2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section{Typecheck arrow notation}
7 module TcArrows ( tcProc ) where
9 #include "HsVersions.h"
11 import {-# SOURCE #-} TcExpr( tcCheckRho, tcInferRho )
14 import TcHsSyn ( mkHsDictLet )
16 import TcMatches ( tcMatchPats, matchCtxt, tcStmts, tcMDoStmt, tcGuardStmt,
17 TcMatchCtxt(..), tcMatchesCase )
19 import TcType ( TcType, TcTauType, TcRhoType, mkFunTys, mkTyConApp,
20 mkTyVarTy, mkAppTys, tcSplitTyConApp_maybe, tcEqType,
22 import TcMType ( newTyFlexiVarTy, newTyFlexiVarTys, tcSkolTyVars, zonkTcType )
23 import TcBinds ( tcLocalBinds )
24 import TcSimplify ( tcSimplifyCheck )
25 import TcUnify ( Expected(..), checkSigTyVarsWrt, zapExpectedTo )
27 import Inst ( tcSyntaxName )
29 import TysWiredIn ( boolTy, pairTyCon )
31 import TysPrim ( alphaTyVar )
32 import Type ( Kind, mkArrowKinds, liftedTypeKind, openTypeKind, tyVarsOfTypes )
34 import SrcLoc ( Located(..) )
36 import Util ( lengthAtLeast )
40 %************************************************************************
44 %************************************************************************
47 tcProc :: InPat Name -> LHsCmdTop Name -- proc pat -> expr
48 -> Expected TcRhoType -- Expected type of whole proc expression
49 -> TcM (OutPat TcId, LHsCmdTop TcId)
54 { arr_ty <- newTyFlexiVarTy arrowTyConKind
55 ; [arg_ty, res_ty] <- newTyFlexiVarTys 2 liftedTypeKind
56 ; zapExpectedTo exp_ty (mkAppTys arr_ty [arg_ty,res_ty])
58 ; let cmd_env = CmdEnv { cmd_arr = arr_ty }
59 ; ([pat'], cmd') <- tcMatchPats [pat] [Check arg_ty] (Check res_ty) $
60 tcCmdTop cmd_env cmd ([], res_ty)
61 -- The False says don't do GADT type refinement
62 -- This is a conservative choice, but I'm not sure of the consequences
63 -- of type refinement in the arrow world!
65 ; return (pat', cmd') }
69 %************************************************************************
73 %************************************************************************
76 type CmdStack = [TcTauType]
79 cmd_arr :: TcType -- arrow type constructor, of kind *->*->*
82 mkCmdArrTy :: CmdEnv -> TcTauType -> TcTauType -> TcTauType
83 mkCmdArrTy env t1 t2 = mkAppTys (cmd_arr env) [t1, t2]
85 ---------------------------------------
88 -> (CmdStack, TcTauType) -- Expected result type; always a monotype
89 -- We know exactly how many cmd args are expected,
90 -- albeit perhaps not their types; so we can pass
92 -> TcM (LHsCmdTop TcId)
94 tcCmdTop env (L loc (HsCmdTop cmd _ _ names)) (cmd_stk, res_ty)
96 do { cmd' <- tcCmd env cmd (cmd_stk, res_ty)
97 ; names' <- mapM (tcSyntaxName ProcOrigin (cmd_arr env)) names
98 ; return (L loc $ HsCmdTop cmd' cmd_stk res_ty names') }
101 ----------------------------------------
102 tcCmd :: CmdEnv -> LHsExpr Name -> (CmdStack, TcTauType) -> TcM (LHsExpr TcId)
103 -- The main recursive function
104 tcCmd env (L loc expr) res_ty
105 = setSrcSpan loc $ do
106 { expr' <- tc_cmd env expr res_ty
107 ; return (L loc expr') }
109 tc_cmd env (HsPar cmd) res_ty
110 = do { cmd' <- tcCmd env cmd res_ty
111 ; return (HsPar cmd') }
113 tc_cmd env (HsLet binds (L body_loc body)) res_ty
114 = do { (binds', body') <- tcLocalBinds binds $
115 setSrcSpan body_loc $
116 tc_cmd env body res_ty
117 ; return (HsLet binds' (L body_loc body')) }
119 tc_cmd env in_cmd@(HsCase scrut matches) (stk, res_ty)
120 = addErrCtxt (cmdCtxt in_cmd) $
121 addErrCtxt (caseScrutCtxt scrut) (
123 ) `thenM` \ (scrut', scrut_ty) ->
124 tcMatchesCase match_ctxt scrut_ty matches (Check res_ty) `thenM` \ matches' ->
125 returnM (HsCase scrut' matches')
127 match_ctxt = MC { mc_what = CaseAlt,
129 mc_body body (Check res_ty') = tcCmd env body (stk, res_ty')
131 tc_cmd env (HsIf pred b1 b2) res_ty
132 = do { pred' <- tcCheckRho pred boolTy
133 ; b1' <- tcCmd env b1 res_ty
134 ; b2' <- tcCmd env b2 res_ty
135 ; return (HsIf pred' b1' b2')
138 -------------------------------------------
140 -- (f -< a) or (f -<< a)
142 tc_cmd env cmd@(HsArrApp fun arg _ ho_app lr) (cmd_stk, res_ty)
143 = addErrCtxt (cmdCtxt cmd) $
144 do { arg_ty <- newTyFlexiVarTy openTypeKind
145 ; let fun_ty = mkCmdArrTy env (foldl mkPairTy arg_ty cmd_stk) res_ty
147 ; fun' <- select_arrow_scope (tcCheckRho fun fun_ty)
149 ; arg' <- tcCheckRho arg arg_ty
151 ; return (HsArrApp fun' arg' fun_ty ho_app lr) }
153 -- Before type-checking f, use the environment of the enclosing
154 -- proc for the (-<) case.
