--- a/nashorn/src/jdk/nashorn/internal/objects/NativeRegExp.java	Thu Sep 26 10:14:24 2013 +0200
+++ b/nashorn/src/jdk/nashorn/internal/objects/NativeRegExp.java	Thu Sep 26 11:47:24 2013 +0200
@@ -191,23 +191,21 @@
     public static NativeRegExp newRegExp(final Object regexp, final Object flags) {
         String  patternString = "";
         String  flagString    = "";
-        boolean flagsDefined  = false;
-
-        if (flags != UNDEFINED) {
-            flagsDefined = true;
-            flagString = JSType.toString(flags);
-        }
 
         if (regexp != UNDEFINED) {
             if (regexp instanceof NativeRegExp) {
-                if (!flagsDefined) {
-                    return (NativeRegExp)regexp; // 15.10.3.1 - undefined flags and regexp as
+                if (flags != UNDEFINED) {
+                    throw typeError("regex.cant.supply.flags");
                 }
-                throw typeError("regex.cant.supply.flags");
+                return (NativeRegExp)regexp; // 15.10.3.1 - undefined flags and regexp as
             }
             patternString = JSType.toString(regexp);
         }
 
+        if (flags != UNDEFINED) {
+            flagString = JSType.toString(flags);
+        }
+
         return new NativeRegExp(patternString, flagString);
     }
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/nashorn/test/script/basic/JDK-8025486.js	Thu Sep 26 11:47:24 2013 +0200
@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ * 
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ * 
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ * 
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ * 
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * JDK-8025486: RegExp constructor arguments are not evaluated in right order
+ *
+ * @test
+ * @run
+ */
+
+new RegExp({
+    toString: function() {
+        print("source");
+        return "a";
+    }
+}, {
+    toString: function() {
+        print("flags");
+        return "g";
+    }
+});
+
+try {
+    new RegExp(/asdf/, {
+        toString: function() {
+            fail("toString should not be called");
+        }
+    });
+    fail("expected TypeError");
+} catch (e) {
+    if (!(e instanceof TypeError)) {
+        fail("expected TypeError");
+    }
+    print(e);
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/nashorn/test/script/basic/JDK-8025486.js.EXPECTED	Thu Sep 26 11:47:24 2013 +0200
@@ -0,0 +1,3 @@
+source
+flags
+TypeError: Cannot supply flags when constructing one RegExp from another