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bugmypy got something wrongmypy got something wrong
Description
Bug Report
When taking the parameter type from the signature, mypy incorrectly thinks that the annotation of type <class 'type'> is the actual type of the variable.
To Reproduce
In the following example, process_signature extracts the type of input from the signature of a function and then tries to match it to int or float. However the type of input_type is <class 'type'> not int or float. Therefore, when the code is run assert_never is reached.
from typing import Callable, assert_never, reveal_type
from inspect import signature
def takes_int(x: int) -> None:
print(f"{x} is a int")
def process_signature(
func: Callable[[int], None] | Callable[[float], None]
) -> None:
input_type = signature(func).parameters['x'].annotation
reveal_type(input_type) # Runtime type is 'type' => should reach `case _:`
match input_type:
case int():
print("This is an int")
case float():
print("This is a float")
case _:
assert_never(input_type) # this is reached during runtime
process_signature(takes_int)Expected Behavior
mypy to complain that input to assert_never is <class 'type'> but expected Never.
Actual Behavior
mypy does not complain.
Your Environment
- Mypy version used:
1.19.1 - Mypy command-line flags: None
- Mypy configuration options from
mypy.ini(and other config files): None - Python version used:
3.13.7
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bugmypy got something wrongmypy got something wrong