155 -- Local bindings, inside the enclosing proc, are not in scope
156 -- inside f. In the higher-order case (-<<), they are.
157 select_arrow_scope tc = case ho_app of
158 HsHigherOrderApp -> tc
159 HsFirstOrderApp -> escapeArrowScope tc
161 -------------------------------------------
162 -- Command application
164 tc_cmd env cmd@(HsApp fun arg) (cmd_stk, res_ty)
165 = addErrCtxt (cmdCtxt cmd) $
167 do { arg_ty <- newTyFlexiVarTy openTypeKind
169 ; fun' <- tcCmd env fun (arg_ty:cmd_stk, res_ty)
171 ; arg' <- tcCheckRho arg arg_ty
173 ; return (HsApp fun' arg') }
175 -------------------------------------------
179 tc_cmd env cmd@(HsLam (MatchGroup [L mtch_loc (match@(Match pats maybe_rhs_sig grhss))] _))
181 = addErrCtxt (matchCtxt match_ctxt match) $
183 do { -- Check the cmd stack is big enough
184 ; checkTc (lengthAtLeast cmd_stk n_pats)
187 -- Check the patterns, and the GRHSs inside
188 ; (pats', grhss') <- setSrcSpan mtch_loc $
189 tcMatchPats pats (map Check cmd_stk) (Check res_ty) $
192 ; let match' = L mtch_loc (Match pats' Nothing grhss')
193 ; return (HsLam (MatchGroup [match'] res_ty))
198 stk' = drop n_pats cmd_stk
199 match_ctxt = LambdaExpr -- Maybe KappaExpr?
200 pg_ctxt = PatGuard match_ctxt
202 tc_grhss (GRHSs grhss binds)
203 = do { (binds', grhss') <- tcLocalBinds binds $
204 mappM (wrapLocM tc_grhs) grhss
205 ; return (GRHSs grhss' binds') }
207 tc_grhs (GRHS guards body)
208 = do { (guards', rhs') <- tcStmts pg_ctxt
211 (tcCmd env body (stk', res_ty))
212 ; return (GRHS guards' rhs') }
214 -------------------------------------------
217 tc_cmd env cmd@(HsDo do_or_lc stmts body ty) (cmd_stk, res_ty)
218 = do { checkTc (null cmd_stk) (nonEmptyCmdStkErr cmd)
219 ; (stmts', body') <- tcStmts do_or_lc tc_stmt stmts $
220 tcCmd env body ([], res_ty)
221 ; return (HsDo do_or_lc stmts' body' res_ty) }
223 tc_stmt = tcMDoStmt res_ty tc_rhs
224 tc_rhs rhs = do { ty <- newTyFlexiVarTy liftedTypeKind
225 ; rhs' <- tcCmd env rhs ([], ty)
226 ; return (rhs', ty) }
229 -----------------------------------------------------------------
230 -- Arrow ``forms'' (| e c1 .. cn |)
232 -- G |-b c : [s1 .. sm] s
233 -- pop(G) |- e : forall w. b ((w,s1) .. sm) s
234 -- -> a ((w,t1) .. tn) t
235 -- e \not\in (s, s1..sm, t, t1..tn)
236 -- ----------------------------------------------
237 -- G |-a (| e c |) : [t1 .. tn] t
239 tc_cmd env cmd@(HsArrForm expr fixity cmd_args) (cmd_stk, res_ty)
240 = addErrCtxt (cmdCtxt cmd) $
241 do { cmds_w_tys <- zipWithM new_cmd_ty cmd_args [1..]
