%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1994
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcMatches]{Typecheck some @Matches@}
\begin{code}
-#include "HsVersions.h"
-
-module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatch ) where
-
-import Ubiq
-
-import HsSyn ( Match(..), GRHSsAndBinds(..), GRHS(..), InPat,
- HsExpr, HsBinds, OutPat, Fake,
- collectPatBinders, pprMatch )
-import RnHsSyn ( RenamedMatch(..) )
-import TcHsSyn ( TcIdOcc(..), TcMatch(..) )
+module TcMatches ( tcMatchesFun, tcMatchesCase, tcMatchLambda,
+ tcDoStmts, tcStmtsAndThen, tcGRHSs, tcThingWithSig
+ ) where
-import TcMonad
-import Inst ( Inst, LIE(..), plusLIE )
-import TcEnv ( newMonoIds )
-import TcLoop ( tcGRHSsAndBinds )
-import TcPat ( tcPat )
-import TcType ( TcType(..), TcMaybe, zonkTcType )
-import Unify ( unifyTauTy, unifyTauTyList )
+#include "HsVersions.h"
-import Kind ( Kind, mkTypeKind )
+import {-# SOURCE #-} TcExpr( tcCheckRho, tcMonoExpr )
+
+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,
+ RenamedPat, RenamedMatchContext )
+import TcHsSyn ( TcMatch, TcGRHSs, TcStmt, TcDictBinds, TcHsBinds,
+ TcMonoBinds, TcPat, TcStmt, ExprCoFn,
+ isIdCoercion, (<$>), (<.>) )
+
+import TcRnMonad
+import TcMonoType ( tcAddScopedTyVars, tcHsSigType, UserTypeCtxt(..) )
+import Inst ( tcSyntaxName, tcInstCall )
+import TcEnv ( TcId, tcLookupLocalIds, tcLookupId, tcExtendLocalValEnv, tcExtendLocalValEnv2 )
+import TcPat ( tcPat, tcMonoPatBndr )
+import TcMType ( newTyVarTy, newTyVarTys, zonkTcType )
+import TcType ( TcType, TcTyVar, TcSigmaType, TcRhoType,
+ tyVarsOfType, tidyOpenTypes, tidyOpenType, isSigmaTy,
+ mkFunTy, isOverloadedTy, liftedTypeKind, openTypeKind,
+ mkArrowKind, mkAppTy )
+import TcBinds ( tcBindsAndThen )
+import TcUnify ( Expected(..), newHole, zapExpectedType, zapExpectedBranches, readExpectedType,
+ unifyTauTy, subFunTy, unifyPArrTy, unifyListTy, unifyFunTy,
+ checkSigTyVarsWrt, tcSubExp, tcGen )
+import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns )
import Name ( Name )
-import Pretty
-import Type ( isTyVarTy, mkFunTy, getFunTy_maybe )
-import Util
+import PrelNames ( monadNames, mfixName )
+import TysWiredIn ( boolTy, mkListTy, mkPArrTy )
+import Id ( idType, mkSysLocal, mkLocalId )
+import CoreFVs ( idFreeTyVars )
+import BasicTypes ( RecFlag(..) )
+import VarSet
+import Var ( Id )
+import Bag
+import Util ( isSingleton, lengthExceeds, notNull, zipEqual )
+import Outputable
+
+import List ( nub )
\end{code}
+%************************************************************************
+%* *
+\subsection{tcMatchesFun, tcMatchesCase}
+%* *
+%************************************************************************
+
@tcMatchesFun@ typechecks a @[Match]@ list which occurs in a
@FunMonoBind@. The second argument is the name of the function, which
is used in error messages. It checks that all the equations have the
\begin{code}
tcMatchesFun :: Name
- -> TcType s -- Expected type
-> [RenamedMatch]
- -> TcM s ([TcMatch s], LIE s)
+ -> Expected TcRhoType -- Expected type
+ -> TcM [TcMatch]
-tcMatchesFun fun_name expected_ty matches@(first_match:_)
- = -- Set the location to that of the first equation, so that
+tcMatchesFun fun_name matches@(first_match:_) expected_ty
+ = -- Check that they all have the same no of arguments
+ -- Set the location to that of the first equation, so that
-- 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 (get_Match_loc first_match) (
-
- -- Check that they all have the same no of arguments
- checkTc (all_same (noOfArgs matches))
- (varyingArgsErr fun_name matches) `thenTc_`
+ addSrcLoc (getMatchLoc first_match) (
+ checkTc (sameNoOfArgs matches)
+ (varyingArgsErr fun_name matches)
+ ) `thenM_`
-- ToDo: Don't use "expected" stuff if there ain't a type signature
-- because inconsistency between branches
-- may show up as something wrong with the (non-existent) type signature
- -- We need to substitute so that we can see as much about the type as possible
- zonkTcType expected_ty `thenNF_Tc` \ expected_ty' ->
- tcMatchesExpected expected_ty' (MFun fun_name) matches
-
- )
- where
- all_same :: [Int] -> Bool
- all_same [] = True -- Should never happen (ToDo: panic?)
