"TypeError: interpreted classes cannot inherit from compiled" after get_customize_class_mro_hook

[kedder]

When using plugin, that provides get_customize_class_mro_hook, mypy errors out with TypeError: interpreted classes cannot inherit from compiled traceback. Tested on mypy-0.701 and python-3.6.

Consider this minimal plugin:

from mypy.plugin import Plugin

class DummyPlugin(Plugin):
    def get_customize_class_mro_hook(self, fullname):
        def analyze(classdef_ctx):
            pass
        return analyze

def plugin(version):
    return DummyPlugin

When mypy is run with this plugin enabled on simple python file, e.g.

class Something:
    pass

Mypy will error out with this traceback:

tmp/sample.py:1: error: INTERNAL ERROR -- please report a bug at https://github.com/python/mypy/issues version: 0.701
Traceback (most recent call last):
  File "ve/bin/mypy", line 10, in <module>
    sys.exit(console_entry())
  File "mypy/semanal.py", line 3791, in accept
  File "mypy/nodes.py", line 895, in accept__Node_glue
  File "mypy/nodes.py", line 896, in accept
  File "mypy/semanal.py", line 804, in visit_class_def__StatementVisitor_glue
  File "mypy/semanal.py", line 807, in visit_class_def
  File "mypy/semanal.py", line 819, in analyze_class
  File "mypy/semanal.py", line 1229, in analyze_base_classes
  File "mypy/semanal.py", line 1250, in calculate_class_mro
TypeError: interpreted classes cannot inherit from compiled
tmp/sample.py:1: : note: use --pdb to drop into pdb

[msullivan]

Could you give the full code for the plugin, with imports?

[msullivan]

(Nevermind, I managed to reproduce it.)

[msullivan]

The error message here is a bad one from mypyc. The actual problem here is that we are trying to instantiate Expression, which is a trait, which is not really supported.

[glyph]

I believe that this broke / is blocking the zope.interface plugin (see also #3960) Shoobx/mypy-zope#7 - should it be treated as a regression?

[msullivan]

... I tracked this down and then forgot to fix it. I'll fix it now.

[glyph]

Thanks so much, @msullivan !