\section[TcExpr]{Typecheck an expression}
\begin{code}
-module TcExpr ( tcExpr, tcStmt, tcId ) where
+module TcExpr ( tcExpr, tcId ) where
#include "HsVersions.h"
import Inst ( Inst, InstOrigin(..), OverloadedLit(..),
LIE, emptyLIE, plusLIE, plusLIEs, newOverloadedLit,
newMethod, newMethodWithGivenTy, newDicts )
-import TcBinds ( tcBindsAndThen, checkSigTyVars, sigThetaCtxt )
+import TcBinds ( tcBindsAndThen, checkSigTyVars )
import TcEnv ( TcIdOcc(..), tcInstId,
tcLookupLocalValue, tcLookupGlobalValue, tcLookupClassByKey,
tcLookupGlobalValueByKey, newMonoIds,
tcLookupTyCon
)
import TcMatches ( tcMatchesCase, tcMatchExpected )
+import TcGRHSs ( tcStmt )
import TcMonoType ( tcHsType )
import TcPat ( tcPat )
import TcSimplify ( tcSimplifyAndCheck )
-import TcType ( TcType, TcMaybe(..),
+import TcType ( TcType, TcTauType, TcMaybe(..),
tcInstType, tcInstSigTcType, tcInstTyVars,
tcInstSigType, tcInstTcType, tcInstTheta, tcSplitRhoTy,
newTyVarTy, newTyVarTys, zonkTcType )
import FieldLabel ( FieldLabel, fieldLabelName, fieldLabelType )
import Id ( idType, dataConFieldLabels, dataConSig, recordSelectorFieldLabel,
isRecordSelector,
- Id, GenId
+ Id
)
import Kind ( Kind, mkBoxedTypeKind, mkTypeKind, mkArrowKind )
import Name ( Name{-instance Eq-} )
mkTyConApp,
splitForAllTys, splitRhoTy, splitSigmaTy,
isTauTy, tyVarsOfType, tyVarsOfTypes,
- splitForAllTy_maybe, splitAlgTyConApp, splitAlgTyConApp_maybe
+ isForAllTy, splitAlgTyConApp, splitAlgTyConApp_maybe
)
import TyVar ( emptyTyVarEnv, zipTyVarEnv,
elementOfTyVarSet, mkTyVarSet, tyVarSetToList
thenMClassOpKey, zeroClassOpKey, returnMClassOpKey
)
import Outputable
-import PprType ( GenType, GenTyVar ) -- Instances
import Maybes ( maybeToBool )
import ListSetOps ( minusList )
import Util
\end{code}
+%************************************************************************
+%* *
+\subsection{Main wrappers}
+%* *
+%************************************************************************
+
\begin{code}
-tcExpr :: RenamedHsExpr -- Expession to type check
- -> TcType s -- Expected type (could be a type variable)
- -> TcM s (TcExpr s, LIE s)
+tcExpr :: RenamedHsExpr -- Expession to type check
+ -> TcType s -- Expected type (could be a polytpye)
+ -> TcM s (TcExpr s, LIE s)
+
+tcExpr expr ty | isForAllTy ty = -- Polymorphic case
+ tcPolyExpr expr ty `thenTc` \ (expr', lie, _, _, _) ->
+ returnTc (expr', lie)
+
+ | otherwise = -- Monomorphic case
+ tcMonoExpr expr ty
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{@tcPolyExpr@ typchecks an application}
+%* *
+%************************************************************************
+
+\begin{code}
+-- tcPolyExpr is like tcMonoExpr, except that the expected type
+-- can be a polymorphic one.
+tcPolyExpr :: RenamedHsExpr
+ -> TcType s -- Expected type
+ -> TcM s (TcExpr s, LIE s, -- Generalised expr with expected type, and LIE
+ TcExpr s, TcTauType s, LIE s) -- Same thing, but instantiated; tau-type returned
+
+tcPolyExpr arg expected_arg_ty
+ = -- Ha! The argument type of the function is a for-all type,
+ -- An example of rank-2 polymorphism.
+
+ -- To ensure that the forall'd type variables don't get unified with each
+ -- other or any other types, we make fresh copy of the alleged type
+ tcInstSigTcType expected_arg_ty `thenNF_Tc` \ (sig_tyvars, sig_rho) ->
+ let
+ (sig_theta, sig_tau) = splitRhoTy sig_rho
+ in
+ -- Type-check the arg and unify with expected type
+ tcExtendGlobalTyVars sig_tyvars (
+ tcMonoExpr arg sig_tau
+ ) `thenTc` \ (arg', lie_arg) ->
+
+ -- Check that the arg_tyvars havn't been constrained
+ -- The interesting bit here is that we must include the free variables
+ -- of the expected arg ty. Here's an example:
+ -- runST (newVar True)
+ -- Here, if we don't make a check, we'll get a type (ST s (MutVar s Bool))
+ -- for (newVar True), with s fresh. Then we unify with the runST's arg type
+ -- forall s'. ST s' a. That unifies s' with s, and a with MutVar s Bool.
