\section[TcMatches]{Typecheck some @Matches@}
\begin{code}
-module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda,
- tcStmts, tcStmtsAndThen, tcGRHSs
+module TcMatches ( tcMatchesFun, tcGRHSsPat, tcMatchesCase, tcMatchLambda,
+ matchCtxt,
+ tcDoStmts, tcStmtsAndThen, tcStmts, tcThingWithSig,
+ tcMatchPats,
+ TcStmtCtxt(..), TcMatchCtxt(..)
) where
#include "HsVersions.h"
-import {-# SOURCE #-} TcExpr( tcExpr )
+import {-# SOURCE #-} TcExpr( tcCheckRho, tcMonoExpr )
-import HsSyn ( HsBinds(..), Match(..), GRHSs(..), GRHS(..),
- MonoBinds(..), Stmt(..), HsMatchContext(..), HsDoContext(..),
- pprMatch, getMatchLoc, pprMatchContext, isDoExpr,
- mkMonoBind, nullMonoBinds, collectSigTysFromPats
+import HsSyn ( HsExpr(..), LHsExpr, HsBindGroup(..),
+ Match(..), LMatch, GRHSs(..), GRHS(..),
+ Stmt(..), LStmt, HsMatchContext(..), HsStmtContext(..),
+ ReboundNames, LPat,
+ pprMatch, isDoExpr,
+ pprMatchContext, pprStmtContext, pprStmtResultContext,
+ collectSigTysFromPats, glueBindsOnGRHSs
)
-import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt, RenamedPat, RenamedMatchContext )
-import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TypecheckedPat )
+import TcHsSyn ( ExprCoFn, TcDictBinds, isIdCoercion, (<$>), (<.>) )
-import TcMonad
-import TcMonoType ( tcAddScopedTyVars, tcHsSigType, UserTypeCtxt(..) )
-import Inst ( LIE, isEmptyLIE, plusLIE, emptyLIE, plusLIEs, lieToList )
-import TcEnv ( TcId, tcLookupLocalIds, tcExtendLocalValEnv, tcExtendGlobalTyVars )
+import TcRnMonad
+import TcHsType ( tcAddScopedTyVars, tcHsSigType, UserTypeCtxt(..) )
+import Inst ( tcSyntaxName, tcInstCall )
+import TcEnv ( TcId, tcLookupLocalIds, tcLookupId, tcExtendLocalValEnv, tcExtendLocalValEnv2 )
import TcPat ( tcPat, tcMonoPatBndr )
-import TcMType ( newTyVarTy )
-import TcType ( TcType, TcTyVar, tyVarsOfType,
- mkFunTy, isOverloadedTy, liftedTypeKind, openTypeKind )
+import TcMType ( newTyVarTy, newTyVarTys, zonkTcType )
+import TcType ( TcType, TcTyVar, TcSigmaType, TcRhoType,
+ tyVarsOfTypes, tidyOpenTypes, isSigmaTy, typeKind,
+ mkFunTy, isOverloadedTy, liftedTypeKind, openTypeKind,
+ mkArrowKind, mkAppTy )
import TcBinds ( tcBindsAndThen )
-import TcUnify ( subFunTy, checkSigTyVars, tcSub, isIdCoercion, (<$>), sigPatCtxt )
+import TcUnify ( Expected(..), newHole, zapExpectedType, zapExpectedBranches, readExpectedType,
+ unifyTauTy, subFunTys, unifyPArrTy, unifyListTy, unifyFunTy,
+ checkSigTyVarsWrt, tcSubExp, tcGen )
import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns )
import Name ( Name )
-import TysWiredIn ( boolTy )
-import Id ( idType )
+import TysWiredIn ( boolTy, mkListTy, mkPArrTy )
+import Id ( idType, mkLocalId )
+import CoreFVs ( idFreeTyVars )
import BasicTypes ( RecFlag(..) )
import VarSet
-import Var ( Id )
import Bag
-import Util ( isSingleton )
+import Util ( isSingleton, notNull )
import Outputable
+import SrcLoc ( Located(..), noLoc )
import List ( nub )
\end{code}
same number of arguments before using @tcMatches@ to do the work.
\begin{code}
-tcMatchesFun :: [(Name,Id)] -- Bindings for the variables bound in this group
- -> Name
- -> TcType -- Expected type
- -> [RenamedMatch]
- -> TcM ([TcMatch], LIE)
+tcMatchesFun :: Name
+ -> [LMatch Name]
+ -> Expected TcRhoType -- Expected type
+ -> TcM [LMatch TcId]
-tcMatchesFun xve fun_name expected_ty matches@(first_match:_)
+tcMatchesFun fun_name matches@(first_match:_) expected_ty
= -- Check that they all have the same no of arguments
- -- Set the location to that of the first equation, so that
+ -- Location is in the monad, set the caller so that
-- any inter-equation error messages get some vaguely
-- sensible location. Note: we have to do this odd
-- ann-grabbing, because we don't always have annotations in
-- hand when we call tcMatchesFun...
