\section[TcExpr]{Typecheck an expression}
\begin{code}
-module TcExpr ( tcApp, tcExpr, tcMonoExpr, tcPolyExpr, tcId ) where
+module TcExpr ( tcExpr, tcMonoExpr, tcId ) where
#include "HsVersions.h"
HsMatchContext(..), HsDoContext(..), mkMonoBind
)
import RnHsSyn ( RenamedHsExpr, RenamedRecordBinds )
-import TcHsSyn ( TcExpr, TcRecordBinds, mkHsLet )
+import TcHsSyn ( TcExpr, TcRecordBinds, simpleHsLitTy )
import TcMonad
+import TcUnify ( tcSubExp, tcGen, (<$>),
+ unifyTauTy, unifyFunTy, unifyListTy, unifyPArrTy,
+ unifyTupleTy )
import BasicTypes ( RecFlag(..), isMarkedStrict )
import Inst ( InstOrigin(..),
LIE, mkLIE, emptyLIE, unitLIE, plusLIE, plusLIEs,
newOverloadedLit, newMethod, newIPDict,
- newDicts,
- instToId, tcInstId
+ newDicts, newMethodWithGivenTy,
+ instToId, tcInstCall
)
import TcBinds ( tcBindsAndThen )
import TcEnv ( tcLookupClass, tcLookupGlobalId, tcLookupGlobal_maybe,
- tcLookupTyCon, tcLookupDataCon, tcLookupId,
- tcExtendGlobalTyVars
+ tcLookupTyCon, tcLookupDataCon, tcLookupId
)
import TcMatches ( tcMatchesCase, tcMatchLambda, tcStmts )
-import TcMonoType ( tcHsSigType, checkSigTyVars, sigCtxt )
-import TcPat ( badFieldCon, simpleHsLitTy )
-import TcSimplify ( tcSimplifyCheck, tcSimplifyIPs )
-import TcMType ( tcInstTyVars, tcInstType,
- newTyVarTy, newTyVarTys, zonkTcType,
- unifyTauTy, unifyFunTy, unifyListTy, unifyTupleTy
- )
-import TcType ( tcSplitFunTys, tcSplitTyConApp,
- isQualifiedTy,
- mkFunTy, mkAppTy, mkTyConTy,
+import TcMonoType ( tcHsSigType, UserTypeCtxt(..) )
+import TcPat ( badFieldCon )
+import TcSimplify ( tcSimplifyIPs )
+import TcMType ( tcInstTyVars, tcInstType, newHoleTyVarTy, zapToType,
+ newTyVarTy, newTyVarTys, zonkTcType, readHoleResult )
+import TcType ( TcType, TcSigmaType, TcRhoType, TyVarDetails(VanillaTv),
+ tcSplitFunTys, tcSplitTyConApp, mkTyVarTys,
+ isSigmaTy, mkFunTy, mkAppTy, mkTyConTy,
mkTyConApp, mkClassPred, tcFunArgTy,
- isTauTy, tyVarsOfType, tyVarsOfTypes,
+ tyVarsOfTypes, isLinearPred,
liftedTypeKind, openTypeKind, mkArrowKind,
tcSplitSigmaTy, tcTyConAppTyCon,
tidyOpenType
import Name ( Name )
import TyCon ( TyCon, tyConTyVars, isAlgTyCon, tyConDataCons )
import Subst ( mkTopTyVarSubst, substTheta, substTy )
-import VarSet ( elemVarSet )
-import TysWiredIn ( boolTy, mkListTy, listTyCon )
+import VarSet ( emptyVarSet, elemVarSet )
+import TysWiredIn ( boolTy, mkListTy, mkPArrTy, listTyCon, parrTyCon )
import PrelNames ( cCallableClassName,
cReturnableClassName,
- enumFromName, enumFromThenName, negateName,
+ enumFromName, enumFromThenName,
enumFromToName, enumFromThenToName,
+ enumFromToPName, enumFromThenToPName,
thenMName, failMName, returnMName, ioTyConName
)
import Outputable
%************************************************************************
\begin{code}
-tcExpr :: RenamedHsExpr -- Expession to type check
- -> TcType -- Expected type (could be a polytpye)
- -> TcM (TcExpr, LIE)
-
-tcExpr expr ty | isQualifiedTy ty = -- Polymorphic case
- tcPolyExpr expr ty `thenTc` \ (expr', lie, _, _, _) ->
- returnTc (expr', lie)
-
- | otherwise = -- Monomorphic case
- tcMonoExpr expr ty
+tcExpr :: RenamedHsExpr -- Expession to type check
+ -> TcSigmaType -- Expected type (could be a polytpye)
+ -> TcM (TcExpr, LIE) -- Generalised expr with expected type, and LIE
+
+tcExpr expr expected_ty
+ | not (isSigmaTy expected_ty) -- Monomorphic case
+ = tcMonoExpr expr expected_ty
+
+ | otherwise
+ = tcGen expected_ty emptyVarSet (
+ tcMonoExpr expr
+ ) `thenTc` \ (gen_fn, expr', lie) ->
+ returnTc (gen_fn <$> expr', lie)
\end{code}
%************************************************************************
%* *
-\subsection{@tcPolyExpr@ typchecks an application}
+\subsection{The TAUT rules for variables}
%* *
%************************************************************************
\begin{code}
--- tcPolyExpr is like tcMonoExpr, except that the expected type
--- can be a polymorphic one.
