dmypy does not recheck files when they are removed and then re-added.

[ramLlama]

• 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.

In a folder, have two files test1.py and test2.py. Contents are:

test1.py:

x: str = 1

test2.py:

y: int = 'hello'

• What is the actual behavior/output?

$ python -m mypy --follow-imports=skip --ignore-missing-imports --cache-fine-grained test1.py
test1.py:1: error: Incompatible types in assignment (expression has type "int", variable has type "str")
$ python -m mypy --follow-imports=skip --ignore-missing-imports --cache-fine-grained test2.py
test2.py:1: error: Incompatible types in assignment (expression has type "str", variable has type "int")
$ dmypy start -- --follow-imports=skip --ignore-missing-imports --use-fine-grained-cache
Daemon started
$ dmypy check test1.py
test1.py:1: error: Incompatible types in assignment (expression has type "int", variable has type "str")
$ dmypy check test1.py
test1.py:1: error: Incompatible types in assignment (expression has type "int", variable has type "str")
$ dmypy check test2.py
test2.py:1: error: Incompatible types in assignment (expression has type "str", variable has type "int")
$ dmypy check test2.py
test2.py:1: error: Incompatible types in assignment (expression has type "str", variable has type "int")
$ dmypy check test1.py
$ dmypy check test2.py
$

• What is the behavior/output you expect?
  I expect that files are rechecked and errors re-outputted after being removed and then re-added to dmypy.
• What are the versions of mypy and Python you are using?
  mypy 0.610, python 3.6.3

[msullivan]

Self-assigning this because I'm about to rampage through the relevant code and think a fix for this might come out the other end.

[msullivan]

This might have gotten fixed though?

[JukkaL]

This still seems to be an issue. I was able to reproduce the problem with using dmypy run -- <files>. Increasing priority since this is pretty bad. Also I somehow got errors from typeshed by doing this.