Typecheck arrow notation
\begin{code}
-{-# OPTIONS -fno-warn-tabs #-}
--- The above warning supression flag is a temporary kludge.
--- While working on this module you are encouraged to remove it and
--- detab the module (please do the detabbing in a separate patch). See
--- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#TabsvsSpaces
--- for details
+{-# LANGUAGE RankNTypes #-}
module TcArrows ( tcProc ) where
-import {-# SOURCE #-} TcExpr( tcMonoExpr, tcInferRho, tcSyntaxOp, tcCheckId )
+import {-# SOURCE #-} TcExpr( tcMonoExpr, tcInferRho, tcSyntaxOp, tcCheckId, tcPolyExpr )
import HsSyn
import TcMatches
+import TcHsSyn( hsLPatType )
import TcType
import TcMType
import TcBinds
import TcUnify
import TcRnMonad
import TcEnv
-import Coercion
+import TcEvidence
import Id( mkLocalId )
import Inst
import Name
+import Coercion ( Role(..) )
import TysWiredIn
import VarSet
import TysPrim
-
+import BasicTypes( Arity )
import SrcLoc
import Outputable
import FastString
import Control.Monad
\end{code}
+Note [Arrow overivew]
+~~~~~~~~~~~~~~~~~~~~~
+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
-%* *
+%* *
+ Proc
+%* *
%************************************************************************
\begin{code}
-tcProc :: InPat Name -> LHsCmdTop Name -- proc pat -> expr
- -> TcRhoType -- Expected type of whole proc expression
- -> TcM (OutPat TcId, LHsCmdTop TcId, LCoercion)
+tcProc :: InPat Name -> LHsCmdTop Name -- proc pat -> expr
+ -> TcRhoType -- Expected type of whole proc expression
+ -> TcM (OutPat TcId, LHsCmdTop TcId, TcCoercion)
tcProc pat cmd exp_ty
= newArrowScope $
- do { (co, (exp_ty1, res_ty)) <- matchExpectedAppTy exp_ty
- ; (co1, (arr_ty, arg_ty)) <- matchExpectedAppTy exp_ty1
- ; let cmd_env = CmdEnv { cmd_arr = arr_ty }
+ do { (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 arg_ty $
- tcCmdTop cmd_env cmd [] res_ty
- ; let res_co = mkTransCo co (mkAppCo co1 (mkReflCo res_ty))
+ tcCmdTop cmd_env cmd (unitTy, res_ty)
+ ; let res_co = mkTcTransCo co (mkTcAppCo co1 (mkTcNomReflCo res_ty))
; return (pat', cmd', res_co) }
\end{code}
%************************************************************************
-%* *
- Commands
-%* *
+%* *
+ Commands
+%* *
%************************************************************************
\begin{code}
-type CmdStack = [TcTauType]
+-- 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 *->*->*
+ cmd_arr :: TcType -- arrow type constructor, of kind *->*->*
}
mkCmdArrTy :: CmdEnv -> TcTauType -> TcTauType -> TcTauType
---------------------------------------
tcCmdTop :: CmdEnv
-> LHsCmdTop Name
- -> CmdStack
- -> TcTauType -- Expected result type; always a monotype
- -- We know exactly how many cmd args are expected,
- -- albeit perhaps not their types; so we can pass
- -- in a CmdStack
- -> TcM (LHsCmdTop TcId)
-
-tcCmdTop env (L loc (HsCmdTop cmd _ _ names)) cmd_stk res_ty
- = setSrcSpan loc $
- do { cmd' <- tcCmd env cmd (cmd_stk, res_ty)
- ; names' <- mapM (tcSyntaxName ProcOrigin (cmd_arr env)) names
- ; return (L loc $ HsCmdTop cmd' cmd_stk res_ty names') }
-
+ -> CmdType
+ -> TcM (LHsCmdTop TcId)