- all_same [x] = True
- all_same (x:xs) = all ((==) x) xs
+ -- No need to zonk expected_ty, because subFunTy does that on the fly
+ tcMatches (FunRhs fun_name) matches expected_ty
\end{code}
@tcMatchesCase@ doesn't do the argument-count check because the
parser guarantees that each equation has exactly one argument.
\begin{code}
-tcMatchesCase :: TcType s -> [RenamedMatch] -> TcM s ([TcMatch s], LIE s)
-tcMatchesCase expected_ty matches = tcMatchesExpected expected_ty MCase matches
+tcMatchesCase :: [RenamedMatch] -- The case alternatives
+ -> Expected TcRhoType -- Type of whole case expressions
+ -> TcM (TcRhoType, -- Inferred type of the scrutinee
+ [TcMatch]) -- Translated alternatives
+
+tcMatchesCase matches (Check expr_ty)
+ = -- This case is a bit yukky, because it prevents the
+ -- scrutinee being higher-ranked, which might just possible
+ -- matter if we were seq'ing on it. But it's awkward to fix.
+ newTyVarTy openTypeKind `thenM` \ scrut_ty ->
+ tcMatches CaseAlt matches (Check (mkFunTy scrut_ty expr_ty)) `thenM` \ matches' ->
+ returnM (scrut_ty, matches')
+
+tcMatchesCase matches (Infer hole)
+ = newHole `thenM` \ fun_hole ->
+ tcMatches CaseAlt matches (Infer fun_hole) `thenM` \ matches' ->
+ readMutVar fun_hole `thenM` \ fun_ty ->
+ -- The result of tcMatches is bound to be a function type
+ unifyFunTy fun_ty `thenM` \ (scrut_ty, res_ty) ->
+ writeMutVar hole res_ty `thenM_`
+ returnM (scrut_ty, matches')
+
+
+tcMatchLambda :: RenamedMatch -> Expected TcRhoType -> TcM TcMatch
+tcMatchLambda match res_ty = tcMatch LambdaExpr match res_ty
\end{code}
\begin{code}
-data FunOrCase = MCase | MFun Name -- Records whether doing fun or case rhss;
- -- used to produced better error messages
-
-tcMatchesExpected :: TcType s
- -> FunOrCase
- -> [RenamedMatch]
- -> TcM s ([TcMatch s], LIE s)
-
-tcMatchesExpected expected_ty fun_or_case [match]
- = tcAddSrcLoc (get_Match_loc match) $
- tcAddErrCtxt (matchCtxt fun_or_case match) $
- tcMatchExpected expected_ty match `thenTc` \ (match', lie) ->
- returnTc ([match'], lie)
-
-tcMatchesExpected expected_ty fun_or_case (match1 : matches)
- = tcAddSrcLoc (get_Match_loc match1) (
- tcAddErrCtxt (matchCtxt fun_or_case match1) $
- tcMatchExpected expected_ty match1
- ) `thenTc` \ (match1', lie1) ->
- tcMatchesExpected expected_ty fun_or_case matches `thenTc` \ (matches', lie2) ->
- returnTc (match1' : matches', plusLIE lie1 lie2)
-
-tcMatches :: [RenamedMatch] -> TcM s ([TcMatch s], LIE s, [TcType s])
-
-tcMatches [match]
- = tcAddSrcLoc (get_Match_loc match) $
- tcMatch match `thenTc` \ (match', lie, ty) ->
- returnTc ([match'], lie, [ty])
-
-tcMatches (match1 : matches)
- = tcAddSrcLoc (get_Match_loc match1) (
- tcMatch match1
- ) `thenTc` \ (match1', lie1, match1_ty) ->
- tcMatches matches `thenTc` \ (matches', lie2, matches_ty) ->
- returnTc (match1' : matches', plusLIE lie1 lie2, match1_ty : matches_ty)
+tcMatches :: RenamedMatchContext
+ -> [RenamedMatch]
+ -> Expected TcRhoType
+ -> TcM [TcMatch]
+
+tcMatches ctxt matches exp_ty
+ = -- If there is more than one branch, and exp_ty is a 'hole',
+ -- all branches must be types, not type schemes, otherwise the
+ -- order in which we check them would affect the result.
