Add some support for the code-point code-unit distinction.

tests/corelib/surrogate_pair_toUpper_test.dart

+// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+class SurrogatePairTest {
+
+  static testMain() {
+    var monkeyFace = "🐵";
+    var aceOfSpades = "🂡";
+    var gronthismata = "𝁅";
+    var segno = "𝄋";
+
+    Expect.equals(monkeyFace, monkeyFace.toUpperCase());
+    Expect.equals(monkeyFace, monkeyFace.toLowerCase());
+    Expect.equals(aceOfSpades, aceOfSpades.toUpperCase());
+    Expect.equals(aceOfSpades, aceOfSpades.toLowerCase());
+    Expect.equals(gronthismata, gronthismata.toUpperCase());
+    Expect.equals(gronthismata, gronthismata.toLowerCase());
+    Expect.equals(segno, segno.toUpperCase());
+    Expect.equals(segno, segno.toLowerCase());
+
+    var mixedMitt = new String.fromCharCodes([0x10423, 0x1042e, 0x1043b]);
+    var upperMitt = new String.fromCharCodes([0x10423, 0x10406, 0x10413]);
+    var lowerMitt = new String.fromCharCodes([0x1044b, 0x1042e, 0x1043b]);
+    Expect.equals(upperMitt, mixedMitt.toUpperCase());
+    Expect.equals(lowerMitt, mixedMitt.toLowerCase());
+    Expect.equals(upperMitt, upperMitt.toUpperCase());
+    Expect.equals(lowerMitt, upperMitt.toLowerCase());
+    Expect.equals(upperMitt, lowerMitt.toUpperCase());
+    Expect.equals(lowerMitt, lowerMitt.toLowerCase());
+
+    var mixedXMitt = new String.fromCharCodes([0x78, 0x10423, 0x1042e, 0x1043b]);
+    var upperXMitt = new String.fromCharCodes([0X58, 0x10423, 0x10406, 0x10413]);
+    var lowerXMitt = new String.fromCharCodes([0x78, 0x1044b, 0x1042e, 0x1043b]);
+    Expect.equals(upperXMitt, mixedXMitt.toUpperCase());
+    Expect.equals(lowerXMitt, mixedXMitt.toLowerCase());
+    Expect.equals(upperXMitt, upperXMitt.toUpperCase());
+    Expect.equals(lowerXMitt, upperXMitt.toLowerCase());
+    Expect.equals(upperXMitt, lowerXMitt.toUpperCase());
+    Expect.equals(lowerXMitt, lowerXMitt.toLowerCase());
+
+    var mixedDotMitt = new String.fromCharCodes([0x2e, 0x10423, 0x1042e, 0x1043b]);
+    var upperDotMitt = new String.fromCharCodes([0X2e, 0x10423, 0x10406, 0x10413]);
+    var lowerDotMitt = new String.fromCharCodes([0x2e, 0x1044b, 0x1042e, 0x1043b]);
+    Expect.equals(upperDotMitt, mixedDotMitt.toUpperCase());
+    Expect.equals(lowerDotMitt, mixedDotMitt.toLowerCase());
+    Expect.equals(upperDotMitt, upperDotMitt.toUpperCase());
+    Expect.equals(lowerDotMitt, upperDotMitt.toLowerCase());
+    Expect.equals(upperDotMitt, lowerDotMitt.toUpperCase());
+    Expect.equals(lowerDotMitt, lowerDotMitt.toLowerCase());
+
+    var lowerOw = new String.fromCharCodes([0x10435]);
+    var upperOw = new String.fromCharCodes([0x1040d]);
+    Expect.equals(lowerOw.codeUnitAt(1), monkeyFace.codeUnitAt(1));
+    Expect.equals(upperOw, lowerOw.toUpperCase());
+    Expect.equals(upperOw, upperOw.toUpperCase());
+    Expect.equals(lowerOw, lowerOw.toLowerCase());
+    Expect.equals(lowerOw, upperOw.toLowerCase());
+  }
+}
+
+main() {
+  SurrogatePairTest.testMain();
+}