Generic bounded dataclass crash

[xanderbailey]

Crash Report

Ran mypy on my user library - no idea what went wrong.

Traceback

  File "/Users/name/.env/myenv/bin/mypy", line 8, in <module>
    sys.exit(console_entry())
  File "/Users/name/.env/myenv/lib/python3.9/site-packages/mypy/__main__.py", line 11, in console_entry
    main(None, sys.stdout, sys.stderr)
  File "/Users/name/.env/myenv/lib/python3.9/site-packages/mypy/main.py", line 98, in main
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "/Users/name/.env/myenv/lib/python3.9/site-packages/mypy/build.py", line 179, in build
    result = _build(
  File "/Users/name/.env/myenv/lib/python3.9/site-packages/mypy/build.py", line 253, in _build
    graph = dispatch(sources, manager, stdout)
  File "/Users/name/.env/myenv/lib/python3.9/site-packages/mypy/build.py", line 2688, in dispatch
    process_graph(graph, manager)
  File "/Users/name/.env/myenv/lib/python3.9/site-packages/mypy/build.py", line 3012, in process_graph
    process_stale_scc(graph, scc, manager)
  File "/Users/name/.env/myenv/lib/python3.9/site-packages/mypy/build.py", line 3104, in process_stale_scc
    mypy.semanal_main.semantic_analysis_for_scc(graph, scc, manager.errors)
  File "/Users/name/.env/myenv/lib/python3.9/site-packages/mypy/semanal_main.py", line 79, in semantic_analysis_for_scc
    process_functions(graph, scc, patches)
  File "/Users/name/.env/myenv/lib/python3.9/site-packages/mypy/semanal_main.py", line 233, in process_functions
    process_top_level_function(analyzer,
  File "/Users/name/.env/myenv/lib/python3.9/site-packages/mypy/semanal_main.py", line 274, in process_top_level_function
    deferred, incomplete, progress = semantic_analyze_target(target, state, node, active_type,
  File "/Users/name/.env/myenv/lib/python3.9/site-packages/mypy/semanal_main.py", line 326, in semantic_analyze_target
    analyzer.refresh_partial(refresh_node,
  File "/Users/name/.env/myenv/lib/python3.9/site-packages/mypy/semanal.py", line 397, in refresh_partial
    self.accept(node)
  File "/Users/name/.env/myenv/lib/python3.9/site-packages/mypy/semanal.py", line 4835, in accept
    node.accept(self)
  File "/Users/name/.env/myenv/lib/python3.9/site-packages/mypy/nodes.py", line 687, in accept
    return visitor.visit_func_def(self)
  File "/Users/name/.env/myenv/lib/python3.9/site-packages/mypy/semanal.py", line 573, in visit_func_def
    self.analyze_func_def(defn)
  File "/Users/name/.env/myenv/lib/python3.9/site-packages/mypy/semanal.py", line 605, in analyze_func_def
    self.defer(defn)
  File "/Users/name/.env/myenv/lib/python3.9/site-packages/mypy/semanal.py", line 4554, in defer
    assert not self.final_iteration, 'Must not defer during final iteration'
AssertionError: Must not defer during final iteration

To Reproduce

from dataclasses import dataclass
import dataclasses
from typing import Any, Dict, Generic, List, Type, TypeVar, Union
from abc import ABC, abstractclassmethod

from occupier.utils import EnhancedJSONEncoder

T = TypeVar("T", bound="DictDataClass")


@dataclass(frozen=True)
class DictDataClass(Generic[T]):
    urn: int

    def to_dict(self) -> Dict[str, Any]:
        return dataclasses.asdict(self)

    @classmethod
    def from_dict(cls: Type[T], dict_: Dict[str, Any]) -> T:
        return cls(**dict_)

    @classmethod
    def field_names(cls) -> List[str]:
        return [field.name for field in dataclasses.fields(cls)]


@dataclass(frozen=True)
class JSONDataClass(ABC, DictDataClass):

    _JSON_ENCODER = EnhancedJSONEncoder()

    def to_json(self) -> str:
        return JSONDataClass._JSON_ENCODER.encode(self)

    @classmethod
    @abstractclassmethod
    def from_json(cls: Type[T], json_str: str) -> Union[List[T], T]:
        pass

Your Environment

• Mypy version used : 0.820+dev.effd970ad1e8bb09fd2a18634339e1d043a83400
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files):
• Python version used: 3.9.1
• Operating system and version: MacOS 10.15.7

[ethframe]

[edit by JukkaL: this is tracked in #12112]

I've encountered similar crash:

