Type checking for higher order function with variadic generics fails without variable assignment #5113
Description
Describe the bug
Given the functions:
from __future__ import annotations
from collections.abc import Callable
from typing import TypeVar, TypeVarTuple
X = TypeVar("X")
Y = TypeVar("Y")
Xs = TypeVarTuple("Xs")
Ys = TypeVarTuple("Ys")
def nil() -> tuple[()]:
return ()
def cons(
f: Callable[[X], Y],
g: Callable[[*Xs], tuple[*Ys]],
) -> Callable[[X, *Xs], tuple[Y, *Ys]]:
def wrapped(x: X, *xs: *Xs) -> tuple[Y, *Ys]:
y, ys = f(x), g(*xs)
return y, *ys
return wrapped
def star(f: Callable[[X], Y]) -> Callable[[*tuple[X, ...]], tuple[Y, ...]]:
def wrapped(*xs: X):
if not xs:
return nil()
return cons(f, star(f))(*xs)
return wrappedI get an error
test.py:31:29 - error: Argument of type "(X@star) -> Y@star" cannot be assigned to parameter "f" of type "(X@star) -> Y@star" in function "star"
Type "(X@star) -> Y@star" cannot be assigned to type "(X@star) -> Union[*Ys@cons]"
Function return type "Y@star" is incompatible with type "Union[*Ys@cons]"
Type "Y@star" cannot be assigned to type "Union[*Ys@cons]" (reportGeneralTypeIssues)
1 error, 0 warnings, 0 informations
However, if I use the walrus trick to store the temporary variable, the issue is not present.
def star(f: Callable[[X], Y]) -> Callable[[*tuple[X, ...]], tuple[Y, ...]]:
def wrapped(*xs: X):
if not xs:
return nil()
return cons(f, _ := star(f))(*xs)
return wrappedThe issue is also not present in pyright 1.1.305, and appears after update.
VS Code extension or command-line
I'm using pyright 1.1.308
Additional context