Tracking Issue for `rwlock_try_upgrade`

Feature gate: #![feature(rwlock_try_upgrade)]

This is a tracking issue RwLock::try_upgrade, which turns a read guard into a write guard if it is the only lock accessor.

Public API

// src/sync/rwlock.rs
impl<'a, T: ?Sized> RwLockReadGuard<'a, T> {
    pub fn try_upgrade(orig: Self) -> Result<RwLockWriteGuard<'a, T>, RwLockReadGuard<'a, T>>;
}

Steps / History

(Remember to update the S-tracking-* label when checking boxes.)

• ACP: https://github.com/rust-lang/libs-team/issues/514
• Partial implementation https://github.com/rust-lang/rust/pull/138560
• Clippy lint to avoid calling try_upgrade in a loop (not blocking)
• Miri tie-in (not blocking)
• Implementation: #...
• Final comment period (FCP)^1
• Stabilization PR

Unresolved Questions

• None yet.

Start with src/sync/rwlock.rs and review the ACP and partial implementation linked in the tracking issue. Follow the remaining checklist items, including the Clippy and Miri work, FCP, and stabilization PR; the issue is complete when the feature has passed the stated stabilization process.