\section[TcExpr]{Typecheck an expression}
\begin{code}
-module TcExpr ( tcExpr, tcExpr_id, tcMonoExpr ) where
+module TcExpr ( tcCheckSigma, tcCheckRho, tcInferRho, tcMonoExpr ) where
#include "HsVersions.h"
import {-# SOURCE #-} TcSplice( tcSpliceExpr, tcBracket )
import HsSyn ( HsReify(..), ReifyFlavour(..) )
import TcType ( isTauTy )
-import TcEnv ( bracketOK, tcMetaTy, tcLookupGlobal,
- wellStaged, metaLevel )
-import TcSimplify ( tcSimplifyBracket )
+import TcEnv ( bracketOK, tcMetaTy, checkWellStaged )
import Name ( isExternalName )
import qualified DsMeta
#endif
import HsSyn ( HsExpr(..), HsLit(..), ArithSeqInfo(..), recBindFields )
import RnHsSyn ( RenamedHsExpr, RenamedRecordBinds )
-import TcHsSyn ( TcExpr, TcRecordBinds, hsLitType, mkHsDictApp, mkHsTyApp, mkHsLet )
+import TcHsSyn ( TcExpr, TcRecordBinds, hsLitType, mkHsDictApp, mkHsTyApp, mkHsLet, (<$>) )
import TcRnMonad
-import TcUnify ( tcSubExp, tcGen, (<$>),
- unifyTauTy, unifyFunTy, unifyListTy, unifyPArrTy,
- unifyTupleTy )
-import BasicTypes ( RecFlag(..), isMarkedStrict )
+import TcUnify ( Expected(..), newHole, zapExpectedType, zapExpectedTo, tcSubExp, tcGen,
+ unifyFunTy, zapToListTy, zapToPArrTy, zapToTupleTy )
+import BasicTypes ( isMarkedStrict )
import Inst ( InstOrigin(..),
newOverloadedLit, newMethodFromName, newIPDict,
newDicts, newMethodWithGivenTy,
instToId, tcInstCall, tcInstDataCon
)
import TcBinds ( tcBindsAndThen )
-import TcEnv ( tcLookupClass, tcLookupGlobal_maybe, tcLookupIdLvl,
- tcLookupTyCon, tcLookupDataCon, tcLookupId
+import TcEnv ( tcLookupClass, tcLookupGlobal_maybe, tcLookup,
+ tcLookupTyCon, tcLookupDataCon, tcLookupId, checkProcLevel
)
-import TcMatches ( tcMatchesCase, tcMatchLambda, tcDoStmts )
+import TcArrows ( tcProc )
+import TcMatches ( tcMatchesCase, tcMatchLambda, tcDoStmts, tcThingWithSig )
import TcMonoType ( tcHsSigType, UserTypeCtxt(..) )
import TcPat ( badFieldCon )
-import TcSimplify ( tcSimplifyIPs )
-import TcMType ( tcInstTyVars, tcInstType, newHoleTyVarTy, zapToType,
- newTyVarTy, newTyVarTys, zonkTcType, readHoleResult )
+import TcMType ( tcInstTyVars, tcInstType, newTyVarTy, newTyVarTys, zonkTcType )
import TcType ( TcType, TcSigmaType, TcRhoType, TyVarDetails(VanillaTv),
tcSplitFunTys, tcSplitTyConApp, mkTyVarTys,
isSigmaTy, mkFunTy, mkFunTys,
- mkTyConApp, mkClassPred, tcFunArgTy,
+ mkTyConApp, mkClassPred,
tyVarsOfTypes, isLinearPred,
liftedTypeKind, openTypeKind,
- tcSplitSigmaTy, tcTyConAppTyCon,
- tidyOpenType
+ tcSplitSigmaTy, tidyOpenType
)
import FieldLabel ( FieldLabel, fieldLabelName, fieldLabelType, fieldLabelTyCon )
-import Id ( Id, idType, recordSelectorFieldLabel, isRecordSelector, isDataConWrapId_maybe )
-import DataCon ( DataCon, dataConFieldLabels, dataConSig, dataConStrictMarks )
+import Id ( Id, idType, recordSelectorFieldLabel, isRecordSelector )
+import DataCon ( DataCon, dataConFieldLabels, dataConSig, dataConStrictMarks, dataConWrapId )
import Name ( Name )
import TyCon ( TyCon, tyConTyVars, tyConTheta, isAlgTyCon, tyConDataCons )
import Subst ( mkTopTyVarSubst, substTheta, substTy )
%************************************************************************
\begin{code}
-tcExpr :: RenamedHsExpr -- Expession to type check
- -> TcSigmaType -- Expected type (could be a polytpye)
- -> TcM TcExpr -- Generalised expr with expected type
+-- tcCheckSigma does type *checking*; it's passed the expected type of the result
+tcCheckSigma :: RenamedHsExpr -- Expession to type check
+ -> TcSigmaType -- Expected type (could be a polytpye)
+ -> TcM TcExpr -- Generalised expr with expected type
-tcExpr expr expected_ty
+tcCheckSigma expr expected_ty
= traceTc (text "tcExpr" <+> (ppr expected_ty $$ ppr expr)) `thenM_`
tc_expr' expr expected_ty
-tc_expr' expr expected_ty
- | not (isSigmaTy expected_ty) -- Monomorphic case
- = tcMonoExpr expr expected_ty
-
- | otherwise
- = tcGen expected_ty emptyVarSet (
- tcMonoExpr expr
+tc_expr' expr sigma_ty
+ | isSigmaTy sigma_ty
+ = tcGen sigma_ty emptyVarSet (
+ \ rho_ty -> tcCheckRho expr rho_ty
) `thenM` \ (gen_fn, expr') ->
returnM (gen_fn <$> expr')
+
+tc_expr' expr rho_ty -- Monomorphic case
+ = tcCheckRho expr rho_ty
+\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 hole to pass in as the expected tyvar.