+ zapExpectedBranches matches exp_ty `thenM` \ exp_ty' ->
+ mappM (tc_match exp_ty') matches
+ where
+ tc_match exp_ty match = tcMatch ctxt match exp_ty
\end{code}
+
+%************************************************************************
+%* *
+\subsection{tcMatch}
+%* *
+%************************************************************************
+
\begin{code}
-tcMatchExpected
- :: TcType s -- This gives the expected
- -- result-type of the Match. Early unification
- -- with this guy gives better error messages
+tcMatch :: RenamedMatchContext
-> RenamedMatch
- -> TcM s (TcMatch s,LIE s) -- NB No type returned, because it was passed
- -- in instead!
-
-tcMatchExpected expected_ty the_match@(PatMatch pat match)
- = case getFunTy_maybe expected_ty of
-
- Nothing -> -- Not a function type (eg type variable)
- -- So use tcMatch instead
- tcMatch the_match `thenTc` \ (match', lie_match, match_ty) ->
- unifyTauTy match_ty expected_ty `thenTc_`
- returnTc (match', lie_match)
-
- Just (arg_ty,rest_ty) -> -- It's a function type!
- let binders = collectPatBinders pat
- in
- newMonoIds binders mkTypeKind (\ _ ->
- tcPat pat `thenTc` \ (pat', lie_pat, pat_ty) ->
- unifyTauTy arg_ty pat_ty `thenTc_`
- tcMatchExpected rest_ty match `thenTc` \ (match', lie_match) ->
- returnTc (PatMatch pat' match',
- plusLIE lie_pat lie_match)
- )
-
-tcMatchExpected expected_ty (GRHSMatch grhss_and_binds)
- = tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds', lie, grhss_ty) ->
- unifyTauTy grhss_ty expected_ty `thenTc_`
- returnTc (GRHSMatch grhss_and_binds', lie)
-
-tcMatch :: RenamedMatch -> TcM s (TcMatch s, LIE s, TcType s)
-
-tcMatch (PatMatch pat match)
- = let binders = collectPatBinders pat
+ -> Expected TcRhoType -- Expected result-type of the Match.
+ -- Early unification with this guy gives better error messages
+ -- We regard the Match as having type
+ -- (ty1 -> ... -> tyn -> result_ty)
+ -- where there are n patterns.
+ -> TcM TcMatch
+
+tcMatch 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'))
+
+ where
+ tc_grhss rhs_ty
+ = -- 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 ->
+ tcThingWithSig sig_ty (tcGRHSs ctxt grhss . Check) rhs_ty `thenM` \ (co_fn, grhss') ->
+
+ -- Pushes the coercion down to the right hand sides,
+ -- because there is no convenient place to hang it otherwise.
