[New-bugs-announce] [issue29246] typing.Union raises RecursionError when comparing Union to other type

[Spiro Sideris]

New submission from Spiro Sideris:

The typing.Union module raises a RecursionError when comparing a Union with no additional tree_args to a type that is not a Union.

An example of the stack trace with the added test looks like the following:

0:00:00 [1/1] test_typing
test test_typing failed -- Traceback (most recent call last):
  File "/Users/spiro/Development/open_source/cpython/Lib/test/test_typing.py", line 221, in test_union_compare_other
    self.assertNotEqual(Union, object)
  File "/Users/spiro/Development/open_source/cpython/Lib/unittest/case.py", line 827, in assertNotEqual
    if not first != second:
  File "/Users/spiro/Development/open_source/cpython/Lib/typing.py", line 760, in __eq__
    return self._subs_tree() == other#return self._subs_tree() is not self and self._subs_tree() == other
  File "/Users/spiro/Development/open_source/cpython/Lib/typing.py", line 760, in __eq__
    return self._subs_tree() == other#return self._subs_tree() is not self and self._subs_tree() == other
  File "/Users/spiro/Development/open_source/cpython/Lib/typing.py", line 760, in __eq__
    return self._subs_tree() == other#return self._subs_tree() is not self and self._subs_tree() == other
  [Previous line repeated 233 more times]
  File "/Users/spiro/Development/open_source/cpython/Lib/typing.py", line 759, in __eq__
    if not isinstance(other, _Union):
RecursionError: maximum recursion depth exceeded in __instancecheck__

test_typing failed

1 test failed:
    test_typing

Total duration: 316 ms
Tests result: FAILURE

The test compares a Union with no tree_args to another type.

----------
components: Library (Lib)
files: spirowork.patch
keywords: patch
messages: 285279
nosy: spiside
priority: normal
severity: normal
status: open
title: typing.Union raises RecursionError when comparing Union to other type
type: crash
versions: Python 2.7, Python 3.3, Python 3.4, Python 3.5, Python 3.6, Python 3.7
Added file: http://bugs.python.org/file46264/spirowork.patch

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue29246>
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