T-Ruby

T-Ruby

TypeScript-style types for Ruby

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What is T-Ruby?

T-Ruby is a typed layer for Ruby, inspired by TypeScript. It ships as a single executable called trc.

Write .trb files with type annotations, compile to standard .rb files. Types are erased at compile time — your Ruby code runs everywhere Ruby runs.

trc hello.trb                  # Compile to Ruby

The trc compiler also generates .rbs signature files for tools like Steep and Ruby LSP. Gradually adopt types in existing Ruby projects with zero runtime overhead.

trc --watch src/               # Watch mode
trc --emit-rbs src/            # Generate .rbs files
trc --check src/               # Type check without compiling

Why T-Ruby?

We are friends of Ruby — Rubyists who still use and love Ruby.

We know Ruby has duck typing and dynamic types in its DNA. But we couldn't ignore that static type systems are becoming essential in real-world production environments.

The Ruby ecosystem has debated this for years, yet hasn't quite found its answer.

Existing Approaches

1) Sorbet

  • Types are written like comments above your code.
  • It feels like writing JSDoc and hoping the IDE catches errors.
# Sorbet
extend T::Sig

sig { params(name: String).returns(String) }
def greet(name)
  "Hello, #{name}!"
end

2) RBS

  • Ruby's official approach, where .rbs files are separate type definition files like TypeScript's .d.ts.
  • But in Ruby, you have to write them manually or rely on "implicit inference + manual fixes" — still cumbersome.
# greet.rbs (separate file)
def greet: (String name) -> String

# greet.rb (no type info)
def greet(name)
  "Hello, #{name}!"
end

T-Ruby

  • Like TypeScript, types live inside your code.
  • Write .trb, and trc generates both .rb and .rbs.
# greet.trb
def greet(name: String): String
  "Hello, #{name}!"
end

trc greet.trb
# => build/greet.rb
#  + build/greet.rbs

Others...

There are new languages like Crystal, but strictly speaking, it's a different language from Ruby.

We still love Ruby, and we want this to be progress within the Ruby ecosystem, not an escape from it.

Install

# with RubyGems (recommended)
gem install t-ruby

# from source
git clone https://github.com/pyhyun/t-ruby
cd t-ruby && bundle install

Verify installation

trc --version

Quick start

1. Write .trb

# hello.trb
def greet(name: String): String
  "Hello, #{name}!"
end

puts greet("world")

2. Compile

trc hello.trb

3. Run

ruby build/hello.rb
# => Hello, world!

Features

  • Type annotations — Parameter and return types, erased at compile time
  • Union types — String | Integer | nil
  • Generics — Array<User>, Hash<String, Integer>
  • Interfaces — Define contracts between objects
  • Type aliases — type UserID = Integer
  • RBS generation — Works with Steep, Ruby LSP, Sorbet
  • IDE support — VS Code, Neovim with LSP
  • Watch mode — Recompile on file changes

Getting Started

Guides

Status

Experimental — T-Ruby is under active development. APIs may change. Not recommended for production use yet.

Milestone Status
Type Parsing & Erasure ✅
Core Type System ✅
LSP & IDE Support ✅
Advanced Features ✅

See ROADMAP.md for details.

Contributing

Contributions are welcome! Please feel free to submit issues and pull requests.

License

MIT