\section[TcMatches]{Typecheck some @Matches@}
\begin{code}
-module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda, tcStmts, tcGRHSs ) where
+module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda,
+ tcDoStmts, tcStmtsAndThen, tcGRHSs
+ ) where
#include "HsVersions.h"
-import {-# SOURCE #-} TcExpr( tcExpr )
+import {-# SOURCE #-} TcExpr( tcMonoExpr )
-import HsSyn ( HsBinds(..), Match(..), GRHSs(..), GRHS(..),
- MonoBinds(..), StmtCtxt(..), Stmt(..),
- pprMatch, getMatchLoc, consLetStmt,
- mkMonoBind, collectSigTysFromPats
+import HsSyn ( HsExpr(..), HsBinds(..), Match(..), GRHSs(..), GRHS(..),
+ MonoBinds(..), Stmt(..), HsMatchContext(..), HsStmtContext(..),
+ pprMatch, getMatchLoc, isDoExpr,
+ pprMatchContext, pprStmtContext, pprStmtResultContext,
+ mkMonoBind, collectSigTysFromPats, andMonoBindList
)
-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 ( tcExtendTyVarEnv, tcExtendLocalValEnv, tcExtendGlobalTyVars )
-import TcPat ( tcPat, tcPatBndr_NoSigs, polyPatSig )
-import TcType ( TcType, newTyVarTy )
+import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt,
+ RenamedPat, RenamedMatchContext )
+import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TcHsBinds,
+ TcMonoBinds, TcPat, TcStmt )
+
+import TcRnMonad
+import TcMonoType ( tcAddScopedTyVars, tcHsSigType, UserTypeCtxt(..) )
+import Inst ( tcSyntaxName )
+import TcEnv ( TcId, tcLookupLocalIds, tcLookupId, tcExtendLocalValEnv, tcExtendLocalValEnv2 )
+import TcPat ( tcPat, tcMonoPatBndr )
+import TcMType ( newTyVarTy, newTyVarTys, zonkTcType, zapToType )
+import TcType ( TcType, TcTyVar, tyVarsOfType, tidyOpenTypes, tidyOpenType,
+ mkFunTy, isOverloadedTy, liftedTypeKind, openTypeKind,
+ mkArrowKind, mkAppTy )
import TcBinds ( tcBindsAndThen )
-import TcSimplify ( tcSimplifyAndCheck, bindInstsOfLocalFuns )
-import TcUnify ( unifyFunTy, unifyTauTy )
+import TcUnify ( unifyPArrTy,subFunTy, unifyListTy, unifyTauTy,
+ checkSigTyVarsWrt, tcSubExp, isIdCoercion, (<$>) )
+import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns )
import Name ( Name )
-import TysWiredIn ( boolTy )
-
+import PrelNames ( monadNames, mfixName )
+import TysWiredIn ( boolTy, mkListTy, mkPArrTy )
+import Id ( idType, mkSysLocal, mkLocalId )
+import CoreFVs ( idFreeTyVars )
import BasicTypes ( RecFlag(..) )
-import Type ( tyVarsOfType, isTauTy, mkFunTy, boxedTypeKind, openTypeKind )
import VarSet
import Var ( Id )
import Bag
+import Util ( isSingleton, lengthExceeds, notNull, zipEqual )
import Outputable
+
import List ( nub )
\end{code}
-> Name
-> TcType -- Expected type
-> [RenamedMatch]
- -> TcM ([TcMatch], LIE)
+ -> TcM [TcMatch]
tcMatchesFun xve fun_name expected_ty matches@(first_match:_)
= -- Check that they all have the same no of arguments
-- 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) (
+ addSrcLoc (getMatchLoc first_match) (
