Add rebindable syntax for if-then-else

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

diff --git a/compiler/typecheck/TcArrows.lhs b/compiler/typecheck/TcArrows.lhs
index 14e561b..53b3c97 100644 (file)
--- a/compiler/typecheck/TcArrows.lhs
+++ b/compiler/typecheck/TcArrows.lhs
@@ -7,7 +7,7 @@ Typecheck arrow notation
 \begin{code}
 module TcArrows ( tcProc ) where
 
-import {-# SOURCE #-}  TcExpr( tcMonoExpr, tcInferRho )
+import {-# SOURCE #-}  TcExpr( tcMonoExpr, tcInferRho, tcSyntaxOp )
 
 import HsSyn
 import TcMatches
@@ -48,7 +48,7 @@ tcProc pat cmd exp_ty
     do { (coi, (exp_ty1, res_ty)) <- matchExpectedAppTy exp_ty 
        ; (coi1, (arr_ty, arg_ty)) <- matchExpectedAppTy exp_ty1
        ; let cmd_env = CmdEnv { cmd_arr = arr_ty }
-       ; (pat', cmd') <- tcPat ProcExpr pat arg_ty res_ty $
+       ; (pat', cmd') <- tcPat ProcExpr pat arg_ty $
                          tcCmdTop cmd_env cmd [] res_ty
         ; let res_coi = mkTransCoI coi (mkAppTyCoI coi1 (IdCo res_ty))
        ; return (pat', cmd', res_coi) }
@@ -125,11 +125,17 @@ tc_cmd env in_cmd@(HsCase scrut matches) (stk, res_ty)
                       mc_body = mc_body }
     mc_body body res_ty' = tcGuardedCmd env body stk res_ty'
 
-tc_cmd env (HsIf pred b1 b2) res_ty
-  = do         { pred' <- tcMonoExpr pred boolTy
-       ; b1'   <- tcCmd env b1 res_ty
-       ; b2'   <- tcCmd env b2 res_ty
-       ; return (HsIf pred' b1' b2')
+tc_cmd env (HsIf mb_fun pred b1 b2) (stack_ty,res_ty)
+  = do         { pred_ty <- newFlexiTyVarTy openTypeKind
+       ; b_ty <- newFlexiTyVarTy openTypeKind
+        ; let if_ty = mkFunTys [pred_ty, b_ty, b_ty] res_ty
+       ; mb_fun' <- case mb_fun of 
+              Nothing  -> return Nothing
+              Just fun -> liftM Just (tcSyntaxOp IfOrigin fun if_ty)
+       ; pred' <- tcMonoExpr pred pred_ty
+       ; b1'   <- tcCmd env b1 (stack_ty,b_ty)
+       ; b2'   <- tcCmd env b2 (stack_ty,b_ty)
+       ; return (HsIf mb_fun' pred' b1' b2')
     }
 
 -------------------------------------------
@@ -180,8 +186,8 @@ tc_cmd env cmd@(HsLam (MatchGroup [L mtch_loc (match@(Match pats _maybe_rhs_sig
                  (kappaUnderflow cmd)
 
                -- Check the patterns, and the GRHSs inside
-       ; (pats', grhss') <- setSrcSpan mtch_loc                        $
-                            tcPats LambdaExpr pats cmd_stk res_ty      $
+       ; (pats', grhss') <- setSrcSpan mtch_loc                $
+                            tcPats LambdaExpr pats cmd_stk     $
                             tc_grhss grhss res_ty
 
        ; let match' = L mtch_loc (Match pats' Nothing grhss')
@@ -241,10 +247,9 @@ tc_cmd env cmd@(HsArrForm expr fixity cmd_args) (cmd_stk, res_ty)
                --   -> a ((w,t1) .. tn) t
        ; let e_ty = mkFunTys [mkAppTys b [tup,s] | (_,_,b,tup,s) <- cmds_w_tys] 
                              e_res_ty
-              free_tvs = tyVarsOfTypes (res_ty:cmd_stk)
 
                -- Check expr
-       ; (inst_binds, expr') <- checkConstraints ArrowSkol free_tvs [w_tv] [] $
+       ; (inst_binds, expr') <- checkConstraints ArrowSkol [w_tv] [] $
                                  escapeArrowScope (tcMonoExpr expr e_ty)
 
                -- OK, now we are in a position to unscramble