2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
5 Typecheck arrow notation
9 -- The above warning supression flag is a temporary kludge.
10 -- While working on this module you are encouraged to remove it and fix
11 -- any warnings in the module. See
12 -- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
15 module TcArrows ( tcProc ) where
17 #include "HsVersions.h"
19 import {-# SOURCE #-} TcExpr( tcMonoExpr, tcInferRho )
48 %************************************************************************
52 %************************************************************************
55 tcProc :: InPat Name -> LHsCmdTop Name -- proc pat -> expr
56 -> BoxyRhoType -- Expected type of whole proc expression
57 -> TcM (OutPat TcId, LHsCmdTop TcId, CoercionI)
61 do { ((exp_ty1, res_ty), coi) <- boxySplitAppTy exp_ty
62 ; ((arr_ty, arg_ty), coi1) <- boxySplitAppTy exp_ty1
63 ; let cmd_env = CmdEnv { cmd_arr = arr_ty }
64 ; (pat', cmd') <- tcProcPat pat arg_ty res_ty $
65 tcCmdTop cmd_env cmd []
66 ; let res_coi = mkTransCoI coi (mkAppTyCoI exp_ty1 coi1 res_ty IdCo)
67 ; return (pat', cmd', res_coi)
72 %************************************************************************
76 %************************************************************************
79 type CmdStack = [TcTauType]
82 cmd_arr :: TcType -- arrow type constructor, of kind *->*->*
85 mkCmdArrTy :: CmdEnv -> TcTauType -> TcTauType -> TcTauType
86 mkCmdArrTy env t1 t2 = mkAppTys (cmd_arr env) [t1, t2]
88 ---------------------------------------
92 -> TcTauType -- Expected result type; always a monotype
93 -- We know exactly how many cmd args are expected,
94 -- albeit perhaps not their types; so we can pass
96 -> TcM (LHsCmdTop TcId)
98 tcCmdTop env (L loc (HsCmdTop cmd _ _ names)) cmd_stk res_ty
100 do { cmd' <- tcGuardedCmd env cmd cmd_stk res_ty
101 ; names' <- mapM (tcSyntaxName ProcOrigin (cmd_arr env)) names
102 ; return (L loc $ HsCmdTop cmd' cmd_stk res_ty names') }
105 ----------------------------------------
106 tcGuardedCmd :: CmdEnv -> LHsExpr Name -> CmdStack
107 -> TcTauType -> TcM (LHsExpr TcId)
108 -- A wrapper that deals with the refinement (if any)
109 tcGuardedCmd env expr stk res_ty
110 = do { body <- tcCmd env expr (stk, res_ty)
114 tcCmd :: CmdEnv -> LHsExpr Name -> (CmdStack, TcTauType) -> TcM (LHsExpr TcId)
115 -- The main recursive function
116 tcCmd env (L loc expr) res_ty
117 = setSrcSpan loc $ do
118 { expr' <- tc_cmd env expr res_ty
119 ; return (L loc expr') }
121 tc_cmd env (HsPar cmd) res_ty
122 = do { cmd' <- tcCmd env cmd res_ty
123 ; return (HsPar cmd') }
125 tc_cmd env (HsLet binds (L body_loc body)) res_ty
126 = do { (binds', body') <- tcLocalBinds binds $
127 setSrcSpan body_loc $
128 tc_cmd env body res_ty
129 ; return (HsLet binds' (L body_loc body')) }
131 tc_cmd env in_cmd@(HsCase scrut matches) (stk, res_ty)
132 = addErrCtxt (cmdCtxt in_cmd) $ do
133 (scrut', scrut_ty) <- addErrCtxt (caseScrutCtxt scrut) $
135 matches' <- tcMatchesCase match_ctxt scrut_ty matches res_ty
136 return (HsCase scrut' matches')
138 match_ctxt = MC { mc_what = CaseAlt,
140 mc_body body res_ty' = tcGuardedCmd env body stk res_ty'
142 tc_cmd env (HsIf pred b1 b2) res_ty
143 = do { pred' <- tcMonoExpr pred boolTy
144 ; b1' <- tcCmd env b1 res_ty
145 ; b2' <- tcCmd env b2 res_ty
146 ; return (HsIf pred' b1' b2')
149 -------------------------------------------
151 -- (f -< a) or (f -<< a)
153 tc_cmd env cmd@(HsArrApp fun arg _ ho_app lr) (cmd_stk, res_ty)
154 = addErrCtxt (cmdCtxt cmd) $
155 do { arg_ty <- newFlexiTyVarTy openTypeKind
156 ; let fun_ty = mkCmdArrTy env (foldl mkPairTy arg_ty cmd_stk) res_ty
158 ; fun' <- select_arrow_scope (tcMonoExpr fun fun_ty)
160 ; arg' <- tcMonoExpr arg arg_ty
162 ; return (HsArrApp fun' arg' fun_ty ho_app lr) }
164 -- Before type-checking f, use the environment of the enclosing
165 -- proc for the (-<) case.
