\section[TcExpr]{Typecheck an expression}
\begin{code}
-module TcExpr ( tcPolyExpr, tcPolyExprNC,
- tcMonoExpr, tcInferRho, tcSyntaxOp ) where
+{-# OPTIONS -w #-}
+-- The above warning supression flag is a temporary kludge.
+-- While working on this module you are encouraged to remove it and fix
+-- any warnings in the module. See
+-- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
+-- for details
+
+module TcExpr ( tcPolyExpr, tcPolyExprNC, tcMonoExpr, tcInferRho, tcSyntaxOp) where
#include "HsVersions.h"
import TcPat
import TcMType
import TcType
+import TcIface ( checkWiredInTyCon )
import Id
import DataCon
import Name
import TyCon
import Type
+import TypeRep
+import Coercion
import Var
import VarSet
import TysWiredIn
tcPolyExpr expr res_ty
= addErrCtxt (exprCtxt (unLoc expr)) $
- tcPolyExprNC expr res_ty
+ (do {traceTc (text "tcPolyExpr") ; tcPolyExprNC expr res_ty })
tcPolyExprNC expr res_ty
| isSigmaTy res_ty
- = do { (gen_fn, expr') <- tcGen res_ty emptyVarSet (\_ -> tcPolyExprNC expr)
+ = do { traceTc (text "tcPolyExprNC" <+> ppr res_ty)
+ ; (gen_fn, expr') <- tcGen res_ty emptyVarSet (\_ -> tcPolyExprNC expr)
-- Note the recursive call to tcPolyExpr, because the
-- type may have multiple layers of for-alls
-- E.g. forall a. Eq a => forall b. Ord b => ....
\end{code}
-
%************************************************************************
%* *
tcExpr: the main expression typechecker
tcExpr :: HsExpr Name -> BoxyRhoType -> TcM (HsExpr TcId)
tcExpr (HsVar name) res_ty = tcId (OccurrenceOf name) name res_ty
-tcExpr (HsLit lit) res_ty = do { boxyUnify (hsLitType lit) res_ty
- ; return (HsLit lit) }
+tcExpr (HsLit lit) res_ty = do { let lit_ty = hsLitType lit
+ ; coi <- boxyUnify lit_ty res_ty
+ ; return $ mkHsWrapCoI coi (HsLit lit)
+ }
tcExpr (HsPar expr) res_ty = do { expr' <- tcMonoExpr expr res_ty
; return (HsPar expr') }
go lfun@(L loc fun) args
= do { (fun', args') <- -- addErrCtxt (callCtxt lfun args) $
tcApp fun (length args) (tcArgs lfun args) res_ty
+ ; traceTc (text "tcExpr args': " <+> ppr args')
; return (unLoc (foldl mkHsApp (L loc fun') args')) }
tcExpr (HsLam match) res_ty
= tcDoStmts do_or_lc stmts body res_ty
tcExpr in_expr@(ExplicitList _ exprs) res_ty -- Non-empty list
- = do { elt_ty <- boxySplitListTy res_ty
+ = do { (elt_ty, coi) <- boxySplitListTy res_ty
; exprs' <- mappM (tc_elt elt_ty) exprs
- ; return (ExplicitList elt_ty exprs') }
+ ; return $ mkHsWrapCoI coi (ExplicitList elt_ty exprs') }
where
tc_elt elt_ty expr = tcPolyExpr expr elt_ty
tcExpr in_expr@(ExplicitPArr _ exprs) res_ty -- maybe empty
- = do { [elt_ty] <- boxySplitTyConApp parrTyCon res_ty
+ = do { (elt_ty, coi) <- boxySplitPArrTy res_ty
; exprs' <- mappM (tc_elt elt_ty) exprs
; ifM (null exprs) (zapToMonotype elt_ty)
-- If there are no expressions in the comprehension
-- we must still fill in the box
-- (Not needed for [] and () becuase they happen
-- to parse as data constructors.)
