Built-in generic now work without limitations (#1068)

Closes: #1067

Author: srittau

docs/source/stubs.rst

@@ -174,18 +174,20 @@ Type checkers support cyclic imports in stub files.
 Built-in Generics
 -----------------
 
-PEP 585 [#pep585]_ built-in generics are generally supported, with
-the following exceptions [#ts-4820]_:
+PEP 585 [#pep585]_ built-in generics are supported and should be used instead
+of the corresponding types from ``typing``::
 
-* Built-in generics don't work in type aliases.
-* Built-in generics don't work in base classes.
-* ``type`` is not supported.
-* Variable length tuples (``tuple[X, ...]``) are not supported.
+    from collections import defaultdict
 
-In these cases, the appropriate types from ``typing`` must be used.
+    def foo(t: type[MyClass]) -> list[int]: ...
+    x: defaultdict[int]
 
 Using imports from ``collections.abc`` instead of ``typing`` is
-generally possible and recommended.
+generally possible and recommended::
+
+    from collections.abc import Iterable
+
+    def foo(iter: Iterable[int]) -> None: ...
 
 Unions
 ------
@@ -1102,7 +1104,6 @@ Bugs
 ----
 
 .. [#ts-4819] typeshed issue #4819 -- PEP 604 tracker (https://github.com/python/typeshed/issues/4819)
-.. [#ts-4820] typeshed issue #4820 -- PEP 585 tracker (https://github.com/python/typeshed/issues/4820)
 .. [#ts-4913] typeshed issue #4913 -- PEP 613 tracker (https://github.com/python/typeshed/issues/4913)
 .. [#ts-4972] typeshed issue #4972 -- PEP 570 tracker (https://github.com/python/typeshed/issues/4972)