- tcAddSrcLoc (getMatchLoc first_match) (
- checkTc (sameNoOfArgs matches)
- (varyingArgsErr fun_name matches)
- ) `thenTc_`
+ checkTc (sameNoOfArgs matches)
+ (varyingArgsErr fun_name matches) `thenM_`
-- ToDo: Don't use "expected" stuff if there ain't a type signature
-- because inconsistency between branches
-- may show up as something wrong with the (non-existent) type signature
- -- No need to zonk expected_ty, because subFunTy does that on the fly
- tcMatches xve (FunRhs fun_name) matches expected_ty
+ -- No need to zonk expected_ty, because subFunTys does that on the fly
+ tcMatches match_ctxt matches expected_ty
+ where
+ match_ctxt = MC { mc_what = FunRhs fun_name,
+ mc_body = tcMonoExpr }
\end{code}
@tcMatchesCase@ doesn't do the argument-count check because the
parser guarantees that each equation has exactly one argument.
\begin{code}
-tcMatchesCase :: [RenamedMatch] -- The case alternatives
- -> TcType -- Type of whole case expressions
- -> TcM (TcType, -- Inferred type of the scrutinee
- [TcMatch], -- Translated alternatives
- LIE)
-
-tcMatchesCase matches expr_ty
- = newTyVarTy openTypeKind `thenNF_Tc` \ scrut_ty ->
- tcMatches [] CaseAlt matches (mkFunTy scrut_ty expr_ty) `thenTc` \ (matches', lie) ->
- returnTc (scrut_ty, matches', lie)
-
-tcMatchLambda :: RenamedMatch -> TcType -> TcM (TcMatch, LIE)
-tcMatchLambda match res_ty = tcMatch [] LambdaExpr match res_ty
+tcMatchesCase :: TcMatchCtxt -- Case context
+ -> [LMatch Name] -- The case alternatives
+ -> Expected TcRhoType -- Type of whole case expressions
+ -> TcM (TcRhoType, -- Inferred type of the scrutinee
+ [LMatch TcId]) -- Translated alternatives
+
+tcMatchesCase ctxt matches (Check expr_ty)
+ = newTyVarTy openTypeKind `thenM` \ scrut_ty ->
+ -- openTypeKind because the scrutinee can be an unboxed type
+ tcMatches ctxt matches (Check (mkFunTy scrut_ty expr_ty)) `thenM` \ matches' ->
+ returnM (scrut_ty, matches')
+
+tcMatchesCase ctxt matches (Infer hole)
+ = newHole `thenM` \ fun_hole ->
+ tcMatches ctxt matches (Infer fun_hole) `thenM` \ matches' ->
+ readMutVar fun_hole `thenM` \ fun_ty ->
+ -- The result of tcMatches is bound to be a function type
+ unifyFunTy fun_ty `thenM` \ (scrut_ty, res_ty) ->
+ writeMutVar hole res_ty `thenM_`
+ returnM (scrut_ty, matches')
+
+
+tcMatchLambda :: LMatch Name -> Expected TcRhoType -> TcM (LMatch TcId)
+tcMatchLambda match res_ty = tcMatch match_ctxt res_ty match
+ where
+ match_ctxt = MC { mc_what = LambdaExpr,
+ mc_body = tcMonoExpr }
\end{code}
+@tcGRHSsPat@ typechecks @[GRHSs]@ that occur in a @PatMonoBind@.
\begin{code}
-tcMatches :: [(Name,Id)]
- -> RenamedMatchContext
- -> [RenamedMatch]
- -> TcType
- -> TcM ([TcMatch], LIE)
-
-tcMatches xve fun_or_case matches expected_ty
- = mapAndUnzipTc tc_match matches `thenTc` \ (matches, lies) ->
- returnTc (matches, plusLIEs lies)
+tcGRHSsPat :: GRHSs Name
+ -> Expected TcRhoType
+ -> TcM (GRHSs TcId)
+tcGRHSsPat grhss exp_ty = tcGRHSs match_ctxt grhss exp_ty
where
- tc_match match = tcMatch xve fun_or_case match expected_ty
+ match_ctxt = MC { mc_what = PatBindRhs,
+ mc_body = tcMonoExpr }
+\end{code}
+
+\begin{code}
+data TcMatchCtxt -- c.f. TcStmtCtxt, also in this module
+ = MC { mc_what :: HsMatchContext Name, -- What kind of thing this is
+ mc_body :: LHsExpr Name -- Type checker for a body of an alternative
+ -> Expected TcRhoType
+ -> TcM (LHsExpr TcId) }
+
+tcMatches :: TcMatchCtxt
+ -> [LMatch Name]
+ -> Expected TcRhoType
+ -> TcM [LMatch TcId]
+
+tcMatches ctxt matches exp_ty
+ = -- If there is more than one branch, and exp_ty is a 'hole',
+ -- all branches must be types, not type schemes, otherwise the
+ -- order in which we check them would affect the result.
+ zapExpectedBranches matches exp_ty `thenM` \ exp_ty' ->
+ mappM (tcMatch ctxt exp_ty') matches
\end{code}
%************************************************************************
\begin{code}
-tcMatch :: [(Name,Id)]
- -> RenamedMatchContext
- -> RenamedMatch
- -> TcType -- Expected result-type of the Match.
+tcMatch :: TcMatchCtxt
+ -> Expected TcRhoType -- Expected result-type of the Match.
-- Early unification with this guy gives better error messages
-- We regard the Match as having type
-- (ty1 -> ... -> tyn -> result_ty)
-- where there are n patterns.
