PEP 728: TypedDict with Typed Extra Items

PEPs
157

It looks like there’s an error in one of the examples under “The extra_items Class Parameter”:

class MovieBase(TypedDict, extra_items=int | None):
    name: str

class Movie(MovieBase):
    year: int

a: Movie = {"name": "Blade Runner", "year": None}  # Not OK. 'None' is incompatible with 'int'
b: Movie = {
    "name": "Blade Runner",
    "year": 1982,
    "other_extra_key": None,
}  # OK

I think MoviedBase should be defined like this, using ReadOnly, based on the discussion in section “Inheritance”, for Movie to be valid:

class MovieBase(TypedDict, extra_items=ReadOnly[int | None]):
    name: str
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