2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
5 Typecheck arrow notation
8 module TcArrows ( tcProc ) where
10 import {-# SOURCE #-} TcExpr( tcMonoExpr, tcInferRho, tcSyntaxOp )
35 %************************************************************************
39 %************************************************************************
42 tcProc :: InPat Name -> LHsCmdTop Name -- proc pat -> expr
43 -> TcRhoType -- Expected type of whole proc expression
44 -> TcM (OutPat TcId, LHsCmdTop TcId, CoercionI)
48 do { (coi, (exp_ty1, res_ty)) <- matchExpectedAppTy exp_ty
49 ; (coi1, (arr_ty, arg_ty)) <- matchExpectedAppTy exp_ty1
50 ; let cmd_env = CmdEnv { cmd_arr = arr_ty }
51 ; (pat', cmd') <- tcPat ProcExpr pat arg_ty $
52 tcCmdTop cmd_env cmd [] res_ty
53 ; let res_coi = mkTransCoI coi (mkAppTyCoI coi1 (IdCo res_ty))
54 ; return (pat', cmd', res_coi) }
58 %************************************************************************
62 %************************************************************************
65 type CmdStack = [TcTauType]
68 cmd_arr :: TcType -- arrow type constructor, of kind *->*->*
71 mkCmdArrTy :: CmdEnv -> TcTauType -> TcTauType -> TcTauType
72 mkCmdArrTy env t1 t2 = mkAppTys (cmd_arr env) [t1, t2]
74 ---------------------------------------
78 -> TcTauType -- Expected result type; always a monotype
79 -- We know exactly how many cmd args are expected,
80 -- albeit perhaps not their types; so we can pass
82 -> TcM (LHsCmdTop TcId)
84 tcCmdTop env (L loc (HsCmdTop cmd _ _ names)) cmd_stk res_ty
86 do { cmd' <- tcGuardedCmd env cmd cmd_stk res_ty
87 ; names' <- mapM (tcSyntaxName ProcOrigin (cmd_arr env)) names
88 ; return (L loc $ HsCmdTop cmd' cmd_stk res_ty names') }
91 ----------------------------------------
92 tcGuardedCmd :: CmdEnv -> LHsExpr Name -> CmdStack
93 -> TcTauType -> TcM (LHsExpr TcId)
94 -- A wrapper that deals with the refinement (if any)
95 tcGuardedCmd env expr stk res_ty
96 = do { body <- tcCmd env expr (stk, res_ty)
100 tcCmd :: CmdEnv -> LHsExpr Name -> (CmdStack, TcTauType) -> TcM (LHsExpr TcId)
101 -- The main recursive function
102 tcCmd env (L loc expr) res_ty
103 = setSrcSpan loc $ do
104 { expr' <- tc_cmd env expr res_ty
105 ; return (L loc expr') }
107 tc_cmd :: CmdEnv -> HsExpr Name -> (CmdStack, TcTauType) -> TcM (HsExpr TcId)
108 tc_cmd env (HsPar cmd) res_ty
109 = do { cmd' <- tcCmd env cmd res_ty
110 ; return (HsPar cmd') }
112 tc_cmd env (HsLet binds (L body_loc body)) res_ty
113 = do { (binds', body') <- tcLocalBinds binds $
114 setSrcSpan body_loc $
115 tc_cmd env body res_ty
116 ; return (HsLet binds' (L body_loc body')) }
118 tc_cmd env in_cmd@(HsCase scrut matches) (stk, res_ty)
119 = addErrCtxt (cmdCtxt in_cmd) $ do
120 (scrut', scrut_ty) <- tcInferRho scrut
121 matches' <- tcMatchesCase match_ctxt scrut_ty matches res_ty
122 return (HsCase scrut' matches')
124 match_ctxt = MC { mc_what = CaseAlt,
126 mc_body body res_ty' = tcGuardedCmd env body stk res_ty'
128 tc_cmd env (HsIf mb_fun pred b1 b2) (stack_ty,res_ty)
129 = do { pred_ty <- newFlexiTyVarTy openTypeKind
130 ; b_ty <- newFlexiTyVarTy openTypeKind
131 ; let if_ty = mkFunTys [pred_ty, b_ty, b_ty] res_ty
132 ; mb_fun' <- case mb_fun of
133 Nothing -> return Nothing
134 Just fun -> liftM Just (tcSyntaxOp IfOrigin fun if_ty)
135 ; pred' <- tcMonoExpr pred pred_ty
136 ; b1' <- tcCmd env b1 (stack_ty,b_ty)
137 ; b2' <- tcCmd env b2 (stack_ty,b_ty)
138 ; return (HsIf mb_fun' pred' b1' b2')
141 -------------------------------------------
143 -- (f -< a) or (f -<< a)
145 tc_cmd env cmd@(HsArrApp fun arg _ ho_app lr) (cmd_stk, res_ty)
146 = addErrCtxt (cmdCtxt cmd) $
147 do { arg_ty <- newFlexiTyVarTy openTypeKind
148 ; let fun_ty = mkCmdArrTy env (foldl mkPairTy arg_ty cmd_stk) res_ty
150 ; fun' <- select_arrow_scope (tcMonoExpr fun fun_ty)
152 ; arg' <- tcMonoExpr arg arg_ty
154 ; return (HsArrApp fun' arg' fun_ty ho_app lr) }
156 -- Before type-checking f, use the environment of the enclosing
157 -- proc for the (-<) case.