+
+\begin{code}
+tcCheckRho :: RenamedHsExpr -> TcRhoType -> TcM TcExpr
+tcCheckRho expr rho_ty = tcMonoExpr expr (Check rho_ty)
+
+tcInferRho :: RenamedHsExpr -> TcM (TcExpr, TcRhoType)
+tcInferRho (HsVar name) = tcId name
+tcInferRho expr = newHole `thenM` \ hole ->
+ tcMonoExpr expr (Infer hole) `thenM` \ expr' ->
+ readMutVar hole `thenM` \ rho_ty ->
+ returnM (expr', rho_ty)
\end{code}
+
%************************************************************************
%* *
\subsection{The TAUT rules for variables}
\begin{code}
tcMonoExpr :: RenamedHsExpr -- Expession to type check
- -> TcRhoType -- Expected type (could be a type variable)
+ -> Expected TcRhoType -- Expected type (could be a type variable)
-- Definitely no foralls at the top
-- Can be a 'hole'.
-> TcM TcExpr
\begin{code}
tcMonoExpr in_expr@(ExprWithTySig expr poly_ty) res_ty
- = addErrCtxt (exprSigCtxt in_expr) $
- tcHsSigType ExprSigCtxt poly_ty `thenM` \ sig_tc_ty ->
- tcExpr expr sig_tc_ty `thenM` \ expr' ->
-
- -- 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
- tcInstCall SignatureOrigin sig_tc_ty `thenM` \ (inst_fn, inst_sig_ty) ->
- tcSubExp res_ty inst_sig_ty `thenM` \ co_fn ->
-
- returnM (co_fn <$> inst_fn expr')
+ = addErrCtxt (exprSigCtxt in_expr) $
+ tcHsSigType ExprSigCtxt poly_ty `thenM` \ sig_tc_ty ->
+ tcThingWithSig sig_tc_ty (tcCheckRho expr) res_ty `thenM` \ (co_fn, expr') ->
+ returnM (co_fn <$> expr')
tcMonoExpr (HsType ty) res_ty
= failWithTc (text "Can't handle type argument:" <+> ppr ty)
\begin{code}
tcMonoExpr (HsLit lit) res_ty = tcLit lit res_ty
-tcMonoExpr (HsOverLit lit) res_ty = newOverloadedLit (LiteralOrigin lit) lit res_ty
+tcMonoExpr (HsOverLit lit) res_ty = zapExpectedType res_ty `thenM` \ res_ty' ->
+ newOverloadedLit (LiteralOrigin lit) lit res_ty'
tcMonoExpr (HsPar expr) res_ty = tcMonoExpr expr res_ty `thenM` \ expr' ->
returnM (HsPar expr')
tcMonoExpr (HsSCC lbl expr) res_ty = tcMonoExpr expr res_ty `thenM` \ expr' ->
returnM (HsSCC lbl expr')
-
+tcMonoExpr (HsCoreAnn lbl expr) res_ty = tcMonoExpr expr res_ty `thenM` \ expr' -> -- hdaume: core annotation
+ returnM (HsCoreAnn lbl expr')
tcMonoExpr (NegApp expr neg_name) res_ty
= tcMonoExpr (HsApp (HsVar neg_name) expr) res_ty
-- ToDo: use tcSyntaxName
-- op e
tcMonoExpr in_expr@(SectionL arg1 op) res_ty
- = tcExpr_id op `thenM` \ (op', op_ty) ->
+ = tcInferRho op `thenM` \ (op', op_ty) ->
split_fun_ty op_ty 2 {- two args -} `thenM` \ ([arg1_ty, arg2_ty], op_res_ty) ->
tcArg op (arg1, arg1_ty, 1) `thenM` \ arg1' ->
addErrCtxt (exprCtxt in_expr) $
-- \ x -> op x expr
tcMonoExpr in_expr@(SectionR op arg2) res_ty
- = tcExpr_id op `thenM` \ (op', op_ty) ->
+ = tcInferRho op `thenM` \ (op', op_ty) ->
split_fun_ty op_ty 2 {- two args -} `thenM` \ ([arg1_ty, arg2_ty], op_res_ty) ->
tcArg op (arg2, arg2_ty, 2) `thenM` \ arg2' ->
addErrCtxt (exprCtxt in_expr) $
-- equivalent to (op e1) e2:
tcMonoExpr in_expr@(OpApp arg1 op fix arg2) res_ty
- = tcExpr_id op `thenM` \ (op', op_ty) ->
+ = tcInferRho op `thenM` \ (op', op_ty) ->
split_fun_ty op_ty 2 {- two args -} `thenM` \ ([arg1_ty, arg2_ty], op_res_ty) ->
tcArg op (arg1, arg1_ty, 1) `thenM` \ arg1' ->
tcArg op (arg2, arg2_ty, 2) `thenM` \ arg2' ->
-- case (map f) of
-- (x:xs) -> ...
