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Confusing error: incompatible type "Type[bytes]"; expected "Type[bytes]" #9756
Description
Bug Report
Error message seems to indicate it requires the type it is getting. I could be reading the error message wrong, but this one confuses me.
To Reproduce
- put the code in a file e.g. scratchpad.py
from typing import Type def f(class_type: Type[object]): if class_type in [bytes, bytearray]: return True
- run
mypy scratchpad.py
Expected Behavior
no errors
Actual Behavior
scratchpad.py:4: error: List item 0 has incompatible type "Type[bytes]"; expected "Type[bytes]"
Your Environment
- Mypy version used: 0.790
- Mypy command-line flags: n/a
- Mypy configuration options from
mypy.ini(and other config files): n/a - Python version used: 3.8.3
- Operating system and version: OSX 10.15.7
Activity
hauntsaninja commentedon Nov 25, 2020
Here's a shorter repro:
See python/typing#552 for some more context.
A good workaround here is to use a tuple instead of a list (since tuples are heterogeneous, mypy won't need to perform a join).
JelleZijlstra commentedon Nov 25, 2020
There's still something strange going on here that the linked issue doesn't fully explain, though surely the implicit promotion has something to do with it. The error doesn't repro with
[float, int]or[int, float], even though these are also implicitly promoted, or with[bytearray, bytes].EugeneN commentedon Oct 28, 2022
the error reproduces with arbitrary types, in function arguments, assigning etc
EugeneN commentedon Oct 28, 2022
Argument 3 to "..." has incompatible type "List[PlatformFees]"; expected "List[PlatformFees]" mypy(error)Argument 2 to "..." has incompatible type "CIPSolution"; expected "CIPSolution" mypy(error)Make join of callables a bit more principled (python#22296)