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Description
I feel confident that x should have type T2 in the else clause here. Instead, it has type T1 | T2 which doesn't seem at all consistent.
from typing import TypeVar
from typing_extensions import assert_type
T1 = TypeVar("T1")
T2 = TypeVar("T2")
def f(x: T1 | T2, type1: type[T1]) -> T1 | T2:
t1: T1
t2: T2
if isinstance(x, type1):
# mismatch(pyright): expected "T1@f" but received "object* | T1@f"
assert_type(x, T1)
t1 = x
assert_type(t1, T1)
return t1
else:
# mismatch(pyright): expected "T2@f" but received "object*"
# error(mypy): Expression is of type "T1 | T2", not "T2"
assert_type(x, T2)
# error(pyright): Type "object*" is not assignable to declared type "T2@f"
# error(mypy): Incompatible types in assignment (expression has type "T1 | T2", variable has type "T2")
t2 = x
assert_type(t2, T2)
return t2