== Why is this an issue?

Checking if a variable or parameter is ``++None++`` should only be done when you expect that it can be ``++None++``. Doing so when the variable is always None or never None is confusing at best. At worse, there is a bug and the variable is not updated properly.


This rule raises an issue when expressions ``++X is None++``, ``++X is not None++``, ``++X == None++`` or ``++X != None++`` are constant, i.e. ``++X++`` is always None or never None.


=== Noncompliant code example

[source,python]
----
mynone = None
result = mynone is None: # Noncompliant. Always True.

if mynone == None: # Noncompliant. Always True.
    pass

if mynone is not None:  # Noncompliant. Always False.
    pass

if mynone == None:  # Noncompliant. Always False.
    pass

myint = 42
result = myint is None: # Noncompliant. Always False.

if myint == None: # Noncompliant. Always False.
    pass

if myint is not None:  # Noncompliant. Always True.
    pass

if myint == None:  # Noncompliant. Always True.
    pass
----


:link-with-uscores1: https://docs.python.org/3/reference/datamodel.html#object.__eq__

== Resources

* Python documentation - https://docs.python.org/3/reference/expressions.html#is-not[Identity comparisons]
* Python documentation - {link-with-uscores1}[``++__eq__++`` operator]



ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

* Remove this identity check; it will always be True/False
* Remove this == comparison; it will always be True/False
* Remove this != comparison; it will always be True/False


=== Highlighting

the "is", "is not", "==" or "!=" operator


'''
== Comments And Links
(visible only on this page)

=== is related to: S5914

endif::env-github,rspecator-view[]
