Adrian Buehlmann <adrian@cadifra.com> [Sun, 21 Nov 2010 11:52:27 +0100] rev 13026
check-code: catch Python 'is' comparing number or string literals
The Python 'is' operator compares object identity, so it should
definitely not be applied to string or number literals, which Python
implementations are free to represent with a temporary object.
This should catch the following kinds of bogus expressions (examples):
x is 'foo' x is not 'foo'
x is "bar" x is not "bar"
x is 42 x is not 42
x is -36 x is not -36
As originally proposed by Martin Geisler, amended with catching
negative numbers.