-tcPolyExpr :: RenamedHsExpr
- -> TcType -- Expected type
- -> TcM (TcExpr, LIE, -- Generalised expr with expected type, and LIE
- TcExpr, TcTauType, LIE) -- 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
- tcInstType expected_arg_ty `thenNF_Tc` \ (sig_tyvars, sig_theta, sig_tau) ->
- let
- free_tvs = tyVarsOfType expected_arg_ty
- in
- -- Type-check the arg and unify with expected type
- tcMonoExpr arg sig_tau `thenTc` \ (arg', lie_arg) ->
-
- -- Check that the sig_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 free_tvs $
- tcAddErrCtxtM (sigCtxt sig_msg sig_tyvars sig_theta sig_tau) $
-
- newDicts SignatureOrigin sig_theta `thenNF_Tc` \ sig_dicts ->
- tcSimplifyCheck
- (text "the type signature of an expression")
- sig_tyvars
- sig_dicts lie_arg `thenTc` \ (free_insts, inst_binds) ->
-
- checkSigTyVars sig_tyvars free_tvs `thenTc` \ zonked_sig_tyvars ->
+tcMonoExpr :: RenamedHsExpr -- Expession to type check
+ -> TcRhoType -- Expected type (could be a type variable)
+ -- Definitely no foralls at the top
+ -- Can be a 'hole'.
+ -> TcM (TcExpr, LIE)
- 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 (map instToId sig_dicts) $
- mkHsLet inst_binds $
- arg'
- in
- returnTc ( generalised_arg, free_insts,
- arg', sig_tau, lie_arg )
- where
- sig_msg = ptext SLIT("When checking an expression type signature")
+tcMonoExpr (HsVar name) res_ty
+ = tcId name `thenNF_Tc` \ (expr', lie1, id_ty) ->
+ tcSubExp res_ty id_ty `thenTc` \ (co_fn, lie2) ->
+ returnTc (co_fn <$> expr', lie1 `plusLIE` lie2)
+
+tcMonoExpr (HsIPVar ip) res_ty
+ = -- Implicit parameters must have a *tau-type* not a
+ -- type scheme. We enforce this by creating a fresh
+ -- type variable as its type. (Because res_ty may not
+ -- be a tau-type.)
+ newTyVarTy openTypeKind `thenNF_Tc` \ ip_ty ->
+ newIPDict (IPOcc ip) ip ip_ty `thenNF_Tc` \ (ip', inst) ->
+ tcSubExp res_ty ip_ty `thenTc` \ (co_fn, lie) ->
+ returnNF_Tc (co_fn <$> HsIPVar ip', lie `plusLIE` unitLIE inst)
\end{code}
+
%************************************************************************
%* *
-\subsection{The TAUT rules for variables}
+\subsection{Expressions type signatures}
%* *
%************************************************************************
\begin{code}
-tcMonoExpr :: RenamedHsExpr -- Expession to type check
- -> TcTauType -- Expected type (could be a type variable)
- -> TcM (TcExpr, LIE)
-
-tcMonoExpr (HsVar name) res_ty
- = tcId name `thenNF_Tc` \ (expr', lie, id_ty) ->
- unifyTauTy res_ty id_ty `thenTc_`
+tcMonoExpr in_expr@(ExprWithTySig expr poly_ty) res_ty
+ = tcHsSigType ExprSigCtxt poly_ty `thenTc` \ sig_tc_ty ->
+ tcExpr expr sig_tc_ty `thenTc` \ (expr', lie1) ->
- -- Check that the result type doesn't have any nested for-alls.