+ if isIdCoercion co_fn then
+ returnM grhss'
+ else
+ readExpectedType rhs_ty `thenM` \ rhs_ty' ->
+ returnM (lift_grhss co_fn rhs_ty' grhss')
+
+lift_grhss co_fn rhs_ty (GRHSs grhss binds ty)
+ = GRHSs (map lift_grhs grhss) binds rhs_ty -- Change the type, since the coercion does
+ 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
+
+
+tcGRHSs :: RenamedMatchContext -> RenamedGRHSs
+ -> Expected TcRhoType
+ -> TcM TcGRHSs
+
+ -- 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 [GRHS [ResultStmt rhs loc1] loc2] binds _) exp_ty
+ = tcBindsAndThen glue_on binds $
+ tcMonoExpr rhs exp_ty `thenM` \ rhs' ->
+ readExpectedType exp_ty `thenM` \ exp_ty' ->
+ returnM (GRHSs [GRHS [ResultStmt rhs' loc1] loc2] EmptyBinds exp_ty')
+
+tcGRHSs ctxt (GRHSs grhss binds _) exp_ty
+ = tcBindsAndThen glue_on binds $
+ zapExpectedType exp_ty `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
+ tc_grhs (GRHS guarded locn)
+ = addSrcLoc locn $
+ tcStmts (PatGuard ctxt) m_ty guarded `thenM` \ guarded' ->
+ returnM (GRHS guarded' locn)
+
+ m_ty = (\ty -> ty, exp_ty')
in
- newMonoIds binders mkTypeKind (\ _ ->
- tcPat pat `thenTc` \ (pat', lie_pat, pat_ty) ->
- tcMatch match `thenTc` \ (match', lie_match, match_ty) ->
- returnTc (PatMatch pat' match',
- plusLIE lie_pat lie_match,
- mkFunTy pat_ty match_ty)
- )
+ mappM tc_grhs grhss `thenM` \ grhss' ->
+ returnM (GRHSs grhss' EmptyBinds exp_ty')
+\end{code}
-tcMatch (GRHSMatch grhss_and_binds)
- = tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds', lie, grhss_ty) ->
- returnTc (GRHSMatch grhss_and_binds', lie, grhss_ty)
+
+\begin{code}
+tcThingWithSig :: TcSigmaType -- Type signature
+ -> (TcRhoType -> TcM r) -- How to type check the thing inside
+ -> Expected TcRhoType -- Overall expected result type
+ -> TcM (ExprCoFn, r)
+-- Used for expressions with a type signature, and for result type signatures
+
+tcThingWithSig sig_ty thing_inside res_ty
+ | not (isSigmaTy sig_ty)
+ = thing_inside sig_ty `thenM` \ result ->
+ tcSubExp res_ty sig_ty `thenM` \ co_fn ->
+ returnM (co_fn, result)
+
+ | otherwise -- The signature has some outer foralls
+ = -- Must instantiate the outer for-alls of sig_tc_ty
+ -- else we risk instantiating a ? res_ty to a forall-type
+ -- which breaks the invariant that tcMonoExpr only returns phi-types
+ tcGen sig_ty emptyVarSet thing_inside `thenM` \ (gen_fn, result) ->
+ tcInstCall SignatureOrigin sig_ty `thenM` \ (inst_fn, inst_sig_ty) ->
+ tcSubExp res_ty inst_sig_ty `thenM` \ co_fn ->
+ returnM (co_fn <.> inst_fn <.> gen_fn, result)
+ -- Note that we generalise, then instantiate. Ah well.
\end{code}
-@noOfArgs@ takes a @[RenamedMatch]@ and returns a list telling how
-many arguments were used in each of the equations. This is used to
-report a sensible error message when different equations have
-different numbers of arguments.
+%************************************************************************
+%* *
+\subsection{tcMatchPats}
+%* *
+%************************************************************************
+
+\begin{code}
+tcMatchPats
+ :: [RenamedPat] -> Expected TcRhoType
+ -> (Expected TcRhoType -> 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
+ readExpectedType expected_ty `thenM` \ exp_ty ->
+ tcCheckExistentialPat ex_tvs ex_ids ex_lie lie_req exp_ty `thenM` \ ex_binds ->
+ -- NB: we *must* pass "exp_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
+ )
-\begin{code}
-noOfArgs :: [RenamedMatch] -> [Int]
-noOfArgs ms = map args_in_match ms
+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) ->
+
+ -- 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_`
+
+ returnM (dict_binds `AndMonoBinds` inst_binds)
where
- args_in_match :: RenamedMatch -> Int
- args_in_match (GRHSMatch _) = 0
- args_in_match (PatMatch _ match) = 1 + args_in_match match
+ doc = text ("existential context of a data constructor")
+ tv_list = bagToList ex_tvs
+ not_overloaded id = not (isOverloadedTy (idType id))
\end{code}
-@get_Match_loc@ takes a @RenamedMatch@ and returns the
-source-location gotten from the GRHS inside.
