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