- ; return (ExplicitPArr elt_ty exprs') }
+ ; return $ mkHsWrapCoI coi (ExplicitPArr elt_ty exprs') }
where
tc_elt elt_ty expr = tcPolyExpr expr elt_ty
= do { tvs <- newBoxyTyVars [argTypeKind | e <- exprs]
; let tup_tc = tupleTyCon boxity (length exprs)
tup_res_ty = mkTyConApp tup_tc (mkTyVarTys tvs)
- ; arg_tys <- preSubType tvs (mkVarSet tvs) tup_res_ty res_ty
- ; exprs' <- tcPolyExprs exprs arg_tys
+ ; checkWiredInTyCon tup_tc -- Ensure instances are available
+ ; arg_tys <- preSubType tvs (mkVarSet tvs) tup_res_ty res_ty
+ ; exprs' <- tcPolyExprs exprs arg_tys
; arg_tys' <- mapM refineBox arg_tys
- ; co_fn <- tcFunResTy (tyConName tup_tc) (mkTyConApp tup_tc arg_tys') res_ty
+ ; co_fn <- tcFunResTy (tyConName tup_tc) (mkTyConApp tup_tc arg_tys') res_ty
; return (mkHsWrap co_fn (ExplicitTuple exprs' boxity)) }
tcExpr (HsProc pat cmd) res_ty
- = do { (pat', cmd') <- tcProc pat cmd res_ty
- ; return (HsProc pat' cmd') }
+ = do { (pat', cmd', coi) <- tcProc pat cmd res_ty
+ ; return $ mkHsWrapCoI coi (HsProc pat' cmd') }
tcExpr e@(HsArrApp _ _ _ _ _) _
= failWithTc (vcat [ptext SLIT("The arrow command"), nest 2 (ppr e),
-- don't know how to do the update otherwise.
-tcExpr expr@(RecordUpd record_expr rbinds _ _) res_ty
+tcExpr expr@(RecordUpd record_expr rbinds _ _ _) res_ty
= -- STEP 0
-- Check that the field names are really field names
- ASSERT( notNull rbinds )
let
- field_names = map fst rbinds
+ field_names = hsRecFields rbinds
in
- mappM (tcLookupField . unLoc) field_names `thenM` \ sel_ids ->
+ ASSERT( notNull field_names )
+ mappM tcLookupField field_names `thenM` \ sel_ids ->
-- The renamer has already checked that they
-- are all in scope
let
bad_guys = [ setSrcSpan loc $ addErrTc (notSelector field_name)
- | (L loc field_name, sel_id) <- field_names `zip` sel_ids,
- not (isRecordSelector sel_id) -- Excludes class ops
+ | (fld, sel_id) <- rec_flds rbinds `zip` sel_ids,
+ not (isRecordSelector sel_id), -- Excludes class ops
+ let L loc field_name = hsRecFieldId fld
]
in
checkM (null bad_guys) (sequenceM bad_guys `thenM_` failM) `thenM_`
-- Figure out the tycon and data cons from the first field name
let
-- It's OK to use the non-tc splitters here (for a selector)
- upd_field_lbls = recBindFields rbinds
sel_id : _ = sel_ids
(tycon, _) = recordSelectorFieldLabel sel_id -- We've failed already if
- data_cons = tyConDataCons tycon -- it's not a field label
+ data_cons = tyConDataCons tycon -- it's not a field label
+ -- NB: for a data type family, the tycon is the instance tycon
+
relevant_cons = filter is_relevant data_cons
- is_relevant con = all (`elem` dataConFieldLabels con) upd_field_lbls
+ is_relevant con = all (`elem` dataConFieldLabels con) field_names
in
-- STEP 2
let
-- A constructor is only relevant to this process if
-- it contains *all* the fields that are being updated
- con1 = head relevant_cons -- A representative constructor
- con1_tyvars = dataConUnivTyVars con1
- con1_flds = dataConFieldLabels con1
- con1_arg_tys = dataConOrigArgTys con1
- common_tyvars = exactTyVarsOfTypes [ty | (fld,ty) <- con1_flds `zip` con1_arg_tys
