Preliminary monad-comprehension patch (Trac #4370)

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

diff --git a/compiler/typecheck/TcArrows.lhs b/compiler/typecheck/TcArrows.lhs
index 227c6ce..8fdb47c 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
@@ -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')
     }
 
 -------------------------------------------
@@ -207,11 +213,11 @@ tc_cmd env cmd@(HsLam (MatchGroup [L mtch_loc (match@(Match pats _maybe_rhs_sig
 -------------------------------------------
 --             Do notation
 
-tc_cmd env cmd@(HsDo do_or_lc stmts body _ty) (cmd_stk, res_ty)
+tc_cmd env cmd@(HsDo do_or_lc stmts body _ _ty) (cmd_stk, res_ty)
   = do         { checkTc (null cmd_stk) (nonEmptyCmdStkErr cmd)
        ; (stmts', body') <- tcStmts do_or_lc (tcMDoStmt tc_rhs) stmts res_ty $
                             tcGuardedCmd env body []
-       ; return (HsDo do_or_lc stmts' body' res_ty) }
+       ; return (HsDo do_or_lc stmts' body' noSyntaxExpr res_ty) }
   where
     tc_rhs rhs = do { ty <- newFlexiTyVarTy liftedTypeKind
                    ; rhs' <- tcCmd env rhs ([], ty)
@@ -231,7 +237,7 @@ tc_cmd env cmd@(HsDo do_or_lc stmts body _ty) (cmd_stk, res_ty)
 tc_cmd env cmd@(HsArrForm expr fixity cmd_args) (cmd_stk, res_ty)      
   = addErrCtxt (cmdCtxt cmd)   $
     do { cmds_w_tys <- zipWithM new_cmd_ty cmd_args [1..]
-       ; [w_tv]     <- tcInstSkolTyVars ArrowSkol [alphaTyVar]
+        ; [w_tv]     <- tcInstSkolTyVars [alphaTyVar]
        ; let w_ty = mkTyVarTy w_tv     -- Just a convenient starting point
 
                --  a ((w,t1) .. tn) t