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

[peacefulotter]

Still having this issue with mypy 1.18.2

Traceback (most recent call last):
  File "AppData\Local\Programs\Python\Python310\lib\runpy.py", line 196, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "AppData\Local\Programs\Python\Python310\lib\runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "\.venv\Scripts\mypy.exe\__main__.py", line 10, in <module>
  File "\.venv\lib\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
    # some other object -- pass it through.
NotImplementedError: Cannot serialize TypeGuardedType instance 

[skywall]

@peacefulotter 1.18.2 was actually affected by this. We have to wait for new release.

[peacefulotter]

This issue should be reopened then