Fix issue 24043: do not trust the pattern. Enable a 'hidden' test.

If there is a performance issues, I can add specialized code for String patterns.

BUG=24043
R=rmacnak@google.com

Review URL: https://codereview.chromium.org//1286823003 .

runtime/lib/string_patch.dart

@@ -896,14 +896,16 @@ class _StringBase {
     List<String> result = new List<String>();
     int startIndex = 0;
     int previousIndex = 0;
+    // 'pattern' may not be implemented correctly and therefore we cannot
+    // call _substringUnhchecked unless it is a trustworthy type (e.g. String).
     while (true) {
       if (startIndex == length || !iterator.moveNext()) {
-        result.add(this._substringUnchecked(previousIndex, length));
+        result.add(this.substring(previousIndex, length));
         break;
       }
       Match match = iterator.current;
       if (match.start == length) {
-        result.add(this._substringUnchecked(previousIndex, length));
+        result.add(this.substring(previousIndex, length));
         break;
       }
       int endIndex = match.end;
@@ -911,7 +913,7 @@ class _StringBase {
         ++startIndex;  // empty match, advance and restart
         continue;
       }
-      result.add(this._substringUnchecked(previousIndex, match.start));
+      result.add(this.substring(previousIndex, match.start));
       startIndex = previousIndex = endIndex;
     }
     return result;

tests/language/string_interpolation_and_buffer_test.dart

@@ -5,6 +5,8 @@
 // Test to ensure that StringBuffer and string interpolation behaves
 // the same and fail fast.
 
+import "package:expect/expect.dart";
+
 class ToStringWrapper {
   final value;
 

tests/language/string_split_test.dart

@@ -0,0 +1,29 @@
+// Copyright (c) 2012, 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.
+// Issue 24043.
+
+import "package:expect/expect.dart";
+
+class EvilMatch implements Match {
+  int get start => 100000000;
+  int get end => 3;
+}
+
+class EvilIterator implements Iterator {
+  bool moveNext() => true;
+  EvilMatch get current => new EvilMatch();
+}
+
+class EvilIterable extends Iterable {
+  Iterator get iterator => new EvilIterator();
+}
+
+class EvilPattern {
+  Iterable allMatches(String s) => new EvilIterable();
+}
+
+void main() {
+  Expect.throws(() => "foo".split(new EvilPattern())[0].length,
+      (e) => e is RangeError);
+}