astral-sh/ruff
non-pep695-generic-function (UP047) weirdness
Aberta
#19.155 aberto em 5 de jul. de 2025
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Description
Summary
Proposed fix seems to break the typing, as it would remoev the existing type boundaries of a TypeVar:
import sys
from typing import TypeVar
class Class1:
param = 1
class Class2:
param = 2
type AnyofTwo = Class1 | Class2
SameClassT = TypeVar("SameClassT", Class1, Class2)
def print_foo(arg: AnyofTwo) -> None:
sys.stderr.write(f"{arg.param}\n")
def universal_func_1(arg: SameClassT) -> SameClassT: # RUFF /* W: Generic function `universal_func_1` should use type parameters
print_foo(arg)
return arg
def universal_func_2[T](arg: T) -> T:
"""
This is how `ruff check --fix` would modify `universal_func_1()`.
"""
print_foo(arg) # MYPY /* E: Argument 1 to "print_foo" has incompatible type "T"; expected "Class1 | Class2" [arg-type]
return arg
$ ruff check test_pyrefly_01.py
test_pyrefly_01.py:21:5: UP047 [*] Generic function `universal_func_1` should use type parameters
|
21 | def universal_func_1(arg: SameClassT) -> SameClassT:
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ UP047
22 | print_foo(arg)
23 | return arg
|
= help: Use type parameters
Found 1 error.
[*] 1 fixable with the --fix option.
Version
ruff 0.12.1