Issue2367

Take two subclasses of dict which define __hash__ and __eq__ (for example, we want to create an ImmutableMap) so that their hashes are equal, and dict.__eq__(dict1, dict2) returns True, but the objects are NOT equal due to their custom __eq__.

When using them BOTH as dictionary keys, Jython ignores the custom __eq__ upon hash collision and simply overwrites one key with the other. Note from the included tests that a hash collision is NOT the cause; if dict.__eq__(d1, d2) is False, both will still be used as keys.

This problem does not show up when inserting from list, tuple, object or any other classes I have tried.

Of the included unit tests, "test_distinct_in_set" and "test_distinct_as_keys" fail in Jython alone; the rest pass in Jython, CPython 2 and 3, and PyPy 2 and 3.

Not sure how to edit a submission, as I have not used this tracker before. Anyway, it should say "inheriting" instead of inserting in the third paragraph.

Additionally:

a = Dict1
b = Dict2

>>> a.__eq__(b)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unbound method __eq__() must be called with Dict1 instance as first argument (got type instance instead)

First draft of a patch that addressed this. I tested this with a version of the sample jythonbug.py, but not yet regressed.

Thoughts?

This bug and possible resolution didn't get the triage it needed in 2.7.1. Defer to 2.7.2 for a fresh look.

... and not for 2.7.2 either.