Fix B008 edge case with lambda functions (#243)

bugbear.py

@@ -791,6 +791,11 @@ def visit_Call(self, node):
         # Check for nested functions.
         self.generic_visit(node)
 
+    def visit_Lambda(self, node):
+        # Don't recurse into lambda expressions
+        # as they are evaluated at call time.
+        pass
+
     def visit(self, node):
         """Like super-visit but supports iteration over lists."""
         self.arg_depth += 1

tests/b006_b008.py

@@ -180,3 +180,8 @@ def no_nested_b006(a=map(lambda s: s.upper(), ["a", "b", "c"])):
 # B008-ception.
 def nested_b008(a=random.randint(0, dt.datetime.now().year)):
     pass
+
+
+# Ignore lambda contents since they are evaluated at call time.
+def foo(f=lambda x: print(x)):
+    f(1)

tests/test_bugbear.py

@@ -124,7 +124,6 @@ def test_b006_b008(self):
                 B008(170, 20),
                 B008(170, 30),
                 B008(176, 21),
-                B008(176, 35),
                 B008(181, 18),
                 B008(181, 36),
             ),