Crash Report
When using TypeGuard to narrow a Literal-based union from a StrEnum, mypy raises an internal error.
I found a workaround, but I prefer my first implementation as it is more concise.
Traceback
main.py: error: INTERNAL ERROR -- Please try using mypy master on GitHub:
https://mypy.readthedocs.io/en/stable/common_issues.html#using-a-development-mypy-build
If this issue continues with mypy master, please report a bug at https://github.com/python/mypy/issues
version: 1.10.0
main.py: : note: please use --show-traceback to print a traceback when reporting a bug
To Reproduce
from typing import TypeGuard, Literal, TypeAlias
from enum import StrEnum
class Model(StrEnum):
MODEL_A1 = 'model_a1'
MODEL_A2 = 'model_a2'
MODEL_B = 'model_b'
MODEL_A: TypeAlias = Literal[Model.MODEL_A1, Model.MODEL_A2]
MODEL_B: TypeAlias = Literal[Model.MODEL_B]
def is_model_a(model: str) -> TypeGuard[MODEL_A]:
return model in (Model.MODEL_A1, Model.MODEL_A2)
def is_model_b(model: str) -> TypeGuard[MODEL_B]:
return model == Model.MODEL_B
def process_model(model: MODEL_A | MODEL_B) -> int:
return 42
# Works
def handle_1(model: Model) -> int:
if is_model_a(model):
return process_model(model)
if is_model_b(model):
return process_model(model)
return 0
# Crashes
def handle_2(model: Model) -> int:
if is_model_a(model) or is_model_b(model): # ❌ This line causes a crash
return process_model(model)
return 0
# Crashes
def handle_3(model: Model) -> int:
match model:
case m if is_model_a(m) or is_model_b(m): # ❌ Also crashes
return process_model(m)
case _:
return 0
Your Environment
- Mypy version used: 1.15.0
- Mypy command-line flags:
- Mypy configuration options from
mypy.ini (and other config files):
- Python version used: 3.12
- Operating system and version: Linux 6.13.8
Crash Report
When using TypeGuard to narrow a Literal-based union from a StrEnum, mypy raises an internal error.
I found a workaround, but I prefer my first implementation as it is more concise.
Traceback
To Reproduce
Your Environment
mypy.ini(and other config files):