-- will report that map is applied to too few arguments
- --
- -- Not only that, but it's better to check the matches on their
- -- own, so that we get the expected results for scoped type variables.
- -- f x = case x of
- -- (p::a, q::b) -> (q,p)
- -- The above should work: the match (p,q) -> (q,p) is polymorphic as
- -- claimed by the pattern signatures. But if we typechecked the
- -- match with x in scope and x's type as the expected type, we'd be hosed.
tcMatchesCase matches res_ty `thenM` \ (scrut_ty, matches') ->
addErrCtxt (caseScrutCtxt scrut) (
- tcMonoExpr scrut scrut_ty
+ tcCheckRho scrut scrut_ty
) `thenM` \ scrut' ->
returnM (HsCase scrut' matches' src_loc)
tcMonoExpr (HsIf pred b1 b2 src_loc) res_ty
= addSrcLoc src_loc $
addErrCtxt (predCtxt pred) (
- tcMonoExpr pred boolTy ) `thenM` \ pred' ->
+ tcCheckRho pred boolTy ) `thenM` \ pred' ->
- zapToType res_ty `thenM` \ res_ty' ->
+ zapExpectedType res_ty `thenM` \ res_ty' ->
-- C.f. the call to zapToType in TcMatches.tcMatches
- tcMonoExpr b1 res_ty' `thenM` \ b1' ->
- tcMonoExpr b2 res_ty' `thenM` \ b2' ->
+ tcCheckRho b1 res_ty' `thenM` \ b1' ->
+ tcCheckRho b2 res_ty' `thenM` \ b2' ->
returnM (HsIf pred' b1' b2' src_loc)
tcMonoExpr (HsDo do_or_lc stmts method_names _ src_loc) res_ty
- = addSrcLoc src_loc $
- tcDoStmts do_or_lc stmts method_names res_ty `thenM` \ (binds, stmts', methods') ->
- returnM (mkHsLet binds (HsDo do_or_lc stmts' methods' res_ty src_loc))
+ = addSrcLoc src_loc $
+ zapExpectedType res_ty `thenM` \ res_ty' ->
+ -- All comprehensions yield a monotype
+ tcDoStmts do_or_lc stmts method_names res_ty' `thenM` \ (stmts', methods') ->
+ returnM (HsDo do_or_lc stmts' methods' res_ty' src_loc)
tcMonoExpr in_expr@(ExplicitList _ exprs) res_ty -- Non-empty list
- = unifyListTy res_ty `thenM` \ elt_ty ->
+ = zapToListTy res_ty `thenM` \ elt_ty ->
mappM (tc_elt elt_ty) exprs `thenM` \ exprs' ->
returnM (ExplicitList elt_ty exprs')
where
tc_elt elt_ty expr
= addErrCtxt (listCtxt expr) $
- tcMonoExpr expr elt_ty
+ tcCheckRho expr elt_ty
tcMonoExpr in_expr@(ExplicitPArr _ exprs) res_ty -- maybe empty
- = unifyPArrTy res_ty `thenM` \ elt_ty ->
+ = zapToPArrTy res_ty `thenM` \ elt_ty ->
mappM (tc_elt elt_ty) exprs `thenM` \ exprs' ->
returnM (ExplicitPArr elt_ty exprs')
where
tc_elt elt_ty expr
= addErrCtxt (parrCtxt expr) $
- tcMonoExpr expr elt_ty
+ tcCheckRho expr elt_ty
tcMonoExpr (ExplicitTuple exprs boxity) res_ty
- = unifyTupleTy boxity (length exprs) res_ty `thenM` \ arg_tys ->
- tcMonoExprs exprs arg_tys `thenM` \ exprs' ->
+ = zapToTupleTy boxity (length exprs) res_ty `thenM` \ arg_tys ->
+ tcCheckRhos exprs arg_tys `thenM` \ exprs' ->
returnM (ExplicitTuple exprs' boxity)
+
+tcMonoExpr (HsProc pat cmd loc) res_ty
+ = addSrcLoc loc $
+ tcProc pat cmd res_ty `thenM` \ (pat', cmd') ->
+ returnM (HsProc pat' cmd' loc)
\end{code}
| otherwise = [1..length args]
in
newTyVarTys (length tv_idxs) openTypeKind `thenM` \ arg_tys ->
- tcMonoExprs args arg_tys `thenM` \ args' ->
+ tcCheckRhos args arg_tys `thenM` \ args' ->
-- The argument types can be unlifted or lifted; the result
-- type must, however, be lifted since it's an argument to the IO
let
io_result_ty = mkTyConApp ioTyCon [result_ty]
in
- unifyTauTy res_ty io_result_ty `thenM_`
+ zapExpectedTo res_ty io_result_ty `thenM_`
-- Construct the extra insts, which encode the
-- constraints on the argument and result types.
