\section[TcMatches]{Typecheck some @Matches@}
\begin{code}
-module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda,
- tcStmts, tcStmtsAndThen, tcGRHSs
+module TcMatches ( tcMatchesFun, tcGRHSsPat, tcMatchesCase, tcMatchLambda,
+ matchCtxt, TcMatchCtxt(..),
+ tcStmts, tcDoStmts,
+ tcDoStmt, tcMDoStmt, tcGuardStmt
) where
#include "HsVersions.h"
-import {-# SOURCE #-} TcExpr( tcMonoExpr )
-
-import HsSyn ( HsBinds(..), Match(..), GRHSs(..), GRHS(..),
- MonoBinds(..), Stmt(..), HsMatchContext(..), HsDoContext(..),
- pprMatch, getMatchLoc, pprMatchContext, isDoExpr,
- mkMonoBind, nullMonoBinds, collectSigTysFromPats
- )
-import RnHsSyn ( RenamedMatch, RenamedGRHSs, RenamedStmt, RenamedPat, RenamedMatchContext )
-import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TypecheckedPat )
-
-import TcMonad
-import TcMonoType ( tcAddScopedTyVars, tcHsSigType, UserTypeCtxt(..) )
-import Inst ( LIE, isEmptyLIE, plusLIE, emptyLIE, plusLIEs, lieToList )
-import TcEnv ( TcId, tcLookupLocalIds, tcExtendLocalValEnv2 )
-import TcPat ( tcPat, tcMonoPatBndr )
-import TcMType ( newTyVarTy, zonkTcType, zapToType )
-import TcType ( TcType, TcTyVar, tyVarsOfType, tidyOpenTypes, tidyOpenType,
- mkFunTy, isOverloadedTy, liftedTypeKind, openTypeKind )
-import TcBinds ( tcBindsAndThen )
-import TcUnify ( subFunTy, checkSigTyVarsWrt, tcSubExp, isIdCoercion, (<$>) )
-import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns )
+import {-# SOURCE #-} TcExpr( tcSyntaxOp, tcInferRho, tcMonoExpr, tcPolyExpr )
+
+import HsSyn ( HsExpr(..), LHsExpr, MatchGroup(..),
+ Match(..), LMatch, GRHSs(..), GRHS(..),
+ Stmt(..), LStmt, HsMatchContext(..), HsStmtContext(..),
+ pprMatch, isIrrefutableHsPat, mkHsCoerce,
+ pprMatchContext, pprStmtContext,
+ noSyntaxExpr, matchGroupArity, pprMatches,
+ ExprCoFn )
+
+import TcRnMonad
+import TcHsType ( tcPatSig, UserTypeCtxt(..) )
+import Inst ( newMethodFromName )
+import TcEnv ( TcId, tcLookupLocalIds, tcLookupId, tcExtendIdEnv,
+ tcExtendTyVarEnv2 )
+import TcPat ( PatCtxt(..), tcPats, tcPat )
+import TcMType ( newFlexiTyVarTy, newFlexiTyVarTys )
+import TcType ( TcType, TcRhoType,
+ BoxySigmaType, BoxyRhoType,
+ mkFunTys, mkFunTy, mkAppTy, mkTyConApp,
+ liftedTypeKind )
+import TcBinds ( tcLocalBinds )
+import TcUnify ( boxySplitAppTy, boxySplitTyConApp, boxySplitListTy,
+ subFunTys, tcSubExp, withBox )
+import TcSimplify ( bindInstsOfLocalFuns )
import Name ( Name )
-import TysWiredIn ( boolTy )
-import Id ( idType )
-import CoreFVs ( idFreeTyVars )
-import BasicTypes ( RecFlag(..) )
-import VarSet
-import Var ( Id )
-import Bag
-import Util ( isSingleton, lengthExceeds, notNull )
+import TysWiredIn ( stringTy, boolTy, parrTyCon, listTyCon, mkListTy, mkPArrTy )
+import PrelNames ( bindMName, returnMName, mfixName, thenMName, failMName )
+import Id ( idType, mkLocalId )
+import TyCon ( TyCon )
+import Util ( isSingleton )
import Outputable
+import SrcLoc ( Located(..), getLoc )
+import ErrUtils ( Message )
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
+ -> BoxyRhoType -- Expected type of function
+ -> TcM (ExprCoFn, 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...