+tcCmdTop env (L loc (HsCmdTop cmd _ _ names)) 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 cmd' cmd_stk res_ty names') }
----------------------------------------
-tcCmd :: CmdEnv -> LHsExpr Name -> (CmdStack, TcTauType) -> TcM (LHsExpr TcId)
- -- The main recursive function
-tcCmd env (L loc expr) res_ty
+tcCmd :: CmdEnv -> LHsCmd Name -> CmdType -> TcM (LHsCmd TcId)
+ -- The main recursive function
+tcCmd env (L loc cmd) res_ty
= setSrcSpan loc $ do
- { expr' <- tc_cmd env expr res_ty
- ; return (L loc expr') }
+ { cmd' <- tc_cmd env cmd res_ty
+ ; return (L loc cmd') }
-tc_cmd :: CmdEnv -> HsExpr Name -> (CmdStack, TcTauType) -> TcM (HsExpr TcId)
-tc_cmd env (HsPar cmd) res_ty
- = do { cmd' <- tcCmd env cmd res_ty
- ; return (HsPar cmd') }
+tc_cmd :: CmdEnv -> HsCmd Name -> CmdType -> TcM (HsCmd TcId)
+tc_cmd env (HsCmdPar cmd) res_ty
+ = do { cmd' <- tcCmd env cmd res_ty
+ ; return (HsCmdPar cmd') }
-tc_cmd env (HsLet binds (L body_loc body)) res_ty
- = do { (binds', body') <- tcLocalBinds binds $
- setSrcSpan body_loc $
- tc_cmd env body res_ty
- ; return (HsLet binds' (L body_loc body')) }
+tc_cmd env (HsCmdLet binds (L body_loc body)) res_ty
+ = do { (binds', body') <- tcLocalBinds binds $
+ setSrcSpan body_loc $
+ tc_cmd env body res_ty
+ ; return (HsCmdLet binds' (L body_loc body')) }
-tc_cmd env in_cmd@(HsCase scrut matches) (stk, res_ty)
+tc_cmd env in_cmd@(HsCmdCase scrut matches) (stk, res_ty)
= addErrCtxt (cmdCtxt in_cmd) $ do
(scrut', scrut_ty) <- tcInferRho scrut
matches' <- tcMatchesCase match_ctxt scrut_ty matches res_ty
- return (HsCase scrut' matches')
+ return (HsCmdCase scrut' matches')
where
match_ctxt = MC { mc_what = CaseAlt,
mc_body = mc_body }
mc_body body res_ty' = tcCmd env body (stk, res_ty')
-tc_cmd env (HsIf Nothing pred b1 b2) res_ty -- Ordinary 'if'
+tc_cmd env (HsCmdIf Nothing pred b1 b2) res_ty -- Ordinary 'if'
= do { pred' <- tcMonoExpr pred boolTy
; b1' <- tcCmd env b1 res_ty
; b2' <- tcCmd env b2 res_ty
- ; return (HsIf Nothing pred' b1' b2')
+ ; return (HsCmdIf Nothing pred' b1' b2')
}
-tc_cmd env (HsIf (Just fun) pred b1 b2) res_ty -- Rebindable syntax for if
- = do { pred_ty <- newFlexiTyVarTy openTypeKind
+tc_cmd env (HsCmdIf (Just fun) pred b1 b2) res_ty -- Rebindable syntax for if
+ = do { pred_ty <- newFlexiTyVarTy openTypeKind
-- 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
+ ; (_, [r_tv]) <- tcInstSkolTyVars [alphaTyVar]
+ ; let r_ty = mkTyVarTy r_tv
; let if_ty = mkFunTys [pred_ty, r_ty, r_ty] r_ty
; checkTc (not (r_tv `elemVarSet` tyVarsOfType pred_ty))
(ptext (sLit "Predicate type of `ifThenElse' depends on result type"))
- ; fun' <- tcSyntaxOp IfOrigin fun if_ty
- ; pred' <- tcMonoExpr pred pred_ty
- ; b1' <- tcCmd env b1 res_ty
- ; b2' <- tcCmd env b2 res_ty
- ; return (HsIf (Just fun') pred' b1' b2')
+ ; fun' <- tcSyntaxOp IfOrigin fun if_ty
+ ; pred' <- tcMonoExpr pred pred_ty
+ ; b1' <- tcCmd env b1 res_ty
+ ; b2' <- tcCmd env b2 res_ty
+ ; return (HsCmdIf (Just fun') pred' b1' b2')
}
-------------------------------------------
--- Arrow application
--- (f -< a) or (f -<< a)
