Rusty-JavaC

[!WARNING] This project is still under heavy development. It is not intended to replace the official Java compiler yet.

Rusty-JavaC is a Java compiler written in Rust. It parses Java source, lowers it into an internal representation, resolves types and calls, and writes JVM .class files.

Why

The official Java compiler is written in Java. Rusty-JavaC explores a Rust implementation with:

• explicit ownership and error handling inside the compiler
• Cargo-based distribution for Rust tooling
• a reusable library API for Java analysis and bytecode-producing tools
• room for experiments around diagnostics, incremental compilation, and classpath analysis

Pipeline

The compiler is one Cargo package with stages split into modules under src/:

Java source
  -> lexer
  -> parser
  -> ast
  -> hir lowering
  -> type and call resolution
  -> bytecode generation
  -> JVM .class file

Use It

As a library:

cargo add rusty-javac

Or in Cargo.toml:

rusty-javac = "VERSION"

As the example compiler:

cargo run --example compiler-example -- --output-dir target/classes tests/java/HelloWorld.java

Build

Requirements:

• Rust 1.85+
• Java 21+ for fixture comparison, javap, and JVM verification

git clone https://github.com/Eatgrapes/Rusty-JavaC.git
cd Rusty-JavaC
cargo build --locked
cargo test --locked

Status

The compiler already handles a growing subset of Java syntax, bytecode generation, classpath/source lookup, package output, lambda lowering, anonymous classes, and platform class signatures.

Large parts of Java are still incomplete. See TODO.md for the current backlog.

Contributing

Read CONTRIBUTING.md before opening a PR. Good contributions usually include a focused Java fixture, verifier coverage when applicable, and a commit message following Conventional Commits.

License

MIT