(tycon, ty_args) = tcSplitTyConApp record_ty
in
ASSERT( isAlgTyCon tycon )
- unifyTauTy res_ty record_ty `thenM_`
+ zapExpectedTo res_ty record_ty `thenM_`
-- Check that the record bindings match the constructor
-- con_name is syntactically constrained to be a data constructor
- tcLookupDataCon con_name `thenM` \ data_con ->
+ tcLookupDataCon con_name `thenM` \ data_con ->
let
bad_fields = badFields rbinds data_con
in
let
bad_guys = [ addErrTc (notSelector field_name)
| (field_name, maybe_sel_id) <- field_names `zip` maybe_sel_ids,
- case maybe_sel_id of
- Just (AnId sel_id) -> not (isRecordSelector sel_id)
- other -> True
+ not (is_selector maybe_sel_id)
]
+ is_selector (Just (AnId sel_id)) = isRecordSelector sel_id -- Excludes class ops
+ is_selector other = False
in
checkM (null bad_guys) (sequenceM bad_guys `thenM_` failM) `thenM_`
let
-- It's OK to use the non-tc splitters here (for a selector)
(Just (AnId sel_id) : _) = maybe_sel_ids
-
- (_, _, tau) = tcSplitSigmaTy (idType sel_id) -- Selectors can be overloaded
- -- when the data type has a context
- data_ty = tcFunArgTy tau -- Must succeed since sel_id is a selector
- tycon = tcTyConAppTyCon data_ty
+ field_lbl = recordSelectorFieldLabel sel_id -- We've failed already if
+ tycon = fieldLabelTyCon field_lbl -- it's not a field label
data_cons = tyConDataCons tycon
tycon_tyvars = tyConTyVars tycon -- The data cons use the same type vars
in
let
result_record_ty = mkTyConApp tycon result_inst_tys
in
- unifyTauTy res_ty result_record_ty `thenM_`
+ zapExpectedTo res_ty result_record_ty `thenM_`
tcRecordBinds tycon result_inst_tys rbinds `thenM` \ rbinds' ->
-- STEP 4
let
record_ty = mkTyConApp tycon inst_tys
in
- tcMonoExpr record_expr record_ty `thenM` \ record_expr' ->
+ tcCheckRho record_expr record_ty `thenM` \ record_expr' ->
-- STEP 6
-- Figure out the LIE we need. We have to generate some
\begin{code}
tcMonoExpr (ArithSeqIn seq@(From expr)) res_ty
- = unifyListTy res_ty `thenM` \ elt_ty ->
- tcMonoExpr expr elt_ty `thenM` \ expr' ->
+ = zapToListTy res_ty `thenM` \ elt_ty ->
+ tcCheckRho expr elt_ty `thenM` \ expr' ->
newMethodFromName (ArithSeqOrigin seq)
elt_ty enumFromName `thenM` \ enum_from ->
tcMonoExpr in_expr@(ArithSeqIn seq@(FromThen expr1 expr2)) res_ty
= addErrCtxt (arithSeqCtxt in_expr) $
- unifyListTy res_ty `thenM` \ elt_ty ->
- tcMonoExpr expr1 elt_ty `thenM` \ expr1' ->
- tcMonoExpr expr2 elt_ty `thenM` \ expr2' ->
+ zapToListTy res_ty `thenM` \ elt_ty ->
+ tcCheckRho expr1 elt_ty `thenM` \ expr1' ->
+ tcCheckRho expr2 elt_ty `thenM` \ expr2' ->
