Fixed #22020 by checking for oo in numerical equals

[oscargus]

References to other Issues or PRs

Closes #22020

Brief description of what is fixed or changed

It seems like evalf now returns oo instead of throwing ZeroDivisionError for some cases. This breaks equals resulting in an error that oo cannot be turned into an int.

Other comments

Release Notes

• core
  • Fixed issue when performing is_constant() on certain expressions which may result in division by zero.

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• core
  • Fixed issue when performing is_constant() on certain expressions which may result in division by zero. (#22022 by @oscargus)

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Closes #22020

#### Brief description of what is fixed or changed
It seems like `evalf` now returns `oo`  instead of throwing `ZeroDivisionError` for some cases. This breaks equals resulting in an error that `oo` cannot be turned into an `int`.

#### Other comments


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* core
    * Fixed issue when performing `is_constant()` on certain expressions which may result in division by zero.
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[oscarbenjamin]

It seems like evalf now returns oo instead of throwing ZeroDivisionError for some cases.

May it is evalf that should be fixed... The problem originates from #20885

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[oscargus]

May it is evalf that should be fixed...

I do not disagree with it. However, there may be cases where we actually want to return oo from evalf, while this should take care of those cases as well (as I assume that just because two expressions both evaluate to oo does not make them equal and that oo may show up from evalf in cases that does not involve a division by zero).

So either wait for a "proper" fix or go with this that will not break anything (as far as I can tell, maybe one should check for S.ComplexInfinity as well though).

[smichr]

from sympy.polys.polyutils import illegal
...
if a is not None and a not in illegals:

[oscargus]

Weirdly enough adding S.ComplexInfinity, i.e., using illegal (should be in a better location, right? In core somewhere?) leads to that the following test fails:

    x = Symbol('x', positive=True)
    e5 = (1 + x)/x
    assert e5.is_constant() is False

I realize by checking the blame that I added it a while back, but do not really remember the circumstances. It is stated in the documentation that it is tested for denominators being zero. However, in this case returning None should be more correct than False since x cannot be zero...

[oscargus]

Found a better way to fix it, so I close this (as it is done in a completely different way).