\section[TcMatches]{Typecheck some @Matches@}
\begin{code}
-module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda, tcStmts, tcGRHSs ) where
+module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda,
+ tcStmts, tcStmtsAndThen, tcGRHSs
+ ) where
#include "HsVersions.h"
import {-# SOURCE #-} TcExpr( tcExpr )
import HsSyn ( HsBinds(..), Match(..), GRHSs(..), GRHS(..),
- MonoBinds(..), StmtCtxt(..), Stmt(..),
- pprMatch, getMatchLoc, consLetStmt,
- mkMonoBind, collectSigTysFromPats
+ MonoBinds(..), Stmt(..), HsMatchContext(..),
+ pprMatch, getMatchLoc, pprMatchContext, isDoExpr,
+ mkMonoBind, nullMonoBinds, collectSigTysFromPats
)
import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt )
-import TcHsSyn ( TcMatch, TcGRHSs, TcStmt )
+import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds )
import TcMonad
import TcMonoType ( kcHsSigType, tcTyVars, checkSigTyVars, tcHsSigType, sigPatCtxt )
-import Inst ( LIE, plusLIE, emptyLIE, plusLIEs )
-import TcEnv ( TcId, tcExtendTyVarEnv, tcExtendLocalValEnv, tcExtendGlobalTyVars )
-import TcPat ( tcPat, tcPatBndr_NoSigs, polyPatSig )
+import Inst ( LIE, isEmptyLIE, plusLIE, emptyLIE, plusLIEs, lieToList )
+import TcEnv ( TcId, tcLookupLocalIds, tcExtendTyVarEnv, tcExtendLocalValEnv, tcExtendGlobalTyVars )
+import TcPat ( tcPat, tcMonoPatBndr, polyPatSig )
import TcType ( TcType, newTyVarTy )
import TcBinds ( tcBindsAndThen )
-import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns )
-import TcUnify ( unifyFunTy, unifyTauTy, unifyListTy )
+import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns )
+import TcUnify ( unifyFunTy, unifyTauTy )
import Name ( Name )
-import TysWiredIn ( boolTy )
-
+import TysWiredIn ( boolTy, mkListTy )
+import Id ( idType )
import BasicTypes ( RecFlag(..) )
-import Type ( tyVarsOfType, isTauTy, mkArrowKind, mkAppTy, mkFunTy,
- liftedTypeKind, openTypeKind )
-import SrcLoc ( SrcLoc )
+import Type ( tyVarsOfType, isTauTy, mkFunTy,
+ liftedTypeKind, openTypeKind, splitSigmaTy )
import VarSet
import Var ( Id )
import Bag
returnTc (scrut_ty, matches', lie)
tcMatchLambda :: RenamedMatch -> TcType -> TcM (TcMatch, LIE)
-tcMatchLambda match res_ty = tcMatch [] match res_ty LambdaBody
+tcMatchLambda match res_ty = tcMatch [] match res_ty LambdaExpr
\end{code}
tcMatches :: [(Name,Id)]
-> [RenamedMatch]
-> TcType
- -> StmtCtxt
+ -> HsMatchContext
-> TcM ([TcMatch], LIE)
tcMatches xve matches expected_ty fun_or_case
-> RenamedMatch
-> TcType -- Expected result-type of the Match.
-- Early unification with this guy gives better error messages
- -> StmtCtxt
+ -> HsMatchContext
-> TcM (TcMatch, LIE)
tcMatch xve1 match@(Match sig_tvs pats maybe_rhs_sig grhss) expected_ty ctxt
let
xve2 = bagToList pat_bndrs
pat_ids = map snd xve2
- ex_tv_list = bagToList ex_tvs
in
-- STEP 2: Check that the remaining "expected type" is not a rank-2 type
)) `thenTc` \ (grhss', lie_req2) ->
-- STEP 5: Check for existentially bound type variables
- tcExtendGlobalTyVars (tyVarsOfType rhs_ty) (
- tcAddErrCtxtM (sigPatCtxt ex_tv_list pat_ids) $
- checkSigTyVars ex_tv_list emptyVarSet `thenTc` \ zonked_ex_tvs ->
- tcSimplifyAndCheck
- (text ("the existential context of a data constructor"))
- (mkVarSet zonked_ex_tvs)
- lie_avail (lie_req1 `plusLIE` lie_req2)
- ) `thenTc` \ (lie_req', ex_binds) ->
-
- -- STEP 6 In case there are any polymorpic, overloaded binders in the pattern
- -- (which can happen in the case of rank-2 type signatures, or data constructors
- -- with polymorphic arguments), we must do a bindInstsOfLocalFns here
- bindInstsOfLocalFuns lie_req' pat_ids `thenTc` \ (lie_req'', inst_binds) ->
+ tcCheckExistentialPat pat_ids ex_tvs lie_avail
+ (lie_req1 `plusLIE` lie_req2)
+ rhs_ty `thenTc` \ (lie_req', ex_binds) ->
-- Phew! All done.
