Throw when case mapping result > max string length

test/intl/general/case-mapping.js

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Flags: --icu_case_mapping
 
 // Some edge cases that unibrow got wrong
 
 assertEquals("𐐘", "𐑀".toUpperCase());
 assertEquals("𐑀", "𐐘".toLowerCase());
@@ skipping 118 matching lines @@
 assertEquals("\u{1D400}\u{1D41A}", "\u{1D400}\u{1D41A}".toUpperCase());
 assertEquals("\u{1D400}\u{1D41A}", "\u{1D400}\u{1D41A}".toLowerCase());
 // Plane 1; New characters in Unicode 8.0
 assertEquals("\u{10C80}", "\u{10CC0}".toUpperCase());
 assertEquals("\u{10CC0}", "\u{10C80}".toLowerCase());
 assertEquals("\u{10C80}", "\u{10CC0}".toLocaleUpperCase());
 assertEquals("\u{10CC0}", "\u{10C80}".toLocaleLowerCase());
 assertEquals("\u{10C80}", "\u{10CC0}".toLocaleUpperCase(["tr"]));
 assertEquals("\u{10C80}", "\u{10CC0}".toLocaleUpperCase(["tr"]));
 assertEquals("\u{10CC0}", "\u{10C80}".toLocaleLowerCase());
+
+// If the result of case mapping is longer than the max string length
+// (1<<28 - 16), it should throw a range error instead of crashing.
+var invalidValues = [
+  { s: "\u0390", opType: 0 },
+  { s: "ß", opType: 0 },
+  { s: "\uFB01", opType: 0 }, // fi ligature
+  { s: "\uFB04", opType: 0 }, // ffl ligature
+  { s: "\u0390", opType: 1, locale: "und" },
+  { s: "\u00CC", opType: 2, locale: "lt" },
+  { s: "\u0130", opType: 2, locale: "en" },
+];
+
+invalidValues.forEach(function(value) {

[Dan Ehrenberg, 2016/08/10 19:06:23]

Wouldn't this be a great place to use destructuring? function({s, locale,
opType})... :)

+  var error;
+  try {
+    var s = value.s.repeat(1<<27);
+    switch (value.opType) {
+      case 0:
+        s.toUpperCase();
+        break;
+      case 1:
+        s.toLocaleUpperCase(value.locale);
+        break;
+      case 2:
+        s.toLocaleLowerCase(value.locale);
+        break;
+    }
+  } catch (e) {
+    error = e;
+  }
+
+  assertTrue(error !== undefined);
+  assertEquals('RangeError', error.name);

[Dan Ehrenberg, 2016/08/10 19:08:02]

You could also do assertThrows(() => s.toLocaleUpperCase(value.locale),
RangeError).

+});