newMethodFromName (ArithSeqOrigin seq)
elt_ty enumFromThenName `thenM` \ enum_from_then ->
tcMonoExpr in_expr@(ArithSeqIn seq@(FromTo expr1 expr2)) res_ty
= addErrCtxt (arithSeqCtxt in_expr) $
- unifyListTy res_ty `thenM` \ elt_ty ->
- tcMonoExpr expr1 elt_ty `thenM` \ expr1' ->
- tcMonoExpr expr2 elt_ty `thenM` \ expr2' ->
+ zapToListTy res_ty `thenM` \ elt_ty ->
+ tcCheckRho expr1 elt_ty `thenM` \ expr1' ->
+ tcCheckRho expr2 elt_ty `thenM` \ expr2' ->
newMethodFromName (ArithSeqOrigin seq)
elt_ty enumFromToName `thenM` \ enum_from_to ->
tcMonoExpr in_expr@(ArithSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty
= addErrCtxt (arithSeqCtxt in_expr) $
- unifyListTy res_ty `thenM` \ elt_ty ->
- tcMonoExpr expr1 elt_ty `thenM` \ expr1' ->
- tcMonoExpr expr2 elt_ty `thenM` \ expr2' ->
- tcMonoExpr expr3 elt_ty `thenM` \ expr3' ->
+ zapToListTy res_ty `thenM` \ elt_ty ->
+ tcCheckRho expr1 elt_ty `thenM` \ expr1' ->
+ tcCheckRho expr2 elt_ty `thenM` \ expr2' ->
+ tcCheckRho expr3 elt_ty `thenM` \ expr3' ->
newMethodFromName (ArithSeqOrigin seq)
elt_ty enumFromThenToName `thenM` \ eft ->
tcMonoExpr in_expr@(PArrSeqIn seq@(FromTo expr1 expr2)) res_ty
= addErrCtxt (parrSeqCtxt in_expr) $
- unifyPArrTy res_ty `thenM` \ elt_ty ->
- tcMonoExpr expr1 elt_ty `thenM` \ expr1' ->
- tcMonoExpr expr2 elt_ty `thenM` \ expr2' ->
+ zapToPArrTy res_ty `thenM` \ elt_ty ->
+ tcCheckRho expr1 elt_ty `thenM` \ expr1' ->
+ tcCheckRho expr2 elt_ty `thenM` \ expr2' ->
newMethodFromName (PArrSeqOrigin seq)
elt_ty enumFromToPName `thenM` \ enum_from_to ->
tcMonoExpr in_expr@(PArrSeqIn seq@(FromThenTo expr1 expr2 expr3)) res_ty
= addErrCtxt (parrSeqCtxt in_expr) $
- unifyPArrTy res_ty `thenM` \ elt_ty ->
- tcMonoExpr expr1 elt_ty `thenM` \ expr1' ->
- tcMonoExpr expr2 elt_ty `thenM` \ expr2' ->
- tcMonoExpr expr3 elt_ty `thenM` \ expr3' ->
+ zapToPArrTy res_ty `thenM` \ elt_ty ->
+ tcCheckRho expr1 elt_ty `thenM` \ expr1' ->
+ tcCheckRho expr2 elt_ty `thenM` \ expr2' ->
+ tcCheckRho expr3 elt_ty `thenM` \ expr3' ->
newMethodFromName (PArrSeqOrigin seq)
elt_ty enumFromThenToPName `thenM` \ eft ->
-- Rename excludes these cases otherwise
tcMonoExpr (HsSplice n expr loc) res_ty = addSrcLoc loc (tcSpliceExpr n expr res_ty)
-
-tcMonoExpr (HsBracket brack loc) res_ty
- = addSrcLoc loc $
- getStage `thenM` \ level ->
- case bracketOK level of {
- Nothing -> failWithTc (illegalBracket level) ;
- Just next_level ->
-
- -- Typecheck expr to make sure it is valid,
- -- but throw away the results. We'll type check
- -- it again when we actually use it.
