panic: entered unreachable code: Expected a QuantifiedValue, got @_

[jrdnh]

Update

The original issue (preserved below) is fixed, but pyrefly still crashes on this:

class C[T: C](set[object]):
    pass

---

Describe the Bug

Recently tried running on the repo below which caused the crash logs below.

Steps to reproduce:

git clone git@github.com:Orcaset/orcaset.git && cd orcaset
uv venv && uv pip install -r pyproject.toml 
source .venv/bin/activate
uvx pyrefly check

Output:

% uvx pyrefly check
 INFO Found `~/orcaset/pyproject.toml` marking project root, checking root directory with default configuration
[00:00:00] ░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░       0/58     ERROR Thread panicked, shutting down: panicked at pyrefly/lib/alt/solve.rs:1359:30:
internal error: entered unreachable code
Backtrace:
   0: __mh_execute_header
   1: __mh_execute_header
   2: __mh_execute_header
   3: __mh_execute_header
   4: __mh_execute_header
   5: __mh_execute_header
   6: __mh_execute_header
   7: __mh_execute_header
   8: __mh_execute_header
   9: __mh_execute_header
  10: __mh_execute_header
  11: __mh_execute_header
  12: __mh_execute_header
  13: __mh_execute_header
  14: __mh_execute_header
  15: __mh_execute_header
  16: __mh_execute_header
  17: __mh_execute_header
  18: __mh_execute_header
  19: __mh_execute_header
  20: __mh_execute_header
  21: __mh_execute_header
  22: __mh_execute_header
  23: __mh_execute_header
  24: __mh_execute_header
  25: __mh_execute_header
  26: __mh_execute_header
  27: __mh_execute_header
  28: __mh_execute_header
  29: __mh_execute_header
  30: __mh_execute_header
  31: __mh_execute_header
  32: __mh_execute_header
  33: __pthread_cond_wait

PANIC Sorry, Pyrefly crashed, this is always a bug in Pyrefly itself.
PANIC Please report the bug at https://github.com/facebook/pyrefly/issues/new

Python 3.13.9
pyrefly 0.42.3

Sandbox Link

No response

(Only applicable for extension issues) IDE Information

No response

[jrdnh]

Closing, think this was likely driven by the python>=3.12 config in the pyproject.toml, however PEP 696 syntax is used that requires Python 3.13+.

[rchen152]

Glad you were able to figure it out! Pyrefly should never crash, even on unsupported syntax, so I'm going to reopen this issue to track a fix for that. Knowing that this is caused by PEP 696 syntax is helpful.

[rchen152]

Here's a small reproducer:

# node.py
class Node[P]: ...

# test.py
from node import Node
class A[P: A](Node[P]): ...

pyrefly check test.py crashes. Interestingly, the crash only happens when Node is defined in a different file.

[rchen152]

Another example from a user:

class C[T: C]([object]):
    pass