Problem with setting one TypedDict variable to another TypedDict variable

• Are you reporting a bug, or opening a feature request?

Bug

• Please insert below the code you are checking with mypy,
  or a mock-up repro if the source is private. We would appreciate
  if you try to simplify your case to a minimal repro.

TestOne = TypedDict('TestOne', {'test': int, 'another': str}, total=False)
TestTwo = TypedDict('TestTwo', {'test': int}, total=False)

var_1: TestOne = {'test': 1, 'another': 'hi'}
var_2: TestTwo = var_1  # Doesn't cause a type error... why not?? 'another' is not a valid key on a TestTwo
var_3: TestTwo = {  # Does cause a type error, correctly. "Extra key 'another' for TypedDict 'TestTwo'"
    'test': 2, 'another': 'hi'
}

TestThree = TypedDict('TestThree', {'test': int}, total=False)
TestFour = TypedDict('TestFour', {'test': int, 'another': str}, total=False)
var_4: TestThree = {'test': 3}
var_5: TestFour = var_4  # Causes a type error.... WHY???? "Incompatible types in assignment (expression has type "TestThree", variable has type "TestFour")"

• What is the actual behavior/output?

Basically, the code above, including its inline notes, but I'll summarize:

If you assign a value who's type is a TypedDict with some keys and total=False to be the value of a variable who's type is another TypedDict with total=False and a subset of the first TypedDict's keys, it throws an error, but it should not.

If you assign a value who's type is a TypedDict with some keys and total=False to be the value of a variable who's type is another TypedDict with total=False and a superset of the first TypedDict's keys, it does not throw an error, but it should.

• What are the versions of mypy and Python you are using?

Python version 3.6.4
Mypy version 0.670

• Do you see the same issue after installing mypy from Git master?

After installing mypy-0.680+dev.4e0a1583aeb00b248e187054980771f1897a1d31 from github, I get the same exact errors.

• What are the mypy flags you are using? (For example --strict-optional)

Here is my mypy.ini:

[mypy]
plugins = sqlmypy
disallow_untyped_calls = False
disallow_untyped_defs = True
ignore_missing_imports = True
warn_return_any = False
follow_imports = silent
allow_redefinition = True

• If mypy crashed with a traceback, please paste

  It did not.

Start by running the minimal TypedDict reproduction in the issue and compare both assignment directions with the reported errors. Trace mypy's TypedDict compatibility checking from the assignment analysis entry point, then add or update focused coverage so subset and superset assignments with total=False produce the expected results.