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Parameters for a call to a function wrapped in a lru_cache are not checked #16261
Description
Bug Report
The parameters used in a call to a function which is wrapped in a functools.lru_cache are not checked.
To Reproduce
from datetime import date
from functools import lru_cache
@lru_cache
def f(v: str, at: date) -> str:
return v
f()
f("abc")
f("abc", date.today())
f("abc", now=date.today())
f("abc", at=date.today())
f("abc", at="wrong_type")Expected Behavior
This should raise several errors about the arguments being wrong. Commenting out the line @lru_cache correctly generates the following errors.
lru_cache_type_test.py:8: error: Missing positional arguments "v", "at" in call to "f" [call-arg]
lru_cache_type_test.py:9: error: Missing positional argument "at" in call to "f" [call-arg]
lru_cache_type_test.py:11: error: Unexpected keyword argument "now" for "f" [call-arg]
lru_cache_type_test.py:13: error: Argument "at" to "f" has incompatible type "str"; expected "date" [arg-type]
Actual Behavior
Success: no issues found in 1 source file
Your Environment
mypy 1.6.0 running on Python 3.11.6
Activity
[-]lru_cache function calls parameters are not checked[/-][+]Parameters for a call to a function wrapped in a lru_cache are not checked[/+]Hnasar commentedon Oct 16, 2023
We encounter this fairly often too. Just linking to some past discussion: #5107 (comment)
andrewjw commentedon Oct 17, 2023
Ah, thanks for that. I assumed I wouldn't be the first to see this, but couldn't find this specific problem. I guess I didn't read that thread closely enough. I guess this can be closed unless the situation has changed since then, and it is possible to fix.
Add functools.lru_cache plugin support
Add functools.lru_cache plugin support
Add functools.lru_cache plugin support
machin0r commentedon Oct 22, 2025
I have a PR (#19432) that implements plugin support to fix this issue.
Would appreciate guidance on getting this reviewed. Thanks!
Add functools.lru_cache plugin support
Add functools.lru_cache plugin support
Add functools.lru_cache plugin support
Add functools.lru_cache plugin support
cj81499 commentedon Jan 9, 2026
Originally posted #19291 (comment) before realizing it's a dupe of this issue.