+ checkArgs 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 subFunTy does that on the fly
- tcMatches xve (FunRhs fun_name) matches expected_ty
+ -- 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.
+ ; subFunTys doc n_pats exp_ty $ \ pat_tys rhs_ty ->
+ tcMatches match_ctxt pat_tys rhs_ty matches
+ }
+ where
+ doc = ptext SLIT("The equation(s) for") <+> quotes (ppr fun_name)
+ <+> ptext SLIT("have") <+> speakNOf n_pats (ptext SLIT("argument"))
+ n_pats = matchGroupArity matches
+ match_ctxt = MC { mc_what = FunRhs fun_name, mc_body = tcPolyExpr }
\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
+ -> TcRhoType -- Type of scrutinee
+ -> MatchGroup Name -- The case alternatives
+ -> BoxyRhoType -- Type of whole case expressions
+ -> TcM (MatchGroup TcId) -- Translated alternatives
+
+tcMatchesCase ctxt scrut_ty matches res_ty
+ = tcMatches ctxt [scrut_ty] res_ty matches
+
+tcMatchLambda :: MatchGroup Name -> BoxyRhoType -> TcM (ExprCoFn, MatchGroup TcId)
+tcMatchLambda match res_ty
+ = subFunTys doc n_pats res_ty $ \ pat_tys rhs_ty ->
+ tcMatches match_ctxt pat_tys rhs_ty match
+ where
+ n_pats = matchGroupArity match
+ doc = sep [ ptext SLIT("The lambda expression")
+ <+> quotes (pprSetDepth 1 $ pprMatches LambdaExpr match),
+ -- The pprSetDepth makes the abstraction print briefly
+ ptext SLIT("has") <+> speakNOf n_pats (ptext SLIT("arguments"))]
+ match_ctxt = MC { mc_what = LambdaExpr,
+ mc_body = tcPolyExpr }
\end{code}
+@tcGRHSsPat@ typechecks @[GRHSs]@ that occur in a @PatMonoBind@.
\begin{code}
-tcMatches :: [(Name,Id)]
- -> RenamedMatchContext
- -> [RenamedMatch]
- -> TcType
- -> TcM ([TcMatch], LIE)
-
-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
- returnNF_Tc expected_ty) `thenNF_Tc` \ expected_ty' ->
-
- mapAndUnzipTc (tc_match expected_ty') matches `thenTc` \ (matches, lies) ->
- returnTc (matches, plusLIEs lies)
+tcGRHSsPat :: GRHSs Name -> BoxyRhoType -> TcM (GRHSs TcId)
+tcGRHSsPat grhss res_ty = tcGRHSs match_ctxt grhss res_ty
where
- tc_match expected_ty match = tcMatch xve ctxt match expected_ty
+ match_ctxt = MC { mc_what = PatBindRhs,
+ mc_body = tcPolyExpr }
\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
- -- We regard the Match as having type
- -- (ty1 -> ... -> tyn -> result_ty)
- -- where there are n patterns.
