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Diffstat (limited to 'compiler/GHC/Tc/Gen/Arrow.hs')
| -rw-r--r-- | compiler/GHC/Tc/Gen/Arrow.hs | 442 |
1 files changed, 442 insertions, 0 deletions
diff --git a/compiler/GHC/Tc/Gen/Arrow.hs b/compiler/GHC/Tc/Gen/Arrow.hs new file mode 100644 index 0000000000..435bf4d89c --- /dev/null +++ b/compiler/GHC/Tc/Gen/Arrow.hs @@ -0,0 +1,442 @@ +{- +(c) The University of Glasgow 2006 +(c) The GRASP/AQUA Project, Glasgow University, 1992-1998 + +-} + +{-# LANGUAGE RankNTypes, TupleSections #-} +{-# LANGUAGE TypeFamilies #-} + +{-# OPTIONS_GHC -Wno-incomplete-record-updates #-} + +-- | Typecheck arrow notation +module GHC.Tc.Gen.Arrow ( tcProc ) where + +import GhcPrelude + +import {-# SOURCE #-} GHC.Tc.Gen.Expr( tcMonoExpr, tcInferRho, tcSyntaxOp, tcCheckId, tcPolyExpr ) + +import GHC.Hs +import GHC.Tc.Gen.Match +import GHC.Tc.Utils.Zonk( hsLPatType ) +import GHC.Tc.Utils.TcType +import GHC.Tc.Utils.TcMType +import GHC.Tc.Gen.Bind +import GHC.Tc.Gen.Pat +import GHC.Tc.Utils.Unify +import GHC.Tc.Utils.Monad +import GHC.Tc.Utils.Env +import GHC.Tc.Types.Origin +import GHC.Tc.Types.Evidence +import GHC.Types.Id( mkLocalId ) +import GHC.Tc.Utils.Instantiate +import TysWiredIn +import GHC.Types.Var.Set +import TysPrim +import GHC.Types.Basic( Arity ) +import GHC.Types.SrcLoc +import Outputable +import Util + +import Control.Monad + +{- +Note [Arrow overview] +~~~~~~~~~~~~~~~~~~~~~ +Here's a summary of arrows and how they typecheck. First, here's +a cut-down syntax: + + expr ::= .... + | proc pat cmd + + cmd ::= cmd exp -- Arrow application + | \pat -> cmd -- Arrow abstraction + | (| exp cmd1 ... cmdn |) -- Arrow form, n>=0 + | ... -- If, case in the usual way + + cmd_type ::= carg_type --> type + + carg_type ::= () + | (type, carg_type) + +Note that + * The 'exp' in an arrow form can mention only + "arrow-local" variables + + * An "arrow-local" variable is bound by an enclosing + cmd binding form (eg arrow abstraction) + + * A cmd_type is here written with a funny arrow "-->", + The bit on the left is a carg_type (command argument type) + which itself is a nested tuple, finishing with () + + * The arrow-tail operator (e1 -< e2) means + (| e1 <<< arr snd |) e2 + + +************************************************************************ +* * + Proc +* * +************************************************************************ +-} + +tcProc :: InPat GhcRn -> LHsCmdTop GhcRn -- proc pat -> expr + -> ExpRhoType -- Expected type of whole proc expression + -> TcM (OutPat GhcTcId, LHsCmdTop GhcTcId, TcCoercion) + +tcProc pat cmd exp_ty + = newArrowScope $ + do { exp_ty <- expTypeToType exp_ty -- no higher-rank stuff with arrows + ; (co, (exp_ty1, res_ty)) <- matchExpectedAppTy exp_ty + ; (co1, (arr_ty, arg_ty)) <- matchExpectedAppTy exp_ty1 + ; let cmd_env = CmdEnv { cmd_arr = arr_ty } + ; (pat', cmd') <- tcPat ProcExpr pat (mkCheckExpType arg_ty) $ + tcCmdTop