SgtMook/sympy — comment on commit 3dbfe6a49eb785237e59dedceabfa5bb581e5a99
File: sympy/core/numbers.py line 1609
By asmeurer:

Sorry, but this logic isn't quite enough. You need to handle things like `oo - Float('inf')`. Also, it turns out there is a `Float('nan')`, which is not the same as `S.NaN`, so that needs to be handled everywhere too (and tests added for everything).