-
Notifications
You must be signed in to change notification settings - Fork 13.6k
Closed
Labels
A-concurrencyArea: ConcurrencyArea: ConcurrencyC-enhancementCategory: An issue proposing an enhancement or a PR with one.Category: An issue proposing an enhancement or a PR with one.E-help-wantedCall for participation: Help is requested to fix this issue.Call for participation: Help is requested to fix this issue.T-libs-apiRelevant to the library API team, which will review and decide on the PR/issue.Relevant to the library API team, which will review and decide on the PR/issue.
Description
Currently RwLockReadGuard
is invariant over its type parameter, meaning that for instance this sound code:
use std::sync::{RwLock, RwLockReadGuard};
fn do_stuff<'a>(_: RwLockReadGuard<'_, &'a i32>, _: &'a i32) {}
fn main() {
let j: i32 = 5;
let lock = RwLock::new(&j);
{
let i = 6;
do_stuff(lock.read().unwrap(), &i);
}
drop(lock);
}
Will not compile. However, since RwLockReadGuard
does not allow for mutation of the inner value, it would be sound to make it covariant, and it would be useful in some circumstances.
See also the same issue in parking_lot.
jyn514, nvzqz and AaronKutch
Metadata
Metadata
Assignees
Labels
A-concurrencyArea: ConcurrencyArea: ConcurrencyC-enhancementCategory: An issue proposing an enhancement or a PR with one.Category: An issue proposing an enhancement or a PR with one.E-help-wantedCall for participation: Help is requested to fix this issue.Call for participation: Help is requested to fix this issue.T-libs-apiRelevant to the library API team, which will review and decide on the PR/issue.Relevant to the library API team, which will review and decide on the PR/issue.