{-# LANGUAGE RankNTypes #-} {-# LANGUAGE TypeFamilies #-} {-# OPTIONS_GHC -Wno-incomplete-record-updates #-} {- (c) The University of Glasgow 2006 (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 -} -- | Typecheck arrow notation module GHC.Tc.Gen.Arrow ( tcProc ) where import GHC.Prelude import {-# SOURCE #-} GHC.Tc.Gen.Expr( tcCheckMonoExpr, tcInferRho, tcSyntaxOp , tcCheckPolyExpr ) import GHC.Hs import GHC.Tc.Gen.Match import GHC.Tc.Gen.Head( tcCheckId ) 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.Core.Multiplicity import GHC.Types.Id( mkLocalId ) import GHC.Tc.Utils.Instantiate import GHC.Builtin.Types import GHC.Types.Var.Set import GHC.Builtin.Types.Prim import GHC.Types.Basic( Arity ) import GHC.Types.SrcLoc import GHC.Utils.Outputable import GHC.Utils.Panic import GHC.Utils.Misc 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 :: LPat GhcRn -> LHsCmdTop GhcRn -- proc pat -> expr -> ExpRhoType -- Expected type of whole proc expression -> TcM (LPat GhcTc, LHsCmdTop GhcTc, TcCoercion) tcProc pat cmd@(L _ (HsCmdTop names _)) exp_ty = 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 -- start with the names as they are used to desugar the proc itself -- See #17423 ; names' <- mapM (tcSyntaxName ProcOrigin arr_ty) names ; let cmd_env = CmdEnv { cmd_arr = arr_ty } ; (pat', cmd') <- newArrowScope $ tcCheckPat (ArrowMatchCtxt ProcExpr) pat (unrestricted arg_ty) $ tcCmdTop cmd_env names' 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 -> CmdSyntaxTable GhcTc -- ^ Type-checked Arrow class methods (arr, (>>>), ...) -> LHsCmdTop GhcRn -> CmdType -> TcM (LHsCmdTop GhcTc) tcCmdTop env names (L loc (HsCmdTop _names cmd)) cmd_ty@(cmd_stk, res_ty) = setSrcSpan loc $ do { cmd' <- tcCmd env cmd cmd_ty ; return (L loc $ HsCmdTop (CmdTopTc cmd_stk res_ty names) cmd') } ---------------------------------------- tcCmd :: CmdEnv -> LHsCmd GhcRn -> CmdType -> TcM (LHsCmd GhcTc) -- The main recursive function tcCmd env (L loc cmd) res_ty = setSrcSpan (locA loc) $ do { cmd' <- tc_cmd env cmd res_ty ; return (L loc cmd') } tc_cmd :: CmdEnv -> HsCmd GhcRn -> CmdType -> TcM (HsCmd GhcTc) tc_cmd env (HsCmdPar x cmd) res_ty = do { cmd' <- tcCmd env cmd res_ty ; return (HsCmdPar x cmd') } tc_cmd env (HsCmdLet x binds (L body_loc body)) res_ty = do { (binds', body') <- tcLocalBinds binds $ setSrcSpan (locA body_loc) $ tc_cmd env body res_ty ; return (HsCmdLet x 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' <- tcCmdMatches env scrut_ty matches (stk, res_ty) return (HsCmdCase x scrut' matches') tc_cmd env in_cmd@(HsCmdLamCase x matches) (stk, res_ty) = addErrCtxt (cmdCtxt in_cmd) $ do (co, [scrut_ty], stk') <- matchExpectedCmdArgs 1 stk matches' <- tcCmdMatches env scrut_ty matches (stk', res_ty) return (mkHsCmdWrap (mkWpCastN co) (HsCmdLamCase x matches')) tc_cmd env (HsCmdIf x NoSyntaxExprRn pred b1 b2) res_ty -- Ordinary 'if' = do { pred' <- tcCheckMonoExpr pred 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) $ \ _ _ -> tcCheckMonoExpr pred 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 (tcCheckMonoExpr fun fun_ty) ; arg' <- tcCheckMonoExpr arg 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' <- tcCheckMonoExpr arg 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') <- setSrcSpanA mtch_loc $ tcPats (ArrowMatchCtxt KappaExpr) pats (map (unrestricted . mkCheckExpType) arg_tys) $ tc_grhss grhss cmd_stk' (mkCheckExpType res_ty) ; let match' = L mtch_loc (Match { m_ext = noAnn , m_ctxt = ArrowMatchCtxt KappaExpr , m_pats = pats' , m_grhss = grhss' }) arg_tys = map (unrestricted . 