Moving to rustc 1.85

[esteve]

We've been using 1.75 as the minium version for rustc that we support, as it's the version that Ubuntu 22.04 LTS ships with. We were hoping we could integrate parts of the ros2-rust project into the official ROS Humble distribution. We managed to get into ROS Lyrical, which will support Ubuntu 26.04 LTS and ships with Rustc 1.88.

Some of the ros2-rust subprojects have dependencies that are no longer compatible with rustc 1.75 and it's becoming tedious and less useful to mantain support for an older version of rustc.

I'm proposing we switch to 1.85, as it's the version of rustc that Debian stable (trixie) ships with as the minimum version we support.

We'll discuss this further in the next WG meeting (January 12th, 2026),

[esteve]

I've created the following PRs to update to 1.85 and Rust 2024:

• build!: require rustc 1.85 #566
• build!: require Rust 2024 edition rosidl_rust#13
• build!: require rustc 1.85 rosidl_runtime_rs#18
• Update rust version to 1.85.0 ros2/ros2#1785

[knmcguire]

I've also started a thread in the zulip channel about this to ask the ROS pmcs as well as well just to keep you in the loop.

https://openrobotics.zulipchat.com/#narrow/channel/526027-ROS-General/topic/rustc.20to.201.2E85.3F/with/567724473