- -- For example, a "build" on its own is no good; it must be
- -- applied to something.
- checkTc (isTauTy id_ty)
- (lurkingRank2Err name id_ty) `thenTc_`
+ -- Must instantiate the outer for-alls of sig_tc_ty
+ -- else we risk instantiating a ? res_ty to a forall-type
+ -- which breaks the invariant that tcMonoExpr only returns phi-types
+ tcAddErrCtxt (exprSigCtxt in_expr) $
+ tcInstCall SignatureOrigin sig_tc_ty `thenNF_Tc` \ (inst_fn, lie2, inst_sig_ty) ->
+ tcSubExp res_ty inst_sig_ty `thenTc` \ (co_fn, lie3) ->
- returnTc (expr', lie)
+ returnTc (co_fn <$> inst_fn expr', lie1 `plusLIE` lie2 `plusLIE` lie3)
\end{code}
-\begin{code}
-tcMonoExpr (HsIPVar name) res_ty
- = newIPDict (IPOcc name) name res_ty `thenNF_Tc` \ ip ->
- returnNF_Tc (HsIPVar (instToId ip), unitLIE ip)
-\end{code}
%************************************************************************
%* *
= tcMatchLambda match res_ty `thenTc` \ (match',lie) ->
returnTc (HsLam match', lie)
-tcMonoExpr (HsApp e1 e2) res_ty = accum e1 [e2]
- where
- accum (HsApp e1 e2) args = accum e1 (e2:args)
- accum fun args
- = tcApp fun args res_ty `thenTc` \ (fun', args', lie) ->
- returnTc (foldl HsApp fun' args', lie)
-
--- equivalent to (op e1) e2:
-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)
+tcMonoExpr (HsApp e1 e2) res_ty
+ = tcApp e1 [e2] res_ty
\end{code}
Note that the operators in sections are expected to be binary, and
-- or just
-- op e
-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
- -- Without this check we barf in the desugarer on
- -- f op = (3 `op`)
- -- because it tries to desugar to
- -- f op = \r -> 3 op r
- -- so (3 `op`) had better be a function!
- tcAddErrCtxt (sectionLAppCtxt in_expr) $
- unifyFunTy res_ty `thenTc_`
-
- returnTc (SectionL arg' op', lie)
+tcMonoExpr in_expr@(SectionL arg1 op) res_ty
+ = tcExpr_id op `thenTc` \ (op', lie1, op_ty) ->
+ split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) ->
+ tcArg op (arg1, arg1_ty, 1) `thenTc` \ (arg1',lie2) ->
+ tcAddErrCtxt (exprCtxt in_expr) $
+ tcSubExp res_ty (mkFunTy arg2_ty op_res_ty) `thenTc` \ (co_fn, lie3) ->
+ returnTc (co_fn <$> SectionL arg1' op', lie1 `plusLIE` lie2 `plusLIE` lie3)
-- Right sections, equivalent to \ x -> x op expr, or
-- \ x -> op x expr
-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) ->
- tcMonoExpr expr arg2_ty `thenTc` \ (expr',lie2) ->
- unifyTauTy res_ty (mkFunTy arg1_ty op_res_ty) `thenTc_`
- returnTc (SectionR op' expr', lie1 `plusLIE` lie2)
+tcMonoExpr in_expr@(SectionR op arg2) res_ty
+ = tcExpr_id op `thenTc` \ (op', lie1, op_ty) ->
+ split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) ->
+ tcArg op (arg2, arg2_ty, 2) `thenTc` \ (arg2',lie2) ->
+ tcAddErrCtxt (exprCtxt in_expr) $
+ tcSubExp res_ty (mkFunTy arg1_ty op_res_ty) `thenTc` \ (co_fn, lie3) ->
+ returnTc (co_fn <$> SectionR op' arg2', lie1 `plusLIE` lie2 `plusLIE` lie3)
+
+-- equivalent to (op e1) e2:
+
+tcMonoExpr in_expr@(OpApp arg1 op fix arg2) res_ty
+ = tcExpr_id op `thenTc` \ (op', lie1, op_ty) ->
+ split_fun_ty op_ty 2 {- two args -} `thenTc` \ ([arg1_ty, arg2_ty], op_res_ty) ->
+ tcArg op (arg1, arg1_ty, 1) `thenTc` \ (arg1',lie2a) ->
+ tcArg op (arg2, arg2_ty, 2) `thenTc` \ (arg2',lie2b) ->
+ tcAddErrCtxt (exprCtxt in_expr) $
+ tcSubExp res_ty op_res_ty `thenTc` \ (co_fn, lie3) ->
+ returnTc (OpApp arg1' op' fix arg2',
+ lie1 `plusLIE` lie2a `plusLIE` lie2b `plusLIE` lie3)
\end{code}
The interesting thing about @ccall@ is that it is just a template
later use.