+-- 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@(HsArrApp fun arg _ ho_app lr) (cmd_stk, res_ty)
- = addErrCtxt (cmdCtxt cmd) $
+tc_cmd env cmd@(HsCmdArrApp fun arg _ ho_app lr) (_, res_ty)
+ = addErrCtxt (cmdCtxt cmd) $
do { arg_ty <- newFlexiTyVarTy openTypeKind
- ; let fun_ty = mkCmdArrTy env (foldl mkPairTy arg_ty cmd_stk) res_ty
-
- ; fun' <- select_arrow_scope (tcMonoExpr fun fun_ty)
+ ; let fun_ty = mkCmdArrTy env arg_ty res_ty
+ ; fun' <- select_arrow_scope (tcMonoExpr fun fun_ty)
+ -- ToDo: There should be no need for the escapeArrowScope stuff
+ -- See Note [Escaping the arrow scope] in TcRnTypes
- ; arg' <- tcMonoExpr arg arg_ty
+ ; arg' <- tcMonoExpr arg arg_ty
- ; return (HsArrApp fun' arg' fun_ty ho_app lr) }
+ ; return (HsCmdArrApp fun' arg' fun_ty 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.
+ -- 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.
select_arrow_scope tc = case ho_app of
- HsHigherOrderApp -> tc
- HsFirstOrderApp -> escapeArrowScope tc
+ HsHigherOrderApp -> tc
+ HsFirstOrderApp -> escapeArrowScope tc
-------------------------------------------
--- Command application
+-- Command application
+--
+-- D,G |- exp : t
+-- D;G |-a cmd : (t,stk) --> res
+-- -----------------------------
+-- D;G |-a cmd exp : stk --> res
-tc_cmd env cmd@(HsApp fun arg) (cmd_stk, res_ty)
- = addErrCtxt (cmdCtxt cmd) $
+tc_cmd env cmd@(HsCmdApp fun arg) (cmd_stk, res_ty)
+ = addErrCtxt (cmdCtxt cmd) $
do { arg_ty <- newFlexiTyVarTy openTypeKind
-
- ; fun' <- tcCmd env fun (arg_ty:cmd_stk, res_ty)
-
- ; arg' <- tcMonoExpr arg arg_ty
-
- ; return (HsApp fun' arg') }
+ ; fun' <- tcCmd env fun (mkPairTy arg_ty cmd_stk, res_ty)
+ ; arg' <- tcMonoExpr arg arg_ty
+ ; return (HsCmdApp fun' arg') }
-------------------------------------------
--- Lambda
+-- Lambda
+--
+-- D;G,x:t |-a cmd : stk --> res
+-- ------------------------------
+-- D;G |-a (\x.cmd) : (t,stk) --> res
-tc_cmd env cmd@(HsLam (MatchGroup [L mtch_loc (match@(Match pats _maybe_rhs_sig grhss))] _))
+tc_cmd env
+ (HsCmdLam (MG { mg_alts = [L mtch_loc (match@(Match pats _maybe_rhs_sig grhss))], mg_origin = origin }))
(cmd_stk, res_ty)
- = addErrCtxt (pprMatchInCtxt match_ctxt match) $
-
- do { -- Check the cmd stack is big enough
- ; checkTc (lengthAtLeast cmd_stk n_pats)
- (kappaUnderflow cmd)
-
- -- Check the patterns, and the GRHSs inside
- ; (pats', grhss') <- setSrcSpan mtch_loc $
- tcPats LambdaExpr pats cmd_stk $
- tc_grhss grhss res_ty
-
- ; let match' = L mtch_loc (Match pats' Nothing grhss')
- ; return (HsLam (MatchGroup [match'] res_ty))
- }
-
+ = addErrCtxt (pprMatchInCtxt match_ctxt 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 arg_tys $
+ tc_grhss grhss cmd_stk' res_ty
+
+ ; let match' = L mtch_loc (Match pats' Nothing grhss')
+ arg_tys = map hsLPatType pats'
+ cmd' = HsCmdLam (MG { mg_alts = [match'], mg_arg_tys = arg_tys
+ , mg_res_ty = res_ty, mg_origin = origin })
+ ; return (mkHsCmdCast co cmd') }
where
n_pats = length pats
- stk' = drop n_pats cmd_stk
- match_ctxt = (LambdaExpr :: HsMatchContext Name) -- Maybe KappaExpr?
