Changed the semantics of Annotated.

[mvaled]

Bug report

What's wrong

typing.Annotated is being reported incorrectly by changing their semantics. I have a small dataclass like:

@dataclass(unsafe_hash=True)
class RatingComposite(LoweringComposite):
    require_picture: Annotated[bool, ExtendedBooleanType(labels={True: "Always", False: "Never")] = True
    max_value: Annotated[int, IntegerType(min_value=1, max_value=10)] = 5

We're using xotl.plato to parse and dump this kind of structures to JSON. However, this code fails to type-check with:

error: Invalid type comment or annotation
note: Suggestion: use ExtendedBooleanType[...] instead of ExtendedBooleanType(...)
error: Incompatible types in assignment (expression has type "bool", variable has type "WithAnnotations[builtins.bool]")

error: Invalid type comment or annotation
note: Suggestion: use IntegerType[...] instead of IntegerType(...)
error: Incompatible types in assignment (expression has type "int", variable has type "WithAnnotations[builtins.int]")

Without django-stubs-ext mypy would accept that annotations and their default values.

How is that should be

• The extension should not impose any syntax to the annotation. The purpose of Annotated is to annotate with 3rd party objects and django-stub-ext should not change the semantics of it. If it doesn't know about ExtendedBooleanType or IntegerType, it should completly ignore them. Notice the second example is quite similar to the use cases described in PEP 593.

• The final erased type WithAnnotations[builtins.bool] should only be introduced for the cases django-stub-ext knows about; in this case I'd expect the final type would be just bool.

System information

• OS: Linux (mostly, Manjaro and also Debian-based containers in a CI pipeline)
• python version: 3.10.2
• django version: 4.0.3 (but is actually not Django related code)
• mypy version: 0.941
• django-stubs version: 1.9.0
• django-stubs-ext version: 0.3.1

[g-as]

Same here, with a pydantic model.