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Class with function fields incorrectly thinks first argument is self #5485
Description
This is a bug report.
Minimal repro
from dataclasses import dataclass
from typing import Callable
@dataclass
class Repro:
fn: Callable[[int], str]
r = Repro(fn=repr)
assert "1" == r.fn(1)Works correctly when dataclass is not used, i.e. when Repro is
class Repro:
def __init__(self, fn: Callable[[int], str]) -> None:
self.fn = fnActual behavior
repro.py:9: error: Invalid self argument "Repro" to attribute function "fn" with type "Callable[[int], str]"
repro.py:9: error: Too many argumentsWhen running with Python, works correctly. Doesn't throw any exceptions.
Expected behavior
Successful type check
Environment
Versions
Tested with two versions, 0.620 and current version from GitHub.
- Python 3.7.0
- mypy 0.620
- mypy 0.630+dev-a2ffde90635baf05e264f8d899f5705c52b27c2a
Mypy config
[mypy]
warn_redundant_casts = True
warn_unused_ignores = True
incremental = True
follow_imports = normal
ignore_missing_imports = True
disallow_untyped_calls = True
disallow_untyped_defs = True
check_untyped_defs = True
warn_return_any = True
warn_no_return = True
no_implicit_optional = True
strict_optional = True
Activity
ilevkivskyi commented on Aug 15, 2018
This is not something specific to dataclasses. There is a simpler repro that gives same errors:
The problem is the same as in #708. I would however not close this as a duplicate, because this issue highlights another aspect of the problem.
vim345 commented on Sep 24, 2018
I just came across the same issue. I guess a lot of people are going to face this issue very soon, as it's very easy to reproduce it using dataclasses.
ilevkivskyi commented on Sep 25, 2018
I guess this should be not hard to fix, mypy cares whether a callable was assigned in class (to match what Python does), so we should just tweak the Vars in plugin to pretend they were assigned on self. But we still need a volunteer who will fix this.
ojii commented on Nov 27, 2018
If someone needs a workaround, this works:
s-knibbs commented on Mar 27, 2019
I've found that another workaround to this is to use a callback protocol instead of Callable
no-longer-on-githu-b commented on Jul 17, 2019
When using NamedTuple instead of dataclass this problem does not arise.
TH3CHARLie commented on Jan 21, 2020
I volunteer to fix this and any guidances will be greatly helpful @ilevkivskyi
ilevkivskyi commented on Jan 22, 2020
@TH3CHARLie Fixing this in general may be tricky, but fixing just the dataclass case, should be easy. In any case, please go ahead!
No coverage on kind.py until problems due to python/mypy#5485 is ok
Squashed commit of the following:
39 remaining items
Fix callable instance variable support (python#10548)
Fix callable instance variable support (take 2) (#13400)
Type get_response with a callback protocol.
Reflect the deprecation of get_response being None. (#1086)