v0.10.0

Released 2026-01-14.

We are happy to announce version 0.10.0 of Roto, the statically-typed, compiled, embedded scripting language! This release is packed with new features such as lists, for loops, type parameters and variant types.

Meta

• We now have a CONTRIBUTING.md, TESTING.md and SECURITY.md. (#333)

Language

Breaking changes

• Changed the type keyword to record. (#297)

# Roto 0.9.0
type Vec2 {
    x: f32,
    y: f32,
}

# Roto 0.10.0
record Vec2 {
    x: f32,
    y: f32,
}

• The LOCALHOSTV4 and LOCALHOSTV6 constants are not longer global but live
  under IpAddr as associated constants. (#292)

Added

• Lists are now supported! See the documentation for more information. (#301)

let x: List[i32] = [1, 2, 3];
let y = [4, 5, 6];
let z = x + y;

• Roto now has variant types. These are much like enum types in Rust. (#293)

variant Either[L, R] {
    Left(L),
    Right(R),
}

• Record types can now have type parameters. (#298)

record Pair[A, B] {
    a: A,
    b: B,
}

• In addition to while loops, there are now for loops to iterate over lists. (#346)

let total = 0;
for x in [1, 2, 3, 4] {
    total = total + x;
}

• The StringBuf type was added to allow building strings character by
  character more efficiently. (#300)

let buf = StringBuf.new();
buf.push_char('H');
buf.push_string("ello, World");
buf.push_char('!');
let s: String = buf.as_string();

• The char type was added, representing a single Unicode code point. (#300)

let a: char = 'a';

• The repository now contains a basic Sublime Text grammar. This can be used
  for syntax highlighting in Sublime Text, VS Code, Typst and other
  applications. (#291)

• If you use common keywords from other languages, Roto will now hint about what
  the appropriate Roto keyword is. (#322)

• If you try to use // or -- for comments, Roto will hint that you should
  use #. (#322)

Bug fixes

• Error messages with non-ASCII characters now display correctly. Thanks @LevitatingBusinessMan! (#325)
• Type errors are now slightly more informative by printing the id's associated
  with type variables, instead of printing just an _. (#308)

Crate

Breaking changes

• The MSRV is now 1.85. (#288)
• The context of a Runtime is now a type parameter of the Runtime type. (#274)
• The Reflect trait has been renamed to Value. (#304)
• Runtime and Package now have a type parameter C, which can be either NoCtx or
  Ctx<T>, representing whether it has a context type. (#274)
• The method Runtime::register_context_type has been replaced with
  Runtime::with_context_type with slightly different behaviour. Instead of
  taking a mutable reference to the runtime, it takes it by value and returns
  it. (#274)

// Roto 0.9.0
let mut rt = Runtime::new();
rt.register_context_type::<MyContext>();

// Roto 0.10.0
let rt = Runtime::new().with_context_type::<MyContext>();

• Package::get_function no longer has a type parameter for the context type. (#274)

// Roto 0.9.0
let f = pkg.get_function::<MyContext, fn(i32) -> i32>();

// Roto 0.10.0
let f = pkg.get_function::<fn(i32) -> i32>();

• Calling a TypedFunc without a context no longer requires the annoying first
  argument &mut (). (#274)

// Roto 0.9.0
let f = pkg.get_function::<(), fn(i32) -> i32>();
f.call(&mut (), 5)

// Roto 0.10.0
let f = pkg.get_function::<fn(i32) -> i32>();
f.call(5)

• Similarly, the Package::run_tests method no longer takes an argument if there is no context argument.

// Roto 0.9.0
pkg.run_tests(());

// Roto 0.10.0
pkg.run_tests();

Added

• It's now possible to register associated constants. (#292)

let lib = library! {
    type MyType = Val<MyType>;
    impl Val<MyType> {
        /// Associated constant FOO!
        const FOO: usize = 0;
    }
}

• The RotoFunc trait is now exposed. (#299)
• The selinux-fix feature flag is added to allow running Roto under SE Linux
  systems. This might become the default behaviour in the future. Thanks
  @LevitatingBusinessMan! (#279)

Bug fixes

• Fixed a bug which prevented registering types in a module. (#315)
• The library! macro will emit more precise errors when it fails to parse. (#306)
• The library! macro will be more precise in reporting the actual problems
  when trait resolution fails on the generated code. (#318)
• Tests are now sorted before being run. (#319)
• We removed some unused dependencies from our dependency tree, though this only
  concerned dev-dependencies. (#337)

Documentation

• Documentation was extended and improved a lot in many PRs.