Ion Compiler

A source-to-source transpiler from Ion to C. Ion is transpiled to human-readable C, then compiled with a C compiler.

What is Ion?

Ion is a systems programming language with:

• Move-only ownership, no GC
• Stack-only, no-escape references (&T, &mut T)
• Channels-only concurrency with OS threads and structural Send checking
• C backend: Ion is transpiled to human-readable C, then compiled with a C compiler

Language Overview

Brief summary; see ION_SPEC.md for the full language reference.

• Ownership: move by default; single owner per value; use-after-move is a compile error
• Borrowing: &T and &mut T are stack-local; references cannot escape the function (no return, no struct fields, no channels, no spawn)
• Types: primitives, structs, enums (tuple and struct variants), generics, [T; N], []T, Box<T>, Vec<T>, String
• Control flow: if/while (bool conditions), for x in expr over Vec<T>, [T; N], or String (bytes as u8), match with guards, defer
• Concurrency: channel<T>() returns (Sender<T>, Receiver<T>); send(&tx, v) and recv(&mut rx); spawn { ... } with structural Send
• FFI: extern "C" blocks, raw pointers *T, calls require unsafe
• Stdlib: stdlib/io.ion and stdlib/fmt.ion for safe stdout output

Known limitations: ION_SPEC.md section 10.2.

Documentation

Resource	Contents
ION_SPEC.md	Language semantics, grammar, stdlib contracts
tests/README.md	Integration test catalog
examples/	Runnable example programs

Building

Prerequisites

• Rust toolchain (stable or nightly)
• A C compiler (GCC, Clang, or MSVC)

Build the Compiler

cargo build --release

The binary will be at target/release/ion-compiler (or target/release/ion-compiler.exe on Windows).

IDE Support

VS Code Extension

Ion has a VS Code / Cursor extension that provides:

• Syntax highlighting
• Real-time diagnostics (syntax and type errors)
• Hover: variable types at use sites; symbol docs at definitions
• Completion: keywords, builtins, and file symbols
• Go to definition: variables only (same file)

Limitations: no hover on let bindings; function calls do not go to definition; completion has no prefix filtering. Full list in ION_SPEC.md section 10.2.

Installation:

1. Build the LSP server:

   cargo build --release --bin ion-lsp

2. Install the extension from the ion-vscode directory:

   cd ion-vscode
   npm install
   npm run compile
   npx @vscode/vsce package --allow-missing-repository
   code --install-extension ion-language-0.1.0.vsix

   On Cursor, use cursor --install-extension ion-language-0.1.0.vsix instead of code.

3. Workspace settings (.vscode/settings.json) point ion.lspPath at target/release/ion-lsp.exe.

Usage

Quick Start

# Compile Ion to C
./target/release/ion-compiler examples/hello_world.ion

# Compile C to executable (from project root)
gcc examples/hello_world.c runtime/ion_runtime.c -o hello_world \
    -I. -I.. -Iruntime -I../runtime -lpthread

# Run
./hello_world

Source: examples/hello_world.ion. For stdlib-based I/O, see examples/hello_world_safe.ion.

Single-File Mode (Default)

Step 1: Compile Ion to C

./target/release/ion-compiler input.ion

This generates input.c in the same directory as the source file.

Step 2: Compile C to Executable

The generated C code requires the Ion runtime library:

gcc input.c runtime/ion_runtime.c -o input -I. -I.. -Iruntime -I../runtime -lpthread

Required flags:

• input.c - generated C file
• runtime/ion_runtime.c - Ion runtime (when running from project root)
• -I. -I.. -Iruntime -I../runtime - include paths for runtime headers
• -lpthread - pthread library (required for channels and spawn)
• -o input - output executable name

Step 3: Run

./input

FFI with POSIX Functions

If your Ion program uses FFI names that conflict with Ion keywords (recv, send), add -D flags when linking:

gcc http_server.c runtime/ion_runtime.c -o http_server \
    -I. -I.. -Iruntime -I../runtime -lpthread \
    -Drecv_sys=recv -Dsend_sys=send -Dclose=closesocket -lws2_32

On Linux or macOS, omit -lws2_32 and -Dclose=closesocket. ion_net_init() is a no-op outside Windows.

Multi-File Mode

./target/release/ion-compiler --mode multi --output myprogram main.ion

This parses imported modules, generates .c and .h per module, compiles object files, and links with the runtime. The --output flag sets the executable name (defaults to the main module name). Multi-file mode handles compilation and linking; you do not need to run gcc manually.

Example Programs

Compile and run any example with the same pattern as the quick start above. For http_server.ion, add -Drecv_sys=recv -Dsend_sys=send when linking.

File	What it demonstrates
examples/hello_world.ion	Minimal FFI write() to stdout
examples/hello_world_safe.ion	stdlib io module
examples/spawn_channel.ion	spawn with cross-thread channels
examples/http_server.ion	Sockets, FFI, concurrent clients via spawn
examples/showcase.ion	Mixed language features (includes spawn/channels)
examples/minimal.ion	Smallest valid program

Project Structure

.
├── src/
│   ├── lexer/      # Tokenizer
│   ├── parser/     # AST construction
│   ├── ast/        # AST node definitions
│   ├── compiler/   # Compilation driver (module resolution, cycle detection)
│   ├── tc/         # Type Checker (safety checks, visibility, qualified names)
│   ├── ir/         # Intermediate representation
│   └── cgen/       # C code generator
├── runtime/        # C runtime headers
├── examples/       # Example Ion programs
└── tests/          # Test programs

Development

Run Tests

Unit tests:

cargo test

Integration tests:

./tests/test_runner.sh

The runner compiles Ion programs and checks exit codes or compile errors. See tests/README.md for the test catalog.

Linting

cargo clippy

License

MIT