discrepencay between mypy and mypyc

Bug Report

Code passes according to mypy but fails with mypyc.

To Reproduce

from pathlib import Path
from typing import TypeVar

PathNoneT = TypeVar("PathNoneT", Path, None)


def return_value(path: PathNoneT) -> PathNoneT:
    if path is None:
        return path
    new_path = path.with_suffix(".test")
    if not new_path.is_file() and path.is_file():
        new_path = path
    # mypyc: error: Incompatible return value type (got "Union[Path, Any]", expected "PathNoneT")  [return-value]
    return new_path

Expected Behavior

mypyc emits exactly the same errors as mypy.

Actual Behavior

Mypyc reports error: Incompatible return value type (got "Union[Path, Any]", expected "PathNoneT") [return-value] .

Your Environment

• Mypy version used: 0.991
• Python version used: 3.10.8
• Mypy configuration options from mypy.ini (and other config files):

show_error_codes = true
enable_error_code = "ignore-without-code"
follow_imports = "silent"
warn_unused_configs = true
warn_redundant_casts = true
warn_unused_ignores = true
warn_no_return = true
no_implicit_optional = true
check_untyped_defs = true
disallow_incomplete_defs = true
disallow_untyped_defs = true
disallow_untyped_decorators = true
strict_equality = true

disallow_any_generics = false
ignore_missing_imports = true
warn_return_any = false

Start by reproducing the provided generic Path example with Python 3.10.8 and compare mypy's result with mypyc's diagnostic. Trace the type-checking path responsible for the differing return-value error; done means mypyc emits the same errors as mypy for this example.