158 -- Local bindings, inside the enclosing proc, are not in scope
159 -- inside f. In the higher-order case (-<<), they are.
160 select_arrow_scope tc = case ho_app of
161 HsHigherOrderApp -> tc
162 HsFirstOrderApp -> escapeArrowScope tc
164 -------------------------------------------
165 -- Command application
167 tc_cmd env cmd@(HsApp fun arg) (cmd_stk, res_ty)
168 = addErrCtxt (cmdCtxt cmd) $
169 do { arg_ty <- newFlexiTyVarTy openTypeKind
171 ; fun' <- tcCmd env fun (arg_ty:cmd_stk, res_ty)
173 ; arg' <- tcMonoExpr arg arg_ty
175 ; return (HsApp fun' arg') }
177 -------------------------------------------
180 tc_cmd env cmd@(HsLam (MatchGroup [L mtch_loc (match@(Match pats _maybe_rhs_sig grhss))] _))
182 = addErrCtxt (pprMatchInCtxt match_ctxt match) $
184 do { -- Check the cmd stack is big enough
185 ; checkTc (lengthAtLeast cmd_stk n_pats)
188 -- Check the patterns, and the GRHSs inside
189 ; (pats', grhss') <- setSrcSpan mtch_loc $
190 tcPats LambdaExpr pats cmd_stk $
191 tc_grhss grhss res_ty
193 ; let match' = L mtch_loc (Match pats' Nothing grhss')
194 ; return (HsLam (MatchGroup [match'] res_ty))
199 stk' = drop n_pats cmd_stk
200 match_ctxt = (LambdaExpr :: HsMatchContext Name) -- Maybe KappaExpr?
201 pg_ctxt = PatGuard match_ctxt
203 tc_grhss (GRHSs grhss binds) res_ty
204 = do { (binds', grhss') <- tcLocalBinds binds $
205 mapM (wrapLocM (tc_grhs res_ty)) grhss
206 ; return (GRHSs grhss' binds') }
208 tc_grhs res_ty (GRHS guards body)
209 = do { (guards', rhs') <- tcStmts pg_ctxt tcGuardStmt guards res_ty $
210 tcGuardedCmd env body stk'
211 ; return (GRHS guards' rhs') }
213 -------------------------------------------
216 tc_cmd env cmd@(HsDo do_or_lc stmts body _ty) (cmd_stk, res_ty)
217 = do { checkTc (null cmd_stk) (nonEmptyCmdStkErr cmd)
218 ; (stmts', body') <- tcStmts do_or_lc (tcMDoStmt tc_rhs) stmts res_ty $
219 tcGuardedCmd env body []
220 ; return (HsDo do_or_lc stmts' body' res_ty) }
222 tc_rhs rhs = do { ty <- newFlexiTyVarTy liftedTypeKind
223 ; rhs' <- tcCmd env rhs ([], ty)
224 ; return (rhs', ty) }
227 -----------------------------------------------------------------
228 -- Arrow ``forms'' (| e c1 .. cn |)
230 -- G |-b c : [s1 .. sm] s
231 -- pop(G) |- e : forall w. b ((w,s1) .. sm) s
232 -- -> a ((w,t1) .. tn) t
233 -- e \not\in (s, s1..sm, t, t1..tn)
234 -- ----------------------------------------------
235 -- G |-a (| e c |) : [t1 .. tn] t
237 tc_cmd env cmd@(HsArrForm expr fixity cmd_args) (cmd_stk, res_ty)
238 = addErrCtxt (cmdCtxt cmd) $
239 do { cmds_w_tys <- zipWithM new_cmd_ty cmd_args [1..]
