Description

Added a section to the incompatible_argument function in mypy.messages that is executed when trying to add an incompatible type to a TypedDict. Required adding some imports from mypy.nodes to allow for the isinstance to work.

Fixes #10253

Test Plan

Verified changes with the sample code provided in the issue as well as some other sample TypedDict implementations, below.

Foo = TypedDict('Foo', {'a': int})
blah: Foo = {'a': 4}
blah['a'] = ["r", 3]

Foo = TypedDict('Foo', {'a': str})
blah: Foo = {'a': 'lol'}
blah['a'] = 1

Also modified the testCannotSetItemOfTypedDictWithIncompatibleValueType test to check for the new error message.