NotImplementedError: Cannot serialize TypeGuardedType instance

[skywall]

Crash Report

When I include aditional dependency onnx-ir==0.1.10 into my pyproject.toml I start to receive error NotImplementedError: Cannot serialize TypeGuardedType instance.

Traceback

(mypy-bug-proj) skywall@me:~/lProjects/mypy-bug-minimal$ mypy . --show-traceback
Traceback (most recent call last):
  File "/home/skywall/lProjects/mypy-bug-minimal/.venv/bin/mypy", line 10, in <module>
    sys.exit(console_entry())
             ^^^^^^^^^^^^^^^
  File "/home/skywall/lProjects/mypy-bug-minimal/.venv/lib/python3.11/site-packages/mypy/__main__.py", line 15, in console_entry
    main()
  File "mypy/main.py", line 127, in main
  File "mypy/main.py", line 211, in run_build
  File "mypy/build.py", line 194, in build
  File "mypy/build.py", line 270, in _build
  File "mypy/build.py", line 2976, in dispatch
  File "mypy/build.py", line 3397, in process_graph
  File "mypy/build.py", line 3524, in process_stale_scc
  File "mypy/build.py", line 2538, in write_cache
  File "mypy/build.py", line 1587, in write_cache
  File "mypy/nodes.py", line 402, in serialize
  File "mypy/nodes.py", line 4641, in serialize
  File "mypy/nodes.py", line 4534, in serialize
  File "mypy/nodes.py", line 3814, in serialize
  File "mypy/nodes.py", line 4641, in serialize
  File "mypy/nodes.py", line 4534, in serialize
  File "mypy/nodes.py", line 1300, in serialize
  File "mypy/types.py", line 722, in serialize
  File "mypy/types.py", line 3300, in serialize
  File "mypy/types.py", line 295, in serialize

NotImplementedError: Cannot serialize TypeGuardedType instance

To Reproduce

This is minimal reproducible project I was able to create:

main.py:

import torch  # yes, only import

pyproject.toml:

[project]
name = "mypy-bug-proj"
version = "1.0.0"
description = "mypy-bug-project"
license-files = ["LICEN[CS]E*"]
keywords = []
requires-python = ">=3.11"
classifiers = [
    "Programming Language :: Python",
    "Intended Audience :: Developers",
]
dependencies = [
    "mypy",
    "torch",
    "onnx==1.17.0",
    "ml-dtypes==0.5.3",
    "onnx-ir==0.1.10",  # <- this is problematic dependency. If it's excluded mypy works fine
]

Your Environment

.python-version:

3.11

uv.lock: uv.lock.txt

• Mypy version used: 1.18.2
• Mypy command-line flags: -
• Mypy configuration options from mypy.ini (and other config files): -
• Python version used: 3.11.5
• Operating system and version: Ubuntu 22.04 WSL

[sterliakov]

This doesn't need huge Torch dependency, just the following (15 MB vs 600+) suffices:

$ uv pip install mypy onnx-ir
$ mypy -c 'import onnx_ir'
Traceback (most recent call last):
  File "/tmp/tmp.lZ8GdcGesY/.venv/bin/mypy", line 10, in <module>
    sys.exit(console_entry())
             ~~~~~~~~~~~~~^^
  File "/tmp/tmp.lZ8GdcGesY/.venv/lib/python3.13/site-packages/mypy/__main__.py", line 15, in console_entry
    main()
    ~~~~^^
  File "mypy/main.py", line 127, in main
  File "mypy/main.py", line 211, in run_build
  File "mypy/build.py", line 194, in build
  File "mypy/build.py", line 270, in _build
  File "mypy/build.py", line 2976, in dispatch
  File "mypy/build.py", line 3397, in process_graph
  File "mypy/build.py", line 3524, in process_stale_scc
  File "mypy/build.py", line 2538, in write_cache
  File "mypy/build.py", line 1587, in write_cache
  File "mypy/nodes.py", line 402, in serialize
  File "mypy/nodes.py", line 4641, in serialize
  File "mypy/nodes.py", line 4534, in serialize
  File "mypy/nodes.py", line 3814, in serialize
  File "mypy/nodes.py", line 4641, in serialize
  File "mypy/nodes.py", line 4534, in serialize
  File "mypy/nodes.py", line 1300, in serialize
  File "mypy/types.py", line 722, in serialize
  File "mypy/types.py", line 3300, in serialize
  File "mypy/types.py", line 295, in serialize
NotImplementedError: Cannot serialize TypeGuardedType instance