checkTc (sameNoOfArgs matches)
(varyingArgsErr fun_name matches)
- ) `thenTc_`
+ ) `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 unifyFunTy does that on the fly
- tcMatches xve matches expected_ty (FunRhs fun_name)
+ -- No need to zonk expected_ty, because subFunTy does that on the fly
+ tcMatches xve (FunRhs fun_name) matches expected_ty
\end{code}
@tcMatchesCase@ doesn't do the argument-count check because the
tcMatchesCase :: [RenamedMatch] -- The case alternatives
-> TcType -- Type of whole case expressions
-> TcM (TcType, -- Inferred type of the scrutinee
- [TcMatch], -- Translated alternatives
- LIE)
+ [TcMatch]) -- Translated alternatives
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)
+ = newTyVarTy openTypeKind `thenM` \ scrut_ty ->
+ tcMatches [] CaseAlt matches (mkFunTy scrut_ty expr_ty) `thenM` \ matches' ->
+ returnM (scrut_ty, matches')
-tcMatchLambda :: RenamedMatch -> TcType -> TcM (TcMatch, LIE)
-tcMatchLambda match res_ty = tcMatch [] match res_ty LambdaBody
+tcMatchLambda :: RenamedMatch -> TcType -> TcM TcMatch
+tcMatchLambda match res_ty = tcMatch [] LambdaExpr match res_ty
\end{code}
\begin{code}
tcMatches :: [(Name,Id)]
+ -> RenamedMatchContext
-> [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)
+ -> TcM [TcMatch]
+
+tcMatches xve ctxt matches expected_ty
+ = -- If there is more than one branch, and expected_ty is a 'hole',
+ -- all branches must be types, not type schemes, otherwise the
+ -- in which we check them would affect the result.
+ (if lengthExceeds matches 1 then
+ zapToType expected_ty
+ else
+ returnM expected_ty) `thenM` \ expected_ty' ->
+
+ mappM (tc_match expected_ty') matches
where
- tc_match match = tcMatch xve match expected_ty fun_or_case
+ tc_match expected_ty match = tcMatch xve ctxt match expected_ty
\end{code}
\begin{code}
tcMatch :: [(Name,Id)]
+ -> RenamedMatchContext
-> RenamedMatch
- -> TcType -- Expected result-type of the Match.
- -- Early unification with this guy gives better error messages
- -> StmtCtxt
- -> TcM (TcMatch, LIE)
+ -> TcType -- 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
+
+tcMatch xve1 ctxt match@(Match pats maybe_rhs_sig grhss) expected_ty
+ = addSrcLoc (getMatchLoc match) $ -- At one stage I removed this;
+ addErrCtxt (matchCtxt ctxt match) $ -- I'm not sure why, so I put it back
+ tcMatchPats pats expected_ty tc_grhss `thenM` \ (pats', grhss', ex_binds) ->
+ returnM (Match pats' Nothing (glue_on ex_binds grhss'))
-tcMatch xve1 match@(Match sig_tvs pats maybe_rhs_sig grhss) expected_ty ctxt
- = tcAddSrcLoc (getMatchLoc match) $
- tcAddErrCtxt (matchCtxt ctxt match) $
+ where
+ tc_grhss rhs_ty
+ = tcExtendLocalValEnv2 xve1 $
+
+ -- Deal with the result signature
+ case maybe_rhs_sig of
+ Nothing -> tcGRHSs ctxt grhss rhs_ty
+
+ Just sig -> tcAddScopedTyVars [sig] $
+ -- Bring into scope the type variables in the signature
