Open issue: (dis)allowing type qualifiers in PEP 695 type aliases

[Viicos]

In the introspection module, the inspect_annotation() function can be used to unpack the underlying type expression:

>>> inspect_annotation(
...     Final[Annotated[ClassVar[Annotated[int, 'meta_1']], 'meta_2']],
...     annotation_source=AnnotationSource.CLASS,
... )
...
InspectedAnnotation(type=int, qualifiers={'class_var', 'final'}, metadata=['meta_1', 'meta_2'])

However, the passed annotation expression could be defined as:

type MyAlias = ClassVar[int]

@my_dataclass
class A:
    f: Annotated[MyAlias, "meta_1"]

Static type checkers raise an error on the MyAlias definition, as type qualifiers can only be used in certain contexts (in the case of ClassVar, it can only be used within a class annotation).

When passing Annotated[MyAlias, "meta_1"] to inspect_annotation() (and setting unpack_type_aliases to 'eager'), we currently don't error:

>>> inspect_annotation(
...     Annotated[MyAlias, "meta_1"],
...     annotation_source=AnnotationSource.CLASS,
...     unpack_type_aliases="eager",
... )
...
InspectedAnnotation(type=int, qualifiers={'class_var'}, metadata=['meta_1'])

Should we error whenever a type qualifier is used inside a PEP 695 type alias? Or provide an option to (dis)allow it/raise a warning?