- -> TcM (TcMatch, LIE)
+ -> LMatch Name
+ -> TcM (LMatch TcId)
-tcMatch xve1 ctxt match@(Match pats maybe_rhs_sig grhss) expected_ty
- = tcAddSrcLoc (getMatchLoc match) $ -- At one stage I removed this;
- tcAddErrCtxt (matchCtxt ctxt match) $ -- I'm not sure why, so I put it back
-
- tcMatchPats pats expected_ty tc_grhss `thenTc` \ ((pats', grhss'), lie, ex_binds) ->
- returnTc (Match pats' Nothing (glue_on Recursive ex_binds grhss'), lie)
+tcMatch ctxt exp_ty match = wrapLocM (tc_match ctxt exp_ty) match
- where
- tc_grhss pats' rhs_ty
- = tcExtendLocalValEnv xve1 $
+tc_match ctxt expected_ty match@(Match pats maybe_rhs_sig grhss)
+ = addErrCtxt (matchCtxt (mc_what ctxt) match) $ -- I'm not sure why, so I put it back
+ subFunTys pats expected_ty $ \ pats_w_tys rhs_ty ->
+ -- This is the unique place we call subFunTys
+ -- The point is that if expected_y is a "hole", we want
+ -- to make arg_ty and rest_ty as "holes" too.
+ tcMatchPats pats_w_tys rhs_ty (tc_grhss rhs_ty) `thenM` \ (pats', grhss', ex_binds) ->
+ returnM (Match pats' Nothing (glueBindsOnGRHSs ex_binds grhss'))
- -- Deal with the result signature
- case maybe_rhs_sig of
- Nothing -> tcGRHSs ctxt grhss rhs_ty `thenTc` \ (grhss', lie) ->
- returnTc ((pats', grhss'), lie)
+ where
+ tc_grhss rhs_ty
+ = case maybe_rhs_sig of -- Deal with the result signature
+ Nothing -> tcGRHSs ctxt grhss rhs_ty
Just sig -> tcAddScopedTyVars [sig] $
-- Bring into scope the type variables in the signature
- tcHsSigType ResSigCtxt sig `thenTc` \ sig_ty ->
- tcGRHSs ctxt grhss sig_ty `thenTc` \ (grhss', lie1) ->
- tcSub rhs_ty sig_ty `thenTc` \ (co_fn, lie2) ->
- returnTc ((pats', lift_grhss co_fn rhs_ty grhss'),
- lie1 `plusLIE` lie2)
-
--- lift_grhss pushes the coercion down to the right hand sides,
--- because there is no convenient place to hang it otherwise.
-lift_grhss co_fn rhs_ty grhss
- | isIdCoercion co_fn = grhss
+ tcHsSigType ResSigCtxt sig `thenM` \ sig_ty ->
+ tcThingWithSig sig_ty (tcGRHSs ctxt grhss . Check) rhs_ty `thenM` \ (co_fn, grhss') ->
+
+ -- Pushes the coercion down to the right hand sides,
+ -- because there is no convenient place to hang it otherwise.
+ if isIdCoercion co_fn then
+ returnM grhss'
+ else
+ readExpectedType rhs_ty `thenM` \ rhs_ty' ->
+ returnM (lift_grhss co_fn rhs_ty' grhss')
+
lift_grhss co_fn rhs_ty (GRHSs grhss binds ty)
- = GRHSs (map lift_grhs grhss) binds rhs_ty -- Change the type, since we
+ = GRHSs (map (fmap lift_grhs) grhss) binds rhs_ty -- Change the type, since the coercion does
where
- lift_grhs (GRHS stmts loc) = GRHS (map lift_stmt stmts) loc
+ lift_grhs (GRHS stmts) = GRHS (map lift_stmt stmts)
- lift_stmt (ResultStmt e l) = ResultStmt (co_fn <$> e) l
- lift_stmt stmt = stmt
-
--- glue_on just avoids stupid dross
-glue_on _ EmptyMonoBinds grhss = grhss -- The common case
-glue_on is_rec mbinds (GRHSs grhss binds ty)
- = GRHSs grhss (mkMonoBind mbinds [] is_rec `ThenBinds` binds) ty
-
+ lift_stmt (L loc (ResultStmt e)) = L loc (ResultStmt (fmap (co_fn <$>) e))
+ lift_stmt stmt = stmt
+
+tcGRHSs :: TcMatchCtxt -> GRHSs Name
+ -> Expected TcRhoType
+ -> TcM (GRHSs TcId)
+
+ -- Special case when there is just one equation with a degenerate
+ -- guard; then we pass in the full Expected type, so that we get
+ -- good inference from simple things like
+ -- f = \(x::forall a.a->a) -> <stuff>
+ -- This is a consequence of the fact that tcStmts takes a TcType,
+ -- not a Expected TcType, a decision we could revisit if necessary
+tcGRHSs ctxt (GRHSs [L loc1 (GRHS [L loc2 (ResultStmt rhs)])] binds _) exp_ty
+ = tcBindsAndThen glueBindsOnGRHSs binds $
+ mc_body ctxt rhs exp_ty `thenM` \ rhs' ->
+ readExpectedType exp_ty `thenM` \ exp_ty' ->
+ returnM (GRHSs [L loc1 (GRHS [L loc2 (ResultStmt rhs')])] [] exp_ty')
+
+tcGRHSs ctxt (GRHSs grhss binds _) exp_ty
+ = tcBindsAndThen glueBindsOnGRHSs binds $
+ zapExpectedType exp_ty openTypeKind `thenM` \ exp_ty' ->
+ -- Even if there is only one guard, we zap the RHS type to
+ -- a monotype. Reason: it makes tcStmts much easier,
+ -- and even a one-armed guard has a notional second arm
+ let
