Document that variable needs to be read for --allow-redefinition to work

[JukkaL]

See #6959.

Part of the motivation is that this shouldn't trigger redefinition:

x = None  # type: List[int]
...  # Do nothing with `x`
x = []  # Want to preserve type context

[Shivansh-khare]

I didn't get the issue can you tell in brief.

[terencehonles]

There look like there are other constraints that should be added where this is documented. Some quick examples is in a try/catch block, if a function is defined in the same scope #10016, and probably others can be pulled from https://github.com/python/mypy/blob/master/mypy/renaming.py

[ikonst]

Current documentation says:

The variable must be used before it can be redefined:

Can we close this? @AlexWaygood

[AlexWaygood]

Current documentation says:

The variable must be used before it can be redefined:

Can we close this? @AlexWaygood

Yup, fixed by @KotlinIsland in #11951! 🥳