Ignore lambda arguments for B020 (#259)

* Ignore "variable.attribute" expression for B020

* use visit_Lambda method to remove used args from catched names

Co-authored-by: Alexey <alexeynktn@yandex.ru>

bugbear.py

@@ -824,6 +824,11 @@ def visit_DictComp(self, node):
     def visit_comprehension(self, node):
         self.visit(node.iter)
 
+    def visit_Lambda(self, node):
+        self.visit(node.body)
+        for lambda_arg in node.args.args:
+            self.names.pop(lambda_arg.arg, None)
+
 
 error = namedtuple("error", "lineno col message type vars")
 Error = partial(partial, error, type=BugBearChecker, vars=())

tests/b020.py

@@ -35,3 +35,6 @@
 # However we still call out reassigning the iterable in the comprehension.
 for vars in [i for i in vars]:
     print(vars)
+
+for var in sorted(range(10), key=lambda var: var.real):
+    print(var)