+ stmt_ctxt = SC { sc_what = PatGuard (mc_what ctxt),
+ sc_rhs = tcCheckRho,
+ sc_body = sc_body,
+ sc_ty = exp_ty' }
+ sc_body body = mc_body ctxt body (Check exp_ty')
+
+ tc_grhs (GRHS guarded)
+ = tcStmts stmt_ctxt guarded `thenM` \ guarded' ->
+ returnM (GRHS guarded')
+ in
+ mappM (wrapLocM tc_grhs) grhss `thenM` \ grhss' ->
+ returnM (GRHSs grhss' [] exp_ty')
+\end{code}
-tcGRHSs :: RenamedMatchContext -> RenamedGRHSs
- -> TcType
- -> TcM (TcGRHSs, LIE)
-tcGRHSs ctxt (GRHSs grhss binds _) expected_ty
- = tcBindsAndThen glue_on binds (tc_grhss grhss)
- where
- tc_grhss grhss
- = mapAndUnzipTc tc_grhs grhss `thenTc` \ (grhss', lies) ->
- returnTc (GRHSs grhss' EmptyBinds expected_ty, plusLIEs lies)
-
- tc_grhs (GRHS guarded locn)
- = tcAddSrcLoc locn $
- tcStmts ctxt (\ty -> ty, expected_ty) guarded `thenTc` \ (guarded', lie) ->
- returnTc (GRHS guarded' locn, lie)
+\begin{code}
+tcThingWithSig :: TcSigmaType -- Type signature
+ -> (TcRhoType -> TcM r) -- How to type check the thing inside
+ -> Expected TcRhoType -- Overall expected result type
+ -> TcM (ExprCoFn, r)
+-- Used for expressions with a type signature, and for result type signatures
+
+tcThingWithSig sig_ty thing_inside res_ty
+ | not (isSigmaTy sig_ty)
+ = thing_inside sig_ty `thenM` \ result ->
+ tcSubExp res_ty sig_ty `thenM` \ co_fn ->
+ returnM (co_fn, result)
+
+ | otherwise -- The signature has some outer foralls
+ = -- 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
+ tcGen sig_ty emptyVarSet thing_inside `thenM` \ (gen_fn, result) ->
+ tcInstCall SignatureOrigin sig_ty `thenM` \ (inst_fn, inst_sig_ty) ->
+ tcSubExp res_ty inst_sig_ty `thenM` \ co_fn ->
+ returnM (co_fn <.> inst_fn <.> gen_fn, result)
+ -- Note that we generalise, then instantiate. Ah well.
\end{code}
\begin{code}
tcMatchPats
- :: [RenamedPat] -> TcType
- -> ([TypecheckedPat] -> TcType -> TcM (a, LIE))
- -> TcM (a, LIE, TcDictBinds)
+ :: [(LPat Name, Expected TcRhoType)]
+ -> Expected TcRhoType
+ -> TcM a
+ -> TcM ([LPat TcId], a, HsBindGroup TcId)
-- Typecheck the patterns, extend the environment to bind the variables,
-- do the thing inside, use any existentially-bound dictionaries to
-- discharge parts of the returning LIE, and deal with pattern type
-- signatures
-tcMatchPats pats expected_ty thing_inside
+tcMatchPats pats_w_tys body_ty thing_inside
= -- STEP 1: Bring pattern-signature type variables into scope
- tcAddScopedTyVars (collectSigTysFromPats pats) (
+ tcAddScopedTyVars (collectSigTysFromPats (map fst pats_w_tys)) (
-- STEP 2: Typecheck the patterns themselves, gathering all the stuff
- tc_match_pats pats expected_ty `thenTc` \ (rhs_ty, pats', lie_req1, ex_tvs, pat_bndrs, lie_avail) ->
-
- -- STEP 3: Extend the environment, and do the thing inside
- let
- xve = bagToList pat_bndrs
- pat_ids = map snd xve
- in
- tcExtendLocalValEnv xve (thing_inside pats' rhs_ty) `thenTc` \ (result, lie_req2) ->
+ -- then do the thing inside
+ getLIE (tc_match_pats pats_w_tys thing_inside)
- returnTc (rhs_ty, lie_req1, ex_tvs, pat_ids, lie_avail, result, lie_req2)
- ) `thenTc` \ (rhs_ty, lie_req1, ex_tvs, pat_ids, lie_avail, result, lie_req2) ->
+ ) `thenM` \ ((pats', ex_tvs, ex_ids, ex_lie, result), lie_req) ->
-- STEP 4: Check for existentially bound type variables
-- Do this *outside* the scope of the tcAddScopedTyVars, else checkSigTyVars
-- I'm a bit concerned that lie_req1 from an 'inner' pattern in the list
-- might need (via lie_req2) something made available from an 'outer'
-- pattern. But it's inconvenient to deal with, and I can't find an example
- tcCheckExistentialPat pat_ids ex_tvs lie_avail lie_req2 expected_ty `thenTc` \ (lie_req2', ex_binds) ->
- -- NB: we *must* pass "expected_ty" not "result_ty" to tcCheckExistentialPat
+ tcCheckExistentialPat ex_tvs ex_ids ex_lie lie_req
+ pats_w_tys body_ty `thenM` \ ex_binds ->
+ -- NB: we *must* pass "pats_w_tys" not just "body_ty" to tcCheckExistentialPat
-- For example, we must reject this program:
-- data C = forall a. C (a -> Int)
-- f (C g) x = g x
- -- Here, result_ty will be simply Int, but expected_ty is (a -> Int).
