\section[TcMatches]{Typecheck some @Matches@}
\begin{code}
-module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda, tcStmts, tcGRHSs ) where
+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, tcInferRho, tcMonoExpr )
-import HsSyn ( HsBinds(..), Match(..), GRHSs(..), GRHS(..),
- MonoBinds(..), StmtCtxt(..), Stmt(..),
- pprMatch, getMatchLoc, consLetStmt,
- mkMonoBind, collectSigTysFromPats
+import HsSyn ( HsExpr(..), LHsExpr, MatchGroup(..),
+ Match(..), LMatch, GRHSs(..), GRHS(..),
+ Stmt(..), LStmt, HsMatchContext(..), HsStmtContext(..),
+ ReboundNames, LPat,
+ pprMatch, isDoExpr,
+ pprMatchContext, pprStmtContext, pprStmtResultContext,
+ collectPatsBinders, glueBindsOnGRHSs
)
-import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt )
-import TcHsSyn ( TcMatch, TcGRHSs, TcStmt )
-
-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 TcType ( TcType, newTyVarTy )
+import TcHsSyn ( ExprCoFn, isIdCoercion, (<$>), (<.>) )
+
+import TcRnMonad
+import TcHsType ( tcHsPatSigType, UserTypeCtxt(..) )
+import Inst ( tcSyntaxName, tcInstCall )
+import TcEnv ( TcId, tcLookupLocalIds, tcLookupId, tcExtendIdEnv,
+ tcExtendTyVarEnv )
+import TcPat ( PatCtxt(..), tcPats )
+import TcMType ( newTyFlexiVarTy, newTyFlexiVarTys, zonkTcType, isRigidType )
+import TcType ( TcType, TcTyVar, TcSigmaType, TcRhoType, mkFunTys,
+ tyVarsOfTypes, tidyOpenTypes, isSigmaTy, mkTyConApp,
+ liftedTypeKind, openTypeKind, mkArrowKind, mkAppTy )
import TcBinds ( tcBindsAndThen )
-import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns )
-import TcUnify ( unifyFunTy, unifyTauTy, unifyListTy )
+import TcUnify ( Expected(..), zapExpectedType, readExpectedType,
+ unifyTauTy, subFunTys, unifyListTy, unifyTyConApp,
+ checkSigTyVarsWrt, zapExpectedBranches, tcSubExp, tcGen,
+ unifyAppTy )
import Name ( Name )
-import TysWiredIn ( boolTy )
-
-import BasicTypes ( RecFlag(..) )
-import Type ( tyVarsOfType, isTauTy, mkArrowKind, mkAppTy, mkFunTy,
- boxedTypeKind, openTypeKind )
-import SrcLoc ( SrcLoc )
+import TysWiredIn ( boolTy, parrTyCon, listTyCon )
+import Id ( idType, mkLocalId )
+import CoreFVs ( idFreeTyVars )
import VarSet
-import Var ( Id )
-import Bag
+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 xve fun_name expected_ty matches@(first_match:_)
- = -- Check that they all have the same no of arguments
- -- Set the location to that of the first equation, 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_`
+tcMatchesFun :: Name
+ -> MatchGroup Name
+ -> Expected TcRhoType -- Expected type of function
+ -> TcM (MatchGroup TcId) -- Returns type of body
+
+tcMatchesFun fun_name matches exp_ty
+ = do { -- Check that they all have the same no of arguments
+ -- 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...
+ checkTc (sameNoOfArgs matches) (varyingArgsErr fun_name matches)
-- 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 unifyFunTy does that on the fly
- tcMatches xve matches expected_ty (FunRhs fun_name)
+ -- This is one of two places places we call subFunTys
+ -- The point is that if expected_y is a "hole", we want
+ -- to make pat_tys and rhs_ty as "holes" too.
