Add note on attribute extension defaults (resolves
@@ -100,7 +100,10 @@ p
| Set a default value for an attribute, which can be overwritten
| manually at any time. Attribute extensions work like "normal"
| variables and are the quickest way to store arbitrary information
- | on a #[code Doc], #[code Span] or #[code Token].
+ | on a #[code Doc], #[code Span] or #[code Token]. Attribute defaults
+ | behaves just like argument defaults
+ | #[+a("http://docs.python-guide.org/en/latest/writing/gotchas/#mutable-default-arguments") in Python functions],
+ | and should not be used for mutable values like dictionaries or lists.
+code-wrapper
+code.