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 = ArrowMatchCtxt KappaExpr pg_ctxt = PatGuard match_ctxt tc_grhss (GRHSs x grhss binds) stk_ty res_ty = do { (binds', grhss') <- tcLocalBinds binds $ mapM (wrapLocM (tc_grhs stk_ty res_ty)) grhss ; return (GRHSs x grhss' binds') } 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') } ------------------------------------------- -- 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 = mkInfForAllTy alphaTyVar $ mkVisFunTysMany cmd_tys $ mkCmdArrTy env (mkPairTy alphaTy cmd_stk) res_ty ; expr' <- tcCheckPolyExpr expr e_ty ; return (HsCmdArrForm x expr' f fixity cmd_args') } where tc_cmd_arg :: LHsCmdTop GhcRn -> TcM (LHsCmdTop GhcTc, TcType) tc_cmd_arg cmd@(L _ (HsCmdTop names _)) = do { arr_ty <- newFlexiTyVarTy arrowTyConKind ; stk_ty <- newFlexiTyVarTy liftedTypeKind ; res_ty <- newFlexiTyVarTy liftedTypeKind ; names' <- mapM (tcSyntaxName ProcOrigin arr_ty) names ; let env' = env { cmd_arr = arr_ty } ; cmd' <- tcCmdTop env' names' cmd (stk_ty, res_ty) ; return (cmd', mkCmdArrTy env' (mkPairTy alphaTy stk_ty) res_ty) } ----------------------------------------------------------------- -- 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"]) -- | Typechecking for case command alternatives. Used for both -- 'HsCmdCase' and 'HsCmdLamCase'. tcCmdMatches :: CmdEnv -> TcType -- ^ type of the scrutinee -> MatchGroup GhcRn (LHsCmd GhcRn) -- ^ case alternatives -> CmdType -> TcM (MatchGroup GhcTc (LHsCmd GhcTc)) tcCmdMatches env scrut_ty matches (stk, res_ty) = tcMatchesCase match_ctxt (unrestricted scrut_ty) matches (mkCheckExpType res_ty) where match_ctxt = MC { mc_what = ArrowMatchCtxt ArrowCaseAlt, mc_body = mc_body } mc_body body res_ty' = do { res_ty' <- expTypeToType res_ty' ; tcCmd env body (stk, res_ty') } 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) <- tcCheckPat (StmtCtxt ctxt) pat (unrestricted pat_ty) $ thing_inside res_ty ; return (mkTcBindStmt pat' rhs', thing) } tcArrDoStmt env ctxt (RecStmt { recS_stmts = L l 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 (\n p -> mkLocalId n Many p) tup_names tup_elt_tys -- Many because it's a recursive definition ; 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] ; let stmt :: Stmt GhcTc (LocatedA (HsCmd GhcTc)) stmt = emptyRecStmtId { recS_stmts = L l stmts' -- { 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} } ; return (stmt, thing) }} tcArrDoStmt _ _ stmt _ _ = pprPanic "tcArrDoStmt: unexpected Stmt" (ppr stmt) tc_arr_rhs :: CmdEnv -> LHsCmd GhcRn -> TcM (LHsCmd GhcTc, 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 = mkVisFunTysMany [liftedTypeKind, liftedTypeKind] liftedTypeKind {- ************************************************************************ * * Errors * * ************************************************************************ -} cmdCtxt :: HsCmd GhcRn -> SDoc cmdCtxt cmd = text "In the command:" <+> ppr cmd