- newMutVar [] `thenM` \ pending_splices ->
- getLIEVar `thenM` \ lie_var ->
-
- setStage (Brack next_level pending_splices lie_var) (
- getLIE (tcBracket brack)
- ) `thenM` \ (meta_ty, lie) ->
- tcSimplifyBracket lie `thenM_`
-
- unifyTauTy res_ty meta_ty `thenM_`
-
- -- Return the original expression, not the type-decorated one
- readMutVar pending_splices `thenM` \ pendings ->
- returnM (HsBracketOut brack pendings)
- }
+tcMonoExpr (HsBracket brack loc) res_ty = addSrcLoc loc (tcBracket brack res_ty)
tcMonoExpr (HsReify (Reify flavour name)) res_ty
= addErrCtxt (ptext SLIT("At the reification of") <+> ppr name) $
- tcMetaTy tycon_name `thenM` \ reify_ty ->
- unifyTauTy res_ty reify_ty `thenM_`
+ tcMetaTy tycon_name `thenM` \ reify_ty ->
+ zapExpectedTo res_ty reify_ty `thenM_`
returnM (HsReify (ReifyOut flavour name))
where
tycon_name = case flavour of
- ReifyDecl -> DsMeta.decTyConName
- ReifyType -> DsMeta.typTyConName
+ ReifyDecl -> DsMeta.decQTyConName
+ ReifyType -> DsMeta.typeQTyConName
ReifyFixity -> pprPanic "tcMonoExpr: cant do reifyFixity yet" (ppr name)
-#endif GHCI
+#endif /* GHCI */
\end{code}
\begin{code}
tcApp :: RenamedHsExpr -> [RenamedHsExpr] -- Function and args
- -> TcType -- Expected result type of application
+ -> Expected TcRhoType -- Expected result type of application
-> TcM TcExpr -- Translated fun and args
tcApp (HsApp e1 e2) args res_ty
tcApp fun args res_ty
= -- First type-check the function
- tcExpr_id fun `thenM` \ (fun', fun_ty) ->
+ tcInferRho fun `thenM` \ (fun', fun_ty) ->
addErrCtxt (wrongArgsCtxt "too many" fun args) (
traceTc (text "tcApp" <+> (ppr fun $$ ppr fun_ty)) `thenM_`
split_fun_ty fun_ty (length args)
) `thenM` \ (expected_arg_tys, actual_result_ty) ->
- -- Now typecheck the args
- mappM (tcArg fun)
- (zip3 args expected_arg_tys [1..]) `thenM` \ args' ->
-
- -- Unify with expected result after type-checking the args
- -- so that the info from args percolates to actual_result_ty.
+ -- Unify with expected result before (was: after) type-checking the args
+ -- so that the info from res_ty (was: args) percolates to args (was 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.)
+ -- [March 2003: I'm experimenting with putting this first. Here's an
+ -- example where it actually makes a real difference
+ -- class C t a b | t a -> b
+ -- instance C Char a Bool
+ --
+ -- data P t a = forall b. (C t a b) => MkP b
+ -- data Q t = MkQ (forall a. P t a)
+
+ -- f1, f2 :: Q Char;
+ -- f1 = MkQ (MkP True)
+ -- f2 = MkQ (MkP True :: forall a. P Char a)
+ --
+ -- With the change, f1 will type-check, because the 'Char' info from
+ -- the signature is propagated into MkQ's argument. With the check
+ -- in the other order, the extra signature in f2 is reqd.]
+
addErrCtxtM (checkArgsCtxt fun args res_ty actual_result_ty)
- (tcSubExp res_ty actual_result_ty) `thenM` \ co_fn ->
+ (tcSubExp res_ty actual_result_ty) `thenM` \ co_fn ->
+
+ -- Now typecheck the args
+ mappM (tcArg fun)
+ (zip3 args expected_arg_tys [1..]) `thenM` \ args' ->
returnM (co_fn <$> foldl HsApp fun' args')
-- If an error happens we try to figure out whether the
-- function has been given too many or too few arguments,
--- and say so
-checkArgsCtxt fun args expected_res_ty actual_res_ty tidy_env
+-- and say so.
