signature f :: (Int->Int) -> Int -> Int
+I.e. (forall a. a->a) <= Int -> Int
+We end up translating this to:
+ f = \g' :: (forall a. a->a). let g = g' Int in g' y
+
+tcSubPat does the work
+ sig_ty is the signature on the pattern itself
+ (Int->Int in the example)
+ expected_ty is the type passed inwards from the context
+ (forall a. a->a in the example)
+
\begin{code}
-patCtxt pat = hang (ptext SLIT("In the pattern:"))
- 4 (ppr pat)
+tcSubPat :: TcSigmaType -> TcHoleType -> TcM (PatCoFn, LIE)
+
+tcSubPat sig_ty exp_ty
+ = tcSubOff sig_ty exp_ty `thenTc` \ (co_fn, lie) ->
+ -- co_fn is a coercion on *expressions*, and we
+ -- need to make a coercion on *patterns*
+ if isIdCoercion co_fn then
+ ASSERT( isEmptyLIE lie )
+ returnNF_Tc (idCoercion, emptyLIE)
+ else
+ tcGetUnique `thenNF_Tc` \ uniq ->
+ let
+ arg_id = mkSysLocal FSLIT("sub") uniq exp_ty
+ the_fn = DictLam [arg_id] (co_fn <$> 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
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}
projects / ghc-hetmet.git / blobdiff