Handle overwriting valueOf on String objects correctly when adding...

test/mjsunit/regress/regress-760-2.js

+// Copyright 2010 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
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+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Check that when valueOf for a String object is overwritten it is called and
+// the result used when that object is added with a string.  
+
+// See: http://code.google.com/p/v8/issues/detail?id=760
+
+function test() {
+  var o = Object('x');
+  o.valueOf = function() { return 'y' };
+  assertEquals('y', o + '');
+  assertEquals('y', '' + o);
+}
+
+for (var i = 0; i < 10; i++) {
+  var o = Object('x');
+  o.valueOf = function() { return 'y' };
+  assertEquals('y', o + '');
+  assertEquals('y', '' + o);
+}
+
+for (var i = 0; i < 10; i++) {
+  test()
+}