Using `update` on a filter with itself fails with "Already mutably borrowed"

[Ronserruya]

Calling update on a filter with itself crashes:

from rbloom import Bloom

b = Bloom(100, 0.01)
b.update(b)

RuntimeError: Already mutably borrowed

Came across this when testing some things regarding updates, obviously this is a minor issue since there's no real use case to do this in the first place, but it's probably not something that should crash, like a noop (or at least it should crash with a predictable exception)

Thank you for your work on this package :)

[KenanHanke]

What system & python are you on? When I run b.add(b) or b.update([b]) I get a
TypeError: unhashable type: 'rbloom.Bloom'
which is more or less expected.

[Ronserruya]

Python 3.9 on osx

import sys; print('Python %s on %s' % (sys.version, sys.platform))
Python 3.9.6 (default, Apr 30 2025, 02:07:17)
[Clang 17.0.0 (clang-1700.0.13.5)] on darwin

b.add(b) or b.update([b]) will get unhashable type, sure, since it tries hashing the bloom filter object itself in order to add it, which isn't the same thing.
b.update(b) merges two filters

In [1]: from rbloom import Bloom
   ...:
   ...: b = Bloom(100, 0.01)

In [2]: c = Bloom(100, 0.01)

In [3]: b.add(1)

In [4]: c.add(2)

In [5]: b.update(c)

In [6]: 2 in b
Out[6]: True

In [7]: b.update(b)
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
Cell In[7], line 1
----> 1 b.update(b)

RuntimeError: Already mutably borrowed

[KenanHanke]

Oh right okay, will take a look, isn't high priority for now though