Assertion failure crash: assert not self.has_type_var_tuple_type

[correctmost]

Crash Report

The snippet below crashes mypy 1.18.2 and the latest code from master (96fac3a).

Traceback

Traceback (most recent call last):
  File ".venv-mypy/bin/mypy", line 7, in <module>
    sys.exit(console_entry())
  File "mypy/mypy/__main__.py", line 15, in console_entry
    main()
  File "mypy/mypy/main.py", line 127, in main
    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
  File "mypy/mypy/main.py", line 211, in run_build
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "mypy/mypy/build.py", line 215, in build
    result = _build(
  File "mypy/mypy/build.py", line 294, in _build
    graph = dispatch(sources, manager, stdout)
  File "mypy/mypy/build.py", line 2945, in dispatch
    process_graph(graph, manager)
  File "mypy/mypy/build.py", line 3336, in process_graph
    done, still_working = manager.wait_for_done(graph)
  File "mypy/mypy/build.py", line 918, in wait_for_done
    process_stale_scc(graph, next_scc, self)
  File "mypy/mypy/build.py", line 3468, in process_stale_scc
    mypy.semanal_main.semantic_analysis_for_scc(graph, scc, manager.errors)
  File "mypy/mypy/semanal_main.py", line 95, in semantic_analysis_for_scc
    process_top_levels(graph, scc, patches)
  File "mypy/mypy/semanal_main.py", line 233, in process_top_levels
    deferred, incomplete, progress = semantic_analyze_target(
  File "mypy/mypy/semanal_main.py", line 410, in semantic_analyze_target
    analyzer.refresh_partial(
  File "mypy/mypy/semanal.py", line 701, in refresh_partial
    self.refresh_top_level(node)
  File "mypy/mypy/semanal.py", line 719, in refresh_top_level
    self.accept(d)
  File "mypy/mypy/semanal.py", line 7563, in accept
    node.accept(self)
    ~~~~~~~~~~~^^^^^^
  File "mypy/mypy/nodes.py", line 1478, in accept
    return visitor.visit_class_def(self)
           ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "mypy/mypy/semanal.py", line 1827, in visit_class_def
    self.analyze_class(defn)
    ~~~~~~~~~~~~~~~~~~^^^^^^
  File "mypy/mypy/semanal.py", line 2021, in analyze_class
    self.setup_type_vars(defn, tvar_defs)
    ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "mypy/mypy/semanal.py", line 2063, in setup_type_vars
    defn.info.add_type_vars()
    ~~~~~~~~~~~~~~~~~~~~~~~^^
  File "mypy/mypy/nodes.py", line 3611, in add_type_vars
    assert not self.has_type_var_tuple_type
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 

To Reproduce

class C[*T, *U]:
   pass

Your Environment

• Mypy version used: 96fac3a (and 1.18.2)
• Mypy command-line flags: N/A
• Mypy configuration options from mypy.ini (and other config files): N/A
• Python version used: 3.13.7
• Operating system and version: Arch Linux

[A5rocks]

Hi, do you have a fuzzing setup? I'd love to see it if so!

[correctmost]

Hi, do you have a fuzzing setup? I'd love to see it if so!

I maintain the OSS-Fuzz integration for astroid and have been running old fuzzing artifacts against other Python tools to see what I can find. I don't have anything public right now, but I can let you know if I create any shared repos or pipelines :).

[A5rocks]

Awesome! I've been thinking about using hypofuzz or something so we get property tests + fuzzing for some basic type checking properties too. But even just catching crashes is great! I hadn't expected any sort of generic fuzzing like what you're describing to work this well...