The Sage coercion system guarantees the return type of certain binary operations. This should be made known to typing - for introspection purposes in IDEs and for static checkers.

References:

• PEP 563 -- Postponed Evaluation of Annotations - upcoming change in Python 3.10

• https://cython.readthedocs.io/en/latest/src/tutorial/pure.html?highlight=annotations#static-typing

CC: @tobiasdiez @mwageringel @egourgoulhon @tscrim @nthiery

Component: coercion

Issue created by migration from https://trac.sagemath.org/ticket/30511