+ match_ctxt = (LambdaExpr :: HsMatchContext Name) -- Maybe KappaExpr?
pg_ctxt = PatGuard match_ctxt
- tc_grhss (GRHSs grhss binds) res_ty
- = do { (binds', grhss') <- tcLocalBinds binds $
- mapM (wrapLocM (tc_grhs res_ty)) grhss
- ; return (GRHSs grhss' binds') }
+ tc_grhss (GRHSs grhss binds) stk_ty res_ty
+ = do { (binds', grhss') <- tcLocalBinds binds $
+ mapM (wrapLocM (tc_grhs stk_ty res_ty)) grhss
+ ; return (GRHSs grhss' binds') }
- tc_grhs res_ty (GRHS guards body)
- = do { (guards', rhs') <- tcStmtsAndThen pg_ctxt tcGuardStmt guards res_ty $
- \ res_ty -> tcCmd env body (stk', res_ty)
- ; return (GRHS guards' rhs') }
+ tc_grhs stk_ty res_ty (GRHS guards body)
+ = do { (guards', rhs') <- tcStmtsAndThen pg_ctxt tcGuardStmt guards res_ty $
+ \ res_ty -> tcCmd env body (stk_ty, res_ty)
+ ; return (GRHS guards' rhs') }
-------------------------------------------
--- Do notation
+-- Do notation
-tc_cmd env cmd@(HsDo do_or_lc stmts _) (cmd_stk, res_ty)
- = do { checkTc (null cmd_stk) (nonEmptyCmdStkErr cmd)
- ; stmts' <- tcStmts do_or_lc (tcArrDoStmt env) stmts res_ty
- ; return (HsDo do_or_lc stmts' res_ty) }
- where
+tc_cmd env (HsCmdDo stmts _) (cmd_stk, res_ty)
+ = do { co <- unifyType unitTy cmd_stk -- Expecting empty argument stack
+ ; stmts' <- tcStmts ArrowExpr (tcArrDoStmt env) stmts res_ty
+ ; return (mkHsCmdCast co (HsCmdDo stmts' res_ty)) }
-----------------------------------------------------------------
--- Arrow ``forms'' (| e c1 .. cn |)
+-- Arrow ``forms'' (| e c1 .. cn |)
--
--- G |-b c : [s1 .. sm] s
--- pop(G) |- e : forall w. b ((w,s1) .. sm) s
--- -> a ((w,t1) .. tn) t
--- e \not\in (s, s1..sm, t, t1..tn)
--- ----------------------------------------------
--- G |-a (| e c |) : [t1 .. tn] t
-
-tc_cmd env cmd@(HsArrForm expr fixity cmd_args) (cmd_stk, res_ty)
- = addErrCtxt (cmdCtxt cmd) $
- do { cmds_w_tys <- zipWithM new_cmd_ty cmd_args [1..]
