Flag variables that 1. aren't reassigned, and 2. are missing `Final`

[hamirmahal]

Summary

I think it'd be helpful if ruff flagged variables that

1. aren't reassigned, and
2. are missing Final

[hamirmahal]

For example,

X: Final = 1
print(X)

is fine, but

X = 1
print(X)

would result in a warning

[MichaReiser]

Can you say more about where this rule would apply? Applying to all variables seems problematic as a variable can be mutated from outside the module.

I'm also not sure what the value is within a single function. It seems overly pedantic to me with questionable value (reminding me of the JavaScript let vs const)

I did take a quick look at your PR and the high number of violations strongly suggests that this rule needs further refinement.

[hamirmahal]

I'm also not sure what the value is within a single function. It seems overly pedantic to me with questionable value (reminding me of the JavaScript let vs const)

It prevents accidental reassignments.