- , not (fld `elem` upd_field_lbls) ]
+ con1 = ASSERT( not (null relevant_cons) ) head relevant_cons -- A representative constructor
+ (con1_tyvars, theta, con1_arg_tys, con1_res_ty) = dataConSig con1
+ con1_flds = dataConFieldLabels con1
+ common_tyvars = exactTyVarsOfTypes [ty | (fld,ty) <- con1_flds `zip` con1_arg_tys
+ , not (fld `elem` field_names) ]
is_common_tv tv = tv `elemVarSet` common_tyvars
| is_common_tv tv = returnM result_inst_ty -- Same as result type
| otherwise = newFlexiTyVarTy (tyVarKind tv) -- Fresh type, of correct kind
in
- tcInstTyVars con1_tyvars `thenM` \ (_, result_inst_tys, inst_env) ->
- zipWithM mk_inst_ty con1_tyvars result_inst_tys `thenM` \ inst_tys ->
+ ASSERT( null theta ) -- Vanilla datacon
+ tcInstTyVars con1_tyvars `thenM` \ (_, result_inst_tys, result_inst_env) ->
+ zipWithM mk_inst_ty con1_tyvars result_inst_tys `thenM` \ scrut_inst_tys ->
- -- STEP 3
- -- Typecheck the update bindings.
- -- (Do this after checking for bad fields in case there's a field that
- -- doesn't match the constructor.)
+ -- STEP 3: Typecheck the update bindings.
+ -- Do this after checking for bad fields in case
+ -- there's a field that doesn't match the constructor.
let
- result_record_ty = mkTyConApp tycon result_inst_tys
- con1_arg_tys' = map (substTy inst_env) con1_arg_tys
+ result_ty = substTy result_inst_env con1_res_ty
+ con1_arg_tys' = map (substTy result_inst_env) con1_arg_tys
in
- tcSubExp result_record_ty res_ty `thenM` \ co_fn ->
+ tcSubExp result_ty res_ty `thenM` \ co_fn ->
tcRecordBinds con1 con1_arg_tys' rbinds `thenM` \ rbinds' ->
- -- STEP 5
- -- Typecheck the expression to be updated
+ -- STEP 5: Typecheck the expression to be updated
let
- record_ty = ASSERT( length inst_tys == tyConArity tycon )
- mkTyConApp tycon inst_tys
+ scrut_inst_env = zipTopTvSubst con1_tyvars scrut_inst_tys
+ scrut_ty = substTy scrut_inst_env con1_res_ty
-- This is one place where the isVanilla check is important
- -- So that inst_tys matches the tycon
+ -- So that inst_tys matches the con1_tyvars
in
- tcMonoExpr record_expr record_ty `thenM` \ record_expr' ->
+ tcMonoExpr record_expr scrut_ty `thenM` \ record_expr' ->
- -- STEP 6
- -- Figure out the LIE we need. We have to generate some
- -- dictionaries for the data type context, since we are going to
- -- do pattern matching over the data cons.
+ -- STEP 6: Figure out the LIE we need.
+ -- We have to generate some dictionaries for the data type context,
+ -- since we are going to do pattern matching over the data cons.
--
- -- What dictionaries do we need? The tyConStupidTheta tells us.
+ -- What dictionaries do we need? The dataConStupidTheta tells us.
let
- theta' = substTheta inst_env (tyConStupidTheta tycon)
+ theta' = substTheta scrut_inst_env (dataConStupidTheta con1)
in
instStupidTheta RecordUpdOrigin theta' `thenM_`
+ -- Step 7: make a cast for the scrutinee, in the case that it's from a type family
+ let scrut_co | Just co_con <- tyConFamilyCoercion_maybe tycon
+ = WpCo $ mkTyConApp co_con scrut_inst_tys
+ | otherwise
+ = idHsWrapper
+ in
-- Phew!