-
- returnTc (result, lie_req1 `plusLIE` lie_req2', ex_binds)
-
-tcCheckExistentialPat :: [TcId] -- Ids bound by this pattern
- -> Bag TcTyVar -- Existentially quantified tyvars bound by pattern
- -> LIE -- and context
- -> LIE -- Required context
- -> TcType -- and type of the Match; vars in here must not escape
- -> TcM (LIE, TcDictBinds) -- LIE to float out and dict bindings
-tcCheckExistentialPat ids ex_tvs lie_avail lie_req match_ty
- | isEmptyBag ex_tvs && all not_overloaded ids
+ -- Here, result_ty will be simply Int, but expected_ty is (C -> a -> Int).
+
+ returnM (pats', result, HsBindGroup ex_binds [] Recursive)
+
+tc_match_pats [] thing_inside
+ = thing_inside `thenM` \ answer ->
+ returnM ([], emptyBag, [], [], answer)
+
+tc_match_pats ((pat,pat_ty):pats) thing_inside
+ = tcPat tcMonoPatBndr pat pat_ty `thenM` \ (pat', ex_tvs, pat_bndrs, ex_lie) ->
+ let
+ xve = bagToList pat_bndrs
+ ex_ids = [id | (_, id) <- xve]
+ -- ex_ids is all the pattern-bound Ids, a superset
+ -- of the existential Ids used in checkExistentialPat
+ in
+ tcExtendLocalValEnv2 xve $
+ traceTc (text "tc_match_pats" <+> (ppr xve $$ ppr (map (idType . snd) xve) $$
+ ppr (map (typeKind . idType . snd) xve))) `thenM_`
+ tc_match_pats pats thing_inside `thenM` \ (pats', exs_tvs, exs_ids, exs_lie, answer) ->
+ returnM ( pat':pats',
+ ex_tvs `unionBags` exs_tvs,
+ ex_ids ++ exs_ids,
+ ex_lie ++ exs_lie,
+ answer
+ )
+
+
+tcCheckExistentialPat :: Bag TcTyVar -- Existentially quantified tyvars bound by pattern
+ -> [TcId] -- Ids bound by this pattern; used
+ -- (a) by bindsInstsOfLocalFuns
+ -- (b) to generate helpful error messages
+ -> [Inst] -- and context
+ -> [Inst] -- Required context
+ -> [(pat,Expected TcRhoType)] -- Types of the patterns
+ -> Expected TcRhoType -- Type of the body of the match
+ -- Tyvars in either of these must not escape
+ -> TcM TcDictBinds -- LIE to float out and dict bindings
+tcCheckExistentialPat ex_tvs ex_ids ex_lie lie_req pats_w_tys body_ty
+ | isEmptyBag ex_tvs && all not_overloaded ex_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)
+ = ASSERT( null ex_lie )
+ extendLIEs lie_req `thenM_`
+ returnM emptyBag
| otherwise
- = tcExtendGlobalTyVars (tyVarsOfType match_ty) $
- tcAddErrCtxtM (sigPatCtxt tv_list ids) $
+ = -- Read the by-now-filled-in expected types
+ mapM readExpectedType (body_ty : map snd pats_w_tys) `thenM` \ tys ->
+ addErrCtxtM (sigPatCtxt tv_list ex_ids tys) $
-- 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) ->
+ getLIE (bindInstsOfLocalFuns lie_req ex_ids) `thenM` \ (inst_binds, lie) ->
-- 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_`
+ tcSimplifyCheck doc tv_list ex_lie lie `thenM` \ dict_binds ->
+
+ -- Check for type variable escape
+ checkSigTyVarsWrt (tyVarsOfTypes tys) tv_list `thenM_`
- returnTc (lie2, dict_binds `AndMonoBinds` inst_binds)
+ returnM (dict_binds `unionBags` inst_binds)
where
- doc = text ("the existential context of a data constructor")
+ doc = text ("existential context of a data constructor")
tv_list = bagToList ex_tvs
not_overloaded id = not (isOverloadedTy (idType id))
+\end{code}
-tc_match_pats [] expected_ty
- = returnTc (expected_ty, [], emptyLIE, emptyBag, emptyBag, emptyLIE)
-tc_match_pats (pat:pats) expected_ty
- = subFunTy expected_ty `thenTc` \ (arg_ty, rest_ty) ->
- -- This is the unique place we call subFunTy
- -- The point is that if expected_y is a "hole", we want
- -- to make arg_ty and rest_ty as "holes" too.
