crash with namespace_packages and incorrect import sources

[DanAlbert]

Crash Report

The core of the issue might be that an automatic import done by an IDE caused game.theater.frontline to import game.theater.missiontarget.MissionTarget from game.theater.controlpoint instead of the module that defines it. That's the one piece of the original project that does seem outright incorrect, and importing the type from the correct module does fix the crash. In any case, mypy should not crash.

Traceback

game\commander\tasks\packageplanningtask.py:4: error: Name "MissionTarget" is not defined
game\commander\tasks\primitive\cas.py:8: error: INTERNAL ERROR -- Please try using mypy master on Github:
https://mypy.readthedocs.io/en/stable/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 0.940+dev.2d30dbaa34eab9d7519e440480f360fc9a1e65c3
game\commander\tasks\primitive\cas.py:8: : note: use --pdb to drop into pdb
game\theater\controlpoint.py:1: error: Module "game.coalition" has no attribute "Coalition"
Traceback (most recent call last):
  File "C:\Users\dan\src\mypy-repro\venv\Scripts\mypy-script.py", line 33, in <module>
    sys.exit(load_entry_point('mypy', 'console_scripts', 'mypy')())
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\__main__.py", line 12, in console_entry
    main(None, sys.stdout, sys.stderr)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\main.py", line 96, in main
    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\main.py", line 173, in run_build
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\build.py", line 180, in build
    result = _build(
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\build.py", line 256, in _build
    graph = dispatch(sources, manager, stdout)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\build.py", line 2722, in dispatch
    process_graph(graph, manager)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\build.py", line 3066, in process_graph
    process_stale_scc(graph, scc, manager)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\build.py", line 3158, in process_stale_scc
    mypy.semanal_main.semantic_analysis_for_scc(graph, scc, manager.errors)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\semanal_main.py", line 78, in semantic_analysis_for_scc
    process_top_levels(graph, scc, patches)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\semanal_main.py", line 199, in process_top_levels
    deferred, incomplete, progress = semantic_analyze_target(next_id, state,
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\semanal_main.py", line 326, in semantic_analyze_target
    analyzer.refresh_partial(refresh_node,
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\semanal.py", line 412, in refresh_partial
    self.refresh_top_level(node)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\semanal.py", line 423, in refresh_top_level
    self.accept(d)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\semanal.py", line 5215, in accept
    node.accept(self)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\nodes.py", line 1008, in accept
    return visitor.visit_class_def(self)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\semanal.py", line 1111, in visit_class_def
    self.analyze_class(defn)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\semanal.py", line 1189, in analyze_class
    self.analyze_class_body_common(defn)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\semanal.py", line 1198, in analyze_class_body_common
    self.apply_class_plugin_hooks(defn)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\semanal.py", line 1244, in apply_class_plugin_hooks
    hook(ClassDefContext(defn, decorator, self))
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\plugins\dataclasses.py", line 518, in dataclass_class_maker_callback
    transformer.transform()
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\plugins\dataclasses.py", line 121, in transform
    attributes = self.collect_attributes()
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\plugins\dataclasses.py", line 404, in collect_attributes
    attr.expand_typevar_from_subtype(ctx.cls.info)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\plugins\dataclasses.py", line 107, in expand_typevar_from_subtype
    self.type = map_type_from_supertype(self.type, sub_type, self.info)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\typeops.py", line 147, in map_type_from_supertype
    inst_type = map_instance_to_supertype(inst_type, super_info)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\maptype.py", line 24, in map_instance_to_supertype
    return map_instance_to_supertypes(instance, superclass)[0]
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\maptype.py", line 37, in map_instance_to_supertypes
    a.extend(map_instance_to_direct_supertypes(t, sup))
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\maptype.py", line 82, in map_instance_to_direct_supertypes
    t = expand_type(b, env)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\expandtype.py", line 17, in expand_type
    return typ.accept(ExpandTypeVisitor(env))
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\types.py", line 1065, in accept
    return visitor.visit_instance(self)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\expandtype.py", line 89, in visit_instance
    args = self.expand_types(t.args)
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\expandtype.py", line 181, in expand_types
    a.append(t.accept(self))
  File "c:\users\dan\src\mypy-repro\venv\src\mypy\mypy\types.py", line 2200, in accept
    assert isinstance(visitor, SyntheticTypeVisitor)
AssertionError: 

To Reproduce

https://github.com/DanAlbert/mypy-repro. Note that this is heavily minimized, so some parts might look just wrong, like importing types that don't exist. Defining the types where they belong doesn't make the crash go away, so they're omitted.

$ python -m venv venv # I'm using Python 3.10
$ .\venv\Scripts\activate # Or source venv/bin/activate for non-Windows
$ python -m pip install -r requirements.txt # Only installs HEAD mypy, so skip if you have your own installed
$ mypy --no-incremental game

Your Environment

• Mypy version used: mypy 0.940+dev.2d30dbaa34eab9d7519e440480f360fc9a1e65c3
• Mypy command-line flags: --no-incremental for testing purposes, but it doesn't matter
• Mypy configuration options from mypy.ini (and other config files): namespace_packages = True
• Python version used: Python 3.10.2
• Operating system and version: Windows 10 Pro 21H2 19044.1526

I haven't verified if this affects other environments or not. I have no reason to believe this is Windows specific though.

[Michael0x2a]

Looks like this was fixed by #12762, according to git-bisect.

Running mypy against the repro now produces the following output:

$ mypy --no-incremental game
game\commander\tasks\packageplanningtask.py:4: error: Name "MissionTarget" is not defined
game\theater\frontline.py:1: error: Module "game.theater.controlpoint" has no attribute "MissionTarget"
game\theater\controlpoint.py:1: error: Module "game.coalition" has no attribute "Coalition"
game\commander\theatercommander.py:1: error: Module "game.commander.tasks.compound.nextaction" has no attribute "PlanNextAction"
game\commander\tasks\compound\nextaction.py:1: error: Module "game.commander.tasks.compound.defendbases" has no attribute "DefendBases"; maybe "DefendBase"?
game\commander\tasks\compound\defendbases.py:1: error: Module "game.commander.tasks.compound.defendbase" has no attribute "DefendBase"
game\commander\__init__.py:1: error: Module "game.commander.theatercommander" has no attribute "TheaterCommander"
Found 7 errors in 7 files (checked 12 source files)

These errors do all seem legitimate, based on a quick skim.