-THis is something of a nuisance, but no more.
+
+%************************************************************************
+%* *
+\subsection{@tcDoStmts@ typechecks a {\em list} of do statements}
+%* *
+%************************************************************************
\begin{code}
-get_Match_loc :: RenamedMatch -> SrcLoc
-
-get_Match_loc (PatMatch _ m) = get_Match_loc m
-get_Match_loc (GRHSMatch (GRHSsAndBindsIn (g:_) _))
- = get_GRHS_loc g
- where
- get_GRHS_loc (OtherwiseGRHS _ locn) = locn
- get_GRHS_loc (GRHS _ _ locn) = locn
+tcDoStmts :: HsStmtContext Name -> [RenamedStmt] -> [Name]
+ -> TcRhoType -- To keep it simple, we don't have an "expected" type here
+ -> 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}
-Errors and contexts
-~~~~~~~~~~~~~~~~~~~
-\begin{code}
-matchCtxt MCase match sty
- = ppHang (ppStr "In a \"case\" branch:")
- 4 (pprMatch sty True{-is_case-} match)
-matchCtxt (MFun fun) match sty
- = ppHang (ppBesides [ppStr "In an equation for function ", ppr sty fun, ppChar ':'])
- 4 (ppBesides [ppr sty fun, ppSP, pprMatch sty False{-not case-} match])
+%************************************************************************
+%* *
+\subsection{tcStmts}
+%* *
+%************************************************************************
+
+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 (returnM [])
+
+tcStmtsAndThen
+ :: (TcStmt -> thing -> thing) -- Combiner
+ -> HsStmtContext Name
+ -> (TcType -> TcType, TcType) -- m, the relationship type of pat and rhs in pat <- rhs
+ -- res_ty, the type of the entire comprehension
+ -- used at the end for the type of (return x)
+ -- or the final expression in do-notation
+ -> [RenamedStmt]
+ -> TcM thing
+ -> TcM thing
+
+ -- 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
+ = addSrcLoc src_loc $
+ addErrCtxt (stmtCtxt do_or_lc stmt) $
+ newTyVarTy liftedTypeKind `thenM` \ pat_ty ->
+ tcCheckRho exp (m pat_ty) `thenM` \ exp' ->
+ tcMatchPats [pat] (Check (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 (Check mono_ty) (idType poly_id) `thenM` \ co_fn ->
+ returnM (co_fn <$> HsVar poly_id)
+
+ -- ExprStmt
+tcStmtAndThen combine do_or_lc m_ty@(m, _) stmt@(ExprStmt exp _ locn) thing_inside
+ = addErrCtxt (stmtCtxt do_or_lc stmt) (
+ if isDoExpr do_or_lc then
+ newTyVarTy openTypeKind `thenM` \ any_ty ->
+ tcCheckRho exp (m any_ty) `thenM` \ exp' ->
+ returnM (ExprStmt exp' any_ty locn)
+ else
+ tcCheckRho 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
+ tcCheckRho exp (m res_elt_ty)
+ else
+ tcCheckRho 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}
+%************************************************************************
+%* *
+\subsection{Errors and contexts}
+%* *
+%************************************************************************
+
+@sameNoOfArgs@ takes a @[RenamedMatch]@ and decides whether the same
+number of args are used in each equation.
+
+\begin{code}
+sameNoOfArgs :: [RenamedMatch] -> Bool
+sameNoOfArgs matches = isSingleton (nub (map args_in_match matches))
+ where
+ args_in_match :: RenamedMatch -> Int
+ args_in_match (Match pats _ _) = length pats
+\end{code}
+
\begin{code}
-varyingArgsErr name matches sty
- = ppSep [ppStr "Varying number of arguments for function", ppr sty name]
+varyingArgsErr name matches
+ = sep [ptext SLIT("Varying number of arguments for function"), quotes (ppr name)]
+
+matchCtxt ctxt match = hang (ptext SLIT("In") <+> pprMatchContext ctxt <> colon) 4 (pprMatch ctxt match)
+stmtCtxt 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)
+
+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
+ 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