+ tcHsSigType ResSigCtxt sig `thenM` \ sig_ty ->
+ tcGRHSs ctxt grhss sig_ty `thenM` \ grhss' ->
+ tcSubExp rhs_ty sig_ty `thenM` \ co_fn ->
+ returnM (lift_grhss co_fn rhs_ty grhss')
+
+-- 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
+lift_grhss co_fn rhs_ty (GRHSs grhss binds ty)
+ = GRHSs (map lift_grhs grhss) binds rhs_ty -- Change the type, since we
+ where
+ lift_grhs (GRHS stmts loc) = GRHS (map lift_stmt stmts) loc
+
+ lift_stmt (ResultStmt e l) = ResultStmt (co_fn <$> e) l
+ lift_stmt stmt = stmt
+
+-- glue_on just avoids stupid dross
+glue_on EmptyBinds grhss = grhss -- The common case
+glue_on binds1 (GRHSs grhss binds2 ty)
+ = GRHSs grhss (binds1 `ThenBinds` binds2) ty
- 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 ->
+tcGRHSs :: RenamedMatchContext -> RenamedGRHSs
+ -> TcType
+ -> TcM TcGRHSs
- -- 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) ->
+tcGRHSs ctxt (GRHSs grhss binds _) expected_ty
+ = tcBindsAndThen glue_on binds (tc_grhss grhss)
+ where
+ m_ty = (\ty -> ty, expected_ty)
- -- Check that the scoped type variables from the patterns
- -- have not been constrained
- tcAddErrCtxtM (sigPatCtxt sig_tyvars pat_ids) (
- checkSigTyVars sig_tyvars emptyVarSet
- ) `thenTc_`
+ tc_grhss grhss
+ = mappM tc_grhs grhss `thenM` \ grhss' ->
+ returnM (GRHSs grhss' EmptyBinds expected_ty)
- -- *Now* we're free to unify with expected_ty
- unifyTauTy expected_ty tyvar_ty `thenTc_`
+ tc_grhs (GRHS guarded locn)
+ = addSrcLoc locn $
+ tcStmts (PatGuard ctxt) m_ty guarded `thenM` \ guarded' ->
+ returnM (GRHS guarded' locn)
+\end{code}
- returnTc match_and_lie
- where
- sig_tys = case maybe_rhs_sig of { Just t -> [t]; Nothing -> [] }
- ++ collectSigTysFromPats pats
-
- 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) ->
+%************************************************************************
+%* *
+\subsection{tcMatchPats}
+%* *
+%************************************************************************
- -- 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''))
+\begin{code}
+tcMatchPats
+ :: [RenamedPat] -> TcType
+ -> (TcType -> TcM a)
+ -> TcM ([TcPat], a, TcHsBinds)
+-- 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
+ = -- STEP 1: Bring pattern-signature type variables into scope
+ tcAddScopedTyVars (collectSigTysFromPats pats) (
+
+ -- STEP 2: Typecheck the patterns themselves, gathering all the stuff
+ -- then do the thing inside
+ getLIE (tc_match_pats pats expected_ty thing_inside)
+
+ ) `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
+ -- complains that 'a' is captured by the inscope 'a'! (Test (d) in 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 ex_tvs ex_ids ex_lie lie_req expected_ty `thenM` \ ex_binds ->
+ -- NB: we *must* pass "expected_ty" not "result_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).
