Rue

Rue is an experimental systems programming language exploring memory safety without garbage collection and higher-level ergonomics than Rust or Zig. It is implemented in Rust and emits native code directly, without LLVM.

fn fib(n: i32) -> i32 {
    if n <= 1 { n } else { fib(n - 1) + fib(n - 2) }
}

fn main() -> i32 {
    @dbg(fib(10));
    0
}

[!CAUTION] Rue is an early-stage language. Its syntax, semantics, runtime, and standard library are still changing, and it is not ready for production use.

What is here

The repository contains a complete native compiler pipeline, including:

• lexer, parser, semantic analysis, and several inspectable IRs;
• affine ownership, borrowing modes, destructors, structs, enums, arrays, strings, modules, comptime, and unsafe/raw-pointer support;
• x86-64 Linux, AArch64 Linux, and AArch64 macOS code generation;
• a small runtime, ELF/Mach-O object and linking support, and direct machine-code emitters;
• specification, UI, CLI, differential-oracle, fuzz, sanitizer, and stress suites.

The authoritative language definition is the Rue specification. The tutorial is the best introduction to writing Rue programs. Architecture and design rationale live in docs/architecture.md and docs/designs/.

Build and try Rue

Rue uses Buck2 rather than Cargo. Install Dotslash; Buck2 and the Rust toolchain are then bootstrapped hermetically by the repository.

scripts/rue build
scripts/rue exec examples/welcome.rue   # prints 1, 2, 3, 42 and exits 0
scripts/rue test

examples/welcome.rue is the setup health check: it prints recognizable output and exits 0, so a successful run is not mistaken for a failure under set -e or CI. (Programs like examples/fibonacci.rue return a value from main, which becomes the process exit code — informative, but a nonzero status.)

Use scripts/rue-bin when you need the compiler path, or run the real CLI through the wrapper:

RUE="$(scripts/rue-bin)"
"$RUE" --help
"$RUE" examples/welcome.rue -o welcome
./welcome

Supported targets are x86-64-linux, aarch64-linux, and aarch64-macos. Cross-target machine-code and assembly emission is available, but producing an executable may require target-specific system tools.

See CONTRIBUTING.md and docs/development.md for the development workflow.

Project status

Rue is developed in public as both a language-design project and an experiment in agent-assisted compiler engineering. Accepted features may remain behind --preview until their implementation and specification are complete. The test suite tracks normative specification coverage and known implementation gaps explicitly.

License

Rue is dual-licensed under the Apache License 2.0 or MIT license, at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in Rue is dual-licensed on the same terms.