Bug Report

[Python 3.13]mypy does not accept nestingClassVar andFinal in class body

Theofficial docs of thetyping module say:

Changed in version 3.13:ClassVar can now be nested inFinal and vice versa.

Thetyping specs on qualifiers are more specific:

Final may be wrapped only by other type qualifiers (e.g.ClassVar or
Annotation).

In particular, nestingClassVar andFinal is a special case for dataclasses:

Type checkers should infer a final attribute that is initialized in a class
body as being a class variable, except in the case ofdataclasses, where
x: Final[int] = 3 creates a dataclass field and instance-level final
attributex with default value3;x: ClassVar[Final[int]] = 3 is
necessary to create a final class variable with value3. In
non-dataclasses, combiningClassVar andFinal is redundant, and type
checkers may choose to warn or error on the redundancy.

To Reproduce

In both classes below thefoo statement is not accepted bymypy:

fromdataclassesimportdataclassfromtypingimportClassVar,Final@dataclassclassBar:foo:ClassVar[Final[int]]=0@dataclassclassBaz:foo:Final[ClassVar[int]]=0

Note that the docs only mentionClassVar[Final[int]] and notFinal[ClassVar[int]]. In fact, the latter is not considered a class variable by the currentdataclasses implementation:

>>>Bar(foo=1)# foo is a class variableTraceback (mostrecentcalllast):File"<python-input-2>",line1,in<module>Bar(foo=1)~~~^^^^^^^TypeError:Bar.__init__()gotanunexpectedkeywordargument'foo'>>>Baz(foo=1)# foo is an instance variableBaz(foo=1)

Expected Behavior

[Python 3.13]mypy should acceptClassVar[Final[<type>]] in the body of a dataclass

The formClassVar[Final[int]] conforms with the official typing specs and behaves as expected. I think it should be accepted as part of Python 3.13 support.

The typing specs allow for a warning or error whenClassVar andFinal are nested outside of a dataclass body. I think this should result in an error since it is redundant, perhaps only in strict mode.

For the formFinal[ClassVar[int]] I am not sure. It could either result in an error or simply be parsed as a final instance variable.

Actual Behavior

The formClassVar[Final[int]] results in:
error: Final can be only used as an outermost qualifier in a variable annotation [valid-type]

The formFinal[ClassVar[int]] results in:
error: Variable should not be annotated with both ClassVar and Final [misc]

The behavior is the same with or without the@dataclass decorator.

Your Environment

• Mypy version used: 1.13.0
• Mypy command-line flags:
• Mypy configuration options frommypy.ini (and other config files):strict = true
• Python version used: 3.13.0

Notes

The typing specs were changed inpython/typing#1669

Related discussion is found inpython/cpython#89547

The difference betweenClassVar[Final[int]] andFinal[ClassVar[int]] was noticed inmicrosoft/pyright#8676 (comment)

This issue is about Python 3.13 so could be added to#17264

This issue is related to#12061