+
+ returnM (pats', result, mkMonoBind Recursive ex_binds)
+
+tc_match_pats [] expected_ty thing_inside
+ = thing_inside expected_ty `thenM` \ answer ->
+ returnM ([], emptyBag, [], [], answer)
+
+tc_match_pats (pat:pats) expected_ty thing_inside
+ = subFunTy expected_ty $ \ 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 `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 $
+ tc_match_pats pats rest_ty 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
+ )
- -- 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)
+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
+ -> TcType -- and type of the Match; vars in here must not escape
+ -> TcM TcDictBinds -- LIE to float out and dict bindings
+tcCheckExistentialPat ex_tvs ex_ids ex_lie lie_req match_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( null ex_lie )
+ extendLIEs lie_req `thenM_`
+ returnM EmptyMonoBinds
+
+ | otherwise
+ = addErrCtxtM (sigPatCtxt tv_list ex_ids match_ty) $
+
+ -- 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
+ getLIE (bindInstsOfLocalFuns lie_req ex_ids) `thenM` \ (inst_binds, 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)
+ -- Deal with overloaded functions bound by the pattern
+ tcSimplifyCheck doc tv_list ex_lie lie `thenM` \ dict_binds ->
+ checkSigTyVarsWrt (tyVarsOfType match_ty) tv_list `thenM_`
- tc_grhs (GRHS guarded locn)
- = tcAddSrcLoc locn $
- tcStmts ctxt (\ty -> ty) guarded expected_ty `thenTc` \ (guarded', lie) ->
- returnTc (GRHS guarded' locn, lie)
+ returnM (dict_binds `AndMonoBinds` inst_binds)
+ where
+ doc = text ("existential context of a data constructor")
+ tv_list = bagToList ex_tvs
+ not_overloaded id = not (isOverloadedTy (idType id))
\end{code}
%************************************************************************
%* *
-\subsection{tcMatchPats}
+\subsection{@tcDoStmts@ typechecks a {\em list} of do statements}
%* *
%************************************************************************
\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
- )
+tcDoStmts :: HsStmtContext Name -> [RenamedStmt] -> [Name] -> TcType
+ -> TcM (TcMonoBinds, [TcStmt], [Id])
+tcDoStmts PArrComp stmts method_names res_ty
+ = unifyPArrTy res_ty `thenM` \elt_ty ->
+ tcStmts PArrComp (mkPArrTy, elt_ty) stmts `thenM` \ stmts' ->
+ returnM (EmptyMonoBinds, stmts', [{- unused -}])
+
+tcDoStmts ListComp stmts method_names res_ty
+ = unifyListTy res_ty `thenM` \ elt_ty ->
+ tcStmts ListComp (mkListTy, elt_ty) stmts `thenM` \ stmts' ->
+ returnM (EmptyMonoBinds, stmts', [{- unused -}])
+
+tcDoStmts do_or_mdo_expr 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_`
+
+ tcStmts do_or_mdo_expr (mkAppTy m_ty, elt_ty) 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.
+ --
+ mapAndUnzipM (tc_syn_name m_ty)
+ (zipEqual "tcDoStmts" currentMonadNames method_names) `thenM` \ (binds, ids) ->
+ returnM (andMonoBindList binds, stmts', ids)
+ where
+ currentMonadNames = case do_or_mdo_expr of
+ DoExpr -> monadNames
+ MDoExpr -> monadNames ++ [mfixName]
+ tc_syn_name :: TcType -> (Name,Name) -> TcM (TcMonoBinds, Id)
+ tc_syn_name m_ty (std_nm, usr_nm)
+ = tcSyntaxName DoOrigin m_ty std_nm usr_nm `thenM` \ (expr, expr_ty) ->
+ case expr of
+ HsVar v -> returnM (EmptyMonoBinds, v)
+ other -> newUnique `thenM` \ uniq ->
+ let
+ id = mkSysLocal FSLIT("syn") uniq expr_ty
+ in
+ returnM (VarMonoBind id expr, id)
\end{code}
%* *
%************************************************************************
+Typechecking statements is rendered a bit tricky by parallel list comprehensions:
-\begin{code}
-tcStmts :: StmtCtxt
- -> (TcType -> TcType) -- m, the relationship type of pat and rhs in pat <- rhs
- -> [RenamedStmt]
- -> TcType -- elt_ty, where type of the comprehension is (m elt_ty)
- -> TcM ([TcStmt], LIE)
-
-tcStmts do_or_lc m (stmt@(ReturnStmt exp) : stmts) elt_ty
- = 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 [stmt@(ExprStmt exp src_loc)] elt_ty
- = 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 (stmt@(ExprStmt exp src_loc) : stmts) elt_ty
- = 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 stmts elt_ty `thenTc` \ (stmts', stmts_lie) ->
- returnTc (ExprStmt exp' src_loc : stmts',
- exp_lie `plusLIE` stmts_lie)
-
-tcStmts do_or_lc m (stmt@(GuardStmt exp src_loc) : stmts) elt_ty
- = 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 stmts elt_ty `thenTc` \ (stmts', stmts_lie) ->
- returnTc (GuardStmt exp' src_loc : stmts',
- exp_lie `plusLIE` stmts_lie)
-
-tcStmts do_or_lc m (stmt@(BindStmt pat exp src_loc) : stmts) elt_ty
- = 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) ->
- let
- new_val_env = bagToList pat_bndrs
- pat_ids = map snd new_val_env
- pat_tv_list = bagToList pat_tvs
- in
+ [ (g x, h x) | ... ; let g v = ...