- -> TcM (TcMatch, LIE)
-
-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)
-
+tcMatches :: TcMatchCtxt
+ -> [BoxySigmaType] -- Expected pattern types
+ -> BoxyRhoType -- 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
+ -> BoxyRhoType
+ -> TcM (LHsExpr TcId) }
+
+tcMatches ctxt pat_tys rhs_ty (MatchGroup matches _)
+ = do { matches' <- mapM (tcMatch ctxt pat_tys rhs_ty) matches
+ ; return (MatchGroup matches' (mkFunTys pat_tys rhs_ty)) }
+
+-------------
+tcMatch :: TcMatchCtxt
+ -> [BoxySigmaType] -- Expected pattern types
+ -> BoxyRhoType -- 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
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 `thenTc` \ sig_ty ->
- tcGRHSs ctxt grhss sig_ty `thenTc` \ (grhss', lie1) ->
- tcSubExp rhs_ty sig_ty `thenTc` \ (co_fn, lie2) ->
- returnTc (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
-lift_grhss co_fn rhs_ty (GRHSs grhss binds ty)
- = GRHSs (map lift_grhs grhss) binds rhs_ty -- Change the type, since we
+ tc_match ctxt pat_tys rhs_ty match@(Match pats maybe_rhs_sig grhss)
+ = addErrCtxt (matchCtxt (mc_what ctxt) match) $
+ do { (pats', grhss') <- tcPats LamPat pats pat_tys rhs_ty $
+ tc_grhss ctxt maybe_rhs_sig grhss
+ ; 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 { (inner_ty, sig_tvs) <- tcPatSig ResSigCtxt res_sig rhs_ty
+ ; tcExtendTyVarEnv2 sig_tvs $
+ tcGRHSs ctxt grhss inner_ty }
+
+-------------
+tcGRHSs :: TcMatchCtxt -> GRHSs Name -> BoxyRhoType -> TcM (GRHSs TcId)
+
+-- Notice that we pass in the full res_ty, so that we get
+-- good inference from simple things like
+-- f = \(x::forall a.a->a) -> <stuff>
+-- We used to force it to be a monotype when there was more than one guard
+-- but we don't need to do that any more
+
+tcGRHSs ctxt (GRHSs grhss binds) res_ty
+ = do { (binds', grhss') <- tcLocalBinds binds $
+ mappM (wrapLocM (tcGRHS ctxt res_ty)) grhss
+
+ ; returnM (GRHSs grhss' binds') }
+
+-------------
+tcGRHS :: TcMatchCtxt -> BoxyRhoType -> GRHS Name -> TcM (GRHS TcId)
+
+tcGRHS ctxt res_ty (GRHS guards rhs)
+ = do { (guards', rhs') <- tcStmts stmt_ctxt tcGuardStmt guards res_ty $
+ mc_body ctxt rhs
+ ; return (GRHS guards' rhs') }
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 _ 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 :: 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)
+ stmt_ctxt = PatGuard (mc_what ctxt)
\end{code}
%************************************************************************
%* *
-\subsection{tcMatchPats}
+\subsection{@tcDoStmts@ typechecks a {\em list} of do statements}
%* *
%************************************************************************
-\begin{code}
-tcMatchPats
- :: [RenamedPat] -> TcType
- -> (TcType -> TcM (a, LIE))
- -> TcM ([TypecheckedPat], a, LIE, TcDictBinds)
--- 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
- tc_match_pats pats expected_ty thing_inside
-
- ) `thenTc` \ (pats', lie_req, ex_tvs, ex_ids, ex_lie, result) ->
-
- -- 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 `thenTc` \ (lie_req', 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 (pats', result, lie_req', ex_binds)
-
-tc_match_pats [] expected_ty thing_inside
- = thing_inside expected_ty `thenTc` \ (answer, lie) ->