\begin{code}
-tcMonoExpr (HsCCall lbl args may_gc is_asm ignored_fake_result_ty) res_ty
- = -- Get the callable and returnable classes.
+tcMonoExpr e0@(HsCCall lbl args may_gc is_casm ignored_fake_result_ty) res_ty
+
+ = getDOptsTc `thenNF_Tc` \ dflags ->
+
+ checkTc (not (is_casm && dopt_HscLang dflags /= HscC))
+ (vcat [text "_casm_ is only supported when compiling via C (-fvia-C).",
+ text "Either compile with -fvia-C, or, better, rewrite your code",
+ text "to use the foreign function interface. _casm_s are deprecated",
+ text "and support for them may one day disappear."])
+ `thenTc_`
+
+ -- Get the callable and returnable classes.
tcLookupClass cCallableClassName `thenNF_Tc` \ cCallableClass ->
tcLookupClass cReturnableClassName `thenNF_Tc` \ cReturnableClass ->
tcLookupTyCon ioTyConName `thenNF_Tc` \ ioTyCon ->
in
-- Arguments
- let n_args = length args
- tv_idxs | n_args == 0 = []
- | otherwise = [1..n_args]
+ let tv_idxs | null args = []
+ | otherwise = [1..length args]
in
newTyVarTys (length tv_idxs) openTypeKind `thenNF_Tc` \ arg_tys ->
tcMonoExprs args arg_tys `thenTc` \ (args', args_lie) ->
-- constraints on the argument and result types.
mapNF_Tc new_arg_dict (zipEqual "tcMonoExpr:CCall" args arg_tys) `thenNF_Tc` \ ccarg_dicts_s ->
newDicts result_origin [mkClassPred cReturnableClass [result_ty]] `thenNF_Tc` \ ccres_dict ->
- returnTc (HsCCall lbl args' may_gc is_asm io_result_ty,
+ returnTc (HsCCall lbl args' may_gc is_casm io_result_ty,
mkLIE (ccres_dict ++ concat ccarg_dicts_s) `plusLIE` args_lie)
\end{code}
tcAddErrCtxt (predCtxt pred) (
tcMonoExpr pred boolTy ) `thenTc` \ (pred',lie1) ->
- tcMonoExpr b1 res_ty `thenTc` \ (b1',lie2) ->
- tcMonoExpr b2 res_ty `thenTc` \ (b2',lie3) ->
+ zapToType res_ty `thenTc` \ res_ty' ->
+ -- C.f. the call to zapToType in TcMatches.tcMatches
+
+ 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}
= tcAddErrCtxt (listCtxt expr) $
tcMonoExpr expr elt_ty
+tcMonoExpr in_expr@(ExplicitPArr _ exprs) res_ty -- maybe empty
+ = unifyPArrTy res_ty `thenTc` \ elt_ty ->
+ mapAndUnzipTc (tc_elt elt_ty) exprs `thenTc` \ (exprs', lies) ->
+ returnTc (ExplicitPArr elt_ty exprs', plusLIEs lies)
+ where
+ tc_elt elt_ty expr
+ = tcAddErrCtxt (parrCtxt expr) $
+ tcMonoExpr expr elt_ty
+
tcMonoExpr (ExplicitTuple exprs boxity) res_ty
= unifyTupleTy boxity (length exprs) res_ty `thenTc` \ arg_tys ->
mapAndUnzipTc (\ (expr, arg_ty) -> tcMonoExpr expr arg_ty)
data_cons = tyConDataCons tycon
(con_tyvars, _, _, _, _, _) = dataConSig (head data_cons)
in
- tcInstTyVars con_tyvars `thenNF_Tc` \ (_, result_inst_tys, _) ->