- ; [w_tv] <- tcInstSkolTyVars [alphaTyVar]
- ; let w_ty = mkTyVarTy w_tv -- Just a convenient starting point
-
- -- a ((w,t1) .. tn) t
- ; let e_res_ty = mkCmdArrTy env (foldl mkPairTy w_ty cmd_stk) res_ty
-
- -- b ((w,s1) .. sm) s
- -- -> a ((w,t1) .. tn) t
- ; let e_ty = mkFunTys [mkAppTys b [tup,s] | (_,_,b,tup,s) <- cmds_w_tys]
- e_res_ty
-
- -- Check expr
- ; (inst_binds, expr') <- checkConstraints ArrowSkol [w_tv] [] $
- escapeArrowScope (tcMonoExpr expr e_ty)
-
- -- OK, now we are in a position to unscramble
- -- the s1..sm and check each cmd
- ; cmds' <- mapM (tc_cmd w_tv) cmds_w_tys
-
- ; let wrap = WpTyLam w_tv <.> mkWpLet inst_binds
- ; return (HsArrForm (mkLHsWrap wrap expr') fixity cmds') }
+-- 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 expr fixity cmd_args) (cmd_stk, res_ty)
+ = addErrCtxt (cmdCtxt cmd) $
+ do { (cmd_args', cmd_tys) <- mapAndUnzipM tc_cmd_arg cmd_args
+ ; let e_ty = mkForAllTy alphaTyVar $ -- We use alphaTyVar for 'w'
+ mkFunTys cmd_tys $
+ mkCmdArrTy env (mkPairTy alphaTy cmd_stk) res_ty
+ ; expr' <- tcPolyExpr expr e_ty
+ ; return (HsCmdArrForm expr' fixity cmd_args') }
+
where
- -- Make the types
- -- b, ((e,s1) .. sm), s
- new_cmd_ty :: LHsCmdTop Name -> Int
- -> TcM (LHsCmdTop Name, Int, TcType, TcType, TcType)
- new_cmd_ty cmd i
- = do { b_ty <- newFlexiTyVarTy arrowTyConKind
- ; tup_ty <- newFlexiTyVarTy liftedTypeKind
- -- We actually make a type variable for the tuple
- -- because we don't know how deeply nested it is yet
- ; s_ty <- newFlexiTyVarTy liftedTypeKind
- ; return (cmd, i, b_ty, tup_ty, s_ty)
- }
-
- tc_cmd w_tv (cmd, i, b, tup_ty, s)
- = do { tup_ty' <- zonkTcType tup_ty
- ; let (corner_ty, arg_tys) = unscramble tup_ty'
-
- -- Check that it has the right shape:
- -- ((w,s1) .. sn)
- -- where the si do not mention w
- ; _bogus <- unifyType corner_ty (mkTyVarTy w_tv)
- ; checkTc (not (w_tv `elemVarSet` tyVarsOfTypes arg_tys))
- (badFormFun i tup_ty')
- -- JPM: WARNING: this test is utterly bogus; see #5609
- -- We are not using the coercion returned by the unify;
- -- and (even more seriously) the w not in arg_tys test is totally
- -- bogus if there are suspended equality constraints. This code
- -- needs to be re-architected.
-
- ; tcCmdTop (env { cmd_arr = b }) cmd arg_tys s }
-
- unscramble :: TcType -> (TcType, [TcType])
- -- unscramble ((w,s1) .. sn) = (w, [s1..sn])
- unscramble ty = unscramble' ty []
-
- unscramble' ty ss
- = case tcSplitTyConApp_maybe ty of
- Just (tc, [t,s]) | tc == pairTyCon
- -> unscramble' t (s:ss)
- _ -> (ty, ss)
+ tc_cmd_arg :: LHsCmdTop Name -> TcM (LHsCmdTop TcId, 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) }
-----------------------------------------------------------------
--- Base case for illegal commands
+-- Base case for illegal commands
-- This is where expressions that aren't commands get rejected
tc_cmd _ cmd _
= failWithTc (vcat [ptext (sLit "The expression"), nest 2 (ppr cmd),
- ptext (sLit "was found where an arrow command was expected")])
+ ptext (sLit "was found where an arrow command was expected")])
+
+
+matchExpectedCmdArgs :: Arity -> TcType -> TcM (TcCoercion, [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) }
\end{code}
%************************************************************************
-%* *
- Stmts
-%* *
+%* *
+ Stmts
+%* *
%************************************************************************
\begin{code}
--------------------------------
--- Mdo-notation
+-- Mdo-notation
-- The distinctive features here are
--- (a) RecStmts, and
--- (b) no rebindable syntax
+-- (a) RecStmts, and
+-- (b) no rebindable syntax