- tcPat tcMonoPatBndr pat arg_ty `thenTc` \ (pat', lie_req, pat_tvs, pat_ids, lie_avail) ->
- tc_match_pats pats rest_ty `thenTc` \ (rhs_ty, pats', lie_reqs, pats_tvs, pats_ids, lie_avails) ->
- returnTc ( rhs_ty,
- pat':pats',
- lie_req `plusLIE` lie_reqs,
- pat_tvs `unionBags` pats_tvs,
- pat_ids `unionBags` pats_ids,
- lie_avail `plusLIE` lie_avails
- )
+%************************************************************************
+%* *
+\subsection{@tcDoStmts@ typechecks a {\em list} of do statements}
+%* *
+%************************************************************************
+
+\begin{code}
+tcDoStmts :: HsStmtContext Name
+ -> [LStmt Name] -> ReboundNames Name
+ -> TcRhoType -- To keep it simple, we don't have an "expected" type here
+ -> TcM ([LStmt TcId], ReboundNames TcId)
+tcDoStmts PArrComp stmts method_names res_ty
+ = unifyPArrTy res_ty `thenM` \elt_ty ->
+ tcComprehension PArrComp mkPArrTy elt_ty stmts `thenM` \ stmts' ->
+ returnM (stmts', [{- unused -}])
+
+tcDoStmts ListComp stmts method_names res_ty
+ = unifyListTy res_ty ` thenM` \ elt_ty ->
+ tcComprehension ListComp mkListTy elt_ty stmts `thenM` \ stmts' ->
+ returnM (stmts', [{- unused -}])
+
+tcDoStmts do_or_mdo stmts method_names res_ty
+ = newTyVarTy (mkArrowKind liftedTypeKind liftedTypeKind) `thenM` \ m_ty ->
+ newTyVarTy liftedTypeKind `thenM` \ elt_ty ->
+ unifyTauTy res_ty (mkAppTy m_ty elt_ty) `thenM_`
+ let
+ ctxt = SC { sc_what = do_or_mdo,
+ sc_rhs = \ rhs rhs_elt_ty -> tcCheckRho rhs (mkAppTy m_ty rhs_elt_ty),
+ sc_body = \ body -> tcCheckRho body res_ty,
+ sc_ty = res_ty }
+ in
+ tcStmts ctxt stmts `thenM` \ stmts' ->
+
+ -- 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,
+ -- not only for typechecker efficiency, but also because otherwise during
+ -- simplification we end up with silly stuff like
+ -- then = case d of (t,r) -> t
+ -- then = then
+ -- where the second "then" sees that it already exists in the "available" stuff.
+ mapM (tcSyntaxName DoOrigin m_ty) method_names `thenM` \ methods ->
+
+ returnM (stmts', methods)
+
+tcComprehension do_or_lc mk_mty elt_ty stmts
+ = tcStmts ctxt stmts
+ where
+ ctxt = SC { sc_what = do_or_lc,
+ sc_rhs = \ rhs rhs_elt_ty -> tcCheckRho rhs (mk_mty rhs_elt_ty),
+ sc_body = \ body -> tcCheckRho body elt_ty, -- Note: no mk_mty!
+ sc_ty = mk_mty elt_ty }
\end{code}
group. But that's fine; there's no shadowing to worry about.
\begin{code}
-tcStmts do_or_lc m_ty stmts
- = tcStmtsAndThen (:) do_or_lc m_ty stmts (returnTc ([], emptyLIE))
-
+tcStmts ctxt stmts
+ = ASSERT( notNull stmts )
+ tcStmtsAndThen (:) ctxt stmts (returnM [])
+
+data TcStmtCtxt
+ = SC { sc_what :: HsStmtContext Name, -- What kind of thing this is
+ sc_rhs :: LHsExpr Name -> TcType -> TcM (LHsExpr TcId), -- Type checker for RHS computations
+ sc_body :: LHsExpr Name -> TcM (LHsExpr TcId), -- Type checker for return computation
+ sc_ty :: TcType } -- Return type; used *only* to check
+ -- for escape in existential patterns
tcStmtsAndThen
- :: (TcStmt -> thing -> thing) -- Combiner
- -> RenamedMatchContext
- -> (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 (thing, LIE)
- -> TcM (thing, LIE)
+ :: (LStmt TcId -> thing -> thing) -- Combiner
+ -> TcStmtCtxt
+ -> [LStmt Name]
+ -> TcM thing
+ -> TcM thing
-- Base case
-tcStmtsAndThen combine do_or_lc m_ty [] do_next
- = do_next
+tcStmtsAndThen combine ctxt [] thing_inside
+ = thing_inside
-tcStmtsAndThen combine do_or_lc m_ty (stmt:stmts) do_next
- = tcStmtAndThen combine do_or_lc m_ty stmt
- (tcStmtsAndThen combine do_or_lc m_ty stmts do_next)
+tcStmtsAndThen combine ctxt (stmt:stmts) thing_inside
+ = tcStmtAndThen combine ctxt stmt $
+ tcStmtsAndThen combine ctxt stmts $
+ thing_inside
-- LetStmt
-tcStmtAndThen combine do_or_lc m_ty (LetStmt binds) thing_inside
