PEP 634: Change so __match_args__ must be a tuple (#1909)

Author: gvanrossum

pep-0634.rst

@@ -492,10 +492,10 @@ as follows:
   the entire subject; for these types no keyword patterns are accepted.
 - The equivalent of ``getattr(cls, "__match_args__", ()))`` is called.
 - If this raises an exception the exception bubbles up.
-- If the returned value is not a list or tuple, the conversion fails
+- If the returned value is not a tuple, the conversion fails
   and ``TypeError`` is raised.
 - If there are more positional patterns than the length of
-  ``__match_args__``` (as obtained using ``len()``), ``TypeError`` is raised.
+  ``__match_args__`` (as obtained using ``len()``), ``TypeError`` is raised.
 - Otherwise, positional pattern ``i`` is converted to a keyword pattern
   using ``__match_args__[i]`` as the keyword,
   provided it the latter is a string;
@@ -513,7 +513,7 @@ positional subpatterns is different:
 This behavior is roughly equivalent to the following::
 
   class C:
-      __match_args__ = ["__match_self_prop__"]
+      __match_args__ = ("__match_self_prop__",)
       @property
       def __match_self_prop__(self):
           return self