pprMatch, getMatchLoc, pprMatchContext, isDoExpr,
mkMonoBind, nullMonoBinds, collectSigTysFromPats
)
-import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt, RenamedPat, RenamedHsType,
- RenamedMatchContext, extractHsTyVars )
+import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt, RenamedPat, RenamedMatchContext )
import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TypecheckedPat )
import TcMonad
-import TcMonoType ( kcHsSigTypes, tcScopedTyVars, checkSigTyVars, tcHsSigType, UserTypeCtxt(..), sigPatCtxt )
+import TcMonoType ( tcAddScopedTyVars, tcHsSigType, UserTypeCtxt(..) )
import Inst ( LIE, isEmptyLIE, plusLIE, emptyLIE, plusLIEs, lieToList )
-import TcEnv ( TcId, tcLookupLocalIds, tcExtendLocalValEnv, tcExtendGlobalTyVars,
- tcInLocalScope )
+import TcEnv ( TcId, tcLookupLocalIds, tcExtendLocalValEnv, tcExtendGlobalTyVars )
import TcPat ( tcPat, tcMonoPatBndr, polyPatSig )
-import TcMType ( newTyVarTy, unifyFunTy, unifyTauTy )
-import TcType ( tyVarsOfType, isTauTy, mkFunTy, isOverloadedTy,
- liftedTypeKind, openTypeKind )
+import TcMType ( newTyVarTy )
+import TcType ( TcType, TcTyVar, tyVarsOfType, isTauTy,
+ mkFunTy, isOverloadedTy, liftedTypeKind, openTypeKind )
import TcBinds ( tcBindsAndThen )
+import TcUnify ( subFunTy, unifyTauTy, checkSigTyVars, sigPatCtxt )
import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns )
import Name ( Name )
import TysWiredIn ( boolTy )
import Id ( idType )
import BasicTypes ( RecFlag(..) )
-import NameSet
import VarSet
import Var ( Id )
import Bag
+import Util ( isSingleton )
import Outputable
+
import List ( nub )
\end{code}
-- 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
+ -- No need to zonk expected_ty, because subFunTy does that on the fly
tcMatches xve (FunRhs fun_name) matches expected_ty
\end{code}
tcMatch :: [(Name,Id)]
-> RenamedMatchContext
-> RenamedMatch
- -> TcType -- Expected result-type of the Match.
- -- Early unification with this guy gives better error messages
+ -> 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, LIE)
-tcMatch xve1 ctxt match@(Match sig_tvs pats maybe_rhs_sig grhss) expected_ty
+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)
+ returnTc (Match pats' Nothing (glue_on Recursive ex_binds grhss'), lie)
where
tc_grhss pats' rhs_ty
= -- 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_`
+ checkTc (isTauTy rhs_ty) lurkingRank2SigErr `thenTc` \_ ->
-- Deal with the result signature
- tc_result_sig maybe_rhs_sig (
+ -- It "wraps" the rest of the body typecheck because it may
+ -- bring into scope the type variables in the signature
+ tc_result_sig maybe_rhs_sig rhs_ty $
-- Typecheck the body
- tcExtendLocalValEnv xve1 $
- tcGRHSs ctxt grhss rhs_ty `thenTc` \ (grhss', lie) ->
- returnTc ((pats', grhss'), lie)
- )
+ tcExtendLocalValEnv xve1 $
+ tcGRHSs ctxt grhss rhs_ty `thenTc` \ (grhss', lie) ->
+ returnTc ((pats', grhss'), lie)
- tc_result_sig Nothing thing_inside
+ tc_result_sig Nothing rhs_ty thing_inside
= thing_inside
- tc_result_sig (Just sig) thing_inside
+ tc_result_sig (Just sig) rhs_ty thing_inside
= tcAddScopedTyVars [sig] $
tcHsSigType ResSigCtxt 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 expected_ty sig_ty `thenTc_`
+ unifyTauTy sig_ty rhs_ty `thenTc_`
thing_inside
tcMatchPats pats expected_ty thing_inside
= -- STEP 1: Bring pattern-signature type variables into scope
- tcAddScopedTyVars (collectSigTysFromPats pats) $
+ tcAddScopedTyVars (collectSigTysFromPats pats) (
-- 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) ->
+ 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
+ let
xve = bagToList pat_bndrs
pat_ids = map snd xve
- in
- tcExtendLocalValEnv xve (thing_inside pats' rhs_ty) `thenTc` \ (result, lie_req2) ->
+ in
+ tcExtendLocalValEnv xve (thing_inside pats' rhs_ty) `thenTc` \ (result, lie_req2) ->
+
+ 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) ->
-- 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 pat_ids ex_tvs lie_avail lie_req2 rhs_ty `thenTc` \ (lie_req2', ex_binds) ->
+ 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
+ -- 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)
-tcAddScopedTyVars :: [RenamedHsType] -> TcM a -> TcM a
--- Find the not-already-in-scope signature type variables,
--- kind-check them, and bring them into scope
---
--- We no longer specify that these type variables must be univerally
--- quantified (lots of email on the subject). If you want to put that
--- back in, you need to
--- a) Do a checkSigTyVars after thing_inside
--- b) More insidiously, don't pass in expected_ty, else
--- we unify with it too early and checkSigTyVars barfs
--- Instead you have to pass in a fresh ty var, and unify
--- it with expected_ty afterwards
-tcAddScopedTyVars sig_tys thing_inside
- = tcGetEnv `thenNF_Tc` \ env ->
- let
- all_sig_tvs = foldr (unionNameSets . extractHsTyVars) emptyNameSet sig_tys
- sig_tvs = filter not_in_scope (nameSetToList all_sig_tvs)
- not_in_scope tv = not (tcInLocalScope env tv)
- in
- tcScopedTyVars sig_tvs (kcHsSigTypes sig_tys) thing_inside
-
tcCheckExistentialPat :: [TcId] -- Ids bound by this pattern
-> Bag TcTyVar -- Existentially quantified tyvars bound by pattern
-> LIE -- and context
-> LIE -- Required context
- -> TcType -- and result type; vars in here must not escape
+ -> 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 result_ty
+tcCheckExistentialPat ids ex_tvs lie_avail lie_req match_ty
| isEmptyBag ex_tvs && all not_overloaded ids
-- Short cut for case when there are no existentials
-- and no polymorphic overloaded variables
returnTc (lie_req, EmptyMonoBinds)
| otherwise
- = tcExtendGlobalTyVars (tyVarsOfType result_ty) $
+ = tcExtendGlobalTyVars (tyVarsOfType match_ty) $
tcAddErrCtxtM (sigPatCtxt tv_list ids) $
-- In case there are any polymorpic, overloaded binders in the pattern
bindInstsOfLocalFuns lie_req ids `thenTc` \ (lie1, inst_binds) ->
-- Deal with overloaded functions bound by the pattern
- tcSimplifyCheck doc tv_list
- (lieToList lie_avail) lie1 `thenTc` \ (lie2, dict_binds) ->
+ tcSimplifyCheck doc tv_list (lieToList lie_avail) lie1 `thenTc` \ (lie2, dict_binds) ->
checkSigTyVars tv_list emptyVarSet `thenTc_`
returnTc (lie2, dict_binds `AndMonoBinds` inst_binds)
= returnTc (expected_ty, [], emptyLIE, emptyBag, emptyBag, emptyLIE)
tc_match_pats (pat:pats) expected_ty
- = unifyFunTy expected_ty `thenTc` \ (arg_ty, rest_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,
\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}
projects / ghc-hetmet.git / blobdiff