+ -- So now s' isn't unconstrained because it's linked to a.
+ -- Conclusion: include the free vars of the expected arg type in the
+ -- list of "free vars" for the signature check.
+
+ tcExtendGlobalTyVars (tyVarSetToList (tyVarsOfType expected_arg_ty)) $
+
+ checkSigTyVars sig_tyvars sig_tau `thenTc` \ zonked_sig_tyvars ->
+ newDicts SignatureOrigin sig_theta `thenNF_Tc` \ (sig_dicts, dict_ids) ->
+ -- ToDo: better origin
+
+ tcSimplifyAndCheck
+ (text "tcPolyExpr")
+ (mkTyVarSet zonked_sig_tyvars)
+ sig_dicts lie_arg `thenTc` \ (free_insts, inst_binds) ->
+
+ let
+ -- This HsLet binds any Insts which came out of the simplification.
+ -- It's a bit out of place here, but using AbsBind involves inventing
+ -- a couple of new names which seems worse.
+ generalised_arg = TyLam zonked_sig_tyvars $
+ DictLam dict_ids $
+ HsLet (MonoBind inst_binds [] Recursive)
+ arg'
+ in
+ returnTc ( generalised_arg, free_insts,
+ arg', sig_tau, lie_arg )
\end{code}
%************************************************************************
%************************************************************************
\begin{code}
-tcExpr (HsVar name) res_ty
+tcMonoExpr :: RenamedHsExpr -- Expession to type check
+ -> TcTauType s -- Expected type (could be a type variable)
+ -> TcM s (TcExpr s, LIE s)
+
+tcMonoExpr (HsVar name) res_ty
= tcId name `thenNF_Tc` \ (expr', lie, id_ty) ->
unifyTauTy res_ty id_ty `thenTc_`
Overloaded literals.
\begin{code}
-tcExpr (HsLit (HsInt i)) res_ty
+tcMonoExpr (HsLit (HsInt i)) res_ty
= newOverloadedLit (LiteralOrigin (HsInt i))
(OverloadedIntegral i)
res_ty `thenNF_Tc` \ stuff ->
returnTc stuff
-tcExpr (HsLit (HsFrac f)) res_ty
+tcMonoExpr (HsLit (HsFrac f)) res_ty
= newOverloadedLit (LiteralOrigin (HsFrac f))
(OverloadedFractional f)
res_ty `thenNF_Tc` \ stuff ->
returnTc stuff
-tcExpr (HsLit lit@(HsLitLit s)) res_ty
+tcMonoExpr (HsLit lit@(HsLitLit s)) res_ty
= tcLookupClassByKey cCallableClassKey `thenNF_Tc` \ cCallableClass ->
newDicts (LitLitOrigin (_UNPK_ s))
[(cCallableClass, [res_ty])] `thenNF_Tc` \ (dicts, _) ->
Primitive literals:
\begin{code}
-tcExpr (HsLit lit@(HsCharPrim c)) res_ty
- = unifyTauTy charPrimTy res_ty `thenTc_`
+tcMonoExpr (HsLit lit@(HsCharPrim c)) res_ty
+ = unifyTauTy res_ty charPrimTy `thenTc_`
returnTc (HsLitOut lit charPrimTy, emptyLIE)
-tcExpr (HsLit lit@(HsStringPrim s)) res_ty
- = unifyTauTy addrPrimTy res_ty `thenTc_`
+tcMonoExpr (HsLit lit@(HsStringPrim s)) res_ty
+ = unifyTauTy res_ty addrPrimTy `thenTc_`
returnTc (HsLitOut lit addrPrimTy, emptyLIE)
-tcExpr (HsLit lit@(HsIntPrim i)) res_ty
- = unifyTauTy intPrimTy res_ty `thenTc_`
+tcMonoExpr (HsLit lit@(HsIntPrim i)) res_ty
+ = unifyTauTy res_ty intPrimTy `thenTc_`
returnTc (HsLitOut lit intPrimTy, emptyLIE)
-tcExpr (HsLit lit@(HsFloatPrim f)) res_ty
- = unifyTauTy floatPrimTy res_ty `thenTc_`
+tcMonoExpr (HsLit lit@(HsFloatPrim f)) res_ty
+ = unifyTauTy res_ty floatPrimTy `thenTc_`
returnTc (HsLitOut lit floatPrimTy, emptyLIE)
-tcExpr (HsLit lit@(HsDoublePrim d)) res_ty
- = unifyTauTy doublePrimTy res_ty `thenTc_`
+tcMonoExpr (HsLit lit@(HsDoublePrim d)) res_ty
+ = unifyTauTy res_ty doublePrimTy `thenTc_`
returnTc (HsLitOut lit doublePrimTy, emptyLIE)
\end{code}
Unoverloaded literals:
\begin{code}
-tcExpr (HsLit lit@(HsChar c)) res_ty
- = unifyTauTy charTy res_ty `thenTc_`
+tcMonoExpr (HsLit lit@(HsChar c)) res_ty
+ = unifyTauTy res_ty charTy `thenTc_`
returnTc (HsLitOut lit charTy, emptyLIE)
-tcExpr (HsLit lit@(HsString str)) res_ty
- = unifyTauTy stringTy res_ty `thenTc_`
+tcMonoExpr (HsLit lit@(HsString str)) res_ty
+ = unifyTauTy res_ty stringTy `thenTc_`
returnTc (HsLitOut lit stringTy, emptyLIE)
\end{code}
%************************************************************************
\begin{code}
-tcExpr (HsPar expr) res_ty -- preserve parens so printing needn't guess where they go
- = tcExpr expr res_ty
+tcMonoExpr (HsPar expr) res_ty -- preserve parens so printing needn't guess where they go
+ = tcMonoExpr expr res_ty
-- perform the negate *before* overloading the integer, since the case
-- of minBound on Ints fails otherwise. Could be done elsewhere, but
-- convenient to do it here.
