Mypyc 1.13.0 crashes on specific match statement #18614

Crash Report

First time trying to compile my Python project with Mypyc; it seems to hang itself up on a specific match statement. Although there are a couple more in the code, it only complains about this one as far as I can tell. Replacing it with an semantically equivalent if-else gives me type warnings and errors instead (the expected result considering that these seem all valid).

Traceback

❯ uv run --with mypy[mypyc] mypyc -p nyl --show-traceback
Traceback (most recent call last):
  File "mypyc/irbuild/builder.py", line 272, in accept
  File "mypy/nodes.py", line 1648, in accept
  File "mypyc/irbuild/visitor.py", line 252, in visit_match_stmt
  File "mypyc/irbuild/statement.py", line 1022, in transform_match_stmt
  File "mypy/nodes.py", line 1648, in accept
  File "mypyc/irbuild/match.py", line 92, in visit_match_stmt
  File "mypy/patterns.py", line 150, in accept
  File "mypyc/irbuild/match.py", line 164, in visit_class_pattern
src/nyl/generator/components.py:81: AssertionError: 

To Reproduce

1. Clone https://github.com/helsing-ai/nyl and check out 0.8.1 (that is HEAD today)
2. Run uv run --with mypy[mypyc]==1.13.0 mypyc -p nyl

The specific piece of code that it seems to hiccup on is this:

https://github.com/helsing-ai/nyl/blob/659ffec8e4b8362f8012e0b096fe4b2606861586/src/nyl/generator/components.py#L81-L92

        match component:
            case HelmComponent(path):
                chart = HelmChart(
                    metadata=instance.metadata,
                    spec=HelmChartSpec(
                        chart=ChartRef(path=str(path.resolve())),
                        values={"metadata": resource["metadata"], **instance.spec},
                    ),
                )
                return self.helm_generator.generate(chart)
            case _:
                raise RuntimeError(f"unexpected component type: {component}")

There are a couple more match statements in the code which it doesn't seem to complain about after changing this to use if-else instead. I'm not exactly sure where best to start to reduce it to a smaller example.

Your Environment

• Mypy version used: 1.13.0
• Mypy command-line flags: -p nyl
• Mypy configuration options from mypy.ini (and other config files):

  explicit_package_bases = true
  namespace_packages = true
  show_column_numbers = true
  strict = true
  mypy_path = ["src"]
  

• Python version used: 3.11.9
• Operating system and version: WSL2 Ubuntu 22.04.5 LTS