gh-160766: Handle nested annotated and generic aliases that contain forward references in annotations - #160769

This adds another special case to _Stringifier.__convert_to_ast to handle types.GenericAlias and typing.Annotated similar to the handling of list, set, tuple, dict that constructs the ast to rebuild the GenericAlias or Annotated object.

This is to prevent the ForwardRef objects from becoming "hidden" inside the GenericAlias or Annotated objects.

For GenericAlias an ast.Call node is created to reconstruct the GenericAlias as there's no guarantee it was created through subscripting. The call is converted back to subscript format when evaluating the ForwardRef in STRING format in order to match the repr of GenericAlias objects.

For Annotated, subscripting is used. Are there any other types that need to be handled?

from annotationlib import get_annotations, Format

class X:
    a: Y[list[Z]]

# Get annotations here to get the ForwardRef
anno = get_annotations(X, format=Format.FORWARDREF)['a']

class Y[T]:
    pass

class Z:
    pass

print(anno.evaluate(format=Format.STRING))
print(anno.evaluate(format=Format.VALUE))

Main:

Y[list[ForwardRef('Z', is_class=True, owner=<class '__main__.X'>)]]
__main__.Y[list[ForwardRef('Z', is_class=True, owner=<class '__main__.X'>)]]

PR:

Y[list[Z]]
__main__.Y[list[__main__.Z]]

• Issue: Annotations: Nested generics containing forward references can evade evaluation in ForwardRef.evaluate #160766