Revert "remove specific for Optional"

This reverts commit 61f6a59.

Author: tharvik

mypy/stubgen.py

@@ -513,6 +513,10 @@ def get_str_type_of_node(self, rvalue: Node) -> str:
             return 'int'
         if isinstance(rvalue, NameExpr) and rvalue.name in ('True', 'False'):
             return 'bool'
+        if isinstance(rvalue, NameExpr) and rvalue.name == 'None':
+            self.add_typing_import('Optional')
+            self.add_typing_import('Any')
+            return 'Optional[Any]'
         self.add_typing_import('Any')
         return 'Any'
 

test-data/unit/stubgen.test

@@ -26,9 +26,9 @@ def g(b: int = ..., c: int = ...): ...
 [case testDefaultArgNone]
 def f(x=None): ...
 [out]
-from typing import Any
+from typing import Any, Optional
 
-def f(x: Any = ...): ...
+def f(x: Optional[Any] = ...): ...
 
 [case testDefaultArgBool]
 def f(x=True, y=False): ...