+ tcInstTyVars VanillaTv con_tyvars `thenNF_Tc` \ (_, result_inst_tys, _) ->
-- STEP 2
-- Check that at least one constructor has all the named fields
mk_inst_ty (tyvar, result_inst_ty)
| tyvar `elemVarSet` common_tyvars = returnNF_Tc result_inst_ty -- Same as result type
- | otherwise = newTyVarTy liftedTypeKind -- Fresh type
+ | otherwise = newTyVarTy liftedTypeKind -- Fresh type
in
mapNF_Tc mk_inst_ty (zip con_tyvars result_inst_tys) `thenNF_Tc` \ inst_tys ->
returnTc (ArithSeqOut (HsVar (instToId eft))
(FromThenTo expr1' expr2' expr3'),
lie1 `plusLIE` lie2 `plusLIE` lie3 `plusLIE` unitLIE eft)
+
+tcMonoExpr in_expr@(PArrSeqIn seq@(FromTo expr1 expr2)) res_ty
+ = tcAddErrCtxt (parrSeqCtxt in_expr) $
+ unifyPArrTy res_ty `thenTc` \ elt_ty ->
+ tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
+ tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
+ tcLookupGlobalId enumFromToPName `thenNF_Tc` \ sel_id ->
+ newMethod (PArrSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ enum_from_to ->
+
+ returnTc (PArrSeqOut (HsVar (instToId enum_from_to))
+ (FromTo expr1' expr2'),
+ lie1 `plusLIE` lie2 `plusLIE` unitLIE enum_from_to)
+
+tcMonoExpr in_expr@(PArrSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty
+ = tcAddErrCtxt (parrSeqCtxt in_expr) $
+ unifyPArrTy res_ty `thenTc` \ elt_ty ->
+ tcMonoExpr expr1 elt_ty `thenTc` \ (expr1',lie1) ->
+ tcMonoExpr expr2 elt_ty `thenTc` \ (expr2',lie2) ->
+ tcMonoExpr expr3 elt_ty `thenTc` \ (expr3',lie3) ->
+ tcLookupGlobalId enumFromThenToPName `thenNF_Tc` \ sel_id ->
+ newMethod (PArrSeqOrigin seq) sel_id [elt_ty] `thenNF_Tc` \ eft ->
+
+ returnTc (PArrSeqOut (HsVar (instToId eft))
+ (FromThenTo expr1' expr2' expr3'),
+ lie1 `plusLIE` lie2 `plusLIE` lie3 `plusLIE` unitLIE eft)
+
+tcMonoExpr (PArrSeqIn _) _
+ = panic "TcExpr.tcMonoExpr: Infinite parallel array!"
+ -- the parser shouldn't have generated it and the renamer shouldn't have
+ -- let it through
\end{code}
%************************************************************************
%* *
-\subsection{Expressions type signatures}
+\subsection{Implicit Parameter bindings}
%* *
%************************************************************************
\begin{code}
-tcMonoExpr in_expr@(ExprWithTySig expr poly_ty) res_ty
- = tcAddErrCtxt (exprSigCtxt in_expr) $
- tcHsSigType poly_ty `thenTc` \ sig_tc_ty ->
-
- if not (isQualifiedTy 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 tcSimplifyCheck (inside tcPolyExpr), except for any default
- -- resolution it may have done, which is recorded in the
- -- substitution.
- returnTc (expr, lie)
-\end{code}
-
-Implicit Parameter bindings.