+ ; exp_ty' <- zapExpectedBranches matches exp_ty
+ ; subFunTys matches exp_ty' $ \ pat_tys rhs_ty ->
+ tcMatches match_ctxt pat_tys rhs_ty matches
+ }
+ 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 [] matches (mkFunTy scrut_ty expr_ty) CaseAlt `thenTc` \ (matches', lie) ->
- returnTc (scrut_ty, matches', lie)
-
-tcMatchLambda :: RenamedMatch -> TcType -> TcM (TcMatch, LIE)
-tcMatchLambda match res_ty = tcMatch [] match res_ty LambdaBody
+tcMatchesCase :: TcMatchCtxt -- Case context
+ -> TcRhoType -- Type of scrutinee
+ -> MatchGroup Name -- The case alternatives
+ -> Expected TcRhoType -- Type of whole case expressions
+ -> TcM (MatchGroup TcId) -- Translated alternatives
+
+tcMatchesCase ctxt scrut_ty matches exp_ty
+ = do { exp_ty' <- zapExpectedBranches matches exp_ty
+ ; tcMatches ctxt [Check scrut_ty] exp_ty' matches }
+
+tcMatchLambda :: MatchGroup Name -> Expected TcRhoType -> TcM (MatchGroup TcId)
+tcMatchLambda match exp_ty -- One branch so no unifyBranches needed
+ = subFunTys match exp_ty $ \ pat_tys rhs_ty ->
+ tcMatches match_ctxt pat_tys rhs_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)]
- -> [RenamedMatch]
- -> TcType
- -> StmtCtxt
- -> TcM ([TcMatch], LIE)
-
-tcMatches xve matches expected_ty fun_or_case
- = 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 match expected_ty fun_or_case
+ match_ctxt = MC { mc_what = PatBindRhs,
+ mc_body = tcMonoExpr }
\end{code}
%************************************************************************
\begin{code}
-tcMatch :: [(Name,Id)]
- -> RenamedMatch
- -> TcType -- Expected result-type of the Match.
- -- Early unification with this guy gives better error messages
- -> StmtCtxt
- -> TcM (TcMatch, LIE)
-
-tcMatch xve1 match@(Match sig_tvs pats maybe_rhs_sig grhss) expected_ty ctxt
- = tcAddSrcLoc (getMatchLoc match) $
- tcAddErrCtxt (matchCtxt ctxt match) $
-
- if null sig_tvs then -- The common case
- tc_match expected_ty `thenTc` \ (_, match_and_lie) ->
- returnTc match_and_lie
-
- else
- -- If there are sig tvs we must be careful *not* to use
- -- expected_ty right away, else we'll unify with tyvars free
- -- in the envt. So invent a fresh tyvar and use that instead
- newTyVarTy openTypeKind `thenNF_Tc` \ tyvar_ty ->
-
- -- Extend the tyvar env and check the match itself
- tcTyVars sig_tvs (mapTc_ kcHsSigType sig_tys) `thenTc` \ sig_tyvars ->
- tcExtendTyVarEnv sig_tyvars (tc_match tyvar_ty) `thenTc` \ (pat_ids, match_and_lie) ->
-
- -- Check that the scoped type variables from the patterns
- -- have not been constrained
- tcAddErrCtxtM (sigPatCtxt sig_tyvars pat_ids) (
- checkSigTyVars sig_tyvars emptyVarSet
- ) `thenTc_`
-
- -- *Now* we're free to unify with expected_ty
- unifyTauTy expected_ty tyvar_ty `thenTc_`
-
- returnTc match_and_lie
-
+tcMatches :: TcMatchCtxt
+ -> [Expected TcRhoType] -- Expected pattern types
+ -> Expected TcRhoType -- Expected result-type of the Match.
+ -> MatchGroup Name
+ -> TcM (MatchGroup TcId)
+
+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 ctxt pat_tys rhs_ty (MatchGroup matches _)
+ = do { matches' <- mapM (tcMatch ctxt pat_tys rhs_ty) matches
+ ; pat_tys' <- mapM readExpectedType pat_tys
+ ; rhs_ty' <- readExpectedType rhs_ty
+ ; return (MatchGroup matches' (mkFunTys pat_tys' rhs_ty')) }
+
+-------------
+tcMatch :: TcMatchCtxt
+ -> [Expected TcRhoType] -- Expected pattern types
+ -> Expected TcRhoType -- Expected result-type of the Match.
