Expression._latex_() triggers “dangerous” comparisons

[mezzarobba]

With commit a5a1e2b76332d136936c7cbe94cf42f93ec6203d from ticket #22029:

sage: Mod(2,7)/x
2/x
sage: latex(Mod(2,7)/x)
...
TypeError: unsupported operand parent(s) for 'lt': 'Ring of integers modulo 7' and 'Number Field in I with defining polynomial x^2 + 1'

It looks like Pynac is comparing the numerator with I under the hood. Even if the branch in question isn't merged, this is likely to cause problems sooner or later.

CC: @rwst

Component: symbolics

Issue created by migration from https://trac.sagemath.org/ticket/22071

[rwst]

comment:1

Note there is a consensus that operations with positive characteristic ring elements and symbolic variables should be discouraged (leading to #21391). Consequently the latexing will fail as well as soon as that is implemented, and you would need something like #10035 to make it work. That doesn't fix this specific odd error but it lowers the urgency level I'm personally having with it.

[rwst]

comment:2

Seems to be no longer an issue.