-tcExpr (NegApp (HsLit (HsInt i)) neg) res_ty
- = tcExpr (HsLit (HsInt (-i))) res_ty
+tcMonoExpr (NegApp (HsLit (HsInt i)) neg) res_ty
+ = tcMonoExpr (HsLit (HsInt (-i))) res_ty
-tcExpr (NegApp expr neg) res_ty
- = tcExpr (HsApp neg expr) res_ty
+tcMonoExpr (NegApp expr neg) res_ty
+ = tcMonoExpr (HsApp neg expr) res_ty
-tcExpr (HsLam match) res_ty
+tcMonoExpr (HsLam match) res_ty
= tcMatchExpected [] res_ty match `thenTc` \ (match',lie) ->
returnTc (HsLam match', lie)
-tcExpr (HsApp e1 e2) res_ty = accum e1 [e2]
+tcMonoExpr (HsApp e1 e2) res_ty = accum e1 [e2]
where
accum (HsApp e1 e2) args = accum e1 (e2:args)
accum fun args
returnTc (foldl HsApp fun' args', lie)
-- equivalent to (op e1) e2:
-tcExpr (OpApp arg1 op fix arg2) res_ty
+tcMonoExpr (OpApp arg1 op fix arg2) res_ty
= tcApp op [arg1,arg2] res_ty `thenTc` \ (op', [arg1', arg2'], lie) ->
returnTc (OpApp arg1' op' fix arg2', lie)
\end{code}
-- or just
-- op e
-tcExpr in_expr@(SectionL arg op) res_ty
+tcMonoExpr in_expr@(SectionL arg op) res_ty
= tcApp op [arg] res_ty `thenTc` \ (op', [arg'], lie) ->
-- Check that res_ty is a function type
-- Right sections, equivalent to \ x -> x op expr, or
-- \ x -> op x expr
-tcExpr in_expr@(SectionR op expr) res_ty
+tcMonoExpr in_expr@(SectionR op expr) res_ty
= tcExpr_id op `thenTc` \ (op', lie1, op_ty) ->
tcAddErrCtxt (sectionRAppCtxt in_expr) $
split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) ->
- tcExpr expr arg2_ty `thenTc` \ (expr',lie2) ->
- unifyTauTy (mkFunTy arg1_ty op_res_ty) res_ty `thenTc_`
+ tcMonoExpr expr arg2_ty `thenTc` \ (expr',lie2) ->
+ unifyTauTy res_ty (mkFunTy arg1_ty op_res_ty) `thenTc_`
returnTc (SectionR op' expr', lie1 `plusLIE` lie2)
\end{code}
later use.
\begin{code}
-tcExpr (CCall lbl args may_gc is_asm ignored_fake_result_ty) res_ty
+tcMonoExpr (CCall lbl args may_gc is_asm ignored_fake_result_ty) res_ty
= -- Get the callable and returnable classes.
tcLookupClassByKey cCallableClassKey `thenNF_Tc` \ cCallableClass ->
tcLookupClassByKey cReturnableClassKey `thenNF_Tc` \ cReturnableClass ->
-- Arguments
mapNF_Tc (\ _ -> newTyVarTy mkTypeKind) [1..(length args)] `thenNF_Tc` \ ty_vars ->
- tcExprs args ty_vars `thenTc` \ (args', args_lie) ->
+ tcMonoExprs args ty_vars `thenTc` \ (args', args_lie) ->
-- The argument types can be unboxed or boxed; the result
-- type must, however, be boxed since it's an argument to the IO
io_result_ty = mkTyConApp ioTyCon [result_ty]
in
case tyConDataCons ioTyCon of { [ioDataCon] ->
- unifyTauTy io_result_ty res_ty `thenTc_`
+ unifyTauTy res_ty io_result_ty `thenTc_`
-- Construct the extra insts, which encode the
-- constraints on the argument and result types.
