Crash on generic class with experimental TypeVarTuple support

[yakMM]

Hello, I'm experimenting a mypy crash trying to build a generic class using TypeVarTuple (incomplete feature).

Happening on last mypy vesion 1.5.1, as well as master. Reproduction here with the master version:

Software:
Mypy version: Master: 7141d6b
Python version: 3.11.4
OS: Windows 10

Mypy command: mypy main.py --enable-incomplete-feature=TypeVarTuple --enable-incomplete-feature=Unpack --show-traceback
No config file.

Minimum reproduction code:

from typing import Generic, Unpack, TypeVarTuple
from collections.abc import Callable

ArgsT = TypeVarTuple("ArgsT")


class Foo(Generic[Unpack[ArgsT]]):
    def __init__(
        self,
        func: Callable[[Unpack[ArgsT]], None],
        *args: Unpack[ArgsT],
    ) -> None:
        self.func = func
        self.args = args

    def bar(self) -> None:
        return self.func(*self.args)  # CRASH here

Traceback:

PS D:\_projets\playground> mypy main.py --enable-incomplete-feature=TypeVarTuple --enable-incomplete-feature=Unpack --show-traceback         
main.py:17: 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: 1.6.0+dev.7141d6bcff9e26e774e88712015ca6bbe8307c9e
Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "D:\_projets\playground\.venv\Scripts\mypy.EXE\__main__.py", line 7, in <module>
    sys.exit(console_entry())
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\__main__.py", line 15, in console_entry
    main()
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\main.py", line 99, in main
    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\main.py", line 178, in run_build
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\build.py", line 189, in build
    result = _build(
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\build.py", line 262, in _build
    graph = dispatch(sources, manager, stdout)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\build.py", line 2938, in dispatch
    process_graph(graph, manager)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\build.py", line 3336, in process_graph
    process_stale_scc(graph, scc, manager)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\build.py", line 3437, in process_stale_scc
    graph[id].type_check_first_pass()
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\build.py", line 2306, in type_check_first_pass
    self.type_checker().check_first_pass()
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checker.py", line 475, in check_first_pass
    self.accept(d)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checker.py", line 585, in accept
    stmt.accept(self)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\nodes.py", line 1145, in accept
    return visitor.visit_class_def(self)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checker.py", line 2298, in visit_class_def
    self.accept(defn.defs)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checker.py", line 585, in accept
    stmt.accept(self)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\nodes.py", line 1226, in accept
    return visitor.visit_block(self)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checker.py", line 2754, in visit_block
    self.accept(s)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checker.py", line 585, in accept
    stmt.accept(self)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\nodes.py", line 790, in accept
    return visitor.visit_func_def(self)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checker.py", line 994, in visit_func_def
    self._visit_func_def(defn)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checker.py", line 998, in _visit_func_def
    self.check_func_item(defn, name=defn.name)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checker.py", line 1071, in check_func_item
    self.check_func_def(defn, typ, name, allow_empty)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checker.py", line 1281, in check_func_def
    self.accept(item.body)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checker.py", line 585, in accept
    stmt.accept(self)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\nodes.py", line 1226, in accept
    return visitor.visit_block(self)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checker.py", line 2754, in visit_block
    self.accept(s)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checker.py", line 585, in accept
    stmt.accept(self)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\nodes.py", line 1422, in accept
    return visitor.visit_return_stmt(self)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checker.py", line 4289, in visit_return_stmt
    self.check_return_stmt(s)
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checker.py", line 4325, in check_return_stmt
    self.expr_checker.accept(
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checkexpr.py", line 5329, in accept
    typ = self.visit_call_expr(node, allow_none_return=True)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checkexpr.py", line 453, in visit_call_expr
    return self.visit_call_expr_inner(e, allow_none_return=allow_none_return)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checkexpr.py", line 582, in visit_call_expr_inner
    ret_type = self.check_call_expr_with_callee_type(
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checkexpr.py", line 1421, in check_call_expr_with_callee_type
    ret_type, callee_type = self.check_call(
                            ^^^^^^^^^^^^^^^^
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checkexpr.py", line 1515, in check_call
    return self.check_callable_call(
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checkexpr.py", line 1716, in check_callable_call
    self.check_argument_types(
  File "D:\_projets\playground\.venv\Lib\site-packages\mypy\checkexpr.py", line 2413, in check_argument_types
    assert isinstance(unpacked_type, Instance)
AssertionError:
main.py:17: : note: use --pdb to drop into pdb