166 -- Local bindings, inside the enclosing proc, are not in scope
167 -- inside f. In the higher-order case (-<<), they are.
168 select_arrow_scope tc = case ho_app of
169 HsHigherOrderApp -> tc
170 HsFirstOrderApp -> escapeArrowScope tc
172 -------------------------------------------
173 -- Command application
175 tc_cmd env cmd@(HsApp fun arg) (cmd_stk, res_ty)
176 = addErrCtxt (cmdCtxt cmd) $
177 do { arg_ty <- newFlexiTyVarTy openTypeKind
179 ; fun' <- tcCmd env fun (arg_ty:cmd_stk, res_ty)
181 ; arg' <- tcMonoExpr arg arg_ty
183 ; return (HsApp fun' arg') }
185 -------------------------------------------
188 tc_cmd env cmd@(HsLam (MatchGroup [L mtch_loc (match@(Match pats maybe_rhs_sig grhss))] _))
190 = addErrCtxt (matchCtxt match_ctxt match) $
192 do { -- Check the cmd stack is big enough
193 ; checkTc (lengthAtLeast cmd_stk n_pats)
196 -- Check the patterns, and the GRHSs inside
197 ; (pats', grhss') <- setSrcSpan mtch_loc $
198 tcLamPats pats cmd_stk res_ty $
201 ; let match' = L mtch_loc (Match pats' Nothing grhss')
202 ; return (HsLam (MatchGroup [match'] res_ty))
207 stk' = drop n_pats cmd_stk
208 match_ctxt = (LambdaExpr :: HsMatchContext Name) -- Maybe KappaExpr?
209 pg_ctxt = PatGuard match_ctxt
211 tc_grhss (GRHSs grhss binds) res_ty
212 = do { (binds', grhss') <- tcLocalBinds binds $
213 mapM (wrapLocM (tc_grhs res_ty)) grhss
214 ; return (GRHSs grhss' binds') }
216 tc_grhs res_ty (GRHS guards body)
217 = do { (guards', rhs') <- tcStmts pg_ctxt tcGuardStmt guards res_ty $
218 tcGuardedCmd env body stk'
219 ; return (GRHS guards' rhs') }
221 -------------------------------------------
224 tc_cmd env cmd@(HsDo do_or_lc stmts body ty) (cmd_stk, res_ty)
225 = do { checkTc (null cmd_stk) (nonEmptyCmdStkErr cmd)
226 ; (stmts', body') <- tcStmts do_or_lc tc_stmt stmts res_ty $
227 tcGuardedCmd env body []
228 ; return (HsDo do_or_lc stmts' body' res_ty) }
230 tc_stmt = tcMDoStmt tc_rhs
231 tc_rhs rhs = do { ty <- newFlexiTyVarTy liftedTypeKind
232 ; rhs' <- tcCmd env rhs ([], ty)
233 ; return (rhs', ty) }
236 -----------------------------------------------------------------
237 -- Arrow ``forms'' (| e c1 .. cn |)
239 -- G |-b c : [s1 .. sm] s
240 -- pop(G) |- e : forall w. b ((w,s1) .. sm) s
241 -- -> a ((w,t1) .. tn) t
242 -- e \not\in (s, s1..sm, t, t1..tn)
243 -- ----------------------------------------------
244 -- G |-a (| e c |) : [t1 .. tn] t
246 tc_cmd env cmd@(HsArrForm expr fixity cmd_args) (cmd_stk, res_ty)
247 = addErrCtxt (cmdCtxt cmd) $
248 do { cmds_w_tys <- zipWithM new_cmd_ty cmd_args [1..]
