final TypedDict with total=False does not allow clear/popitem

[alicederyn]

Bug Report

PEP-589 disallows clear and popitem on TypedDicts, even if all known keys are not required, as there may be other required keys due to structural subtyping. However, a @final-decorated TypedDict cannot be structurally subtyped, so these methods should be available.

To Reproduce

https://mypy-play.net/?mypy=latest&python=3.11&gist=7d42af8206cb1e25a53673bdf4e99df1

from typing import TypedDict, final

@final
class A(TypedDict, total=False):
    k: int

a: A = {"k": 1}
a.clear()

Expected Behavior

No errors

Actual Behavior

error: "A" has no attribute "clear"  [attr-defined]

Your Environment

• Mypy version used: 1.0.0
• Python version used: 3.11

[AlexWaygood]

Kiiiiiind of a duplicate of #7981, in that mypy doesn't currently have any special handling for TypedDicts decorated with @final :)

[alicederyn]

Actually it does now! See #13838

[AlexWaygood]

Actually it does now! See #13838

Oh my bad! Thank you!

[alicederyn]

What return type should popitem have?

• Tuple[str, Any]
• Tuple[str, Union[ValueType1, ValueType2, ...]]
• Union[Tuple[Literal["key1"], ValueType1], Tuple[Literal["key2"], ValueType2], ...]

Normally it would have to be the first one, but because the TypedDict is final, we know the complete possible set of key/value types. The third would be the most accurate but also the most costly to work with and hardest to read if any errors came up.

[AlexWaygood]

I'd personally go with option (2). Silently inferring Any would feel pretty unfortunate here, in my opinion, given that we've got enough information to infer a better type. But the third option feels unnecessarily complex, at least for now.