[project @ 2006-01-18 11:13:06 by simonpj]

[ghc-hetmet.git] / ghc / compiler / typecheck / TcArrows.lhs

diff --git a/ghc/compiler/typecheck/TcArrows.lhs b/ghc/compiler/typecheck/TcArrows.lhs
index 7829785..38ca1f6 100644 (file)
--- a/ghc/compiler/typecheck/TcArrows.lhs
+++ b/ghc/compiler/typecheck/TcArrows.lhs
@@ -11,7 +11,7 @@ module TcArrows ( tcProc ) where
 import {-# SOURCE #-}  TcExpr( tcCheckRho, tcInferRho )
 
 import HsSyn
-import TcHsSyn (  mkHsLet )
+import TcHsSyn (  mkHsDictLet )
 
 import TcMatches ( tcMatchPats, matchCtxt, tcStmts, tcMDoStmt, tcGuardStmt,
                   TcMatchCtxt(..), tcMatchesCase )
@@ -20,7 +20,7 @@ import TcType ( TcType, TcTauType, TcRhoType, mkFunTys, mkTyConApp,
                  mkTyVarTy, mkAppTys, tcSplitTyConApp_maybe, tcEqType, 
                  SkolemInfo(..) )
 import TcMType ( newTyFlexiVarTy, newTyFlexiVarTys, tcSkolTyVars, zonkTcType )
-import TcBinds ( tcBindsAndThen )
+import TcBinds ( tcLocalBinds )
 import TcSimplify ( tcSimplifyCheck )
 import TcUnify ( Expected(..), checkSigTyVarsWrt, zapExpectedTo )
 import TcRnMonad
@@ -50,13 +50,13 @@ tcProc :: InPat Name -> LHsCmdTop Name              -- proc pat -> expr
 
 tcProc pat cmd exp_ty
 -- gaw 2004 FIX?
- = do  { arr_ty <- newTyFlexiVarTy arrowTyConKind
+ = newArrowScope $ do
+       { arr_ty <- newTyFlexiVarTy arrowTyConKind
        ; [arg_ty, res_ty] <- newTyFlexiVarTys 2 liftedTypeKind
        ; zapExpectedTo exp_ty (mkAppTys arr_ty [arg_ty,res_ty])
 
        ; let cmd_env = CmdEnv { cmd_arr = arr_ty }
-       ; ([pat'], cmd') <- incProcLevel $
-                           tcMatchPats [pat] [Check arg_ty] (Check res_ty) $
+       ; ([pat'], cmd') <- tcMatchPats [pat] [Check arg_ty] (Check res_ty) $
                            tcCmdTop cmd_env cmd ([], res_ty)
                -- The False says don't do GADT type refinement
                -- This is a conservative choice, but I'm not sure of the consequences
@@ -74,7 +74,10 @@ tcProc pat cmd exp_ty
 
 \begin{code}
 type CmdStack = [TcTauType]
-data CmdEnv   = CmdEnv { cmd_arr   :: TcType }         -- The arrow type constructor, of kind *->*->*
+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]
@@ -108,11 +111,10 @@ tc_cmd env (HsPar cmd) res_ty
        ; return (HsPar cmd') }
 
 tc_cmd env (HsLet binds (L body_loc body)) res_ty
-  = tcBindsAndThen glue binds  $
-    setSrcSpan body_loc        $
-    tc_cmd env body res_ty
-  where
-    glue binds expr = HsLet [binds] (L body_loc expr)
+  = do { (binds', body') <- tcLocalBinds binds         $
+                            setSrcSpan body_loc        $
+                            tc_cmd env body res_ty
+       ; return (HsLet binds' (L body_loc body')) }
 
 tc_cmd env in_cmd@(HsCase scrut matches) (stk, res_ty)
   = addErrCtxt (cmdCtxt in_cmd)                $
@@ -142,19 +144,19 @@ tc_cmd env cmd@(HsArrApp fun arg _ ho_app lr) (cmd_stk, res_ty)
     do  { arg_ty <- newTyFlexiVarTy openTypeKind
        ; let fun_ty = mkCmdArrTy env (foldl mkPairTy arg_ty cmd_stk) res_ty
 
-       ; fun' <- pop_arrow_binders (tcCheckRho fun fun_ty)
+       ; fun' <- select_arrow_scope (tcCheckRho fun fun_ty)
 
        ; arg' <- tcCheckRho arg arg_ty
 
        ; return (HsArrApp fun' arg' fun_ty ho_app lr) }
   where
-       -- Before type-checking f, remove the "arrow binders" from the 
-       -- environment in the (-<) case.  
+       -- 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.
-    pop_arrow_binders tc = case ho_app of
+    select_arrow_scope tc = case ho_app of
        HsHigherOrderApp -> tc
-       HsFirstOrderApp  -> popArrowBinders tc
+       HsFirstOrderApp  -> escapeArrowScope tc
 
 -------------------------------------------
 --             Command application
@@ -198,9 +200,9 @@ tc_cmd env cmd@(HsLam (MatchGroup [L mtch_loc (match@(Match pats maybe_rhs_sig g
     pg_ctxt    = PatGuard match_ctxt
 
     tc_grhss (GRHSs grhss binds)
-       = tcBindsAndThen glueBindsOnGRHSs binds $
-         do { grhss' <- mappM (wrapLocM tc_grhs) grhss
-            ; return (GRHSs grhss' []) }
+       = do { (binds', grhss') <- tcLocalBinds binds $
+                                  mappM (wrapLocM tc_grhs) grhss
+            ; return (GRHSs grhss' binds') }
 
     tc_grhs (GRHS guards body)
        = do { (guards', rhs') <- tcStmts pg_ctxt
@@ -250,7 +252,7 @@ tc_cmd env cmd@(HsArrForm expr fixity cmd_args) (cmd_stk, res_ty)
                              e_res_ty
 
                -- Check expr
-       ; (expr', lie) <- popArrowBinders (getLIE (tcCheckRho expr e_ty))
+       ; (expr', lie) <- escapeArrowScope (getLIE (tcCheckRho expr e_ty))
        ; inst_binds <- tcSimplifyCheck sig_msg [w_tv] [] lie
 
                -- Check that the polymorphic variable hasn't been unified with anything
@@ -261,7 +263,7 @@ tc_cmd env cmd@(HsArrForm expr fixity cmd_args) (cmd_stk, res_ty)
                -- the s1..sm and check each cmd
        ; cmds' <- mapM (tc_cmd w_tv) cmds_w_tys
 
-       ; returnM (HsArrForm (mkHsTyLam [w_tv] (mkHsLet inst_binds expr')) fixity cmds')
+       ; returnM (HsArrForm (mkHsTyLam [w_tv] (mkHsDictLet inst_binds expr')) fixity cmds')
        }
   where
        -- Make the types       
@@ -289,7 +291,7 @@ tc_cmd env cmd@(HsArrForm expr fixity cmd_args) (cmd_stk, res_ty)
                      not (w_tv `elemVarSet` tyVarsOfTypes arg_tys))
                     (badFormFun i tup_ty')
 
-          ; tcCmdTop (CmdEnv { cmd_arr = b }) cmd (arg_tys, s) }
+          ; tcCmdTop (env { cmd_arr = b }) cmd (arg_tys, s) }
 
     unscramble :: TcType -> (TcType, [TcType])
     -- unscramble ((w,s1) .. sn)       =  (w, [s1..sn])