let
- grhss'' = glue_on Recursive ex_binds $
- glue_on Recursive inst_binds grhss'
+ match' = Match [] pats' Nothing (glue_on Recursive ex_binds grhss')
in
- returnTc (pat_ids, (Match [] pats' Nothing grhss'', lie_req''))
+ returnTc (pat_ids, (match', lie_req'))
-- glue_on just avoids stupid dross
glue_on _ EmptyMonoBinds grhss = grhss -- The common case
= GRHSs grhss (mkMonoBind mbinds [] is_rec `ThenBinds` binds) ty
tcGRHSs :: RenamedGRHSs
- -> TcType -> StmtCtxt
+ -> TcType -> HsMatchContext
-> TcM (TcGRHSs, LIE)
tcGRHSs (GRHSs grhss binds _) expected_ty ctxt
returnTc (GRHSs grhss' EmptyBinds (Just expected_ty), plusLIEs lies)
tc_grhs (GRHS guarded locn)
- = tcAddSrcLoc locn $
- tcStmts ctxt (\ty -> ty) expected_ty locn guarded
- `thenTc` \ ((guarded', _), lie) ->
+ = tcAddSrcLoc locn $
+ tcStmts ctxt (\ty -> ty, expected_ty) guarded `thenTc` \ (guarded', lie) ->
returnTc (GRHS guarded' locn, lie)
+
+
+tcCheckExistentialPat :: [TcId] -- Ids bound by this pattern
+ -> Bag TcTyVar -- Existentially quantified tyvars bound by pattern
+ -> LIE -- and context
+ -> LIE -- Required context
+ -> TcType -- and result type; vars in here must not escape
+ -> TcM (LIE, TcDictBinds) -- LIE to float out and dict bindings
+tcCheckExistentialPat ids ex_tvs lie_avail lie_req result_ty
+ | isEmptyBag ex_tvs && all not_overloaded ids
+ -- Short cut for case when there are no existentials
+ -- and no polymorphic overloaded variables
+ -- e.g. f :: (forall a. Ord a => a -> a) -> Int -> Int
+ -- f op x = ....
+ -- Here we must discharge op Methods
+ = ASSERT( isEmptyLIE lie_avail )
+ returnTc (lie_req, EmptyMonoBinds)
+
+ | otherwise
+ = tcExtendGlobalTyVars (tyVarsOfType result_ty) $
+ tcAddErrCtxtM (sigPatCtxt tv_list ids) $
+
+ -- In case there are any polymorpic, overloaded binders in the pattern
+ -- (which can happen in the case of rank-2 type signatures, or data constructors
+ -- with polymorphic arguments), we must do a bindInstsOfLocalFns here
+ bindInstsOfLocalFuns lie_req ids `thenTc` \ (lie1, inst_binds) ->
+
+ -- Deal with overloaded functions bound by the pattern
+ tcSimplifyCheck doc tv_list
+ (lieToList lie_avail) lie1 `thenTc` \ (lie2, dict_binds) ->
+ checkSigTyVars tv_list emptyVarSet `thenTc_`
+
+ returnTc (lie2, dict_binds `AndMonoBinds` inst_binds)
+ where
+ doc = text ("the existential context of a data constructor")
+ tv_list = bagToList ex_tvs
+ not_overloaded id = case splitSigmaTy (idType id) of
+ (_, theta, _) -> null theta
\end{code}
tcMatchPats (pat:pats) expected_ty
= unifyFunTy expected_ty `thenTc` \ (arg_ty, rest_ty) ->
- tcPat tcPatBndr_NoSigs pat arg_ty `thenTc` \ (pat', lie_req, pat_tvs, pat_ids, lie_avail) ->
+ tcPat tcMonoPatBndr pat arg_ty `thenTc` \ (pat', lie_req, pat_tvs, pat_ids, lie_avail) ->
tcMatchPats pats rest_ty `thenTc` \ (rhs_ty, pats', lie_reqs, pats_tvs, pats_ids, lie_avails) ->
returnTc ( rhs_ty,
pat':pats',
%* *
%************************************************************************
+Typechecking statements is rendered a bit tricky by parallel list comprehensions:
+
+ [ (g x, h x) | ... ; let g v = ...