+ -> LMatch Name
+ -> TcM (LMatch TcId)
+
+tcMatch ctxt pat_tys rhs_ty match
+ = wrapLocM (tc_match ctxt pat_tys rhs_ty) match
+
+tc_match ctxt pat_tys rhs_ty match@(Match pats maybe_rhs_sig grhss)
+ = addErrCtxt (matchCtxt (mc_what ctxt) match) $
+ do { (pats', grhss') <- tcMatchPats pats pat_tys rhs_ty $
+ tc_grhss ctxt maybe_rhs_sig grhss rhs_ty
+ ; returnM (Match pats' Nothing grhss') }
+
+
+-------------
+tc_grhss ctxt Nothing grhss rhs_ty
+ = tcGRHSs ctxt grhss rhs_ty -- No result signature
+
+tc_grhss ctxt (Just res_sig) grhss rhs_ty
+ = do { (sig_tvs, sig_ty) <- tcHsPatSigType ResSigCtxt res_sig
+ ; traceTc (text "tc_grhss" <+> ppr sig_tvs)
+ ; (co_fn, grhss') <- tcExtendTyVarEnv sig_tvs $
+ tcThingWithSig sig_ty (tcGRHSs ctxt grhss . Check) rhs_ty
+
+ -- Push the coercion down to the right hand sides,
+ -- because there is no convenient place to hang it otherwise.
+ ; if isIdCoercion co_fn then
+ return grhss'
+ else
+ return (lift_grhss co_fn grhss') }
+
+-------------
+lift_grhss co_fn (GRHSs grhss binds)
+ = GRHSs (map (fmap lift_grhs) grhss) binds
where
- sig_tys = case maybe_rhs_sig of { Just t -> [t]; Nothing -> [] }
- ++ collectSigTysFromPats pats
+ lift_grhs (GRHS stmts) = GRHS (map lift_stmt stmts)
- tc_match expected_ty -- Any sig tyvars are in scope by now
- = -- STEP 1: Typecheck the patterns
- tcMatchPats pats expected_ty `thenTc` \ (rhs_ty, pats', lie_req1, ex_tvs, pat_bndrs, lie_avail) ->
- 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
- -- If it is it'll mess up the unifier when checking the RHS
- checkTc (isTauTy rhs_ty) lurkingRank2SigErr `thenTc_`
-
- -- STEP 3: Unify with the rhs type signature if any
- (case maybe_rhs_sig of
- Nothing -> returnTc ()
- Just sig -> tcHsSigType sig `thenTc` \ sig_ty ->
-
- -- Check that the signature isn't a polymorphic one, which
- -- we don't permit (at present, anyway)
- checkTc (isTauTy sig_ty) (polyPatSig sig_ty) `thenTc_`
- unifyTauTy rhs_ty sig_ty
- ) `thenTc_`
-
- -- STEP 4: Typecheck the guarded RHSs and the associated where clause
- tcExtendLocalValEnv xve1 (tcExtendLocalValEnv xve2 (
- tcGRHSs grhss rhs_ty ctxt
- )) `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) ->
-
- -- Phew! All done.
- let
- grhss'' = glue_on Recursive ex_binds $
- glue_on Recursive inst_binds grhss'
- in
- returnTc (pat_ids, (Match [] pats' Nothing grhss'', lie_req''))
-
- -- 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
-
-tcGRHSs :: RenamedGRHSs
- -> TcType -> StmtCtxt
- -> TcM (TcGRHSs, LIE)
-
-tcGRHSs (GRHSs grhss binds _) expected_ty ctxt
- = tcBindsAndThen glue_on binds (tc_grhss grhss)
- where
- tc_grhss grhss
- = mapAndUnzipTc tc_grhs grhss `thenTc` \ (grhss', lies) ->
- 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) ->
- returnTc (GRHS guarded' locn, lie)
+ 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' ->
+ returnM (GRHSs [L loc1 (GRHS [L loc2 (ResultStmt rhs')])] [])
+
+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 = tcInferRho,
+ 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' [])
+\end{code}
+
+
+\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 InstSigOrigin 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 [] expected_ty
- = returnTc (expected_ty, [], emptyLIE, emptyBag, emptyBag, emptyLIE)
-
-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) ->
- tcMatchPats 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
- )
+\begin{code}
+tcMatchPats :: [LPat Name]
+ -> [Expected TcSigmaType] -- Pattern types
+ -> Expected TcRhoType -- Result type;
+ -- used only to check existential escape
+ -> TcM a
+ -> TcM ([LPat TcId], a)
+-- 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 tys body_ty thing_inside
+ = do { do_refinement <- can_refine body_ty
+ ; (pats', ex_tvs, res) <- tcPats (LamPat do_refinement) pats tys thing_inside
+ ; tcCheckExistentialPat pats' ex_tvs tys body_ty
+ ; returnM (pats', res) }
+ where
+ -- Do GADT refinement if we are doing checking (not inference)
+ -- and the body_ty is completely rigid
+ -- ToDo: explain why
+ can_refine (Infer _) = return False
+ can_refine (Check ty) = isRigidType ty
+
+tcCheckExistentialPat :: [LPat TcId] -- Patterns (just for error message)
+ -> [TcTyVar] -- Existentially quantified tyvars bound by pattern
+ -> [Expected TcSigmaType] -- Types of the patterns
+ -> Expected TcRhoType -- Type of the body of the match
+ -- Tyvars in either of these must not escape
+ -> TcM ()
+ -- NB: we *must* pass "pats_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 (C -> a -> Int).
