-rnExpr (HsIf p b1 b2)
- = rnLExpr p `thenM` \ (p', fvP) ->
- rnLExpr b1 `thenM` \ (b1', fvB1) ->
- rnLExpr b2 `thenM` \ (b2', fvB2) ->
- return (HsIf p' b1' b2', plusFVs [fvP, fvB1, fvB2])
+rnExpr (HsIf _ p b1 b2)
+ = do { (p', fvP) <- rnLExpr p
+ ; (b1', fvB1) <- rnLExpr b1
+ ; (b2', fvB2) <- rnLExpr b2
+ ; rebind <- xoptM Opt_RebindableSyntax
+ ; if not rebind
+ then return (HsIf Nothing p' b1' b2', plusFVs [fvP, fvB1, fvB2])
+ else do { c <- liftM HsVar (lookupOccRn (mkVarUnqual (fsLit "ifThenElse")))
+ ; return (HsIf (Just c) p' b1' b2', plusFVs [fvP, fvB1, fvB2]) }}