-tcArrDoStmt :: CmdEnv -> TcStmtChecker
+tcArrDoStmt :: CmdEnv -> TcCmdStmtChecker
tcArrDoStmt env _ (LastStmt rhs _) res_ty thing_inside
- = do { rhs' <- tcCmd env rhs ([], res_ty)
- ; thing <- thing_inside (panic "tcArrDoStmt")
- ; return (LastStmt rhs' noSyntaxExpr, thing) }
+ = do { rhs' <- tcCmd env rhs (unitTy, res_ty)
+ ; thing <- thing_inside (panic "tcArrDoStmt")
+ ; return (LastStmt rhs' noSyntaxExpr, thing) }
-tcArrDoStmt env _ (ExprStmt rhs _ _ _) res_ty thing_inside
- = do { (rhs', elt_ty) <- tc_arr_rhs env rhs
- ; thing <- thing_inside res_ty
- ; return (ExprStmt rhs' noSyntaxExpr noSyntaxExpr elt_ty, 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 rhs' noSyntaxExpr noSyntaxExpr elt_ty, 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 pat_ty $
+ = do { (rhs', pat_ty) <- tc_arr_rhs env rhs
+ ; (pat', thing) <- tcPat (StmtCtxt ctxt) pat pat_ty $
thing_inside res_ty
- ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, thing) }
-
-tcArrDoStmt env ctxt (RecStmt { recS_stmts = stmts, recS_later_ids = laterNames
- , recS_rec_ids = 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))
- <- tcStmtsAndThen ctxt (tcArrDoStmt env) stmts res_ty $ \ _res_ty' ->
- -- ToDo: res_ty not really right
- do { rec_rets <- zipWithM tcCheckId recNames rec_tys
- ; later_ids <- tcLookupLocalIds laterNames
- ; return (later_ids, rec_rets) }
-
- ; thing <- tcExtendIdEnv later_ids (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)
+ ; return (BindStmt pat' rhs' noSyntaxExpr noSyntaxExpr, 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 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 HsExpr)
+
+ ; 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 (emptyRecStmt { recS_stmts = stmts', recS_later_ids = later_ids
+ , recS_later_rets = later_rets
, recS_rec_ids = rec_ids, recS_rec_rets = rec_rets
, recS_ret_ty = res_ty }, thing)
- }}
+ }}
tcArrDoStmt _ _ stmt _ _
= pprPanic "tcArrDoStmt: unexpected Stmt" (ppr stmt)
-tc_arr_rhs :: CmdEnv -> LHsExpr Name -> TcM (LHsExpr TcId, TcType)
+tc_arr_rhs :: CmdEnv -> LHsCmd Name -> TcM (LHsCmd TcId, TcType)
tc_arr_rhs env rhs = do { ty <- newFlexiTyVarTy liftedTypeKind
- ; rhs' <- tcCmd env rhs ([], ty)
- ; return (rhs', ty) }
+ ; rhs' <- tcCmd env rhs (unitTy, ty)
+ ; return (rhs', ty) }
\end{code}
%************************************************************************
-%* *
- Helpers
-%* *
+%* *
+ Helpers
+%* *
%************************************************************************
mkPairTy :: Type -> Type -> Type
mkPairTy t1 t2 = mkTyConApp pairTyCon [t1,t2]
-arrowTyConKind :: Kind -- *->*->*
+arrowTyConKind :: Kind -- *->*->*
arrowTyConKind = mkArrowKinds [liftedTypeKind, liftedTypeKind] liftedTypeKind
\end{code}
%************************************************************************
-%* *
- Errors
-%* *
+%* *
+ Errors
+%* *
%************************************************************************
\begin{code}
-cmdCtxt :: HsExpr Name -> SDoc
+cmdCtxt :: HsCmd Name -> SDoc
cmdCtxt cmd = ptext (sLit "In the command:") <+> ppr cmd
-
-nonEmptyCmdStkErr :: HsExpr Name -> SDoc
-nonEmptyCmdStkErr cmd
- = hang (ptext (sLit "Non-empty command stack at command:"))
- 2 (ppr cmd)
-
-kappaUnderflow :: HsExpr Name -> SDoc
-kappaUnderflow cmd
- = hang (ptext (sLit "Command stack underflow at command:"))
- 2 (ppr cmd)
-
-badFormFun :: Int -> TcType -> SDoc
-badFormFun i tup_ty'
- = hang (ptext (sLit "The type of the") <+> speakNth i <+> ptext (sLit "argument of a command form has the wrong shape"))
- 2 (ptext (sLit "Argument type:") <+> ppr tup_ty')
\end{code}
git.haskell.org / ghc.git / blobdiff