+ | ... ; let h v = ... ]
+
+It's possible that g,h are overloaded, so we need to feed the LIE from the
+(g x, h x) up through both lots of bindings (so we get the bindInstsOfLocalFuns).
+Similarly if we had an existential pattern match:
+
+ data T = forall a. Show a => C a
+
+ [ (show x, show y) | ... ; C x <- ...
+ | ... ; C y <- ... ]
+
+Then we need the LIE from (show x, show y) to be simplified against
+the bindings for x and y.
+
+It's difficult to do this in parallel, so we rely on the renamer to
+ensure that g,h and x,y don't duplicate, and simply grow the environment.
+So the binders of the first parallel group will be in scope in the second
+group. But that's fine; there's no shadowing to worry about.
\begin{code}
-tcParStep src_loc stmts
- = newTyVarTy (mkArrowKind liftedTypeKind liftedTypeKind) `thenTc` \ m ->
- newTyVarTy liftedTypeKind `thenTc` \ elt_ty ->
- unifyListTy (mkAppTy m elt_ty) `thenTc_`
-
- tcStmts ListComp (mkAppTy m) elt_ty src_loc stmts `thenTc` \ ((stmts', val_env), stmts_lie) ->
- returnTc (stmts', val_env, stmts_lie)
-
-tcStmts :: StmtCtxt
- -> (TcType -> TcType) -- m, the relationship type of pat and rhs in pat <- rhs
- -> TcType -- elt_ty, where type of the comprehension is (m elt_ty)
- -> SrcLoc
+tcStmts do_or_lc m_ty stmts
+ = tcStmtsAndThen (:) do_or_lc m_ty stmts (returnTc ([], emptyLIE))
+
+tcStmtsAndThen
+ :: (TcStmt -> thing -> thing) -- Combiner
+ -> HsMatchContext
+ -> (TcType -> TcType, TcType) -- m, the relationship type of pat and rhs in pat <- rhs
+ -- elt_ty, where type of the comprehension is (m elt_ty)
-> [RenamedStmt]
- -> TcM (([TcStmt], [(Name, TcId)]), LIE)
-
-tcStmts do_or_lc m elt_ty loc (ParStmtOut bndrstmtss : stmts)
- = let stmtss = map snd bndrstmtss in
- mapAndUnzip3Tc (tcParStep loc) stmtss `thenTc` \ (stmtss', val_envs, lies) ->
- let outstmts = zip (map (map snd) val_envs) stmtss'
- lie = plusLIEs lies
- new_val_env = concat val_envs
- in
- tcExtendLocalValEnv new_val_env (
- tcStmts do_or_lc m elt_ty loc stmts) `thenTc` \ ((stmts', rest_val_env), stmts_lie) ->
- returnTc ((ParStmtOut outstmts : stmts', rest_val_env ++ new_val_env), lie `plusLIE` stmts_lie)
-
-tcStmts do_or_lc m elt_ty loc (stmt@(ReturnStmt exp) : stmts)
- = ASSERT( null stmts )
- tcSetErrCtxt (stmtCtxt do_or_lc stmt) $
- tcExpr exp elt_ty `thenTc` \ (exp', exp_lie) ->
- returnTc (([ReturnStmt exp'], []), exp_lie)
-
- -- ExprStmt at the end
-tcStmts do_or_lc m elt_ty loc [stmt@(ExprStmt exp src_loc)]
- = tcSetErrCtxt (stmtCtxt do_or_lc stmt) $
- tcExpr exp (m elt_ty) `thenTc` \ (exp', exp_lie) ->
- returnTc (([ExprStmt exp' src_loc], []), exp_lie)
-
- -- ExprStmt not at the end
-tcStmts do_or_lc m elt_ty loc (stmt@(ExprStmt exp src_loc) : stmts)
- = ASSERT( isDoStmt do_or_lc )
- tcAddSrcLoc src_loc (
- tcSetErrCtxt (stmtCtxt do_or_lc stmt) $
- -- exp has type (m tau) for some tau (doesn't matter what)
- newTyVarTy openTypeKind `thenNF_Tc` \ any_ty ->
- tcExpr exp (m any_ty)
- ) `thenTc` \ (exp', exp_lie) ->
- tcStmts do_or_lc m elt_ty loc stmts `thenTc` \ ((stmts', rest_val_env), stmts_lie) ->
- returnTc ((ExprStmt exp' src_loc : stmts', rest_val_env),
- exp_lie `plusLIE` stmts_lie)
-
-tcStmts do_or_lc m elt_ty loc (stmt@(GuardStmt exp src_loc) : stmts)
- = ASSERT( not (isDoStmt do_or_lc) )
- tcSetErrCtxt (stmtCtxt do_or_lc stmt) (
- tcAddSrcLoc src_loc $
- tcExpr exp boolTy
- ) `thenTc` \ (exp', exp_lie) ->
- tcStmts do_or_lc m elt_ty loc stmts `thenTc` \ ((stmts', rest_val_env), stmts_lie) ->
- -- ZZ is this right?