- returnM (mkHsWrap co_fn (RecordUpd record_expr' rbinds' record_ty result_record_ty))
+ returnM (mkHsWrap co_fn (RecordUpd (mkLHsWrap scrut_co record_expr') rbinds'
+ relevant_cons scrut_inst_tys result_inst_tys))
\end{code}
\begin{code}
tcExpr (ArithSeq _ seq@(From expr)) res_ty
- = do { elt_ty <- boxySplitListTy res_ty
+ = do { (elt_ty, coi) <- boxySplitListTy res_ty
; expr' <- tcPolyExpr expr elt_ty
; enum_from <- newMethodFromName (ArithSeqOrigin seq)
elt_ty enumFromName
- ; return (ArithSeq (HsVar enum_from) (From expr')) }
+ ; return $ mkHsWrapCoI coi (ArithSeq (HsVar enum_from) (From expr')) }
tcExpr in_expr@(ArithSeq _ seq@(FromThen expr1 expr2)) res_ty
- = do { elt_ty <- boxySplitListTy res_ty
+ = do { (elt_ty, coi) <- boxySplitListTy res_ty
; expr1' <- tcPolyExpr expr1 elt_ty
; expr2' <- tcPolyExpr expr2 elt_ty
; enum_from_then <- newMethodFromName (ArithSeqOrigin seq)
elt_ty enumFromThenName
- ; return (ArithSeq (HsVar enum_from_then) (FromThen expr1' expr2')) }
-
+ ; return $ mkHsWrapCoI coi
+ (ArithSeq (HsVar enum_from_then) (FromThen expr1' expr2')) }
tcExpr in_expr@(ArithSeq _ seq@(FromTo expr1 expr2)) res_ty
- = do { elt_ty <- boxySplitListTy res_ty
+ = do { (elt_ty, coi) <- boxySplitListTy res_ty
; expr1' <- tcPolyExpr expr1 elt_ty
; expr2' <- tcPolyExpr expr2 elt_ty
; enum_from_to <- newMethodFromName (ArithSeqOrigin seq)
elt_ty enumFromToName
- ; return (ArithSeq (HsVar enum_from_to) (FromTo expr1' expr2')) }
+ ; return $ mkHsWrapCoI coi
+ (ArithSeq (HsVar enum_from_to) (FromTo expr1' expr2')) }
tcExpr in_expr@(ArithSeq _ seq@(FromThenTo expr1 expr2 expr3)) res_ty
- = do { elt_ty <- boxySplitListTy res_ty
+ = do { (elt_ty, coi) <- boxySplitListTy res_ty
; expr1' <- tcPolyExpr expr1 elt_ty
; expr2' <- tcPolyExpr expr2 elt_ty
; expr3' <- tcPolyExpr expr3 elt_ty
; eft <- newMethodFromName (ArithSeqOrigin seq)
elt_ty enumFromThenToName
- ; return (ArithSeq (HsVar eft) (FromThenTo expr1' expr2' expr3')) }
+ ; return $ mkHsWrapCoI coi
+ (ArithSeq (HsVar eft) (FromThenTo expr1' expr2' expr3')) }
tcExpr in_expr@(PArrSeq _ seq@(FromTo expr1 expr2)) res_ty
- = do { [elt_ty] <- boxySplitTyConApp parrTyCon res_ty
+ = do { (elt_ty, coi) <- boxySplitPArrTy res_ty
; expr1' <- tcPolyExpr expr1 elt_ty
; expr2' <- tcPolyExpr expr2 elt_ty
; enum_from_to <- newMethodFromName (PArrSeqOrigin seq)
elt_ty enumFromToPName
- ; return (PArrSeq (HsVar enum_from_to) (FromTo expr1' expr2')) }
+ ; return $ mkHsWrapCoI coi
+ (PArrSeq (HsVar enum_from_to) (FromTo expr1' expr2')) }
tcExpr in_expr@(PArrSeq _ seq@(FromThenTo expr1 expr2 expr3)) res_ty
- = do { [elt_ty] <- boxySplitTyConApp parrTyCon res_ty
+ = do { (elt_ty, coi) <- boxySplitPArrTy res_ty
; expr1' <- tcPolyExpr expr1 elt_ty
; expr2' <- tcPolyExpr expr2 elt_ty
; expr3' <- tcPolyExpr expr3 elt_ty
; eft <- newMethodFromName (PArrSeqOrigin seq)
elt_ty enumFromThenToPName
- ; return (PArrSeq (HsVar eft) (FromThenTo expr1' expr2' expr3')) }
+ ; return $ mkHsWrapCoI coi
+ (PArrSeq (HsVar eft) (FromThenTo expr1' expr2' expr3')) }
tcExpr (PArrSeq _ _) _
= panic "TcExpr.tcMonoExpr: Infinite parallel array!"