Traceback (most recent call last):
  File "C:\Users\User\AppData\Local\Programs\Python\Python36\lib\runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "C:\Users\User\AppData\Local\Programs\Python\Python36\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "C:\mypy\mypy\__main__.py", line 23, in <module>
    console_entry()
  File "C:\mypy\mypy\__main__.py", line 11, in console_entry
    main(None, sys.stdout, sys.stderr)
  File "C:\mypy\mypy\main.py", line 98, in main
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "C:\mypy\mypy\build.py", line 180, in build
    sources, options, alt_lib_path, flush_errors, fscache, stdout, stderr, extra_plugins
  File "C:\mypy\mypy\build.py", line 253, in _build
    graph = dispatch(sources, manager, stdout)
  File "C:\mypy\mypy\build.py", line 2688, in dispatch
    process_graph(graph, manager)
  File "C:\mypy\mypy\build.py", line 3012, in process_graph
    process_stale_scc(graph, scc, manager)
  File "C:\mypy\mypy\build.py", line 3104, in process_stale_scc
    mypy.semanal_main.semantic_analysis_for_scc(graph, scc, manager.errors)
  File "C:\mypy\mypy\semanal_main.py", line 79, in semantic_analysis_for_scc
    process_functions(graph, scc, patches)
  File "C:\mypy\mypy\semanal_main.py", line 239, in process_functions
    patches)
  File "C:\mypy\mypy\semanal_main.py", line 275, in process_top_level_function
    final_iteration, patches)
  File "C:\mypy\mypy\semanal_main.py", line 331, in semantic_analyze_target
    active_type=active_type)
  File "C:\mypy\mypy\semanal.py", line 397, in refresh_partial
    self.accept(node)
  File "C:\mypy\mypy\semanal.py", line 4835, in accept
    node.accept(self)
  File "C:\mypy\mypy\nodes.py", line 687, in accept
    return visitor.visit_func_def(self)
  File "C:\mypy\mypy\semanal.py", line 573, in visit_func_def
    self.analyze_func_def(defn)
  File "C:\mypy\mypy\semanal.py", line 616, in analyze_func_def
    self.analyze_function_body(defn)
  File "C:\mypy\mypy\semanal.py", line 940, in analyze_function_body
    defn.body.accept(self)
  File "C:\mypy\mypy\nodes.py", line 1015, in accept
    return visitor.visit_block(self)
  File "C:\mypy\mypy\semanal.py", line 3297, in visit_block
    self.accept(s)
  File "C:\mypy\mypy\semanal.py", line 4835, in accept
    node.accept(self)
  File "C:\mypy\mypy\nodes.py", line 950, in accept
    return visitor.visit_class_def(self)
  File "C:\mypy\mypy\semanal.py", line 1048, in visit_class_def
    self.analyze_class(defn)
  File "C:\mypy\mypy\semanal.py", line 1125, in analyze_class
    self.analyze_class_body_common(defn)
  File "C:\mypy\mypy\semanal.py", line 1133, in analyze_class_body_common
    defn.defs.accept(self)
  File "C:\mypy\mypy\nodes.py", line 1015, in accept
    return visitor.visit_block(self)
  File "C:\mypy\mypy\semanal.py", line 3297, in visit_block
    self.accept(s)
  File "C:\mypy\mypy\semanal.py", line 4835, in accept
    node.accept(self)
  File "C:\mypy\mypy\nodes.py", line 687, in accept
    return visitor.visit_func_def(self)
  File "C:\mypy\mypy\semanal.py", line 573, in visit_func_def
    self.analyze_func_def(defn)
  File "C:\mypy\mypy\semanal.py", line 602, in analyze_func_def
    result = analyzer.visit_callable_type(defn.type, nested=False)
  File "C:\mypy\mypy\typeanal.py", line 537, in visit_callable_type
    variables=self.anal_var_defs(variables),
  File "C:\mypy\mypy\typeanal.py", line 978, in anal_var_defs
    return [self.anal_var_def(vd) for vd in var_defs]
  File "C:\mypy\mypy\typeanal.py", line 978, in <listcomp>
    return [self.anal_var_def(vd) for vd in var_defs]
  File "C:\mypy\mypy\typeanal.py", line 970, in anal_var_def
    var_def.upper_bound.accept(self),
  File "C:\mypy\mypy\types.py", line 1964, in accept
    return visitor.visit_placeholder_type(self)
  File "C:\mypy\mypy\typeanal.py", line 663, in visit_placeholder_type
    self.api.defer()  # Still incomplete
  File "C:\mypy\mypy\semanal.py", line 4554, in defer
    assert not self.final_iteration, 'Must not defer during final iteration'
AssertionError: Must not defer during final iteration

Code to reproduce:

from typing import TypeVar

def test() -> None:
    T = TypeVar('T', bound='Foo')

    class Foo:
        def bar(self, foo: T) -> None:
            pass

• Mypy version used: 0.820+dev.c8bae06919674b9846e3ff864b0a44592db888eb
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.6.8
• Operating system and version: Windows 8.1

[JukkaL]

Here is a simplified version of the first example:

from dataclasses import dataclass
from typing import Generic, TypeVar

T = TypeVar("T", bound="C")

@dataclass
class C(Generic[T]):
    x: int

[dragonpaw]

I think I ran into this with a Django project as well. The following code seems to trigger a crash that seems related.