- returnTc ((GuardStmt exp' src_loc : stmts', rest_val_env),
- exp_lie `plusLIE` stmts_lie)
-
-tcStmts do_or_lc m elt_ty loc (stmt@(BindStmt pat exp src_loc) : stmts)
+ -> TcM (thing, LIE)
+ -> TcM (thing, LIE)
+
+ -- Base case
+tcStmtsAndThen combine do_or_lc m_ty [] do_next
+ = do_next
+
+ -- LetStmt
+tcStmtsAndThen combine do_or_lc m_ty (LetStmt binds : stmts) do_next
+ = tcBindsAndThen -- No error context, but a binding group is
+ (glue_binds combine) -- rather a large thing for an error context anyway
+ binds
+ (tcStmtsAndThen combine do_or_lc m_ty stmts do_next)
+
+ -- BindStmt
+tcStmtsAndThen combine do_or_lc m_ty@(m,elt_ty) (stmt@(BindStmt pat exp src_loc) : stmts) do_next
= tcAddSrcLoc src_loc (
tcSetErrCtxt (stmtCtxt do_or_lc stmt) $
- newTyVarTy liftedTypeKind `thenNF_Tc` \ pat_ty ->
- tcPat tcPatBndr_NoSigs pat pat_ty `thenTc` \ (pat', pat_lie, pat_tvs, pat_ids, avail) ->
- tcExpr exp (m pat_ty) `thenTc` \ (exp', exp_lie) ->
+ newTyVarTy liftedTypeKind `thenNF_Tc` \ pat_ty ->
+ tcPat tcMonoPatBndr pat pat_ty `thenTc` \ (pat', pat_lie, pat_tvs, pat_ids, avail) ->
+ tcExpr exp (m pat_ty) `thenTc` \ (exp', exp_lie) ->
returnTc (pat', exp',
pat_lie `plusLIE` exp_lie,
pat_tvs, pat_ids, avail)
let
new_val_env = bagToList pat_bndrs
pat_ids = map snd new_val_env
- pat_tv_list = bagToList pat_tvs
in
-- Do the rest; we don't need to add the pat_tvs to the envt
-- because they all appear in the pat_ids's types
tcExtendLocalValEnv new_val_env (
- tcStmts do_or_lc m elt_ty loc stmts
- ) `thenTc` \ ((stmts', rest_val_env), stmts_lie) ->
-
+ tcStmtsAndThen combine do_or_lc m_ty stmts do_next
+ ) `thenTc` \ (thing, stmts_lie) ->
-- Reinstate context for existential checks
- tcSetErrCtxt (stmtCtxt do_or_lc stmt) $
- tcExtendGlobalTyVars (tyVarsOfType (m elt_ty)) $
- tcAddErrCtxtM (sigPatCtxt pat_tv_list pat_ids) $
-
- checkSigTyVars pat_tv_list emptyVarSet `thenTc` \ zonked_pat_tvs ->
-
- tcSimplifyAndCheck
- (text ("the existential context of a data constructor"))
- (mkVarSet zonked_pat_tvs)
- lie_avail stmts_lie `thenTc` \ (final_lie, dict_binds) ->
-
- -- ZZ we have to be sure that concating the val_env lists preserves
- -- shadowing properly...