+
+tcCheckExistentialPat pats [] pat_tys body_ty
+ = return () -- Short cut for case when there are no existentials
+
+tcCheckExistentialPat pats ex_tvs pat_tys body_ty
+ = do { tys <- mapM readExpectedType (body_ty : pat_tys)
+ ; addErrCtxtM (sigPatCtxt (collectPatsBinders pats) ex_tvs tys) $
+ checkSigTyVarsWrt (tyVarsOfTypes tys) ex_tvs }
\end{code}
%************************************************************************
%* *
-\subsection{tcStmts}
+\subsection{@tcDoStmts@ typechecks a {\em list} of do statements}
%* *
%************************************************************************
-
\begin{code}
-tcParStep src_loc stmts
- = newTyVarTy (mkArrowKind boxedTypeKind boxedTypeKind) `thenTc` \ m ->
- newTyVarTy boxedTypeKind `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
- -> [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)
- = tcAddSrcLoc src_loc (
- tcSetErrCtxt (stmtCtxt do_or_lc stmt) $
- newTyVarTy boxedTypeKind `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) ->
- returnTc (pat', exp',
- pat_lie `plusLIE` exp_lie,
- pat_tvs, pat_ids, avail)
- ) `thenTc` \ (pat', exp', lie_req, pat_tvs, pat_bndrs, lie_avail) ->
+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
+ = do { [elt_ty] <- unifyTyConApp parrTyCon res_ty
+ ; stmts' <- tcComprehension PArrComp parrTyCon elt_ty stmts
+ ; return (stmts', [{- unused -}]) }
+
+tcDoStmts ListComp stmts method_names res_ty
+ = unifyListTy res_ty ` thenM` \ elt_ty ->
+ tcComprehension ListComp listTyCon elt_ty stmts `thenM` \ stmts' ->
+ returnM (stmts', [{- unused -}])
+
+tcDoStmts do_or_mdo stmts method_names res_ty
+ = newTyFlexiVarTy (mkArrowKind liftedTypeKind liftedTypeKind) `thenM` \ m_ty ->
+ newTyFlexiVarTy liftedTypeKind `thenM` \ elt_ty ->
+ unifyTauTy res_ty (mkAppTy m_ty elt_ty) `thenM_`
let
- new_val_env = bagToList pat_bndrs
- pat_ids = map snd new_val_env
- pat_tv_list = bagToList pat_tvs
- in
+ ctxt = SC { sc_what = do_or_mdo,
+ sc_rhs = \ rhs -> do { (rhs', rhs_ty) <- tcInferRho rhs
+ ; rhs_elt_ty <- unifyAppTy m_ty rhs_ty
+ ; return (rhs', 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 m_tycon elt_ty stmts
+ = tcStmts ctxt stmts
+ where
+ ctxt = SC { sc_what = do_or_lc,
+ sc_rhs = \ rhs -> do { (rhs', rhs_ty) <- tcInferRho rhs
+ ; [rhs_elt_ty] <- unifyTyConApp m_tycon rhs_ty
+ ; return (rhs', rhs_elt_ty) },
+ sc_body = \ body -> tcCheckRho body elt_ty, -- Note: no m_tycon here!