+ | ... ; let h v = ... ]
- -- 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 stmts elt_ty
- ) `thenTc` \ (stmts', stmts_lie) ->
+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
- -- Reinstate context for existential checks
- tcSetErrCtxt (stmtCtxt do_or_lc stmt) $
- tcExtendGlobalTyVars (tyVarsOfType (m elt_ty)) $
- tcAddErrCtxtM (sigPatCtxt pat_tv_list pat_ids) $
+ [ (show x, show y) | ... ; C x <- ...
+ | ... ; C y <- ... ]
- checkSigTyVars pat_tv_list emptyVarSet `thenTc` \ zonked_pat_tvs ->
+Then we need the LIE from (show x, show y) to be simplified against
+the bindings for x and y.
- tcSimplifyAndCheck
- (text ("the existential context of a data constructor"))
- (mkVarSet zonked_pat_tvs)
- lie_avail stmts_lie `thenTc` \ (final_lie, dict_binds) ->
+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.
- returnTc (BindStmt pat' exp' src_loc :
- consLetStmt (mkMonoBind dict_binds [] Recursive) stmts',
- lie_req `plusLIE` final_lie)
+\begin{code}
+tcStmts do_or_lc m_ty stmts
+ = ASSERT( notNull stmts )
+ tcStmtsAndThen (:) do_or_lc m_ty stmts (returnM [])
+
+tcStmtsAndThen
+ :: (TcStmt -> thing -> thing) -- Combiner
+ -> HsStmtContext Name
+ -> (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
+ -> TcM thing
-tcStmts do_or_lc m (LetStmt binds : stmts) elt_ty
- = 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 stmts elt_ty)
- where
- combine is_rec binds' stmts' = consLetStmt (mkMonoBind binds' [] is_rec) stmts'
+ -- Base case
+tcStmtsAndThen combine do_or_lc m_ty [] do_next
+ = do_next
+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)
-isDoStmt DoStmt = True
-isDoStmt other = False
+ -- LetStmt
+tcStmtAndThen combine do_or_lc m_ty (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
+ = addSrcLoc src_loc $
+ addErrCtxt (stmtCtxt do_or_lc stmt) $
+ newTyVarTy liftedTypeKind `thenM` \ pat_ty ->
+ tcMonoExpr exp (m pat_ty) `thenM` \ exp' ->
+ tcMatchPats [pat] (mkFunTy pat_ty (m elt_ty)) (\ _ ->
+ popErrCtxt thing_inside
+ ) `thenM` \ ([pat'], thing, dict_binds) ->
+ returnM (combine (BindStmt pat' exp' src_loc)
+ (glue_binds combine dict_binds thing))
+
+ -- ParStmt
+tcStmtAndThen combine do_or_lc m_ty (ParStmtOut bndr_stmts_s) thing_inside
+ = loop bndr_stmts_s `thenM` \ (pairs', thing) ->
+ returnM (combine (ParStmtOut pairs') thing)
+ where
+ loop []
+ = thing_inside `thenM` \ thing ->
+ returnM ([], thing)
+
+ loop ((bndrs,stmts) : pairs)
+ = tcStmtsAndThen
+ combine_par 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 `thenM` \ bndrs' ->
+ loop pairs `thenM` \ (pairs', thing) ->
+ returnM ([], (bndrs', pairs', thing))) `thenM` \ (stmts', (bndrs', pairs', thing)) ->
+
+ returnM ((bndrs',stmts') : pairs', thing)
+