240 ; [w_tv] <- tcInstSkolTyVars [alphaTyVar]
241 ; let w_ty = mkTyVarTy w_tv -- Just a convenient starting point
243 -- a ((w,t1) .. tn) t
244 ; let e_res_ty = mkCmdArrTy env (foldl mkPairTy w_ty cmd_stk) res_ty
246 -- b ((w,s1) .. sm) s
247 -- -> a ((w,t1) .. tn) t
248 ; let e_ty = mkFunTys [mkAppTys b [tup,s] | (_,_,b,tup,s) <- cmds_w_tys]
252 ; (inst_binds, expr') <- checkConstraints ArrowSkol [w_tv] [] $
253 escapeArrowScope (tcMonoExpr expr e_ty)
255 -- OK, now we are in a position to unscramble
256 -- the s1..sm and check each cmd
257 ; cmds' <- mapM (tc_cmd w_tv) cmds_w_tys
259 ; let wrap = WpTyLam w_tv <.> mkWpLet inst_binds
260 ; return (HsArrForm (mkLHsWrap wrap expr') fixity cmds') }
263 -- b, ((e,s1) .. sm), s
264 new_cmd_ty :: LHsCmdTop Name -> Int
265 -> TcM (LHsCmdTop Name, Int, TcType, TcType, TcType)
267 = do { b_ty <- newFlexiTyVarTy arrowTyConKind
268 ; tup_ty <- newFlexiTyVarTy liftedTypeKind
269 -- We actually make a type variable for the tuple
270 -- because we don't know how deeply nested it is yet
271 ; s_ty <- newFlexiTyVarTy liftedTypeKind
272 ; return (cmd, i, b_ty, tup_ty, s_ty)
275 tc_cmd w_tv (cmd, i, b, tup_ty, s)
276 = do { tup_ty' <- zonkTcType tup_ty
277 ; let (corner_ty, arg_tys) = unscramble tup_ty'
279 -- Check that it has the right shape:
281 -- where the si do not mention w
282 ; checkTc (corner_ty `tcEqType` mkTyVarTy w_tv &&
283 not (w_tv `elemVarSet` tyVarsOfTypes arg_tys))
284 (badFormFun i tup_ty')
286 ; tcCmdTop (env { cmd_arr = b }) cmd arg_tys s }
288 unscramble :: TcType -> (TcType, [TcType])
289 -- unscramble ((w,s1) .. sn) = (w, [s1..sn])
290 unscramble ty = unscramble' ty []
293 = case tcSplitTyConApp_maybe ty of
294 Just (tc, [t,s]) | tc == pairTyCon
295 -> unscramble' t (s:ss)
298 -----------------------------------------------------------------
299 -- Base case for illegal commands
300 -- This is where expressions that aren't commands get rejected
303 = failWithTc (vcat [ptext (sLit "The expression"), nest 2 (ppr cmd),
304 ptext (sLit "was found where an arrow command was expected")])
308 %************************************************************************
312 %************************************************************************
316 mkPairTy :: Type -> Type -> Type
317 mkPairTy t1 t2 = mkTyConApp pairTyCon [t1,t2]
319 arrowTyConKind :: Kind -- *->*->*
320 arrowTyConKind = mkArrowKinds [liftedTypeKind, liftedTypeKind] liftedTypeKind
324 %************************************************************************
328 %************************************************************************
331 cmdCtxt :: HsExpr Name -> SDoc
332 cmdCtxt cmd = ptext (sLit "In the command:") <+> ppr cmd
334 nonEmptyCmdStkErr :: HsExpr Name -> SDoc
335 nonEmptyCmdStkErr cmd
336 = hang (ptext (sLit "Non-empty command stack at command:"))
339 kappaUnderflow :: HsExpr Name -> SDoc
341 = hang (ptext (sLit "Command stack underflow at command:"))
344 badFormFun :: Int -> TcType -> SDoc
346 = hang (ptext (sLit "The type of the") <+> speakNth i <+> ptext (sLit "argument of a command form has the wrong shape"))
347 2 (ptext (sLit "Argument type:") <+> ppr tup_ty')