+ sc_ty = mkTyConApp m_tycon [elt_ty] }
+\end{code}
- -- 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) ->
+%************************************************************************
+%* *
+\subsection{tcStmts}
+%* *
+%************************************************************************
- -- Reinstate context for existential checks
- tcSetErrCtxt (stmtCtxt do_or_lc stmt) $
- tcExtendGlobalTyVars (tyVarsOfType (m elt_ty)) $
- tcAddErrCtxtM (sigPatCtxt pat_tv_list pat_ids) $
+Typechecking statements is rendered a bit tricky by parallel list comprehensions:
- checkSigTyVars pat_tv_list emptyVarSet `thenTc` \ zonked_pat_tvs ->
+ [ (g x, h x) | ... ; let g v = ...
+ | ... ; let h v = ... ]
- tcSimplifyAndCheck
- (text ("the existential context of a data constructor"))
- (mkVarSet zonked_pat_tvs)
- lie_avail stmts_lie `thenTc` \ (final_lie, dict_binds) ->
+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:
- -- 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),
- lie_req `plusLIE` final_lie)
+ data T = forall a. Show a => C a
-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)
+ [ (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.
-tcStmts do_or_lc m elt_ty loc [] = returnTc (([], []), emptyLIE)
+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.
-isDoStmt DoStmt = True
-isDoStmt other = False
+\begin{code}
+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 -> TcM (LHsExpr TcId, TcType), -- Type inference 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
+ -- We use type *inference* for the RHS computations, becuase of GADTs.
+ -- do { pat <- rhs; <rest> }
+ -- is rather like
+ -- case rhs of { pat -> <rest> }
+ -- We do inference on rhs, so that information about its type can be refined
+ -- when type-checking the pattern.
+
+tcStmtsAndThen
+ :: (LStmt TcId -> thing -> thing) -- Combiner
+ -> TcStmtCtxt
+ -> [LStmt Name]
+ -> TcM thing
+ -> TcM thing
+
+ -- Base case
+tcStmtsAndThen combine ctxt [] thing_inside
+ = thing_inside
+
+tcStmtsAndThen combine ctxt (stmt:stmts) thing_inside
+ = tcStmtAndThen combine ctxt stmt $
+ tcStmtsAndThen combine ctxt stmts $
+ thing_inside
+
+ -- LetStmt
+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
+
+ -- BindStmt
+tcStmtAndThen combine ctxt (L src_loc stmt@(BindStmt pat exp)) thing_inside
+ = setSrcSpan src_loc $
+ addErrCtxt (stmtCtxt ctxt stmt) $
+ do { (exp', pat_ty) <- sc_rhs ctxt exp
+ ; ([pat'], thing) <- tcMatchPats [pat] [Check pat_ty] (Check (sc_ty ctxt)) $
+ popErrCtxt thing_inside
+ ; return (combine (L src_loc (BindStmt pat' exp')) thing) }
+
+ -- ExprStmt
+tcStmtAndThen combine ctxt (L src_loc stmt@(ExprStmt exp _)) thing_inside
+ = setSrcSpan src_loc (
+ addErrCtxt (stmtCtxt ctxt stmt) $
+ if isDoExpr (sc_what ctxt)
+ then -- do or mdo; the expression is a computation
+ sc_rhs ctxt exp `thenM` \ (exp', exp_ty) ->
+ returnM (L src_loc (ExprStmt exp' exp_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)
+
+
+ -- 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
+-- gaw 2004
+ = newTyFlexiVarTys (length recNames) liftedTypeKind `thenM` \ recTys ->
+ let
+ rec_ids = zipWith mkLocalId recNames recTys
+ in
+ tcExtendIdEnv 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)) ->
+
+ tcExtendIdEnv 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 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 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 matches = length (nub (map args_in_match matches)) == 1
+sameNoOfArgs :: MatchGroup Name -> Bool
+sameNoOfArgs (MatchGroup 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 CaseAlt match
- = hang (ptext SLIT("In a case alternative:"))
- 4 (pprMatch (True,empty) {-is_case-} match)
-
-matchCtxt (FunRhs fun) match
- = hang (hcat [ptext SLIT("In an equation for function "), quotes (ppr_fun), char ':'])
- 4 (pprMatch (False, ppr_fun) {-not case-} match)
- where
- ppr_fun = ppr fun
-
-matchCtxt LambdaBody match
- = hang (ptext SLIT("In the lambda expression"))
- 4 (pprMatch (True, empty) match)
-
varyingArgsErr name matches
= sep [ptext SLIT("Varying number of arguments for function"), quotes (ppr name)]
-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)
+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_ids bound_tvs 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
- 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")
+ 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