- returnTc ((BindStmt pat' exp' src_loc :
- consLetStmt (mkMonoBind dict_binds [] Recursive) stmts',
- rest_val_env ++ new_val_env),
+ tcSetErrCtxt (stmtCtxt do_or_lc stmt) $
+ tcCheckExistentialPat pat_ids pat_tvs lie_avail
+ stmts_lie (m elt_ty) `thenTc` \ (final_lie, dict_binds) ->
+
+ returnTc (combine (BindStmt pat' exp' src_loc)
+ (glue_binds combine Recursive dict_binds thing),
lie_req `plusLIE` final_lie)
-tcStmts do_or_lc m elt_ty loc (LetStmt binds : stmts)
- = tcBindsAndThen -- No error context, but a binding group is
- combine -- rather a large thing for an error context anyway
- binds
- (tcStmts do_or_lc m elt_ty loc stmts) `thenTc` \ ((stmts', rest_val_env), lie) ->
- -- ZZ fix val_env
- returnTc ((stmts', rest_val_env), lie)
- where
- combine is_rec binds' (stmts', val_env) = (consLetStmt (mkMonoBind binds' [] is_rec) stmts', undefined)
-tcStmts do_or_lc m elt_ty loc [] = returnTc (([], []), emptyLIE)
+ -- ParStmt
+tcStmtsAndThen combine do_or_lc m_ty (ParStmtOut bndr_stmts_s : stmts) do_next
+ = loop bndr_stmts_s `thenTc` \ ((pairs', thing), lie) ->
+ returnTc (combine (ParStmtOut pairs') thing, lie)
+ where
+ loop []
+ = tcStmtsAndThen combine do_or_lc m_ty stmts do_next `thenTc` \ (thing, stmts_lie) ->
+ returnTc (([], thing), stmts_lie)
+
+ loop ((bndrs,stmts) : pairs)
+ = tcStmtsAndThen
+ combine_par ListComp (mkListTy, not_required) stmts
+ (tcLookupLocalIds bndrs `thenNF_Tc` \ bndrs' ->
+ loop pairs `thenTc` \ ((pairs', thing), lie) ->
+ returnTc (([], (bndrs', pairs', thing)), lie)) `thenTc` \ ((stmts', (bndrs', pairs', thing)), lie) ->
+
+ returnTc ( ((bndrs',stmts') : pairs', thing), lie)
+
+ combine_par stmt (stmts, thing) = (stmt:stmts, thing)
+ not_required = panic "tcStmtsAndThen: elt_ty"
+
+ -- The simple-statment case
+tcStmtsAndThen combine do_or_lc m_ty (stmt@(ExprStmt exp locn):stmts) do_next
+ = tcSetErrCtxt (stmtCtxt do_or_lc stmt) (
+ tcExprStmt do_or_lc m_ty exp (null stmts)
+ ) `thenTc` \ (exp', stmt_lie) ->
+
+ tcStmtsAndThen combine do_or_lc m_ty stmts do_next `thenTc` \ (thing, stmts_lie) ->
-isDoStmt DoStmt = True
-isDoStmt other = False
+ returnTc (combine (ExprStmt exp' locn) thing,
+ stmt_lie `plusLIE` stmts_lie)
+
+
+------------------------------
+ -- ExprStmt; see comments with HsExpr.HsStmt
+ -- for meaning of ExprStmt
+tcExprStmt do_or_lc (m, res_elt_ty) exp is_last_stmt
+ = compute_expr_ty `thenNF_Tc` \ expr_ty ->
+ tcExpr exp expr_ty
+ where
+ compute_expr_ty
+ | is_last_stmt = if isDoExpr do_or_lc then
+ returnNF_Tc (m res_elt_ty)
+ else
+ returnNF_Tc res_elt_ty
+
+ | otherwise = if isDoExpr do_or_lc then
+ newTyVarTy openTypeKind `thenNF_Tc` \ any_ty ->
+ returnNF_Tc (m any_ty)
+ else
+ returnNF_Tc boolTy
+
+------------------------------
+glue_binds combine is_rec binds thing
+ | nullMonoBinds binds = thing
+ | otherwise = combine (LetStmt (mkMonoBind binds [] is_rec)) thing
\end{code}
where
ppr_fun = ppr fun
-matchCtxt LambdaBody match
+matchCtxt LambdaExpr match
= hang (ptext SLIT("In the lambda expression"))
4 (pprMatch (True, empty) match)
lurkingRank2SigErr
= ptext SLIT("Too few explicit arguments when defining a function with a rank-2 type")
-stmtCtxt do_or_lc stmt
- = hang (ptext SLIT("In") <+> what <> colon)
- 4 (ppr stmt)
- where
- what = case do_or_lc of
- ListComp -> ptext SLIT("a list-comprehension qualifier")
- DoStmt -> ptext SLIT("a do statement")
- PatBindRhs -> thing <+> ptext SLIT("a pattern binding")
- FunRhs f -> thing <+> ptext SLIT("an equation for") <+> quotes (ppr f)
- CaseAlt -> thing <+> ptext SLIT("a case alternative")
- LambdaBody -> thing <+> ptext SLIT("a lambda abstraction")
- thing = case stmt of
- BindStmt _ _ _ -> ptext SLIT("a pattern guard for")
- GuardStmt _ _ -> ptext SLIT("a guard for")
- ExprStmt _ _ -> ptext SLIT("the right-hand side of")
+stmtCtxt do_or_lc stmt = hang (pprMatchContext do_or_lc <> colon) 4 (ppr stmt)
\end{code}
projects / ghc-hetmet.git / blobdiff