-
-\begin{code}
tcMonoExpr (HsWith expr binds) res_ty
= tcMonoExpr expr res_ty `thenTc` \ (expr', expr_lie) ->
- mapAndUnzipTc tcIPBind binds `thenTc` \ (pairs, bind_lies) ->
+ mapAndUnzip3Tc tcIPBind binds `thenTc` \ (avail_ips, binds', bind_lies) ->
-- If the binding binds ?x = E, we must now
-- discharge any ?x constraints in expr_lie
- tcSimplifyIPs (map fst pairs) expr_lie `thenTc` \ (expr_lie', dict_binds) ->
+ tcSimplifyIPs avail_ips expr_lie `thenTc` \ (expr_lie', dict_binds) ->
let
- binds' = [(instToId ip, rhs) | (ip,rhs) <- pairs]
expr'' = HsLet (mkMonoBind dict_binds [] Recursive) expr'
in
returnTc (HsWith expr'' binds', expr_lie' `plusLIE` plusLIEs bind_lies)
-tcIPBind (name, expr)
+tcIPBind (ip, expr)
= newTyVarTy openTypeKind `thenTc` \ ty ->
tcGetSrcLoc `thenTc` \ loc ->
- newIPDict (IPBind name) name ty `thenNF_Tc` \ ip ->
+ newIPDict (IPBind ip) ip ty `thenNF_Tc` \ (ip', ip_inst) ->
tcMonoExpr expr ty `thenTc` \ (expr', lie) ->
- returnTc ((ip, expr'), lie)
+ returnTc (ip_inst, (ip', expr'), lie)
\end{code}
%************************************************************************
tcApp :: RenamedHsExpr -> [RenamedHsExpr] -- Function and args
-> TcType -- Expected result type of application
- -> TcM (TcExpr, [TcExpr], -- Translated fun and args
- LIE)
+ -> TcM (TcExpr, LIE) -- Translated fun and args
+
+tcApp (HsApp e1 e2) args res_ty
+ = tcApp e1 (e2:args) res_ty -- Accumulate the arguments
tcApp fun args res_ty
= -- First type-check the function
tcExpr_id fun `thenTc` \ (fun', lie_fun, fun_ty) ->
tcAddErrCtxt (wrongArgsCtxt "too many" fun args) (
+ traceTc (text "tcApp" <+> (ppr fun $$ ppr fun_ty)) `thenNF_Tc_`
split_fun_ty fun_ty (length args)
) `thenTc` \ (expected_arg_tys, actual_result_ty) ->
- -- Unify with expected result before type-checking the args
- -- This is when we might detect a too-few args situation
- tcAddErrCtxtM (checkArgsCtxt fun args res_ty actual_result_ty) (
- unifyTauTy res_ty actual_result_ty
- ) `thenTc_`
-
-- Now typecheck the args
mapAndUnzipTc (tcArg fun)
(zip3 args expected_arg_tys [1..]) `thenTc` \ (args', lie_args_s) ->
- -- Check that the result type doesn't have any nested for-alls.
- -- For example, a "build" on its own is no good; it must be applied to something.
- checkTc (isTauTy actual_result_ty)
- (lurkingRank2Err fun actual_result_ty) `thenTc_`
+ -- Unify with expected result after type-checking the args
+ -- so that the info from args percolates to actual_result_ty.
+ -- This is when we might detect a too-few args situation.
+ -- (One can think of cases when the opposite order would give
+ -- a better error message.)
+ tcAddErrCtxtM (checkArgsCtxt fun args res_ty actual_result_ty)
+ (tcSubExp res_ty actual_result_ty) `thenTc` \ (co_fn, lie_res) ->
- returnTc (fun', args', lie_fun `plusLIE` plusLIEs lie_args_s)
+ returnTc (co_fn <$> foldl HsApp fun' args',
+ lie_res `plusLIE` lie_fun `plusLIE` plusLIEs lie_args_s)
-- If an error happens we try to figure out whether the
(exp_args, _) = tcSplitFunTys exp_ty''
(act_args, _) = tcSplitFunTys act_ty''
- message | length exp_args < length act_args = wrongArgsCtxt "too few" fun args
- | length exp_args > length act_args = wrongArgsCtxt "too many" fun args
- | otherwise = appCtxt fun args
+ len_act_args = length act_args
+ len_exp_args = length exp_args
+
+ message | len_exp_args < len_act_args = wrongArgsCtxt "too few" fun args
+ | len_exp_args > len_act_args = wrongArgsCtxt "too many" fun args
+ | otherwise = appCtxt fun args
in
returnNF_Tc (env2, message)
split_fun_ty :: TcType -- The type of the function
- -> Int -- Number of arguments
+ -> Int -- Number of arguments
-> TcM ([TcType], -- Function argument types
- TcType) -- Function result types
+ TcType) -- Function result types
split_fun_ty fun_ty 0
= returnTc ([], fun_ty)
\end{code}
\begin{code}
-tcArg :: RenamedHsExpr -- The function (for error messages)
- -> (RenamedHsExpr, TcType, Int) -- Actual argument and expected arg type
- -> TcM (TcExpr, LIE) -- Resulting argument and LIE
+tcArg :: RenamedHsExpr -- The function (for error messages)
+ -> (RenamedHsExpr, TcSigmaType, Int) -- Actual argument and expected arg type
+ -> TcM (TcExpr, LIE) -- Resulting argument and LIE
tcArg the_fun (arg, expected_arg_ty, arg_no)
= tcAddErrCtxt (funAppCtxt the_fun arg arg_no) $
%* *
%************************************************************************
+tcId instantiates an occurrence of an Id.
