Hylo (formerly Val)

Hylo is a programming language that leverages mutable value semantics and generic programming for high-level systems programming.

This repository contains the sources of the reference implementation of Hylo. Please visit our website to get more information about the language itself.

Development/Use Requirements

This project is written in Swift and distributed in the form of a package, built with either Swift Package Manager or CMake. You will need Swift 6.1 or higher to build the compiler from sources. This repository contains submodules, so after cloning, issue git submodule update --init to populate them.

Windows users: this repository contains symbolic links, so you'll need to enable support for them before checking it out.

LLVM

This package requires LLVM 20. Major versions of LLVM are not interchangeable or backward-compatible.

If you are using this package for development, we strongly recommend the use of an LLVM with assertions enabled; otherwise it's too easy to violate LLVM's preconditions without knowing it. You can download such a prebuilt LLVM package from Hylo's LLVM builds. If you are using development containers, this is already installed preinstalled on the system. Run llvm-config --prefix to see where.

On Windows, set the environment variable VSINSTALLDIR to your visual studio installation path, e.g. C:/Program Files/Microsoft Visual Studio/2022/Community, without / at the end, so LLVM's CMake files can locate the DIA SDK.

Building with CMake and Ninja

1. Configure: choose a build-directory and a CMake build type (usually Debug or Release). <LLVM> is the path to the root directory of your LLVM installation.

   cmake 
     -D LLVM_DIR=<LLVM>/lib/cmake/llvm  \
     -D CMAKE_BUILD_TYPE=<build-type>   \
     -D BUILD_TESTING=1                 \
     -G Ninja -S . -B .build
   

   MacOS-specific flags

   • If you are not using the default Swift toolchain, you may need -D CMAKE_Swift_COMPILER=swiftc to prevent CMake from using Xcode's default swift.
   • Add -D CMAKE_OSX_SYSROOT=$(xcrun --show-sdk-path)

2. Build:

   cmake --build .build
   

3. Test (requires -D BUILD_TESTING=1 in step 1):

   ctest --parallel --test-dir .build
   

Building with CMake and Xcode

You will need CMake 3.30 or newer.

1. Generate Xcode project: choose a build-directory and then, where <LLVM> is the path to the root directory of your LLVM installation,

   cmake 
     -D LLVM_DIR=<LLVM>/lib/cmake/llvm \
     -D BUILD_TESTING=1                \
     -G Xcode -S . -B .build
   

2. Profit: open the .xcodeproj file in the build-directory and use Xcode's UI to build and test.

Building with Swift Package Manager

You can skip the following steps if you are using development containers.

1. Install pkg-config.

• Ubuntu: sudo apt install pkg-config
• Windows: choco install pkgconfiglite (Chocolatey) or install it manually
• MacOS: sudo port install pkgconfig (Mac Ports)

2. Add your LLVM installation's pkgconfig subfolder to PKG_CONFIG_PATH.

Now you should be able to build and test:

swift build -c release
swift test -c release

That command will create an executable named hc in .build/release. That's Hylo's compiler!

To test your compiler,

swift test -c release --parallel

Notes to macOS users:

1. Add platforms: [.macOS("xxx")] to Package.swift where xxx is your macOS version to address the warning complaining that an "object file was built for newer macOS version than being linked".

Building a Hylo Devcontainer with VSCode

While Hylo supports Linux natively, it also provides a Devcontainer specification to develop for Linux on other platforms through a Docker container. Our Linux CI uses this specification; this makes it possible to run Linux CI locally on other operating systems like macOS. While this specification should work for any IDE that supports devcontainers, keep in mind this team only uses VSCode.

When opening the Hylo project in VSCode for the first time, you should be prompted to install the extension recommendations in .vscode/extensions.json. If you are not prompted, manually install the extensions by searching for the extension identifiers in the Extensions Marketplace.

Then, build the Devcontainer with the VSCode command: > Dev Containers: Rebuild and Reopen in Container.

Finally, open a new integrated terminal in VSCode and confirm that the shell user is vscode. You can run whoami to check this.

That integrated terminal is connected to the Devcontainer, as if by ssh.
You can now follow the instructions for Building and testing [with CMake and Ninja](#building_with_ cmake_and_ninja) or with Swift Package Manager. All prerequisites, including the llvm.pc file in the default PKG_CONFIG_PATH, are preinstalled.

The Hylo repository files are mounted into the container, so any changes made locally (in VSCode or in other editors) will be automatically propagated into the Devcontainer. However, if you need to modify any of the files in the .devcontainer directory, you will need to rebuild the container with > Dev Containers: Rebuild and Reopen in Container.

Submitting issues

For submitting issue reports you need to manually update the Hylo version. Without this step, hc --version returns unknown.

./Tools/set-hc-version.sh

Implementation status

This project is under active development; expect things to break and APIs to change.

The compiler pipeline is organized as below. You can select how deep the compiler should go through the pipeline with the following options:

• --emit raw-ast: Only parse the input files and output an untyped AST as a JSON file.
• --typecheck: Run the type checker on the input.
• --emit raw-ir: Lower the typed AST into Hylo IR and output the result in a file.
• --emit ir: Run mandatory IR passes and output the result in a file.
• --emit llvm: Transpile the program to LLVM and output LLVM IR.
• --emit intel-asm: Output Intel assembly for all user module(s).
• --emit binary (default): Produce an executable.

For example, hc --emit raw-ast -o main.json main.hylo will parse main.hylo, write the untyped AST in main.json, and exit the pipeline.

A more detailed description of the current implementation status is available on our roadmap page.

Contributing

We welcome contributions to Hylo. Please read through CONTRIBUTING.md for details on how to get started.

You can also get in touch with the community by joining our Slack or one of our Zoom Meetings (ID: 664 8960 1602, Passcode: 853241) on Tuesdays and Thursdays, 13:00-13:30 Pacific time or 22:00-22:30 Central European time.

License

Hylo is distributed under the terms of the Apache-2.0 license. See LICENSE for details.