-- tcFun work nicely for OpApp and Sections too
; fun' <- instFun orig fun res_subst tv_theta_prs
; co_fn' <- wrapFunResCoercion (substTys res_subst fun_arg_tys) co_fn
+ ; traceTc (text "tcIdApp: " <+> ppr (mkHsWrap co_fn' fun') <+> ppr tv_theta_prs <+> ppr co_fn' <+> ppr fun')
; return (mkHsWrap co_fn' fun', args') }
\end{code}
-- And pack up the results
; fun' <- instFun orig fun res_subst tv_theta_prs
+ ; traceTc (text "tcId yields" <+> ppr (mkHsWrap co_fn fun'))
; return (mkHsWrap co_fn fun') }
-- Note [Push result type in]
instFun orig fun subst tv_theta_prs
= do { let ty_theta_prs' = map subst_pr tv_theta_prs
-
+ ; traceTc (text "instFun" <+> ppr ty_theta_prs')
-- Make two ad-hoc checks
; doStupidChecks fun ty_theta_prs'
-- Now do normal instantiation
- ; go True fun ty_theta_prs' }
+ ; result <- go True fun ty_theta_prs'
+ ; traceTc (text "instFun result" <+> ppr result)
+ ; return result
+ }
where
subst_pr (tvs, theta)
= (substTyVars subst tvs, substTheta subst theta)
- go _ fun [] = return fun
+ go _ fun [] = do {traceTc (text "go _ fun [] returns" <+> ppr fun) ; return fun }
go True (HsVar fun_id) ((tys,theta) : prs)
| want_method_inst theta
- = do { meth_id <- newMethodWithGivenTy orig fun_id tys
+ = do { traceTc (text "go (HsVar fun_id) ((tys,theta) : prs) | want_method_inst theta")
+ ; meth_id <- newMethodWithGivenTy orig fun_id tys
; go False (HsVar meth_id) prs }
-- Go round with 'False' to prevent further use
-- of newMethod: see Note [Multiple instantiation]
go _ fun ((tys, theta) : prs)
= do { co_fn <- instCall orig tys theta
+ ; traceTc (text "go yields co_fn" <+> ppr co_fn)
; go False (HsWrap co_fn fun) prs }
-- See Note [No method sharing]
; qtys' <- mapM refineBox qtys -- Exploit new info
; (qtys'', args') <- go (n+1) qtys' args arg_tys
; return (qtys'', arg':args') }
+ go n qtys args arg_tys = panic "tcArgs"
tcArg :: LHsExpr Name -- The function
-> Int -- and arg number (for error messages)
%************************************************************************
%* *
-\subsection{@tcId@ typchecks an identifier occurrence}
+\subsection{@tcId@ typechecks an identifier occurrence}
%* *
%************************************************************************
ATcId { tct_id = id, tct_type = ty, tct_co = mb_co, tct_level = lvl }
-> do { thLocalId orig id ty lvl
; case mb_co of
- Nothing -> return (HsVar id, ty) -- Wobbly, or no free vars
- Just co -> return (mkHsWrap co (HsVar id), ty) }
+ Unrefineable -> return (HsVar id, ty)
+ Rigid co -> return (mkHsWrap co (HsVar id), ty)
+ Wobbly -> traceTc (text "lookupFun" <+> ppr id) >> return (HsVar id, ty) -- Wobbly, or no free vars
+ WobblyInvisible -> failWithTc (ppr id_name <+> ptext SLIT(" not in scope because it has a wobbly type (solution: add a type annotation)"))
+ }
other -> failWithTc (ppr other <+> ptext SLIT("used where a value identifer was expected"))
}
--------------------------------------
thBrackId orig id ps_var lie_var
- | isExternalName id_name
+ | thTopLevelId id
= -- Top-level identifiers in this module,
-- (which have External Names)
-- are just like the imported case:
-- But we do need to put f into the keep-alive
-- set, because after desugaring the code will
-- only mention f's *name*, not f itself.