+tcStmtAndThen combine ctxt (L _ (LetStmt binds)) thing_inside
= tcBindsAndThen -- No error context, but a binding group is
(glue_binds combine) -- rather a large thing for an error context anyway
binds
thing_inside
-tcStmtAndThen combine do_or_lc m_ty@(m,elt_ty) stmt@(BindStmt pat exp src_loc) thing_inside
- = tcAddSrcLoc src_loc $
- tcAddErrCtxt (stmtCtxt do_or_lc stmt) $
- newTyVarTy liftedTypeKind `thenNF_Tc` \ pat_ty ->
- tcExpr exp (m pat_ty) `thenTc` \ (exp', exp_lie) ->
- tcMatchPats [pat] (mkFunTy pat_ty (m elt_ty)) (\ [pat'] _ ->
- tcPopErrCtxt $
- thing_inside `thenTc` \ (thing, lie) ->
- returnTc ((BindStmt pat' exp' src_loc, thing), lie)
- ) `thenTc` \ ((stmt', thing), lie, dict_binds) ->
- returnTc (combine stmt' (glue_binds combine Recursive dict_binds thing),
- lie `plusLIE` exp_lie)
-
-
- -- ParStmt
-tcStmtAndThen combine do_or_lc m_ty (ParStmtOut bndr_stmts_s) thing_inside
- = loop bndr_stmts_s `thenTc` \ ((pairs', thing), lie) ->
- returnTc (combine (ParStmtOut pairs') thing, lie)
- where
- loop []
- = thing_inside `thenTc` \ (thing, stmts_lie) ->
- returnTc (([], thing), stmts_lie)
-
- loop ((bndrs,stmts) : pairs)
- = tcStmtsAndThen
- combine_par (DoCtxt ListComp) m_ty stmts
- -- Notice we pass on m_ty; the result type is used only
- -- to get escaping type variables for checkExistentialPat
- (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)
+ -- BindStmt
+tcStmtAndThen combine ctxt (L src_loc stmt@(BindStmt pat exp)) thing_inside
+ = addSrcSpan src_loc $
+ addErrCtxt (stmtCtxt ctxt stmt) $
+ newTyVarTy liftedTypeKind `thenM` \ pat_ty ->
+ sc_rhs ctxt exp pat_ty `thenM` \ exp' ->
+ tcMatchPats [(pat, Check pat_ty)] (Check (sc_ty ctxt)) (
+ popErrCtxt thing_inside
+ ) `thenM` \ ([pat'], thing, dict_binds) ->
+ returnM (combine (L src_loc (BindStmt pat' exp'))
+ (glue_binds combine dict_binds thing))
-- ExprStmt
-tcStmtAndThen combine do_or_lc m_ty@(m, res_elt_ty) stmt@(ExprStmt exp _ locn) thing_inside
- = tcSetErrCtxt (stmtCtxt do_or_lc stmt) (
- if isDoExpr do_or_lc then
- newTyVarTy openTypeKind `thenNF_Tc` \ any_ty ->
- tcExpr exp (m any_ty) `thenNF_Tc` \ (exp', lie) ->
- returnTc (ExprStmt exp' any_ty locn, lie)
- else
- tcExpr exp boolTy `thenNF_Tc` \ (exp', lie) ->
- returnTc (ExprStmt exp' boolTy locn, lie)
- ) `thenTc` \ (stmt', stmt_lie) ->
+tcStmtAndThen combine ctxt (L src_loc stmt@(ExprStmt exp _)) thing_inside
+ = addSrcSpan src_loc (
+ addErrCtxt (stmtCtxt ctxt stmt) $
+ if isDoExpr (sc_what ctxt)
+ then -- do or mdo; the expression is a computation
+ newTyVarTy liftedTypeKind `thenM` \ any_ty ->
+ sc_rhs ctxt exp any_ty `thenM` \ exp' ->
+ returnM (L src_loc (ExprStmt exp' any_ty))
+ else -- List comprehensions, pattern guards; expression is a boolean
+ tcCheckRho exp boolTy `thenM` \ exp' ->
+ returnM (L src_loc (ExprStmt exp' boolTy))
+ ) `thenM` \ stmt' ->
+
+ thing_inside `thenM` \ thing ->
+ returnM (combine stmt' thing)
- thing_inside `thenTc` \ (thing, stmts_lie) ->
- returnTc (combine stmt' thing, stmt_lie `plusLIE` stmts_lie)
+ -- ParStmt
+tcStmtAndThen combine ctxt (L src_loc (ParStmt bndr_stmts_s)) thing_inside
+ = loop bndr_stmts_s `thenM` \ (pairs', thing) ->
+ returnM (combine (L src_loc (ParStmt pairs')) thing)
+ where
+ loop [] = thing_inside `thenM` \ thing ->
+ returnM ([], thing)
+ loop ((stmts, bndrs) : pairs)
+ = tcStmtsAndThen combine_par ctxt stmts $
+ -- Notice we pass on ctxt; the result type is used only
+ -- to get escaping type variables for checkExistentialPat
+ tcLookupLocalIds bndrs `thenM` \ bndrs' ->
+ loop pairs `thenM` \ (pairs', thing) ->
+ returnM (([], bndrs') : pairs', thing)
+
+ combine_par stmt ((stmts, bndrs) : pairs , thing) = ((stmt:stmts, bndrs) : pairs, thing)
+
+ -- RecStmt
+tcStmtAndThen combine ctxt (L src_loc (RecStmt stmts laterNames recNames _)) thing_inside