- mapNF_Tc new_arg_dict (zipEqual "tcExpr:CCall" args ty_vars) `thenNF_Tc` \ ccarg_dicts_s ->
+ mapNF_Tc new_arg_dict (zipEqual "tcMonoExpr:CCall" args ty_vars) `thenNF_Tc` \ ccarg_dicts_s ->
newDicts result_origin [(cReturnableClass, [result_ty])] `thenNF_Tc` \ (ccres_dict, _) ->
returnTc (HsApp (HsVar (RealId ioDataCon) `TyApp` [result_ty])
\end{code}
\begin{code}
-tcExpr (HsSCC label expr) res_ty
- = tcExpr expr res_ty `thenTc` \ (expr', lie) ->
+tcMonoExpr (HsSCC label expr) res_ty
+ = tcMonoExpr expr res_ty `thenTc` \ (expr', lie) ->
returnTc (HsSCC label expr', lie)
-tcExpr (HsLet binds expr) res_ty
+tcMonoExpr (HsLet binds expr) res_ty
= tcBindsAndThen
combiner
binds -- Bindings to check
- (tc_expr) `thenTc` \ (expr', lie) ->
+ tc_expr `thenTc` \ (expr', lie) ->
returnTc (expr', lie)
where
- tc_expr = tcExpr expr res_ty `thenTc` \ (expr', lie) ->
+ tc_expr = tcMonoExpr expr res_ty `thenTc` \ (expr', lie) ->
returnTc (expr', lie)
combiner is_rec bind expr = HsLet (MonoBind bind [] is_rec) expr
-tcExpr in_expr@(HsCase scrut matches src_loc) res_ty
+tcMonoExpr in_expr@(HsCase scrut matches src_loc) res_ty
= tcAddSrcLoc src_loc $
tcAddErrCtxt (caseCtxt in_expr) $
tcMatchesCase res_ty matches `thenTc` \ (scrut_ty, matches', lie2) ->
tcAddErrCtxt (caseScrutCtxt scrut) (
- tcExpr scrut scrut_ty
+ tcMonoExpr scrut scrut_ty
) `thenTc` \ (scrut',lie1) ->
returnTc (HsCase scrut' matches' src_loc, plusLIE lie1 lie2)
-tcExpr (HsIf pred b1 b2 src_loc) res_ty
+tcMonoExpr (HsIf pred b1 b2 src_loc) res_ty
= tcAddSrcLoc src_loc $
tcAddErrCtxt (predCtxt pred) (
- tcExpr pred boolTy ) `thenTc` \ (pred',lie1) ->
+ tcMonoExpr pred boolTy ) `thenTc` \ (pred',lie1) ->
- tcExpr b1 res_ty `thenTc` \ (b1',lie2) ->
- tcExpr b2 res_ty `thenTc` \ (b2',lie3) ->
+ tcMonoExpr b1 res_ty `thenTc` \ (b1',lie2) ->
+ tcMonoExpr b2 res_ty `thenTc` \ (b2',lie3) ->
returnTc (HsIf pred' b1' b2' src_loc, plusLIE lie1 (plusLIE lie2 lie3))
\end{code}
\begin{code}
-tcExpr expr@(HsDo do_or_lc stmts src_loc) res_ty
+tcMonoExpr expr@(HsDo do_or_lc stmts src_loc) res_ty
= tcDoStmts do_or_lc stmts src_loc res_ty
\end{code}
\begin{code}
-tcExpr in_expr@(ExplicitList exprs) res_ty -- Non-empty list
+tcMonoExpr in_expr@(ExplicitList exprs) res_ty -- Non-empty list
= unifyListTy res_ty `thenTc` \ elt_ty ->
mapAndUnzipTc (tc_elt elt_ty) exprs `thenTc` \ (exprs', lies) ->
returnTc (ExplicitListOut elt_ty exprs', plusLIEs lies)
where
tc_elt elt_ty expr
= tcAddErrCtxt (listCtxt expr) $
- tcExpr expr elt_ty
+ tcMonoExpr expr elt_ty
-tcExpr (ExplicitTuple exprs) res_ty
+tcMonoExpr (ExplicitTuple exprs) res_ty
= unifyTupleTy (length exprs) res_ty `thenTc` \ arg_tys ->
- mapAndUnzipTc (\ (expr, arg_ty) -> tcExpr expr arg_ty)
+ mapAndUnzipTc (\ (expr, arg_ty) -> tcMonoExpr expr arg_ty)
(exprs `zip` arg_tys) -- we know they're of equal length.
