TypedDict errors on use of merge operator |= even if keys are correct

[RenDelaCruz]

Bug Report

For TypedDict, mypy accepts the use of .update() using a dict with appropriate keys. However, using the merge operator |= for TypedDict gives an error.

To Reproduce

class Foo(TypedDict):
    key: int
    
foo: Foo = {
    "key": 1
}

foo.update({"key": 2}) # Ok!

foo |= {"key": 3}
# error: Incompatible types in assignment (expression has type "dict[str, object]", variable has type "Foo")  [assignment]

mypy Playground

Expected Behavior

Using merge operator |= on TypedDict should be allowed, since .update() is supported.

Actual Behavior

Errors when using |= on TypedDict, even though the given keys are appropriate. This effectively means that projects using mypy cannot use PEP 584 syntax.

[erictraut]

I think you meant for the last line in the code sample to be foo |= {"key": 3}. The value needs to be an int. With this fix, mypy still generates an error (a false positive).

[RenDelaCruz]

Yup sorry, edited now from {"key": "3"} to {"key": 3}.

But yes, mypy still generates an error even though .update() is accepted.