- do { keepAliveTc id_name; return id }
+ do { keepAliveTc id; return id }
| otherwise
= -- Nested identifiers, such as 'x' in
-- Update the pending splices
; ps <- readMutVar ps_var
- ; writeMutVar ps_var ((id_name, nlHsApp (nlHsVar lift) (nlHsVar id)) : ps)
+ ; writeMutVar ps_var ((idName id, nlHsApp (nlHsVar lift) (nlHsVar id)) : ps)
; return id } }
- where
- id_name = idName id
#endif /* GHCI */
\end{code}
-> HsRecordBinds Name
-> TcM (HsRecordBinds TcId)
-tcRecordBinds data_con arg_tys rbinds
+tcRecordBinds data_con arg_tys (HsRecFields rbinds dd)
= do { mb_binds <- mappM do_bind rbinds
- ; return (catMaybes mb_binds) }
+ ; return (HsRecFields (catMaybes mb_binds) dd) }
where
flds_w_tys = zipEqual "tcRecordBinds" (dataConFieldLabels data_con) arg_tys
- do_bind (L loc field_lbl, rhs)
+ do_bind fld@(HsRecField { hsRecFieldId = L loc field_lbl, hsRecFieldArg = rhs })
| Just field_ty <- assocMaybe flds_w_tys field_lbl
= addErrCtxt (fieldCtxt field_lbl) $
do { rhs' <- tcPolyExprNC rhs field_ty
; sel_id <- tcLookupField field_lbl
; ASSERT( isRecordSelector sel_id )
- return (Just (L loc sel_id, rhs')) }
+ return (Just (fld { hsRecFieldId = L loc sel_id, hsRecFieldArg = rhs' })) }
| otherwise
= do { addErrTc (badFieldCon data_con field_lbl)
; return Nothing }
not (fl `elem` field_names_used)
]
- field_names_used = recBindFields rbinds
+ field_names_used = hsRecFields rbinds
field_labels = dataConFieldLabels data_con
field_info = zipEqual "missingFields"
= hang (ptext SLIT("In the predicate expression:")) 4 (ppr expr)
nonVanillaUpd tycon
- = vcat [ptext SLIT("Record update for the non-Haskell-98 data type") <+> quotes (ppr tycon)
+ = vcat [ptext SLIT("Record update for the non-Haskell-98 data type")
+ <+> quotes (pprSourceTyCon tycon)
<+> ptext SLIT("is not (yet) supported"),
ptext SLIT("Use pattern-matching instead")]
badFieldsUpd rbinds
= hang (ptext SLIT("No constructor has all these fields:"))
- 4 (pprQuotedList (recBindFields rbinds))
+ 4 (pprQuotedList (hsRecFields rbinds))
naughtyRecordSel sel_id
= ptext SLIT("Cannot use record selector") <+> quotes (ppr sel_id) <+>
= ptext SLIT("Fields of") <+> quotes (ppr con) <+> ptext SLIT("not initialised:")
<+> pprWithCommas ppr fields
-callCtxt fun args
- = ptext SLIT("In the call") <+> parens (ppr (foldl mkHsApp fun args))
+-- callCtxt fun args = ptext SLIT("In the call") <+> parens (ppr (foldl mkHsApp fun args))
#ifdef GHCI
polySpliceErr :: Id -> SDoc
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