`thenTc` \ (exprs', lies) ->
returnTc (ExplicitTuple exprs', plusLIEs lies)
-tcExpr (RecordCon con_name _ rbinds) res_ty
+tcMonoExpr (RecordCon con_name _ rbinds) res_ty
= tcLookupGlobalValue con_name `thenNF_Tc` \ con_id ->
tcId con_name `thenNF_Tc` \ (con_expr, con_lie, con_tau) ->
let
--
-- All this is done in STEP 4 below.
-tcExpr (RecordUpd record_expr rbinds) res_ty
+tcMonoExpr (RecordUpd record_expr rbinds) res_ty
= tcAddErrCtxt recordUpdCtxt $
-- STEP 1
let
record_ty = mkTyConApp tycon inst_tys
in
- tcExpr record_expr record_ty `thenTc` \ (record_expr', record_lie) ->
+ tcMonoExpr record_expr record_ty `thenTc` \ (record_expr', record_lie) ->
-- STEP 6
-- Figure out the LIE we need. We have to generate some
returnTc (RecordUpdOut record_expr' result_record_ty dicts rbinds',
con_lie `plusLIE` record_lie `plusLIE` rbinds_lie)
-tcExpr (ArithSeqIn seq@(From expr)) res_ty
+tcMonoExpr (ArithSeqIn seq@(From expr)) res_ty
= unifyListTy res_ty `thenTc` \ elt_ty ->
- tcExpr expr elt_ty `thenTc` \ (expr', lie1) ->
+ tcMonoExpr expr elt_ty `thenTc` \ (expr', lie1) ->
tcLookupGlobalValueByKey enumFromClassOpKey `thenNF_Tc` \ sel_id ->
newMethod (ArithSeqOrigin seq)
returnTc (ArithSeqOut (HsVar enum_from_id) (From expr'),
lie1 `plusLIE` lie2)
-tcExpr in_expr@(ArithSeqIn seq@(FromThen expr1 expr2)) res_ty
+tcMonoExpr in_expr@(ArithSeqIn seq@(FromThen expr1 expr2)) res_ty
= tcAddErrCtxt (arithSeqCtxt in_expr) $
unifyListTy res_ty `thenTc` \ elt_ty ->
- tcExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
- tcExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
+ tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
+ tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
tcLookupGlobalValueByKey enumFromThenClassOpKey `thenNF_Tc` \ sel_id ->
newMethod (ArithSeqOrigin seq)
(RealId sel_id) [elt_ty] `thenNF_Tc` \ (lie3, enum_from_then_id) ->
(FromThen expr1' expr2'),
lie1 `plusLIE` lie2 `plusLIE` lie3)
-tcExpr in_expr@(ArithSeqIn seq@(FromTo expr1 expr2)) res_ty
+tcMonoExpr in_expr@(ArithSeqIn seq@(FromTo expr1 expr2)) res_ty
= tcAddErrCtxt (arithSeqCtxt in_expr) $
unifyListTy res_ty `thenTc` \ elt_ty ->
- tcExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
- tcExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
+ tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
+ tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
tcLookupGlobalValueByKey enumFromToClassOpKey `thenNF_Tc` \ sel_id ->
newMethod (ArithSeqOrigin seq)
(RealId sel_id) [elt_ty] `thenNF_Tc` \ (lie3, enum_from_to_id) ->
(FromTo expr1' expr2'),
lie1 `plusLIE` lie2 `plusLIE` lie3)
-tcExpr in_expr@(ArithSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty
+tcMonoExpr in_expr@(ArithSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty
= tcAddErrCtxt (arithSeqCtxt in_expr) $
unifyListTy res_ty `thenTc` \ elt_ty ->
- tcExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
- tcExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
- tcExpr expr3 elt_ty `thenTc` \ (expr3',lie3) ->
+ tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
+ tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
+ tcMonoExpr expr3 elt_ty `thenTc` \ (expr3',lie3) ->
tcLookupGlobalValueByKey enumFromThenToClassOpKey `thenNF_Tc` \ sel_id ->
newMethod (ArithSeqOrigin seq)
(RealId sel_id) [elt_ty] `thenNF_Tc` \ (lie4, eft_id) ->
%************************************************************************
\begin{code}
-tcExpr in_expr@(ExprWithTySig expr poly_ty) res_ty
+tcMonoExpr in_expr@(ExprWithTySig expr poly_ty) res_ty
= tcSetErrCtxt (exprSigCtxt in_expr) $
- tcHsType poly_ty `thenTc` \ sigma_sig ->
-
- -- Check the tau-type part
- tcInstSigType sigma_sig `thenNF_Tc` \ sigma_sig' ->
- let
- (sig_tyvars', sig_theta', sig_tau') = splitSigmaTy sigma_sig'
- in
-
- -- Type check the expression, expecting the signature type
- tcExtendGlobalTyVars sig_tyvars' (
- tcExpr expr sig_tau'
- ) `thenTc` \ (texpr, lie) ->
-
- -- Check the type variables of the signature,
- -- *after* typechecking the expression
- checkSigTyVars sig_tyvars' sig_tau' `thenTc` \ zonked_sig_tyvars ->
-
- -- Check overloading constraints
- newDicts SignatureOrigin sig_theta' `thenNF_Tc` \ (sig_dicts, _) ->
- tcAddErrCtxtM (sigThetaCtxt sig_dicts) (
- tcSimplifyAndCheck
- (text "expr ty sig")
- (mkTyVarSet zonked_sig_tyvars)
- sig_dicts lie
- ) `thenTc_`
-
- -- Now match the signature type with res_ty.
