Yeah, this has nothing to do with the discussion here.
There are two doc sections relevent here (until another is found, but I doubt it).
Binary arithmetic operations, as quoted by @Rosuav, and Numeric types, table 1, note 1, as quoted by me.
The former one is somewhat more precise in its wording, but I don’t find it that explicit : it only says that “floor division of integers results in an integer” but doesn’t address floor division of floats. Also “the result is that of mathematical division with the ‘floor’ function applied to the result” which, if that sentence applied to the type but I don’t think it does, would imply that float floor division results in an int just as math.floor does. And “The numeric arguments are first converted to a common type”, which doesn’t provide any information as for the return type.
(There are other bits about floor divs but not relevent as to the return type.)
The latter is more in form of a warning : “The resultant value is a whole integer, though the result’s type is not necessarily int.” Nothing more.
So, if we accept @CAM-Gerlach’s explanation on the standing of PEPs, it would make the behavior undocumented. But then :
I think the solution is to give proper warning that it’s about to change, as in a deprecation warning, and to remind (never hurts) that it’s not documented and that it may change again one day (who knows).
I mean deprecation warning in the doc sense, not in the warnings module sense, if we could add an actual warning that would be great but I don’t see how. Maybe on calls to .hex() but it would make a lot of false positives if not called on the result of a floor div.
Maybe inside the floordiv implem so as to emit warnings when floordiv-ing an overflow, inf or nan ? when not float_result.is_integer() ?