cmd_env cmd (unitTy, res_ty) + ; let res_co = mkTcTransCo co + (mkTcAppCo co1 (mkTcNomReflCo res_ty)) + ; return (pat', cmd', res_co) } + +{- +************************************************************************ +* * + Commands +* * +************************************************************************ +-} + +-- See Note [Arrow overview] +type CmdType = (CmdArgType, TcTauType) -- cmd_type +type CmdArgType = TcTauType -- carg_type, a nested tuple + +data CmdEnv + = CmdEnv { + cmd_arr :: TcType -- arrow type constructor, of kind *->*->* + } + +mkCmdArrTy :: CmdEnv -> TcTauType -> TcTauType -> TcTauType +mkCmdArrTy env t1 t2 = mkAppTys (cmd_arr env) [t1, t2] + +--------------------------------------- +tcCmdTop :: CmdEnv + -> LHsCmdTop GhcRn + -> CmdType + -> TcM (LHsCmdTop GhcTcId) + +tcCmdTop env (L loc (HsCmdTop names cmd)) cmd_ty@(cmd_stk, res_ty) + = setSrcSpan loc $ + do { cmd' <- tcCmd env cmd cmd_ty + ; names' <- mapM (tcSyntaxName ProcOrigin (cmd_arr env)) names + ; return (L loc $ HsCmdTop (CmdTopTc cmd_stk res_ty names') cmd') } +tcCmdTop _ (L _ (XCmdTop nec)) _ = noExtCon nec + +---------------------------------------- +tcCmd :: CmdEnv -> LHsCmd GhcRn -> CmdType -> TcM (LHsCmd GhcTcId) + -- The main recursive function +tcCmd env (L loc cmd) res_ty + = setSrcSpan loc $ do + { cmd' <- tc_cmd env cmd res_ty + ; return (L loc cmd') } + +tc_cmd :: CmdEnv -> HsCmd GhcRn -> CmdType -> TcM (HsCmd GhcTcId) +tc_cmd env (HsCmdPar x cmd) res_ty + = do { cmd' <- tcCmd env cmd res_ty + ; return (HsCmdPar x cmd') } + +tc_cmd env (HsCmdLet x (L l binds) (L body_loc body)) res_ty + = do { (binds', body') <- tcLocalBinds binds $ + setSrcSpan body_loc $ + tc_cmd env body res_ty + ; return (HsCmdLet x (L l binds') (L body_loc body')) } + +tc_cmd env in_cmd@(HsCmdCase x scrut matches) (stk, res_ty) + = addErrCtxt (cmdCtxt in_cmd) $ do + (scrut', scrut_ty) <- tcInferRho scrut + matches' <- tcMatchesCase match_ctxt scrut_ty matches (mkCheckExpType res_ty) + return (HsCmdCase x scrut' matches') + where + match_ctxt = MC { mc_what = CaseAlt, + mc_body = mc_body } + mc_body body res_ty' = do { res_ty' <- expTypeToType res_ty' + ; tcCmd env body (stk, res_ty') } + +tc_cmd env (HsCmdIf x NoSyntaxExprRn pred b1 b2) res_ty -- Ordinary 'if' + = do { pred' <- tcMonoExpr pred (mkCheckExpType boolTy) + ; b1' <- tcCmd env b1 res_ty + ; b2' <- tcCmd env b2 res_ty + ; return (HsCmdIf x NoSyntaxExprTc pred' b1' b2') + } + +tc_cmd env (HsCmdIf x fun@(SyntaxExprRn {}) pred b1 b2) res_ty -- Rebindable syntax for if + = do { pred_ty <- newOpenFlexiTyVarTy + -- For arrows, need ifThenElse :: forall r. T -> r -> r -> r + -- because we're going to apply it to the environment, not + -- the return value. + ; (_, [r_tv]) <- tcInstSkolTyVars [alphaTyVar] + ; let r_ty = mkTyVarTy r_tv + ; checkTc (not (r_tv `elemVarSet` tyCoVarsOfType pred_ty)) + (text "Predicate type of `ifThenElse' depends on result type") + ; (pred', fun') + <- tcSyntaxOp