closes #74747: don't crash when lookup up a special attribute in class scope

(patch by google)

4 files changed, 18 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index aa70a36..e362719 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -11,7 +11,10 @@ ChangeLog for PyLint
 
     * #74745: make "too general" exception names configurable (patch by Google)
 
+    * #74747: crash occurs when lookup up a special attribute in class scope
+      (patch by google)
 
+	
 2011-07-18  --  0.24.0
     * #69738: add regular expressions support for "generated-members"
 
diff --git a/checkers/variables.py b/checkers/variables.py
index f8748ba..ce98e04 100644
--- a/checkers/variables.py
+++ b/checkers/variables.py
@@ -331,8 +331,15 @@ builtins. Remember that you should avoid to define new builtins when possible.'
             return
         astmts = [stmt for stmt in node.lookup(name)[1]
                   if hasattr(stmt, 'ass_type')]
-        # filter variables according their respective scope
-        if not astmts or astmts[0].statement().parent_of(node):
+        # filter variables according their respective scope test is_statement
+        # and parent to avoid #74747. This is not a total fix, which would
+        # introduce a mechanism similar to special attribute lookup in
+        # modules. Also, in order to get correct inference in this case, the
+        # scope lookup rules would need to be changed to return the initial
+        # assignment (which does not exist in code per se) as well as any later
+        # modifications.
+        if not astmts or (astmts[0].is_statement or astmts[0].parent) \
+             and astmts[0].statement().parent_of(node):
             _astmts = []
         else:
             _astmts = astmts[:1]
diff --git a/test/regrtest_data/special_attr_scope_lookup_crash.py b/test/regrtest_data/special_attr_scope_lookup_crash.py
new file mode 100644
index 0000000..b693a9f
--- /dev/null
+++ b/test/regrtest_data/special_attr_scope_lookup_crash.py
@@ -0,0 +1,3 @@
+class Klass(object):
+    """A"""
+    __doc__ += "B"
diff --git a/test/test_regr.py b/test/test_regr.py
index 1cef0ce..e0261ac 100644
--- a/test/test_regr.py
+++ b/test/test_regr.py
@@ -123,6 +123,9 @@ class NonRegrTC(TestCase):
     def test_import_assign_crash(self):
         linter.check(join(REGR_DATA, 'import_assign.py'))
 
+    def test_special_attr_scope_lookup_crash(self):
+        linter.check(join(REGR_DATA, 'special_attr_scope_lookup_crash.py'))
+
     def test_module_global_crash(self):
         linter.check(join(REGR_DATA, 'module_global.py'))
         got = linter.reporter.finalize().strip()