Unhelpful message "invalid type"

[ruuda]

Consider the following file:

from tempfile import SpooledTemporaryFile

def make_file() -> SpooledTemporaryFile:
    return SpooledTemporaryFile()

temp_file = make_file()

When I typecheck this, I get

invalid.py:3: error: Invalid type "tempfile.SpooledTemporaryFile"
invalid.py:6: error: Need type annotation for 'temp_file'

This message is not helpful; what does it mean for a type to be "invalid", and why is SpooledTemporaryFile invalid?

If I add a type annotation as suggested by the second message, I get the "invalid" message twice:

invalid.py:3: error: Invalid type "tempfile.SpooledTemporaryFile"
invalid.py:6: error: Invalid type "tempfile.SpooledTemporaryFile"

I am using Mypy 0.620.

[ruuda]

Looking into this, SpooledTemporaryFile is a function in typeshed, but it’s a class in my /usr/lib/python3.6/tempfile.py. Is the typeshed annotation wrong?

In any case, it would be nice if the error message could indicate that SpooledTemporaryFile is not a valid type because it is a function, rather than just saying "invalid type".

[ilevkivskyi]

For poor error message, this is a duplicate of #4030

For the signature, yes, report this to typeshed issue tracker.