242 ; span <- getSrcSpanM
243 ; [w_tv] <- tcSkolTyVars (ArrowSkol span) [alphaTyVar]
244 ; let w_ty = mkTyVarTy w_tv -- Just a convenient starting point
246 -- a ((w,t1) .. tn) t
247 ; let e_res_ty = mkCmdArrTy env (foldl mkPairTy w_ty cmd_stk) res_ty
249 -- b ((w,s1) .. sm) s
250 -- -> a ((w,t1) .. tn) t
251 ; let e_ty = mkFunTys [mkAppTys b [tup,s] | (_,_,b,tup,s) <- cmds_w_tys]
255 ; (expr', lie) <- escapeArrowScope (getLIE (tcCheckRho expr e_ty))
256 ; inst_binds <- tcSimplifyCheck sig_msg [w_tv] [] lie
258 -- Check that the polymorphic variable hasn't been unified with anything
259 -- and is not free in res_ty or the cmd_stk (i.e. t, t1..tn)
260 ; checkSigTyVarsWrt (tyVarsOfTypes (res_ty:cmd_stk)) [w_tv]
262 -- OK, now we are in a position to unscramble
263 -- the s1..sm and check each cmd
264 ; cmds' <- mapM (tc_cmd w_tv) cmds_w_tys
266 ; returnM (HsArrForm (mkHsTyLam [w_tv] (mkHsDictLet inst_binds expr')) fixity cmds')
270 -- b, ((e,s1) .. sm), s
271 new_cmd_ty :: LHsCmdTop Name -> Int
272 -> TcM (LHsCmdTop Name, Int, TcType, TcType, TcType)
275 = do { b_ty <- newTyFlexiVarTy arrowTyConKind
276 ; tup_ty <- newTyFlexiVarTy liftedTypeKind
277 -- We actually make a type variable for the tuple
278 -- because we don't know how deeply nested it is yet
279 ; s_ty <- newTyFlexiVarTy liftedTypeKind
280 ; return (cmd, i, b_ty, tup_ty, s_ty)
283 tc_cmd w_tv (cmd, i, b, tup_ty, s)
284 = do { tup_ty' <- zonkTcType tup_ty
285 ; let (corner_ty, arg_tys) = unscramble tup_ty'
287 -- Check that it has the right shape:
289 -- where the si do not mention w
290 ; checkTc (corner_ty `tcEqType` mkTyVarTy w_tv &&
291 not (w_tv `elemVarSet` tyVarsOfTypes arg_tys))
292 (badFormFun i tup_ty')
294 ; tcCmdTop (env { cmd_arr = b }) cmd (arg_tys, s) }
296 unscramble :: TcType -> (TcType, [TcType])
297 -- unscramble ((w,s1) .. sn) = (w, [s1..sn])
299 = case tcSplitTyConApp_maybe ty of
300 Just (tc, [t,s]) | tc == pairTyCon
302 (w,ss) = unscramble t
307 sig_msg = ptext SLIT("expected type of a command form")
309 -----------------------------------------------------------------
310 -- Base case for illegal commands
311 -- This is where expressions that aren't commands get rejected
314 = failWithTc (vcat [ptext SLIT("The expression"), nest 2 (ppr cmd),
315 ptext SLIT("was found where an arrow command was expected")])
319 %************************************************************************
323 %************************************************************************
327 mkPairTy t1 t2 = mkTyConApp pairTyCon [t1,t2]
329 arrowTyConKind :: Kind -- *->*->*
330 arrowTyConKind = mkArrowKinds [liftedTypeKind, liftedTypeKind] liftedTypeKind
334 %************************************************************************
338 %************************************************************************
341 cmdCtxt cmd = ptext SLIT("In the command:") <+> ppr cmd
344 = hang (ptext SLIT("In the scrutinee of a case command:")) 4 (ppr cmd)
346 nonEmptyCmdStkErr cmd
347 = hang (ptext SLIT("Non-empty command stack at command:"))
351 = hang (ptext SLIT("Command stack underflow at command:"))
355 = hang (ptext SLIT("The type of the") <+> speakNth i <+> ptext SLIT("argument of a command form has the wrong shape"))
356 4 (ptext SLIT("Argument type:") <+> ppr tup_ty')