+-- The ~(Check...) is because in the Infer case the tcSubExp
+-- definitely won't fail, so we can be certain we're in the Check branch
+checkArgsCtxt fun args ~(Check expected_res_ty) actual_res_ty tidy_env
= zonkTcType expected_res_ty `thenM` \ exp_ty' ->
zonkTcType actual_res_ty `thenM` \ act_ty' ->
let
returnM (env2, message)
-split_fun_ty :: TcType -- The type of the function
+split_fun_ty :: TcRhoType -- The type of the function
-> Int -- Number of arguments
-> TcM ([TcType], -- Function argument types
TcType) -- Function result types
tcArg the_fun (arg, expected_arg_ty, arg_no)
= addErrCtxt (funAppCtxt the_fun arg arg_no) $
- tcExpr arg expected_arg_ty
+ tcCheckSigma arg expected_arg_ty
\end{code}
b) perhaps fewer separated lambdas
\begin{code}
-tcId :: Name -> TcM (TcExpr, TcType)
+tcId :: Name -> TcM (TcExpr, TcRhoType)
tcId name -- Look up the Id and instantiate its type
- = tcLookupIdLvl name `thenM` \ (id, bind_lvl) ->
+ = -- First check whether it's a DataCon
+ -- Reason: we must not forget to chuck in the
+ -- constraints from their "silly context"
+ tcLookup name `thenM` \ maybe_thing ->
+ case maybe_thing of {
+ AGlobal (ADataCon data_con) -> inst_data_con data_con
+ ; AGlobal (AnId id) -> loop (HsVar id) (idType id)
+ -- A global cannot possibly be ill-staged
+ -- nor does it need the 'lifting' treatment
+
+ ; ATcId id th_level proc_level -> tc_local_id id th_level proc_level
+ ; other -> pprPanic "tcId" (ppr name)
+ }
+ where
+
+#ifndef GHCI
+ tc_local_id id th_bind_lvl proc_lvl -- Non-TH case
+ = checkProcLevel id proc_lvl `thenM_`
+ loop (HsVar id) (idType id)
+
+#else /* GHCI and TH is on */
+ tc_local_id id th_bind_lvl proc_lvl -- TH case
+ = checkProcLevel id proc_lvl `thenM_`
-- Check for cross-stage lifting
-#ifdef GHCI
- getStage `thenM` \ use_stage ->
- case use_stage of
- Brack use_lvl ps_var lie_var
- | use_lvl > bind_lvl && not (isExternalName name)
- -> -- E.g. \x -> [| h x |]
- -- We must behave as if the reference to x was
- -- h $(lift x)
- -- We use 'x' itself as the splice proxy, used by
- -- the desugarer to stitch it all back together
- -- NB: isExernalName is true of top level things,
- -- and false of nested bindings
-
- let
- id_ty = idType id
- in
- checkTc (isTauTy id_ty) (polySpliceErr id) `thenM_`
+ getStage `thenM` \ use_stage ->
+ case use_stage of
+ Brack use_lvl ps_var lie_var
+ | use_lvl > th_bind_lvl
+ -> -- E.g. \x -> [| h x |]
+ -- We must behave as if the reference to x was
+
+ -- h $(lift x)
+ -- We use 'x' itself as the splice proxy, used by
+ -- the desugarer to stitch it all back together.
+ -- If 'x' occurs many times we may get many identical
+ -- bindings of the same splice proxy, but that doesn't
+ -- matter, although it's a mite untidy.
+ let
+ id_ty = idType id
+ in
+ checkTc (isTauTy id_ty) (polySpliceErr id) `thenM_`
-- If x is polymorphic, its occurrence sites might
-- have different instantiations, so we can't use plain
-- 'x' as the splice proxy name. I don't know how to
-- solve this, and it's probably unimportant, so I'm
-- just going to flag an error for now
- setLIEVar lie_var (
- newMethodFromName orig id_ty DsMeta.liftName `thenM` \ lift ->
- -- Put the 'lift' constraint into the right LIE
+ setLIEVar lie_var (
+ newMethodFromName orig id_ty DsMeta.liftName `thenM` \ lift ->
+ -- Put the 'lift' constraint into the right LIE
+
+ -- Update the pending splices
+ readMutVar ps_var `thenM` \ ps ->
+ writeMutVar ps_var ((name, HsApp (HsVar lift) (HsVar id)) : ps) `thenM_`
- -- Update the pending splices
- readMutVar ps_var `thenM` \ ps ->
- writeMutVar ps_var ((name, HsApp (HsVar lift) (HsVar id)) : ps) `thenM_`
+ returnM (HsVar id, id_ty))
- returnM (HsVar id, id_ty))
-
- other ->
- let
- use_lvl = metaLevel use_stage
- in
- checkTc (wellStaged bind_lvl use_lvl)
- (badStageErr id bind_lvl use_lvl) `thenM_`
-#endif
- -- This is the bit that handles the no-Template-Haskell case
- case isDataConWrapId_maybe id of
- Nothing -> loop (HsVar id) (idType id)
- Just data_con -> inst_data_con id data_con
-
- where
- orig = OccurrenceOf name
+ other ->
+ checkWellStaged (quotes (ppr id)) th_bind_lvl use_stage `thenM_`
+ loop (HsVar id) (idType id)
+#endif /* GHCI */
loop (HsVar fun_id) fun_ty
| want_method_inst fun_ty
loop fun fun_ty
| isSigmaTy fun_ty
= tcInstCall orig fun_ty `thenM` \ (inst_fn, tau) ->
- loop (inst_fn fun) tau
+ loop (inst_fn <$> fun) tau
| otherwise
= returnM (fun, 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.
+ -- Hack Alert (want_method_inst)!
-- 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:
-- 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.
