S15.4.4.5_A3.1_T2 tests the execution of step 5 with different objects than strings. However it does not ensure steps 5 and 6 of the algorithm are executed in exactly this order:
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5. Let sep be ToString(separator).
6. If len is zero, return the empty String.
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Implementors may try to skip step 5 if the length is zero instead of calling ToString(separator), which may trigger side effects. For example Opera skips step 5 in this case.
Simple test case to cover this scenario:
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try {
var object = {toString: function() {throw "error"}};
[].join(object);
$ERROR('#X.X: var object = {toString: function() {throw "error"}}; [].join(object) throw "error". Actual: ' + ([].join(object)));
}
catch (e) {
if (e !== "error") {
$ERROR('#X.X: var object = {toString: function() {throw "error"}}; [].join(object) throw "error". Actual: ' + (e));
}
}
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Mark, sounds like the test here is valid; just needs to be made a bit more accurate.
Done.