- -- We must not do this earlier, because res_ty might well
- -- mention variables free in the environment, and we'd get
- -- bogus complaints about not being able to for-all the
- -- sig_tyvars
- unifyTauTy sig_tau' res_ty `thenTc_`
-
- -- If everything is ok, return the stuff unchanged, except for
- -- the effect of any substutions etc. We simply discard the
- -- result of the tcSimplifyAndCheck, except for any default
- -- resolution it may have done, which is recorded in the
- -- substitution.
- returnTc (texpr, lie)
-
+ tcHsType poly_ty `thenTc` \ sig_ty ->
+ tcInstSigType sig_ty `thenNF_Tc` \ sig_tc_ty ->
+
+ if not (isForAllTy sig_tc_ty) then
+ -- Easy case
+ unifyTauTy sig_tc_ty res_ty `thenTc_`
+ tcMonoExpr expr sig_tc_ty
+
+ else -- Signature is polymorphic
+ tcPolyExpr expr sig_tc_ty `thenTc` \ (_, _, expr, expr_ty, lie) ->
+
+ -- Now match the signature type with res_ty.
+ -- We must not do this earlier, because res_ty might well
+ -- mention variables free in the environment, and we'd get
+ -- bogus complaints about not being able to for-all the
+ -- sig_tyvars
+ unifyTauTy res_ty expr_ty `thenTc_`
+
+ -- If everything is ok, return the stuff unchanged, except for
+ -- the effect of any substutions etc. We simply discard the
+ -- result of the tcSimplifyAndCheck (inside tcPolyExpr), except for any default
+ -- resolution it may have done, which is recorded in the
+ -- substitution.
+ returnTc (expr, lie)
\end{code}
Typecheck expression which in most cases will be an Id.
HsVar name -> tcId name `thenNF_Tc` \ stuff ->
returnTc stuff
other -> newTyVarTy mkTypeKind `thenNF_Tc` \ id_ty ->
- tcExpr id_expr id_ty `thenTc` \ (id_expr', lie_id) ->
+ tcMonoExpr id_expr id_ty `thenTc` \ (id_expr', lie_id) ->
returnTc (id_expr', lie_id, id_ty)
\end{code}
tcArg the_fun (arg, expected_arg_ty, arg_no)
= tcAddErrCtxt (funAppCtxt the_fun arg arg_no) $
- tcPolyExpr arg expected_arg_ty
-
-
--- tcPolyExpr is like tcExpr, except that the expected type
--- can be a polymorphic one.
-tcPolyExpr arg expected_arg_ty
- | not (maybeToBool (splitForAllTy_maybe expected_arg_ty))
- = -- The ordinary, non-rank-2 polymorphic case
tcExpr arg expected_arg_ty
-
- | otherwise
- = -- Ha! The argument type of the function is a for-all type,
- -- An example of rank-2 polymorphism.
-
- -- No need to instantiate the argument type... it's must be the result
- -- of instantiating a function involving rank-2 polymorphism, so there
- -- isn't any danger of using the same tyvars twice
- -- The argument type shouldn't be overloaded type (hence ASSERT)
-
- -- To ensure that the forall'd type variables don't get unified with each
- -- other or any other types, we make fresh *signature* type variables
- -- and unify them with the tyvars.
- tcInstSigTcType expected_arg_ty `thenNF_Tc` \ (sig_tyvars, sig_rho) ->
- let
- (sig_theta, sig_tau) = splitRhoTy sig_rho
- in
- -- Type-check the arg and unify with expected type
- tcExpr arg sig_tau `thenTc` \ (arg', lie_arg) ->
-
- -- Check that the arg_tyvars havn't been constrained
- -- The interesting bit here is that we must include the free variables
- -- of the expected arg ty. Here's an example:
- -- runST (newVar True)
- -- Here, if we don't make a check, we'll get a type (ST s (MutVar s Bool))
- -- for (newVar True), with s fresh. Then we unify with the runST's arg type
- -- forall s'. ST s' a. That unifies s' with s, and a with MutVar s Bool.
