`Expected type in class pattern; found "Any"` for ignored missing import in match/case

[ds-cbo]

To Reproduce

from somewhere import Foo

match None:
    case Foo():
        ...

https://mypy-play.net/?mypy=latest&python=3.11&flags=ignore-missing-imports&gist=03694364e4e855575f23ba9c625e804e

Expected Behavior

no error

Actual Behavior

$ mypy --ignore-missing-imports test.py
test.py:4: error: Expected type in class pattern; found "Any"  [misc]
Found 1 error in 1 file (checked 1 source file)

Your Environment

mypy 0.991 without config files on python 3.10 and 3.11

[tinkerware]

This can be an occasional stumbling block that's quite difficult to find a way out of without the right error message. In my case, I ran into two internal libraries, A and B, where A had imports from B. A also had the ignore_missing_imports = true setting to deal with some legacy 3rd-party libraries.

Code that looks like following fails in this set-up with the error in this issue:

from B import Foo, Bar

def do_stuff(value: Foo | Bar) → None:
  match value:
    case Foo(a=a):
      ...
    case Bar(b=b):
      ...

No error is given if library B adds the py.typed marker. At the very least, a more descriptive error with a fix suggestion seems useful. Using ignore_missing_imports = false does give the user a hint with the skipping analyzing ... error.