- returnTc ([], lie, emptyBag, [], emptyLIE, 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 `thenTc` \ (pat', lie_req, 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 `thenTc` \ (pats', lie_reqs, exs_tvs, exs_ids, exs_lie, answer) ->
- returnTc ( pat':pats',
- lie_req `plusLIE` lie_reqs,
- ex_tvs `unionBags` exs_tvs,
- ex_ids ++ exs_ids,
- ex_lie `plusLIE` 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
- -> 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 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( isEmptyLIE ex_lie )
- returnTc (lie_req, EmptyMonoBinds)
-
- | otherwise
- = tcAddErrCtxtM (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
- bindInstsOfLocalFuns lie_req ex_ids `thenTc` \ (lie1, inst_binds) ->
-
- -- Deal with overloaded functions bound by the pattern
- tcSimplifyCheck doc tv_list (lieToList ex_lie) lie1 `thenTc` \ (lie2, dict_binds) ->
- checkSigTyVarsWrt (tyVarsOfType match_ty) tv_list `thenTc_`
-
- returnTc (lie2, 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))
+\begin{code}
+tcDoStmts :: HsStmtContext Name
+ -> [LStmt Name]
+ -> LHsExpr Name
+ -> BoxyRhoType
+ -> TcM (HsExpr TcId) -- Returns a HsDo
+tcDoStmts ListComp stmts body res_ty
+ = do { elt_ty <- boxySplitListTy res_ty
+ ; (stmts', body') <- tcStmts ListComp (tcLcStmt listTyCon) stmts elt_ty $
+ tcBody (doBodyCtxt ListComp body) body
+ ; return (HsDo ListComp stmts' body' (mkListTy elt_ty)) }
+
+tcDoStmts PArrComp stmts body res_ty
+ = do { [elt_ty] <- boxySplitTyConApp parrTyCon res_ty
+ ; (stmts', body') <- tcStmts PArrComp (tcLcStmt parrTyCon) stmts elt_ty $
+ tcBody (doBodyCtxt PArrComp body) body
+ ; return (HsDo PArrComp stmts' body' (mkPArrTy elt_ty)) }
+
+tcDoStmts DoExpr stmts body res_ty
+ = do { (m_ty, elt_ty) <- boxySplitAppTy res_ty
+ ; let res_ty' = mkAppTy m_ty elt_ty -- The boxySplit consumes res_ty
+ ; (stmts', body') <- tcStmts DoExpr (tcDoStmt m_ty) stmts res_ty' $
+ tcBody (doBodyCtxt DoExpr body) body
+ ; return (HsDo DoExpr stmts' body' res_ty') }
+
+tcDoStmts ctxt@(MDoExpr _) stmts body res_ty
+ = do { (m_ty, elt_ty) <- boxySplitAppTy res_ty
+ ; let res_ty' = mkAppTy m_ty elt_ty -- The boxySplit consumes res_ty
+ tc_rhs rhs = withBox liftedTypeKind $ \ pat_ty ->
+ tcMonoExpr rhs (mkAppTy m_ty pat_ty)
+
+ ; (stmts', body') <- tcStmts ctxt (tcMDoStmt tc_rhs) stmts res_ty' $
+ tcBody (doBodyCtxt ctxt body) body
+
+ ; let names = [mfixName, bindMName, thenMName, returnMName, failMName]
+ ; insts <- mapM (newMethodFromName DoOrigin m_ty) names
+ ; return (HsDo (MDoExpr (names `zip` insts)) stmts' body' res_ty') }
+
+tcDoStmts ctxt stmts body res_ty = pprPanic "tcDoStmts" (pprStmtContext ctxt)
+
+tcBody :: Message -> LHsExpr Name -> BoxyRhoType -> TcM (LHsExpr TcId)
+tcBody ctxt body res_ty
+ = -- addErrCtxt ctxt $ -- This context adds little that is useful
+ tcPolyExpr body res_ty
\end{code}
%* *
%************************************************************************
-Typechecking statements is rendered a bit tricky by parallel list comprehensions:
-
- [ (g x, h x) | ... ; let g v = ...
- | ... ; let h v = ... ]
-
-It's possible that g,h are overloaded, so we need to feed the LIE from the
-(g x, h x) up through both lots of bindings (so we get the bindInstsOfLocalFuns).
-Similarly if we had an existential pattern match:
-
- data T = forall a. Show a => C a
-
- [ (show x, show y) | ... ; C x <- ...