+The instantiate_it loop runs round instantiating the Id.
+It has to be a loop because we are now prepared to entertain
+types like
+ f:: forall a. Eq a => forall b. Baz b => tau
+We want to instantiate this to
+ f2::tau {f2 = f1 b (Baz b), f1 = f a (Eq a)}
+
+The -fno-method-sharing flag controls what happens so far as the LIE
+is concerned. The default case is that for an overloaded function we
+generate a "method" Id, and add the Method Inst to the LIE. So you get
+something like
+ f :: Num a => a -> a
+ f = /\a (d:Num a) -> let m = (+) a d in \ (x:a) -> m x x
+If you specify -fno-method-sharing, the dictionary application
+isn't shared, so we get
+ f :: Num a => a -> a
+ f = /\a (d:Num a) (x:a) -> (+) a d x x
+This gets a bit less sharing, but
+ a) it's better for RULEs involving overloaded functions
+ b) perhaps fewer separated lambdas
+
\begin{code}
tcId :: Name -> NF_TcM (TcExpr, LIE, TcType)
tcId name -- Look up the Id and instantiate its type
= tcLookupId name `thenNF_Tc` \ id ->
- tcInstId id
+ loop (OccurrenceOf id) (HsVar id) emptyLIE (idType id)
+ where
+ loop orig (HsVar fun_id) lie fun_ty
+ | want_method_inst fun_ty
+ = tcInstType VanillaTv fun_ty `thenNF_Tc` \ (tyvars, theta, tau) ->
+ newMethodWithGivenTy orig fun_id
+ (mkTyVarTys tyvars) theta tau `thenNF_Tc` \ meth ->
+ loop orig (HsVar (instToId meth))
+ (unitLIE meth `plusLIE` lie) tau
+
+ loop orig fun lie fun_ty
+ | isSigmaTy fun_ty
+ = tcInstCall orig fun_ty `thenNF_Tc` \ (inst_fn, inst_lie, tau) ->
+ loop orig (inst_fn fun) (inst_lie `plusLIE` lie) tau
+
+ | otherwise
+ = returnNF_Tc (fun, lie, fun_ty)
+
+ want_method_inst fun_ty
+ | opt_NoMethodSharing = False
+ | otherwise = case tcSplitSigmaTy fun_ty of
+ (_,[],_) -> False -- Not overloaded
+ (_,theta,_) -> not (any isLinearPred theta)
+ -- This is a slight hack.
+ -- If f :: (%x :: T) => Int -> Int
+ -- Then if we have two separate calls, (f 3, f 4), we cannot
+ -- make a method constraint that then gets shared, thus:
+ -- let m = f %x in (m 3, m 4)
+ -- because that loses the linearity of the constraint.
+ -- The simplest thing to do is never to construct a method constraint
+ -- in the first place that has a linear implicit parameter in it.
\end{code}
Typecheck expression which in most cases will be an Id.
+The expression can return a higher-ranked type, such as
+ (forall a. a->a) -> Int
+so we must create a HoleTyVarTy to pass in as the expected tyvar.
