[intl] Check for duplicate BCP 47 tags in a case-insensitive way

test/test262/local-tests/test/intl402/6.2.2_b.js

Index: test/test262/local-tests/test/intl402/6.2.2_b.js
diff --git a/test/test262/local-tests/test/intl402/6.2.2_b.js b/test/test262/local-tests/test/intl402/6.2.2_b.js
new file mode 100644
index 0000000000000000000000000000000000000000..d9a6d1b24df16e538807e6b966d24563c9229be0
--- /dev/null
+++ b/test/test262/local-tests/test/intl402/6.2.2_b.js
@@ -0,0 +1,42 @@
+// Copyright 2012 Mozilla Corporation. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+es5id: 6.2.2_b
+description: Tests that language tags with "_" are not accepted.
+author: Norbert Lindenberg
+includes: [testIntl.js]
+---*/
+
+var invalidLanguageTags = [
+    "de_DE",
+    "DE_de",
+    "cmn_Hans",
+    "cmn-hans_cn",
+    "es_419",
+    "es-419-u-nu-latn-cu_bob",
+    "i_klingon",
+    "cmn-hans-cn-t-ca-u-ca-x_t-u",
+    "enochian_enochian",
+    "de-gregory_u-ca-gregory",
+    "de-tester-Tester",  // Case-insensitive duplicate variant subtag
+    "de-DE-u-kn-true-U-kn-true",  // Case-insensitive duplicate singleton subtag
+];
+
+testWithIntlConstructors(function (Constructor) {
+    invalidLanguageTags.forEach(function (tag) {
+        var error;
+        try {
+            // this must throw an exception for an invalid language tag
+            var obj = new Constructor([tag]);
+        } catch (e) {
+            error = e;
+        }
+        if (error === undefined) {
+            $ERROR("Invalid language tag " + tag + " was not rejected.");
+        } else if (error.name !== "RangeError") {
+            $ERROR("Invalid language tag " + tag + " was rejected with wrong error " + error.name + ".");
+        }
+    });
+    return true;
+});