- | ... ; C y <- ... ]
-
-Then we need the LIE from (show x, show y) to be simplified against
-the bindings for x and y.
-
-It's difficult to do this in parallel, so we rely on the renamer to
-ensure that g,h and x,y don't duplicate, and simply grow the environment.
-So the binders of the first parallel group will be in scope in the second
-group. But that's fine; there's no shadowing to worry about.
-
\begin{code}
-tcStmts do_or_lc m_ty stmts
- = ASSERT( notNull stmts )
- tcStmtsAndThen (:) do_or_lc m_ty stmts (returnTc ([], emptyLIE))
-
-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)
-
- -- 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)
-
- -- 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
- = tcAddSrcLoc src_loc $
- tcAddErrCtxt (stmtCtxt do_or_lc stmt) $
- newTyVarTy liftedTypeKind `thenNF_Tc` \ pat_ty ->
- tcMonoExpr exp (m pat_ty) `thenTc` \ (exp', exp_lie) ->
- tcMatchPats [pat] (mkFunTy pat_ty (m elt_ty)) (\ _ ->
- tcPopErrCtxt thing_inside
- ) `thenTc` \ ([pat'], thing, lie, dict_binds) ->
- returnTc (combine (BindStmt pat' exp' src_loc)
- (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)
+type TcStmtChecker
+ = forall thing. HsStmtContext Name
+ -> Stmt Name
+ -> BoxyRhoType -- Result type for comprehension
+ -> (BoxyRhoType -> TcM thing) -- Checker for what follows the stmt
+ -> TcM (Stmt TcId, thing)
+
+ -- The incoming BoxyRhoType may be refined by type refinements
+ -- before being passed to the thing_inside
+
+tcStmts :: HsStmtContext Name
+ -> TcStmtChecker -- NB: higher-rank type
+ -> [LStmt Name]
+ -> BoxyRhoType
+ -> (BoxyRhoType -> TcM thing)
+ -> TcM ([LStmt TcId], thing)
+
+-- Note the higher-rank type. stmt_chk is applied at different
+-- types in the equations for tcStmts
+
+tcStmts ctxt stmt_chk [] res_ty thing_inside
+ = do { thing <- thing_inside res_ty
+ ; return ([], thing) }
+
+-- LetStmts are handled uniformly, regardless of context
+tcStmts ctxt stmt_chk (L loc (LetStmt binds) : stmts) res_ty thing_inside
+ = do { (binds', (stmts',thing)) <- tcLocalBinds binds $
+ tcStmts ctxt stmt_chk stmts res_ty thing_inside
+ ; return (L loc (LetStmt binds') : stmts', thing) }
+
+-- For the vanilla case, handle the location-setting part
+tcStmts ctxt stmt_chk (L loc stmt : stmts) res_ty thing_inside
+ = do { (stmt', (stmts', thing)) <-
+ setSrcSpan loc $
+ addErrCtxt (stmtCtxt ctxt stmt) $
+ stmt_chk ctxt stmt res_ty $ \ res_ty' ->
+ popErrCtxt $
+ tcStmts ctxt stmt_chk stmts res_ty' $
+ thing_inside
+ ; return (L loc stmt' : stmts', thing) }
+
+--------------------------------
+-- Pattern guards
+tcGuardStmt :: TcStmtChecker
+tcGuardStmt ctxt (ExprStmt guard _ _) res_ty thing_inside
+ = do { guard' <- tcMonoExpr guard boolTy
+ ; thing <- thing_inside res_ty
+ ; return (ExprStmt guard' noSyntaxExpr boolTy, thing) }
+
+tcGuardStmt ctxt (BindStmt pat rhs _ _) res_ty thing_inside
+ = do { (rhs', rhs_ty) <- tcInferRho rhs
+ ; (pat', thing) <- tcPat LamPat pat rhs_ty res_ty thing_inside
+ ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
+
+tcGuardStmt ctxt stmt res_ty thing_inside
+ = pprPanic "tcGuardStmt: unexpected Stmt" (ppr stmt)
+
+
+--------------------------------
+-- List comprehensions and PArrays
+
+tcLcStmt :: TyCon -- The list/Parray type constructor ([] or PArray)
+ -> TcStmtChecker
+
+-- A generator, pat <- rhs