\begin{code}
tcExpr_id :: RenamedHsExpr -> TcM (TcExpr, LIE, TcType)
tcExpr_id (HsVar name) = tcId name
-tcExpr_id expr = newTyVarTy openTypeKind `thenNF_Tc` \ id_ty ->
- tcMonoExpr expr id_ty `thenTc` \ (expr', lie_id) ->
- returnTc (expr', lie_id, id_ty)
+tcExpr_id expr = newHoleTyVarTy `thenNF_Tc` \ id_ty ->
+ tcMonoExpr expr id_ty `thenTc` \ (expr', lie_id) ->
+ readHoleResult id_ty `thenTc` \ id_ty' ->
+ returnTc (expr', lie_id, id_ty')
\end{code}
%************************************************************************
\begin{code}
+-- I don't like this lumping together of do expression and list/array
+-- comprehensions; creating the monad instances is entirely pointless in the
+-- latter case; I'll leave the list case as it is for the moment, but handle
+-- arrays extra (would be better to handle arrays and lists together, though)
+-- -=chak
+--
+tcDoStmts PArrComp stmts src_loc res_ty
+ =
+ ASSERT( not (null stmts) )
+ tcAddSrcLoc src_loc $
+
+ unifyPArrTy res_ty `thenTc` \elt_ty ->
+ let tc_ty = mkTyConTy parrTyCon
+ m_ty = (mkPArrTy, elt_ty)
+ in
+ tcStmts (DoCtxt PArrComp) m_ty stmts `thenTc` \(stmts', stmts_lie) ->
+ returnTc (HsDoOut PArrComp stmts'
+ undefined undefined undefined -- don't touch!
+ res_ty src_loc,
+ stmts_lie)
+
tcDoStmts do_or_lc stmts src_loc res_ty
= -- get the Monad and MonadZero classes
-- create type consisting of a fresh monad tyvar
-- If it's a comprehension we're dealing with,
-- force it to be a list comprehension.
-- (as of Haskell 98, monad comprehensions are no more.)
+ -- Similarily, array comprehensions must involve parallel arrays types
+ -- -=chak
(case do_or_lc of
ListComp -> unifyListTy res_ty `thenTc` \ elt_ty ->
returnNF_Tc (mkTyConTy listTyCon, (mkListTy, elt_ty))
+ PArrComp -> panic "TcExpr.tcDoStmts: How did we get here?!?"
+
_ -> newTyVarTy (mkArrowKind liftedTypeKind liftedTypeKind) `thenNF_Tc` \ m_ty ->
newTyVarTy liftedTypeKind `thenNF_Tc` \ elt_ty ->
unifyTauTy res_ty (mkAppTy m_ty elt_ty) `thenTc_`
-- The caller of tcRecordBinds has already checked
-- that all the fields come from the same type
- tcPolyExpr rhs field_ty `thenTc` \ (rhs', lie, _, _, _) ->
+ tcExpr rhs field_ty `thenTc` \ (rhs', lie) ->
returnTc ((sel_id, rhs', pun_flag), lie)
field_info = zipEqual "missingFields"
field_labels
- (drop (length ex_theta) (dataConStrictMarks data_con))
+ (dropList ex_theta (dataConStrictMarks data_con))
-- The 'drop' is because dataConStrictMarks
-- includes the existential dictionaries
(_, _, _, ex_theta, _, _) = dataConSig data_con
arithSeqCtxt expr
= hang (ptext SLIT("In an arithmetic sequence:")) 4 (ppr expr)
+parrSeqCtxt expr
+ = hang (ptext SLIT("In a parallel array sequence:")) 4 (ppr expr)
+
caseCtxt expr
= hang (ptext SLIT("In the case expression:")) 4 (ppr expr)
= hang (ptext SLIT("In the scrutinee of a case expression:")) 4 (ppr expr)
exprSigCtxt expr
- = hang (ptext SLIT("In an expression with a type signature:"))
+ = hang (ptext SLIT("When checking the type signature of the expression:"))
4 (ppr expr)
listCtxt expr
= hang (ptext SLIT("In the list element:")) 4 (ppr expr)
+parrCtxt expr
+ = hang (ptext SLIT("In the parallel array element:")) 4 (ppr expr)
+
predCtxt expr
= hang (ptext SLIT("In the predicate expression:")) 4 (ppr expr)
-sectionRAppCtxt expr
- = hang (ptext SLIT("In the right section:")) 4 (ppr expr)
-
-sectionLAppCtxt expr
- = hang (ptext SLIT("In the left section:")) 4 (ppr expr)
+exprCtxt expr
+ = hang (ptext SLIT("In the expression:")) 4 (ppr expr)
funAppCtxt fun arg arg_no
= hang (hsep [ ptext SLIT("In the"), speakNth arg_no, ptext SLIT("argument of"),
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