IfOrigin fun (map synKnownType [pred_ty, r_ty, r_ty]) + (mkCheckExpType r_ty) $ \ _ -> + tcMonoExpr pred (mkCheckExpType pred_ty) + + ; b1' <- tcCmd env b1 res_ty + ; b2' <- tcCmd env b2 res_ty + ; return (HsCmdIf x fun' pred' b1' b2') + } + +------------------------------------------- +-- Arrow application +-- (f -< a) or (f -<< a) +-- +-- D |- fun :: a t1 t2 +-- D,G |- arg :: t1 +-- ------------------------ +-- D;G |-a fun -< arg :: stk --> t2 +-- +-- D,G |- fun :: a t1 t2 +-- D,G |- arg :: t1 +-- ------------------------ +-- D;G |-a fun -<< arg :: stk --> t2 +-- +-- (plus -<< requires ArrowApply) + +tc_cmd env cmd@(HsCmdArrApp _ fun arg ho_app lr) (_, res_ty) + = addErrCtxt (cmdCtxt cmd) $ + do { arg_ty <- newOpenFlexiTyVarTy + ; let fun_ty = mkCmdArrTy env arg_ty res_ty + ; fun' <- select_arrow_scope (tcMonoExpr fun (mkCheckExpType fun_ty)) + + ; arg' <- tcMonoExpr arg (mkCheckExpType arg_ty) + + ; return (HsCmdArrApp fun_ty fun' arg' ho_app lr) } + where + -- Before type-checking f, use the environment of the enclosing + -- proc for the (-<) case. + -- Local bindings, inside the enclosing proc, are not in scope + -- inside f. In the higher-order case (-<<), they are. + -- See Note [Escaping the arrow scope] in GHC.Tc.Types + select_arrow_scope tc = case ho_app of + HsHigherOrderApp -> tc + HsFirstOrderApp -> escapeArrowScope tc + +------------------------------------------- +-- Command application +-- +-- D,G |- exp : t +-- D;G |-a cmd : (t,stk) --> res +-- ----------------------------- +-- D;G |-a cmd exp : stk --> res + +tc_cmd env cmd@(HsCmdApp x fun arg) (cmd_stk, res_ty) + = addErrCtxt (cmdCtxt cmd) $ + do { arg_ty <- newOpenFlexiTyVarTy + ; fun' <- tcCmd env fun (mkPairTy arg_ty cmd_stk, res_ty) + ; arg' <- tcMonoExpr arg (mkCheckExpType arg_ty) + ; return (HsCmdApp x fun' arg') } + +------------------------------------------- +-- Lambda +-- +-- D;G,x:t |-a cmd : stk --> res +-- ------------------------------ +-- D;G |-a (\x.cmd) : (t,stk) --> res + +tc_cmd env + (HsCmdLam x (MG { mg_alts = L l [L mtch_loc + (match@(Match { m_pats = pats, m_grhss = grhss }))], + mg_origin = origin })) + (cmd_stk, res_ty) + = addErrCtxt (pprMatchInCtxt match) $ + do { (co, arg_tys, cmd_stk') <- matchExpectedCmdArgs n_pats cmd_stk + + -- Check the patterns, and the GRHSs inside + ; (pats', grhss') <- setSrcSpan mtch_loc $ + tcPats LambdaExpr pats (map mkCheckExpType arg_tys) $ + tc_grhss grhss cmd_stk' (mkCheckExpType res_ty) + + ; let match' = L mtch_loc (Match { m_ext = noExtField + , m_ctxt = LambdaExpr, m_pats = pats' + , m_grhss = grhss' }) + arg_tys = map hsLPatType pats' + cmd' = HsCmdLam x (MG { mg_alts = L l [match'] + , mg_ext = MatchGroupTc arg_tys res_ty + , mg_origin = origin }) + ; return (mkHsCmdWrap (mkWpCastN co) cmd') } + where + n_pats = length pats + match_ctxt = (LambdaExpr :: HsMatchContext GhcRn) -- Maybe KappaExpr? + pg_ctxt = PatGuard match_ctxt + + tc_grhss (GRHSs x grhss (L l binds)) stk_ty res_ty + = do { (binds', grhss') <- tcLocalBinds binds $ + mapM (wrapLocM (tc_grhs stk_ty res_ty)) grhss + ; return (GRHSs x grhss' (L l binds')) } + tc_grhss (XGRHSs nec) _ _ = noExtCon nec + + tc_grhs stk_ty res_ty (GRHS x guards body) + = do { (guards', rhs') <- tcStmtsAndThen pg_ctxt tcGuardStmt guards res_ty $ + \ res_ty -> tcCmd env body + (stk_ty, checkingExpType "tc_grhs" res_ty) + ; return (GRHS x guards' rhs') } + tc_grhs _ _ (XGRHS nec) = noExtCon nec + +------------------------------------------- +-- Do notation + +tc_cmd env (HsCmdDo _ (L l stmts) ) (cmd_stk, res_ty) + = do { co <- unifyType Nothing unitTy cmd_stk -- Expecting empty argument stack + ; stmts' <- tcStmts ArrowExpr (tcArrDoStmt env) stmts res_ty + ; return (mkHsCmdWrap (mkWpCastN co) (HsCmdDo res_ty (L l stmts') )) } + + +----------------------------------------------------------------- +-- Arrow ``forms'' (| e c1 .. cn |) +-- +-- D; G |-a1 c1 : stk1 --> r1 +-- ... +-- D; G |-an cn : stkn --> rn +-- D |- e :: forall e. a1 (e, stk1) t1 +-- ... +-- -> an (e, stkn) tn +-- -> a (e, stk) t +-- e \not\in (stk, stk1, ..., stkm, t, t1, ..., tn) +-- ---------------------------------------------- +-- D; G |-a (| e c1 ... cn |) : stk --> t + +tc_cmd env cmd@(HsCmdArrForm x expr f fixity cmd_args) (cmd_stk, res_ty) + = addErrCtxt (cmdCtxt cmd) $ + do { (cmd_args', cmd_tys) <- mapAndUnzipM tc_cmd_arg cmd_args + -- We use alphaTyVar for 'w' + ; let e_ty = mkInvForAllTy alphaTyVar $ + mkVisFunTys cmd_tys $ + mkCmdArrTy env (mkPairTy alphaTy cmd_stk) res_ty + ; expr' <- tcPolyExpr expr e_ty + ; return (HsCmdArrForm x expr' f fixity cmd_args') } + + where + tc_cmd_arg :: LHsCmdTop GhcRn -> TcM (LHsCmdTop GhcTcId, TcType) + tc_cmd_arg cmd + = do { arr_ty <- newFlexiTyVarTy arrowTyConKind + ; stk_ty <- newFlexiTyVarTy liftedTypeKind + ; res_ty <- newFlexiTyVarTy liftedTypeKind + ; let env' = env { cmd_arr = arr_ty } + ; cmd' <- tcCmdTop env' cmd (stk_ty, res_ty) + ; return (cmd', mkCmdArrTy env' (mkPairTy alphaTy stk_ty) res_ty) } + +tc_cmd _ (XCmd nec) _ = noExtCon nec + +----------------------------------------------------------------- +-- Base case for illegal commands +-- This is where expressions that aren't commands get rejected + +tc_cmd _ cmd _ + = failWithTc (vcat [text "The expression", nest 2 (ppr cmd), + text "was found where an arrow command was expected"]) + + +matchExpectedCmdArgs :: Arity -> TcType -> TcM (TcCoercionN, [TcType], TcType) +matchExpectedCmdArgs 0 ty + = return (mkTcNomReflCo ty, [], ty) +matchExpectedCmdArgs n ty + = do { (co1, [ty1, ty2]) <- matchExpectedTyConApp pairTyCon ty + ; (co2, tys, res_ty) <- matchExpectedCmdArgs (n-1) ty2 + ; return (mkTcTyConAppCo Nominal pairTyCon [co1, co2], ty1:tys, res_ty) } + +{- +************************************************************************ +* * + Stmts +* * +************************************************************************ +-} + +-------------------------------- +-- Mdo-notation +-- The distinctive features here are +-- (a) RecStmts, and +-- (b) no rebindable syntax + +tcArrDoStmt :: CmdEnv -> TcCmdStmtChecker +tcArrDoStmt env _ (LastStmt x rhs noret _) res_ty thing_inside + = do { rhs' <- tcCmd env rhs (unitTy, res_ty) + ; thing <- thing_inside (panic "tcArrDoStmt") + ; return (LastStmt x rhs' noret noSyntaxExpr, thing) } + +tcArrDoStmt env _ (BodyStmt _ rhs _ _) res_ty thing_inside + = do { (rhs', elt_ty) <- tc_arr_rhs env rhs + ; thing <- thing_inside res_ty + ; return (BodyStmt elt_ty rhs' noSyntaxExpr noSyntaxExpr, thing) } + +tcArrDoStmt env ctxt (BindStmt _ pat rhs _ _) res_ty thing_inside + = do { (rhs', pat_ty) <- tc_arr_rhs env rhs + ; (pat', thing) <- tcPat (StmtCtxt ctxt) pat (mkCheckExpType pat_ty) $ + thing_inside res_ty + ; return (mkTcBindStmt pat' rhs', thing) } + +tcArrDoStmt env ctxt (RecStmt { recS_stmts = stmts, recS_later_ids = later_names + , recS_rec_ids = rec_names }) res_ty thing_inside + = do { let tup_names = rec_names ++ filterOut (`elem` rec_names) later_names + ; tup_elt_tys <- newFlexiTyVarTys (length tup_names) liftedTypeKind + ; let tup_ids = zipWith mkLocalId tup_names tup_elt_tys + ; tcExtendIdEnv tup_ids $ do + { (stmts', tup_rets) + <- tcStmtsAndThen ctxt (tcArrDoStmt env) stmts res_ty $ \ _res_ty' -> + -- ToDo: res_ty not really right + zipWithM tcCheckId tup_names (map mkCheckExpType tup_elt_tys) + + ; thing <- 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 GHC.Hs.Expr) + + ; let rec_ids = takeList rec_names tup_ids + ; later_ids <- tcLookupLocalIds later_names + + ; let rec_rets = takeList rec_names tup_rets + ; let ret_table = zip tup_ids tup_rets + ; let later_rets = [r | i <- later_ids, (j, r) <- ret_table, i == j] + + ; return (emptyRecStmtId { recS_stmts = stmts' + , recS_later_ids = later_ids + , recS_rec_ids = rec_ids + , recS_ext = unitRecStmtTc + { recS_later_rets = later_rets + , recS_rec_rets = rec_rets + , recS_ret_ty = res_ty} }, thing) + }} + +tcArrDoStmt _ _ stmt _ _ + = pprPanic "tcArrDoStmt: unexpected Stmt" (ppr stmt) + +tc_arr_rhs :: CmdEnv -> LHsCmd GhcRn -> TcM (LHsCmd GhcTcId, TcType) +tc_arr_rhs env rhs = do { ty <- newFlexiTyVarTy liftedTypeKind + ; rhs' <- tcCmd env rhs (unitTy, ty) + ; return (rhs', ty) } + +{- +************************************************************************ +* * + Helpers +* * +************************************************************************ +-} + +mkPairTy :: Type -> Type -> Type +mkPairTy t1 t2 = mkTyConApp pairTyCon [t1,t2] + +arrowTyConKind :: Kind -- *->*->* +arrowTyConKind = mkVisFunTys [liftedTypeKind, liftedTypeKind] liftedTypeKind + +{- +************************************************************************ +* * + Errors +* * +************************************************************************ +-} + +cmdCtxt :: HsCmd GhcRn -> SDoc +cmdCtxt cmd = text "In the command:" <+> ppr cmd |