+tcLcStmt m_tc ctxt (BindStmt pat rhs _ _) res_ty thing_inside
+ = do { (rhs', pat_ty) <- withBox liftedTypeKind $ \ ty ->
+ tcMonoExpr rhs (mkTyConApp m_tc [ty])
+ ; (pat', thing) <- tcPat LamPat pat pat_ty res_ty thing_inside
+ ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
+
+-- A boolean guard
+tcLcStmt m_tc ctxt (ExprStmt rhs _ _) res_ty thing_inside
+ = do { rhs' <- tcMonoExpr rhs boolTy
+ ; thing <- thing_inside res_ty
+ ; return (ExprStmt rhs' noSyntaxExpr boolTy, thing) }
+
+-- A parallel set of comprehensions
+-- [ (g x, h x) | ... ; let g v = ...
+-- | ... ; let h v = ... ]
+--
+-- It's possible that g,h are overloaded, so we need to feed the LIE from the
+-- (g x, h x) up through both lots of bindings (so we get the bindInstsOfLocalFuns).
+-- Similarly if we had an existential pattern match:
+--
+-- data T = forall a. Show a => C a
+--
+-- [ (show x, show y) | ... ; C x <- ...
+-- | ... ; C y <- ... ]
+--
+-- Then we need the LIE from (show x, show y) to be simplified against
+-- the bindings for x and y.
+--
+-- It's difficult to do this in parallel, so we rely on the renamer to
+-- ensure that g,h and x,y don't duplicate, and simply grow the environment.
+-- So the binders of the first parallel group will be in scope in the second
+-- group. But that's fine; there's no shadowing to worry about.
+
+tcLcStmt m_tc ctxt (ParStmt bndr_stmts_s) elt_ty thing_inside
+ = do { (pairs', thing) <- loop bndr_stmts_s
+ ; return (ParStmt pairs', thing) }
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)
-
- -- 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 ->
- tcMonoExpr exp (m any_ty) `thenNF_Tc` \ (exp', lie) ->
- returnTc (ExprStmt exp' any_ty locn, lie)
- else
- tcMonoExpr exp boolTy `thenNF_Tc` \ (exp', lie) ->
- returnTc (ExprStmt exp' boolTy locn, lie)
- ) `thenTc` \ (stmt', stmt_lie) ->
-
- thing_inside `thenTc` \ (thing, stmts_lie) ->
-
- returnTc (combine stmt' thing, stmt_lie `plusLIE` stmts_lie)
-
-
- -- 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
- tcMonoExpr exp (m res_elt_ty)
- else
- tcMonoExpr 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)
-
-
-------------------------------
-glue_binds combine is_rec binds thing
- | nullMonoBinds binds = thing
- | otherwise = combine (LetStmt (mkMonoBind binds [] is_rec)) thing
+ -- loop :: [([LStmt Name], [Name])] -> TcM ([([LStmt TcId], [TcId])], thing)
+ loop [] = do { thing <- thing_inside elt_ty -- No refinement from pattern
+ ; return ([], thing) } -- matching in the branches
+
+ loop ((stmts, names) : pairs)
+ = do { (stmts', (ids, pairs', thing))
+ <- tcStmts ctxt (tcLcStmt m_tc) stmts elt_ty $ \ elt_ty' ->
+ do { ids <- tcLookupLocalIds names
+ ; (pairs', thing) <- loop pairs
+ ; return (ids, pairs', thing) }
+ ; return ( (stmts', ids) : pairs', thing ) }
+
+tcLcStmt m_tc ctxt stmt elt_ty thing_inside
+ = pprPanic "tcLcStmt: unexpected Stmt" (ppr stmt)
+
+--------------------------------
+-- Do-notation
+-- The main excitement here is dealing with rebindable syntax
+
+tcDoStmt :: TcType -- Monad type, m
+ -> TcStmtChecker
+
+tcDoStmt m_ty ctxt (BindStmt pat rhs bind_op fail_op) res_ty thing_inside
+ = do { (rhs', pat_ty) <- withBox liftedTypeKind $ \ pat_ty ->
+ tcMonoExpr rhs (mkAppTy m_ty pat_ty)
+ -- We should 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.
