Add checker for membership rules and testsmembership-test-checker

Idea of checking is very simple: value used to the right of the 'in' operator
should support membership test protocol (i.e. define either __contains__ or
__iter__ or __getitem__).

Fixes issue #589.

1 files changed, 4 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index b25533b..957ed56 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -2,6 +2,10 @@ ChangeLog for Pylint
 --------------------
 
 --
+    * Add a new error, 'unsupported-membership-test', emitted when value
+      to the right of the 'in' operator doesn't support membership test
+      protocol (i.e. doesn't define __contains__/__iter__/__getitem__)
+
     * Add new errors, 'not-an-iterable', emitted when non-iterable value
       is used in an iterating context (starargs, for-statement,
       comprehensions, etc), and 'not-a-mapping', emitted when non-mapping