Traceback from master (though it isn't as helpful as it could be, the problem is obviously not in the serialization process itself):

Traceback (most recent call last):
  File "/tmp/tmp.lZ8GdcGesY/.venv/bin/mypy", line 10, in <module>
    sys.exit(console_entry())
             ~~~~~~~~~~~~~^^
  File "/home/stas/Documents/Work/mypy/mypy/__main__.py", line 15, in console_entry
    main()
    ~~~~^^
  File "/home/stas/Documents/Work/mypy/mypy/main.py", line 127, in main
    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
                              ~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/stas/Documents/Work/mypy/mypy/main.py", line 211, in run_build
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "/home/stas/Documents/Work/mypy/mypy/build.py", line 200, in build
    result = _build(
        sources, options, alt_lib_path, flush_errors, fscache, stdout, stderr, extra_plugins
    )
  File "/home/stas/Documents/Work/mypy/mypy/build.py", line 279, in _build
    graph = dispatch(sources, manager, stdout)
  File "/home/stas/Documents/Work/mypy/mypy/build.py", line 2940, in dispatch
    process_graph(graph, manager)
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^
  File "/home/stas/Documents/Work/mypy/mypy/build.py", line 3340, in process_graph
    process_stale_scc(graph, scc, manager)
    ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^
  File "/home/stas/Documents/Work/mypy/mypy/build.py", line 3469, in process_stale_scc
    meta_tuples[id] = graph[id].write_cache()
                      ~~~~~~~~~~~~~~~~~~~~~^^
  File "/home/stas/Documents/Work/mypy/mypy/build.py", line 2501, in write_cache
    new_interface_hash, meta_tuple = write_cache(
                                     ~~~~~~~~~~~^
        self.id,
        ^^^^^^^^
    ...<9 lines>...
        self.manager,
        ^^^^^^^^^^^^^
    )
    ^
  File "/home/stas/Documents/Work/mypy/mypy/build.py", line 1602, in write_cache
    data = tree.serialize()
  File "/home/stas/Documents/Work/mypy/mypy/nodes.py", line 407, in serialize
    "names": self.names.serialize(self._fullname),
             ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^
  File "/home/stas/Documents/Work/mypy/mypy/nodes.py", line 4652, in serialize
    data[key] = value.serialize(fullname, key)
                ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
  File "/home/stas/Documents/Work/mypy/mypy/nodes.py", line 4545, in serialize
    data["node"] = self.node.serialize()
                   ~~~~~~~~~~~~~~~~~~~^^
  File "/home/stas/Documents/Work/mypy/mypy/nodes.py", line 3819, in serialize
    "names": self.names.serialize(self.fullname),
             ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
  File "/home/stas/Documents/Work/mypy/mypy/nodes.py", line 4652, in serialize
    data[key] = value.serialize(fullname, key)
                ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
  File "/home/stas/Documents/Work/mypy/mypy/nodes.py", line 4545, in serialize
    data["node"] = self.node.serialize()
                   ~~~~~~~~~~~~~~~~~~~^^
  File "/home/stas/Documents/Work/mypy/mypy/nodes.py", line 1305, in serialize
    "type": None if self.type is None else self.type.serialize(),
                                           ~~~~~~~~~~~~~~~~~~~^^
  File "/home/stas/Documents/Work/mypy/mypy/types.py", line 699, in serialize
    "upper_bound": self.upper_bound.serialize(),
                   ~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/home/stas/Documents/Work/mypy/mypy/types.py", line 3348, in serialize
    "items": [t.serialize() for t in self.items],
              ~~~~~~~~~~~^^
  File "/home/stas/Documents/Work/mypy/mypy/types.py", line 295, in serialize
    raise NotImplementedError(f"Cannot serialize {self.__class__.__name__} instance")
NotImplementedError: Cannot serialize TypeGuardedType instance

[sterliakov]

MRE:

from typing import Generic, TypeVar, TypeGuard

class A: ...
class B: ...

def is_a(_: object) -> TypeGuard[A]: return True
def is_b(_: object) -> TypeGuard[B]: return True


_T = TypeVar("_T")

class Foo(Generic[_T]):
    def __init__(self, v: _T) -> None:
        if not is_a(v) and not is_b(v):
            raise ValueError
        self.v = v

One type guard is not enough, union is necessary for this crash. Since we started narrowing tvar upper bounds, such logic in constructor can create typevars with TypeGuard/TypeIs in their upper bounds.

[amin-nejad]

Downgrading mypy to 1.16.1 fixes the issue for me