- -- So now s' isn't unconstrained because it's linked to a.
- -- Conclusion: include the free vars of the expected arg type in the
- -- list of "free vars" for the signature check.
-
- tcAddErrCtxt (rank2ArgCtxt arg expected_arg_ty) $
- tcExtendGlobalTyVars (tyVarSetToList (tyVarsOfType expected_arg_ty)) $
-
- checkSigTyVars sig_tyvars sig_tau `thenTc` \ zonked_sig_tyvars ->
- newDicts Rank2Origin sig_theta `thenNF_Tc` \ (sig_dicts, dict_ids) ->
- -- ToDo: better origin
-
- tcAddErrCtxtM (sigThetaCtxt sig_dicts) $
- tcSimplifyAndCheck (text "rank2")
- (mkTyVarSet zonked_sig_tyvars)
- sig_dicts lie_arg `thenTc` \ (free_insts, inst_binds) ->
-
- -- This HsLet binds any Insts which came out of the simplification.
- -- It's a bit out of place here, but using AbsBind involves inventing
- -- a couple of new names which seems worse.
- returnTc ( TyLam zonked_sig_tyvars $
- DictLam dict_ids $
- HsLet (MonoBind inst_binds [] Recursive)
- arg'
- , free_insts
- )
\end{code}
+
%************************************************************************
%* *
\subsection{@tcId@ typchecks an identifier occurrence}
let
tc_stmts [] = returnTc (([], error "tc_stmts"), emptyLIE)
- tc_stmts (stmt:stmts) = tcStmt tcExpr do_or_lc (mkAppTy m) combine_stmts stmt $
+ tc_stmts (stmt:stmts) = tcStmt do_or_lc (mkAppTy m) combine_stmts stmt $
tc_stmts stmts
combine_stmts stmt@(ReturnStmt _) (Just ty) ([], _) = ([stmt], ty)
combine_stmts stmt _ (stmts, ty) = (stmt:stmts, ty)
in
tc_stmts stmts `thenTc` \ ((stmts', result_ty), final_lie) ->
- unifyTauTy result_ty res_ty `thenTc_`
+ unifyTauTy res_ty result_ty `thenTc_`
-- Build the then and zero methods in case we need them
-- It's important that "then" and "return" appear just once in the final LIE,
\end{code}
-\begin{code}
-tcStmt :: (RenamedHsExpr -> TcType s -> TcM s (TcExpr s, LIE s)) -- This is tcExpr
- -- The sole, disgusting, reason for this parameter
- -- is to get the effect of polymorphic recursion
- -- ToDo: rm when booting with Haskell 1.3
- -> DoOrListComp
- -> (TcType s -> TcType s) -- Relationship type of pat and rhs in pat <- rhs
- -> (TcStmt s -> Maybe (TcType s) -> thing -> thing)
- -> RenamedStmt
- -> TcM s (thing, LIE s)
- -> TcM s (thing, LIE s)
-
-tcStmt tc_expr do_or_lc m combine stmt@(ReturnStmt exp) do_next
- = ASSERT( case do_or_lc of { DoStmt -> False; ListComp -> True; Guard -> True } )
- tcSetErrCtxt (stmtCtxt do_or_lc stmt) (
- newTyVarTy mkTypeKind `thenNF_Tc` \ exp_ty ->
- tc_expr exp exp_ty `thenTc` \ (exp', exp_lie) ->
- returnTc (ReturnStmt exp', exp_lie, m exp_ty)
- ) `thenTc` \ (stmt', stmt_lie, stmt_ty) ->
- do_next `thenTc` \ (thing', thing_lie) ->
- returnTc (combine stmt' (Just stmt_ty) thing',
- stmt_lie `plusLIE` thing_lie)
-
-tcStmt tc_expr do_or_lc m combine stmt@(GuardStmt exp src_loc) do_next
- = ASSERT( case do_or_lc of { DoStmt -> False; ListComp -> True; Guard -> True } )
- newTyVarTy mkTypeKind `thenNF_Tc` \ exp_ty ->
- tcAddSrcLoc src_loc (
- tcSetErrCtxt (stmtCtxt do_or_lc stmt) (
- tc_expr exp boolTy `thenTc` \ (exp', exp_lie) ->
- returnTc (GuardStmt exp' src_loc, exp_lie)
- )) `thenTc` \ (stmt', stmt_lie) ->
- do_next `thenTc` \ (thing', thing_lie) ->
- returnTc (combine stmt' Nothing thing',
- stmt_lie `plusLIE` thing_lie)
-
-tcStmt tc_expr do_or_lc m combine stmt@(ExprStmt exp src_loc) do_next
- = ASSERT( case do_or_lc of { DoStmt -> True; ListComp -> False; Guard -> False } )
- newTyVarTy mkTypeKind `thenNF_Tc` \ exp_ty ->
- tcAddSrcLoc src_loc (