249 ; span <- getSrcSpanM
250 ; [w_tv] <- tcInstSkolTyVars ArrowSkol [alphaTyVar]
251 ; let w_ty = mkTyVarTy w_tv -- Just a convenient starting point
253 -- a ((w,t1) .. tn) t
254 ; let e_res_ty = mkCmdArrTy env (foldl mkPairTy w_ty cmd_stk) res_ty
256 -- b ((w,s1) .. sm) s
257 -- -> a ((w,t1) .. tn) t
258 ; let e_ty = mkFunTys [mkAppTys b [tup,s] | (_,_,b,tup,s) <- cmds_w_tys]
262 ; (expr', lie) <- escapeArrowScope (getLIE (tcMonoExpr expr e_ty))
263 ; loc <- getInstLoc (SigOrigin ArrowSkol)
264 ; inst_binds <- tcSimplifyCheck loc [w_tv] [] lie
266 -- Check that the polymorphic variable hasn't been unified with anything
267 -- and is not free in res_ty or the cmd_stk (i.e. t, t1..tn)
268 ; checkSigTyVarsWrt (tyVarsOfTypes (res_ty:cmd_stk)) [w_tv]
270 -- OK, now we are in a position to unscramble
271 -- the s1..sm and check each cmd
272 ; cmds' <- mapM (tc_cmd w_tv) cmds_w_tys
274 ; return (HsArrForm (noLoc $ HsWrap (WpTyLam w_tv)
275 (unLoc $ mkHsDictLet inst_binds expr'))
280 -- b, ((e,s1) .. sm), s
281 new_cmd_ty :: LHsCmdTop Name -> Int
282 -> TcM (LHsCmdTop Name, Int, TcType, TcType, TcType)
284 = do { b_ty <- newFlexiTyVarTy arrowTyConKind
285 ; tup_ty <- newFlexiTyVarTy liftedTypeKind
286 -- We actually make a type variable for the tuple
287 -- because we don't know how deeply nested it is yet
288 ; s_ty <- newFlexiTyVarTy liftedTypeKind
289 ; return (cmd, i, b_ty, tup_ty, s_ty)
292 tc_cmd w_tv (cmd, i, b, tup_ty, s)
293 = do { tup_ty' <- zonkTcType tup_ty
294 ; let (corner_ty, arg_tys) = unscramble tup_ty'
296 -- Check that it has the right shape:
298 -- where the si do not mention w
299 ; checkTc (corner_ty `tcEqType` mkTyVarTy w_tv &&
300 not (w_tv `elemVarSet` tyVarsOfTypes arg_tys))
301 (badFormFun i tup_ty')
303 ; tcCmdTop (env { cmd_arr = b }) cmd arg_tys s }
305 unscramble :: TcType -> (TcType, [TcType])
306 -- unscramble ((w,s1) .. sn) = (w, [s1..sn])
308 = case tcSplitTyConApp_maybe ty of
309 Just (tc, [t,s]) | tc == pairTyCon
311 (w,ss) = unscramble t
316 -----------------------------------------------------------------
317 -- Base case for illegal commands
318 -- This is where expressions that aren't commands get rejected
321 = failWithTc (vcat [ptext SLIT("The expression"), nest 2 (ppr cmd),
322 ptext SLIT("was found where an arrow command was expected")])
326 %************************************************************************
330 %************************************************************************
334 mkPairTy t1 t2 = mkTyConApp pairTyCon [t1,t2]
336 arrowTyConKind :: Kind -- *->*->*
337 arrowTyConKind = mkArrowKinds [liftedTypeKind, liftedTypeKind] liftedTypeKind
341 %************************************************************************
345 %************************************************************************
348 cmdCtxt cmd = ptext SLIT("In the command:") <+> ppr cmd
351 = hang (ptext SLIT("In the scrutinee of a case command:")) 4 (ppr cmd)
353 nonEmptyCmdStkErr cmd
354 = hang (ptext SLIT("Non-empty command stack at command:"))
358 = hang (ptext SLIT("Command stack underflow at command:"))
362 = hang (ptext SLIT("The type of the") <+> speakNth i <+> ptext SLIT("argument of a command form has the wrong shape"))
363 4 (ptext SLIT("Argument type:") <+> ppr tup_ty')