+ combine_par stmt (stmts, thing) = (stmt:stmts, thing)
+
+ -- RecStmt
+tcStmtAndThen combine do_or_lc m_ty (RecStmt recNames stmts _) thing_inside
+ = newTyVarTys (length recNames) liftedTypeKind `thenM` \ recTys ->
+ let
+ mono_ids = zipWith mkLocalId recNames recTys
+ in
+ tcExtendLocalValEnv mono_ids $
+ tcStmtsAndThen combine_rec do_or_lc m_ty stmts (
+ mappM tc_ret (recNames `zip` recTys) `thenM` \ rets ->
+ returnM ([], rets)
+ ) `thenM` \ (stmts', rets) ->
+
+ -- NB: it's the mono_ids that scope over this part
+ thing_inside `thenM` \ thing ->
+
+ returnM (combine (RecStmt mono_ids stmts' 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 mono_ty (idType poly_id) `thenM` \ co_fn ->
+ returnM (co_fn <$> HsVar poly_id)
+
+ -- ExprStmt
+tcStmtAndThen combine do_or_lc m_ty@(m, res_elt_ty) stmt@(ExprStmt exp _ locn) thing_inside
+ = addErrCtxt (stmtCtxt do_or_lc stmt) (
+ if isDoExpr do_or_lc then
+ newTyVarTy openTypeKind `thenM` \ any_ty ->
+ tcMonoExpr exp (m any_ty) `thenM` \ exp' ->
+ returnM (ExprStmt exp' any_ty locn)
+ else
+ tcMonoExpr exp boolTy `thenM` \ exp' ->
+ returnM (ExprStmt exp' boolTy locn)
+ ) `thenM` \ stmt' ->
+
+ thing_inside `thenM` \ thing ->
+ returnM (combine stmt' thing)
+
+
+ -- Result statements
+tcStmtAndThen combine do_or_lc m_ty@(m, res_elt_ty) stmt@(ResultStmt exp locn) thing_inside
+ = addErrCtxt (resCtxt do_or_lc stmt) (
+ if isDoExpr do_or_lc then
+ tcMonoExpr exp (m res_elt_ty)
+ else
+ tcMonoExpr exp res_elt_ty
+ ) `thenM` \ exp' ->
+
+ thing_inside `thenM` \ thing ->
+
+ returnM (combine (ResultStmt exp' locn) thing)
+
+
+------------------------------
+glue_binds combine EmptyBinds thing = thing
+glue_binds combine other_binds thing = combine (LetStmt other_binds) thing
\end{code}
\begin{code}
sameNoOfArgs :: [RenamedMatch] -> Bool
-sameNoOfArgs matches = length (nub (map args_in_match matches)) == 1
+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 (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")
+matchCtxt ctxt match = hang (ptext SLIT("In") <+> pprMatchContext ctxt <> colon) 4 (pprMatch ctxt match)
+stmtCtxt do_or_lc stmt = hang (ptext SLIT("In") <+> pprStmtContext do_or_lc <> colon) 4 (ppr stmt)
+resCtxt do_or_lc stmt = hang (ptext SLIT("In") <+> pprStmtResultContext do_or_lc <> colon) 4 (ppr stmt)
-stmtCtxt do_or_lc stmt
- = hang (ptext SLIT("In") <+> what <> colon)
- 4 (ppr stmt)
+sigPatCtxt bound_tvs bound_ids match_ty tidy_env
+ = zonkTcType match_ty `thenM` \ match_ty' ->
+ let
+ (env1, tidy_tys) = tidyOpenTypes tidy_env (map idType show_ids)
+ (env2, tidy_mty) = tidyOpenType env1 match_ty'
+ 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("and whose type is") <+> ppr tidy_mty])
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