+
+ ; (pat', thing) <- tcPat LamPat pat pat_ty res_ty thing_inside
+
+ -- Deal with rebindable syntax; (>>=) :: m a -> (a -> m b) -> m b
+ ; let bind_ty = mkFunTys [mkAppTy m_ty pat_ty,
+ mkFunTy pat_ty res_ty] res_ty
+ ; bind_op' <- tcSyntaxOp DoOrigin bind_op bind_ty
+ -- If (but only if) the pattern can fail,
+ -- typecheck the 'fail' operator
+ ; fail_op' <- if isIrrefutableHsPat pat'
+ then return noSyntaxExpr
+ else tcSyntaxOp DoOrigin fail_op (mkFunTy stringTy res_ty)
+ ; return (BindStmt pat' rhs' bind_op' fail_op', thing) }
+
+
+tcDoStmt m_ty ctxt (ExprStmt rhs then_op _) res_ty thing_inside
+ = do { -- Deal with rebindable syntax; (>>) :: m a -> m b -> m b
+ a_ty <- newFlexiTyVarTy liftedTypeKind
+ ; let rhs_ty = mkAppTy m_ty a_ty
+ then_ty = mkFunTys [rhs_ty, res_ty] res_ty
+ ; then_op' <- tcSyntaxOp DoOrigin then_op then_ty
+ ; rhs' <- tcPolyExpr rhs rhs_ty
+ ; thing <- thing_inside res_ty
+ ; return (ExprStmt rhs' then_op' rhs_ty, thing) }
+
+tcDoStmt m_ty ctxt stmt res_ty thing_inside
+ = pprPanic "tcDoStmt: unexpected Stmt" (ppr stmt)
+
+--------------------------------
+-- Mdo-notation
+-- The distinctive features here are
+-- (a) RecStmts, and
+-- (b) no rebindable syntax
+
+tcMDoStmt :: (LHsExpr Name -> TcM (LHsExpr TcId, TcType)) -- RHS inference
+ -> TcStmtChecker
+tcMDoStmt tc_rhs ctxt (BindStmt pat rhs bind_op fail_op) res_ty thing_inside
+ = do { (rhs', pat_ty) <- tc_rhs rhs
+ ; (pat', thing) <- tcPat LamPat pat pat_ty res_ty thing_inside
+ ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
+
+tcMDoStmt tc_rhs ctxt (ExprStmt rhs then_op _) res_ty thing_inside
+ = do { (rhs', elt_ty) <- tc_rhs rhs
+ ; thing <- thing_inside res_ty
+ ; return (ExprStmt rhs' noSyntaxExpr elt_ty, thing) }
+
+tcMDoStmt tc_rhs ctxt (RecStmt stmts laterNames recNames _ _) res_ty thing_inside
+ = do { rec_tys <- newFlexiTyVarTys (length recNames) liftedTypeKind
+ ; let rec_ids = zipWith mkLocalId recNames rec_tys
+ ; tcExtendIdEnv rec_ids $ do
+ { (stmts', (later_ids, rec_rets))
+ <- tcStmts ctxt (tcMDoStmt tc_rhs) stmts res_ty $ \ res_ty' ->
+ -- ToDo: res_ty not really right
+ do { rec_rets <- zipWithM tc_ret recNames rec_tys
+ ; later_ids <- tcLookupLocalIds laterNames
+ ; return (later_ids, rec_rets) }
+
+ ; (thing,lie) <- tcExtendIdEnv later_ids (getLIE (thing_inside res_ty))
+ -- NB: The rec_ids for the recursive things
+ -- already scope over this part. This binding may shadow
+ -- some of them with polymorphic things with the same Name
+ -- (see note [RecStmt] in HsExpr)
