[issue44642] Union of a type and the typing module function

[Serhiy Storchaka]

Serhiy Storchaka <storchaka+cpython at gmail.com> added the comment:

It is only reminder that our test for NewType is arbitrary. And it is not compatible with PR 9951. Possible solutions are:

1. Make NewType a class and add more strict test. Pro -- we can make arbitrary repr, contra -- it has small negative effect on performance. See issue34963.

2. Remove the test for NewType at all and allow or-ing types and arbitrary functions.

3. Introduce a special attribute to distinguish unionable objects. It will make the code of unionobject.c simpler.

I lean towards option 1 (not excluding 3). Small performance losses seem inevitable.

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