+ want_method_inst fun_ty
+ | opt_NoMethodSharing = False
+ | otherwise = case tcSplitSigmaTy fun_ty of
+ (_,[],_) -> False -- Not overloaded
+ (_,theta,_) -> not (any isLinearPred theta)
+
-- We treat data constructors differently, because we have to generate
-- constraints for their silly theta, which no longer appears in
- -- the type of dataConWrapId. It's dual to TcPat.tcConstructor
- inst_data_con id data_con
+ -- the type of dataConWrapId (see note on "stupid context" in DataCon.lhs
+ -- It's dual to TcPat.tcConstructor
+ inst_data_con data_con
= tcInstDataCon orig data_con `thenM` \ (ty_args, ex_dicts, arg_tys, result_ty, _) ->
extendLIEs ex_dicts `thenM_`
- returnM (mkHsDictApp (mkHsTyApp (HsVar id) ty_args) (map instToId ex_dicts),
+ returnM (mkHsDictApp (mkHsTyApp (HsVar (dataConWrapId data_con)) ty_args)
+ (map instToId ex_dicts),
mkFunTys arg_tys result_ty)
-\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, TcType)
-tcExpr_id (HsVar name) = tcId name
-tcExpr_id expr = newHoleTyVarTy `thenM` \ id_ty ->
- tcMonoExpr expr id_ty `thenM` \ expr' ->
- readHoleResult id_ty `thenM` \ id_ty' ->
- returnM (expr', id_ty')
+ orig = OccurrenceOf name
\end{code}
-
%************************************************************************
%* *
\subsection{Record bindings}
-- The caller of tcRecordBinds has already checked
-- that all the fields come from the same type
- tcExpr rhs field_ty `thenM` \ rhs' ->
+ tcCheckSigma rhs field_ty `thenM` \ rhs' ->
returnM (sel_id, rhs')
%************************************************************************
%* *
-\subsection{@tcMonoExprs@ typechecks a {\em list} of expressions}
+\subsection{@tcCheckRhos@ typechecks a {\em list} of expressions}
%* *
%************************************************************************
\begin{code}
-tcMonoExprs :: [RenamedHsExpr] -> [TcType] -> TcM [TcExpr]
+tcCheckRhos :: [RenamedHsExpr] -> [TcType] -> TcM [TcExpr]
-tcMonoExprs [] [] = returnM []
-tcMonoExprs (expr:exprs) (ty:tys)
- = tcMonoExpr expr ty `thenM` \ expr' ->
- tcMonoExprs exprs tys `thenM` \ exprs' ->
+tcCheckRhos [] [] = returnM []
+tcCheckRhos (expr:exprs) (ty:tys)
+ = tcCheckRho expr ty `thenM` \ expr' ->
+ tcCheckRhos exprs tys `thenM` \ exprs' ->
returnM (expr':exprs')
\end{code}
Overloaded literals.
\begin{code}
-tcLit :: HsLit -> TcType -> TcM TcExpr
+tcLit :: HsLit -> Expected TcRhoType -> TcM TcExpr
tcLit (HsLitLit s _) res_ty
- = tcLookupClass cCallableClassName `thenM` \ cCallableClass ->
+ = zapExpectedType res_ty `thenM` \ res_ty' ->
+ tcLookupClass cCallableClassName `thenM` \ cCallableClass ->
newDicts (LitLitOrigin (unpackFS s))
- [mkClassPred cCallableClass [res_ty]] `thenM` \ dicts ->
+ [mkClassPred cCallableClass [res_ty']] `thenM` \ dicts ->
extendLIEs dicts `thenM_`
- returnM (HsLit (HsLitLit s res_ty))
+ returnM (HsLit (HsLitLit s res_ty'))
tcLit lit res_ty
- = unifyTauTy res_ty (hsLitType lit) `thenM_`
+ = zapExpectedTo res_ty (hsLitType lit) `thenM_`
returnM (HsLit lit)
\end{code}
arithSeqCtxt expr
= hang (ptext SLIT("In an arithmetic sequence:")) 4 (ppr expr)
-
-badStageErr id bind_lvl use_lvl
- = ptext SLIT("Stage error:") <+> quotes (ppr id) <+>
- hsep [ptext SLIT("is bound at stage") <+> ppr bind_lvl,
- ptext SLIT("but used at stage") <+> ppr use_lvl]
-
parrSeqCtxt expr
= hang (ptext SLIT("In a parallel array sequence:")) 4 (ppr expr)
predCtxt expr
= hang (ptext SLIT("In the predicate expression:")) 4 (ppr expr)
-illegalBracket level
- = ptext SLIT("Illegal bracket at level") <+> ppr level
-
appCtxt fun args
= ptext SLIT("In the application") <+> quotes (ppr the_app)
where
header = ptext SLIT("Constructor") <+> quotes (ppr con) <+>
ptext SLIT("does not have the required strict field(s)")
-
missingFields :: DataCon -> [FieldLabel] -> SDoc
missingFields con fields
= ptext SLIT("Fields of") <+> quotes (ppr con) <+> ptext SLIT("not initialised:")
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