Rust 1.62: What's New, Release History & Support Lifecycle

What Is New in Rust 1.62

How can I add dependencies directly from the command line with Cargo?

In Rust 1.62 you can add new crates without editing Cargo.toml by using the new cargo add subcommand.

• Basic addition:

  cargo add log

• Specify features:

  cargo add serde --features derive

• Pin a version:

  cargo add nom@5

This matters if you want to prototype quickly or automate dependency updates in CI pipelines.

How do I derive Default for enums in Rust 1.62?

You can now annotate a unit variant with #[default] and keep the automatic #[derive(Default)] implementation.

#[derive(Default)]\nenum Maybe {\n    #[default]\n    Nothing,\n    Something(T),\n}

Only variants without fields are allowed to be the default, which simplifies boilerplate for many option-like enums.

What performance gains do the new Linux mutex implementations bring?

The standard library now uses a raw futex-based lock on Linux, shrinking the internal state of Mutex to just 5 bytes.

• No hidden heap allocation - the lock lives entirely on the stack.
• Reduced memory footprint improves cache locality for high-contention workloads.
• Future work may further shrink Condvar and RwLock similarly.

In practice this matters for low-level services, embedded daemons, or any code that creates many synchronization primitives.

How do I target bare-metal x86_64 with the new Tier-2 support?

Rust 1.62 promotes the x86_64-unknown-none target to Tier 2, making it easy to build OS-less binaries.

rustup target add x86_64-unknown-none\nrustc --target x86_64-unknown-none my_no_std_program.rs

This matters if you are writing kernels, bootloaders, or other no_std environments; the target is now officially supported and receives regular updates.