Upgrade Rust nightly toolchain to 2025-12-15 #2001
Description
Summary
Upgrade the Rust nightly toolchain from nightly-2025-05-09 to nightly-2025-12-15 to incorporate the latest compiler improvements and bug fixes.
Motivation
- Keep Rust toolchain up-to-date with recent improvements
- Benefit from compiler optimizations and bug fixes in the past 220 days
- Maintain compatibility with the latest Rust ecosystem dependencies
Changes
- Update
rust-toolchain.toml:nightly-2025-05-09→nightly-2025-12-15 - No breaking changes to existing code expected