T = TypeVar("T", bound="MyModel")

class MyModel(Generic[T], models.Model):
    field = models.DateField(db_index=True)

Oddly enough, it's specific to the field type. A CharField won't cause a crash. A DateField will.

/Users/ash/src/ticketing-django/ticketing/utils/models.py:191: error: INTERNAL ERROR -- Please try using mypy master on Github:
https://mypy.rtfd.io/en/latest/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 0.812
Traceback (most recent call last):
  File "/Users/ash/.pyenv/versions/django/bin/mypy", line 8, in <module>
    sys.exit(console_entry())
  File "/Users/ash/.pyenv/versions/3.9.4/envs/django/lib/python3.9/site-packages/mypy/__main__.py", line 11, in console_entry
    main(None, sys.stdout, sys.stderr)
  File "/Users/ash/.pyenv/versions/3.9.4/envs/django/lib/python3.9/site-packages/mypy/main.py", line 90, in main
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "/Users/ash/.pyenv/versions/3.9.4/envs/django/lib/python3.9/site-packages/mypy/build.py", line 179, in build
    result = _build(
  File "/Users/ash/.pyenv/versions/3.9.4/envs/django/lib/python3.9/site-packages/mypy/build.py", line 253, in _build
    graph = dispatch(sources, manager, stdout)
  File "/Users/ash/.pyenv/versions/3.9.4/envs/django/lib/python3.9/site-packages/mypy/build.py", line 2638, in dispatch
    process_graph(graph, manager)
  File "/Users/ash/.pyenv/versions/3.9.4/envs/django/lib/python3.9/site-packages/mypy/build.py", line 2962, in process_graph
    process_stale_scc(graph, scc, manager)
  File "/Users/ash/.pyenv/versions/3.9.4/envs/django/lib/python3.9/site-packages/mypy/build.py", line 3054, in process_stale_scc
    mypy.semanal_main.semantic_analysis_for_scc(graph, scc, manager.errors)
  File "/Users/ash/.pyenv/versions/3.9.4/envs/django/lib/python3.9/site-packages/mypy/semanal_main.py", line 79, in semantic_analysis_for_scc
    process_functions(graph, scc, patches)
  File "/Users/ash/.pyenv/versions/3.9.4/envs/django/lib/python3.9/site-packages/mypy/semanal_main.py", line 233, in process_functions
    process_top_level_function(analyzer,
  File "/Users/ash/.pyenv/versions/3.9.4/envs/django/lib/python3.9/site-packages/mypy/semanal_main.py", line 274, in process_top_level_function
    deferred, incomplete, progress = semantic_analyze_target(target, state, node, active_type,
  File "/Users/ash/.pyenv/versions/3.9.4/envs/django/lib/python3.9/site-packages/mypy/semanal_main.py", line 326, in semantic_analyze_target
    analyzer.refresh_partial(refresh_node,
  File "/Users/ash/.pyenv/versions/3.9.4/envs/django/lib/python3.9/site-packages/mypy/semanal.py", line 397, in refresh_partial
    self.accept(node)
  File "/Users/ash/.pyenv/versions/3.9.4/envs/django/lib/python3.9/site-packages/mypy/semanal.py", line 4835, in accept
    node.accept(self)
  File "/Users/ash/.pyenv/versions/3.9.4/envs/django/lib/python3.9/site-packages/mypy/nodes.py", line 687, in accept
    return visitor.visit_func_def(self)
  File "/Users/ash/.pyenv/versions/3.9.4/envs/django/lib/python3.9/site-packages/mypy/semanal.py", line 573, in visit_func_def
    self.analyze_func_def(defn)
  File "/Users/ash/.pyenv/versions/3.9.4/envs/django/lib/python3.9/site-packages/mypy/semanal.py", line 605, in analyze_func_def
    self.defer(defn)
  File "/Users/ash/.pyenv/versions/3.9.4/envs/django/lib/python3.9/site-packages/mypy/semanal.py", line 4554, in defer
    assert not self.final_iteration, 'Must not defer during final iteration'
AssertionError: Must not defer during final iteration
/Users/ash/src/myproject-repo/myproject/utils/models.py:191: : note: use --pdb to drop into pdb

[AlexWaygood]

Looks like the same assertion that's hit in #12113, #12252, #11728, #10672 and #12112