+ = newTyVarTys (length recNames) liftedTypeKind `thenM` \ recTys ->
+ let
+ rec_ids = zipWith mkLocalId recNames recTys
+ in
+ tcExtendLocalValEnv rec_ids $
+ tcStmtsAndThen combine_rec ctxt stmts (
+ zipWithM tc_ret recNames recTys `thenM` \ rec_rets ->
+ tcLookupLocalIds laterNames `thenM` \ later_ids ->
+ returnM ([], (later_ids, rec_rets))
+ ) `thenM` \ (stmts', (later_ids, rec_rets)) ->
+
+ tcExtendLocalValEnv later_ids $
+ -- NB: The rec_ids for the recursive things
+ -- already scope over this part
+ thing_inside `thenM` \ thing ->
+
+ returnM (combine (L src_loc (RecStmt stmts' later_ids rec_ids rec_rets)) thing)
+ where
+ combine_rec stmt (stmts, thing) = (stmt:stmts, thing)
+
+ -- Unify the types of the "final" Ids with those of "knot-tied" Ids
+ tc_ret rec_name mono_ty
+ = tcLookupId rec_name `thenM` \ poly_id ->
+ -- poly_id may have a polymorphic type
+ -- but mono_ty is just a monomorphic type variable
+ tcSubExp (Check mono_ty) (idType poly_id) `thenM` \ co_fn ->
+ returnM (L src_loc (co_fn <$> HsVar poly_id))
-- Result statements
-tcStmtAndThen combine do_or_lc m_ty@(m, res_elt_ty) stmt@(ResultStmt exp locn) thing_inside
- = tcSetErrCtxt (stmtCtxt do_or_lc stmt) (
- if isDoExpr do_or_lc then
- tcExpr exp (m res_elt_ty)
- else
- tcExpr exp res_elt_ty
- ) `thenTc` \ (exp', stmt_lie) ->
-
- thing_inside `thenTc` \ (thing, stmts_lie) ->
-
- returnTc (combine (ResultStmt exp' locn) thing,
- stmt_lie `plusLIE` stmts_lie)
+tcStmtAndThen combine ctxt (L src_loc stmt@(ResultStmt exp)) thing_inside
+ = addErrCtxt (stmtCtxt ctxt stmt) (sc_body ctxt exp) `thenM` \ exp' ->
+ thing_inside `thenM` \ thing ->
+ returnM (combine (L src_loc (ResultStmt exp')) thing)
------------------------------
-glue_binds combine is_rec binds thing
- | nullMonoBinds binds = thing
- | otherwise = combine (LetStmt (mkMonoBind binds [] is_rec)) thing
+glue_binds combine binds thing = combine (noLoc (LetStmt [binds])) thing
+ -- ToDo: fix the noLoc
\end{code}
number of args are used in each equation.
\begin{code}
-sameNoOfArgs :: [RenamedMatch] -> Bool
+sameNoOfArgs :: [LMatch Name] -> Bool
sameNoOfArgs matches = isSingleton (nub (map args_in_match matches))
where
- args_in_match :: RenamedMatch -> Int
- args_in_match (Match pats _ _) = length pats
+ args_in_match :: LMatch Name -> Int
+ args_in_match (L _ (Match pats _ _)) = length pats
\end{code}
\begin{code}
-matchCtxt ctxt match = hang (pprMatchContext ctxt <> colon) 4 (pprMatch ctxt match)
-stmtCtxt do_or_lc stmt = hang (pprMatchContext do_or_lc <> colon) 4 (ppr stmt)
-
varyingArgsErr name matches
= sep [ptext SLIT("Varying number of arguments for function"), quotes (ppr name)]
+
+matchCtxt ctxt match = hang (ptext SLIT("In") <+> pprMatchContext ctxt <> colon)
+ 4 (pprMatch ctxt match)
+
+stmtCtxt ctxt stmt = hang (ptext SLIT("In") <+> pp_ctxt (sc_what ctxt) <> colon) 4 (ppr stmt)
+ where
+ pp_ctxt = case stmt of
+ ResultStmt _ -> pprStmtResultContext
+ other -> pprStmtContext
+
+sigPatCtxt bound_tvs bound_ids tys tidy_env
+ = -- tys is (body_ty : pat_tys)
+ mapM zonkTcType tys `thenM` \ tys' ->
+ let
+ (env1, tidy_tys) = tidyOpenTypes tidy_env (map idType show_ids)
+ (_env2, tidy_body_ty : tidy_pat_tys) = tidyOpenTypes env1 tys'
+ in
+ returnM (env1,
+ sep [ptext SLIT("When checking an existential match that binds"),
+ nest 4 (vcat (zipWith ppr_id show_ids tidy_tys)),
+ ptext SLIT("The pattern(s) have type(s):") <+> vcat (map ppr tidy_pat_tys),
+ ptext SLIT("The body has type:") <+> ppr tidy_body_ty
+ ])
+ where
+ show_ids = filter is_interesting bound_ids
+ is_interesting id = any (`elemVarSet` idFreeTyVars id) bound_tvs
+
+ ppr_id id ty = ppr id <+> dcolon <+> ppr ty
+ -- Don't zonk the types so we get the separate, un-unified versions
\end{code}
projects / ghc-hetmet.git / blobdiff