- tcSetErrCtxt (stmtCtxt do_or_lc stmt) (
- newTyVarTy mkTypeKind `thenNF_Tc` \ tau ->
- let
- -- exp has type (m tau) for some tau (doesn't matter what)
- exp_ty = m tau
- in
- tc_expr exp exp_ty `thenTc` \ (exp', exp_lie) ->
- returnTc (ExprStmt exp' src_loc, exp_lie, exp_ty)
- )) `thenTc` \ (stmt', stmt_lie, stmt_ty) ->
- do_next `thenTc` \ (thing', thing_lie) ->
- returnTc (combine stmt' (Just stmt_ty) thing',
- stmt_lie `plusLIE` thing_lie)
-
-tcStmt tc_expr do_or_lc m combine stmt@(BindStmt pat exp src_loc) do_next
- = newMonoIds (collectPatBinders pat) mkBoxedTypeKind $ \ _ ->
- tcAddSrcLoc src_loc (
- tcSetErrCtxt (stmtCtxt do_or_lc stmt) (
- tcPat pat `thenTc` \ (pat', pat_lie, pat_ty) ->
- tc_expr exp (m pat_ty) `thenTc` \ (exp', exp_lie) ->
-
- -- NB: the environment has been extended with the new binders
- -- which the rhs can't "see", but the renamer should have made
- -- sure that everything is distinct by now, so there's no problem.
- -- Putting the tcExpr before the newMonoIds messes up the nesting
- -- of error contexts, so I didn't bother
-
- returnTc (BindStmt pat' exp' src_loc, pat_lie `plusLIE` exp_lie)
- )) `thenTc` \ (stmt', stmt_lie) ->
- do_next `thenTc` \ (thing', thing_lie) ->
- returnTc (combine stmt' Nothing thing',
- stmt_lie `plusLIE` thing_lie)
-
-tcStmt tc_expr do_or_lc m combine (LetStmt binds) do_next
- = tcBindsAndThen -- No error context, but a binding group is
- combine' -- rather a large thing for an error context anyway
- binds
- do_next
- where
- combine' is_rec binds' thing' = combine (LetStmt (MonoBind binds' [] is_rec)) Nothing thing'
-\end{code}
%************************************************************************
%* *
Just (record_ty, field_ty) = splitFunTy_maybe tau
in
unifyTauTy expected_record_ty record_ty `thenTc_`
- tcPolyExpr rhs field_ty `thenTc` \ (rhs', lie) ->
+ tcPolyExpr rhs field_ty `thenTc` \ (rhs', lie, _, _, _) ->
returnTc ((RealId sel_id, rhs', pun_flag), lie)
badFields rbinds data_con
%************************************************************************
%* *
-\subsection{@tcExprs@ typechecks a {\em list} of expressions}
+\subsection{@tcMonoExprs@ typechecks a {\em list} of expressions}
%* *
%************************************************************************
\begin{code}
-tcExprs :: [RenamedHsExpr] -> [TcType s] -> TcM s ([TcExpr s], LIE s)
+tcMonoExprs :: [RenamedHsExpr] -> [TcType s] -> TcM s ([TcExpr s], LIE s)
-tcExprs [] [] = returnTc ([], emptyLIE)
-tcExprs (expr:exprs) (ty:tys)
- = tcExpr expr ty `thenTc` \ (expr', lie1) ->
- tcExprs exprs tys `thenTc` \ (exprs', lie2) ->
+tcMonoExprs [] [] = returnTc ([], emptyLIE)
+tcMonoExprs (expr:exprs) (ty:tys)
+ = tcMonoExpr expr ty `thenTc` \ (expr', lie1) ->
+ tcMonoExprs exprs tys `thenTc` \ (exprs', lie2) ->
returnTc (expr':exprs', lie1 `plusLIE` lie2)
\end{code}
quotes (ppr fun) <> text ", namely"])
4 (quotes (ppr arg))
-stmtCtxt do_or_lc stmt
- = hang (ptext SLIT("In a") <+> whatever <> colon)
- 4 (ppr stmt)
- where
- whatever = case do_or_lc of
- ListComp -> ptext SLIT("list-comprehension qualifier")
- DoStmt -> ptext SLIT("do statement")
- Guard -> ptext SLIT("guard")
-
wrongArgsCtxt too_many_or_few fun args
= hang (ptext SLIT("Probable cause:") <+> ppr fun
<+> ptext SLIT("is applied to") <+> text too_many_or_few
<+> ptext SLIT("arguments in the call"))
- 4 (ppr the_app)
+ 4 (parens (ppr the_app))
where
the_app = foldl HsApp fun args -- Used in error messages
projects / ghc-hetmet.git / blobdiff