Issue2357

The following code fails with an infinite recursion in Jython 2.7. It works well on CPython. The problem is apparent in SQLAlchemy's SortedSet implementation.


class TestSet(set):

    def difference_update(self, other):
        set.difference_update(self, other)
        return self

    __isub__ = difference_update

a = TestSet('a')
print a.difference_update(a) # inifinite recursion

The error occurs in a more general case than above (`other` doesn't need to be `self` or to contain the same members).

class TestSet(set):

    def difference_update(self, other):
        set.difference_update(self, other)
        return self

    __isub__ = difference_update

a = TestSet('a')
print a.difference_update(TestSet('b')) # inifinite recursion

Fixed as of https://hg.python.org/jython/rev/a7d1380c4594 - as is often the case, comprehensive testing all possible ways this problem could manifest was more work than actually fixing __isub__/difference_update along with the other failing case of __iand__/intersection_update