+ ; lie_binds <- bindInstsOfLocalFuns lie later_ids
+
+ ; return (RecStmt stmts' later_ids rec_ids rec_rets lie_binds, thing)
+ }}
+ where
+ -- Unify the types of the "final" Ids with those of "knot-tied" Ids
+ tc_ret rec_name mono_ty
+ = do { poly_id <- tcLookupId rec_name
+ -- poly_id may have a polymorphic type
+ -- but mono_ty is just a monomorphic type variable
+ ; co_fn <- tcSubExp (idType poly_id) mono_ty
+ ; return (mkHsCoerce co_fn (HsVar poly_id)) }
+
+tcMDoStmt tc_rhs ctxt stmt res_ty thing_inside
+ = pprPanic "tcMDoStmt: unexpected Stmt" (ppr stmt)
+
\end{code}
number of args are used in each equation.
\begin{code}
-sameNoOfArgs :: [RenamedMatch] -> Bool
-sameNoOfArgs matches = isSingleton (nub (map args_in_match matches))
+checkArgs :: Name -> MatchGroup Name -> TcM ()
+checkArgs fun (MatchGroup (match1:matches) _)
+ | null bad_matches = return ()
+ | otherwise
+ = failWithTc (vcat [ptext SLIT("Equations for") <+> quotes (ppr fun) <+>
+ ptext SLIT("have different numbers of arguments"),
+ nest 2 (ppr (getLoc match1)),
+ nest 2 (ppr (getLoc (head bad_matches)))])
where
- args_in_match :: RenamedMatch -> Int
- args_in_match (Match pats _ _) = length pats
+ n_args1 = args_in_match match1
+ bad_matches = [m | m <- matches, args_in_match m /= n_args1]
+
+ args_in_match :: LMatch Name -> Int
+ args_in_match (L _ (Match pats _ _)) = length pats
\end{code}
\begin{code}
-varyingArgsErr name matches
- = sep [ptext SLIT("Varying number of arguments for function"), quotes (ppr name)]
-
-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)
-
-sigPatCtxt bound_tvs bound_ids match_ty tidy_env
- = zonkTcType match_ty `thenNF_Tc` \ match_ty' ->
- let
- (env1, tidy_tys) = tidyOpenTypes tidy_env (map idType show_ids)
- (env2, tidy_mty) = tidyOpenType env1 match_ty'
- in
- returnNF_Tc (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
- show_ids = filter is_interesting bound_ids
- is_interesting id = any (`elemVarSet` idFreeTyVars id) bound_tvs
+matchCtxt ctxt match = hang (ptext SLIT("In") <+> pprMatchContext ctxt <> colon)
+ 4 (pprMatch ctxt match)
+
+doBodyCtxt :: HsStmtContext Name -> LHsExpr Name -> SDoc
+doBodyCtxt ctxt body = hang (ptext SLIT("In the result of") <+> pprStmtContext ctxt <> colon)
+ 4 (ppr body)
- ppr_id id ty = ppr id <+> dcolon <+> ppr ty
- -- Don't zonk the types so we get the separate, un-unified versions
+stmtCtxt ctxt stmt = hang (ptext SLIT("In") <+> pprStmtContext ctxt <> colon)
+ 4 (ppr stmt)
\end{code}
projects / ghc-hetmet.git / blobdiff