weekly 2024-06-03

Language Update

• A new syntax T? has been added for type annotations to represent Option[T].

struct Cell[T] {
  val: T
  next: Cell[T]?
}

fn f(x : Cell[T]?) -> Unit { ... }

This is equivalent to

struct Cell[T] {
  val: T
  next: Option[Cell[T]]
}

fn f(x : Option[Cell[T]]) -> Unit { ... }

The old Option[T] is still compatible, but it is recommended to use the shorter new syntax. moonfmt will also format Option[T] as T?.

• The core library API restructuring continues
  • The Iter package has been merged into the builtin package. Now Iter[T] can be used without the @iter. prefix.

pub fn any[T](xs : Iter[T], predicate : (T) -> Bool) -> Bool {
                // ^no @iter. is required
  match xs.find_first(predicate) {
    None => false
    Some(_) => true
  }
}

• The Stack package has been moved to moonbitlang/x

• The List package has been removed, along with the to_list and from_list functions for various data structures. It is recommended to use Iter[T] and Array[T] for data structure conversion and intermediate representation.

• Performance improvements

  • The compiler will now perform partial closure conversion during the separate compilation phase, improving compilation performance. Closure conversion has also been applied to code generated for the JavaScript backend in specific situations.
  • The types Option[Bool], Option[Char], Option[Byte], and Option[Unit] are now represented using 32-bit integers, where None is represented by -1 and Some(x) by x. The type Option[Int] is represented by a 64-bit integer in the wasm backend, where None is represented by 0x1_0000_0000, and Some(x) by x. In the JavaScript backend, Option[Int] is represented as int | undefined , where undefined represents None.

• abort behavior change

  • To remove the dependency of Wasm programs on the non-standard spectest.print_char, the error output functionality is being restructured.
  • abort will no longer use spectest.print_char to print error messages. Its behavior will be the same as panic until the functionality is further improved.

  Plugin Update

• [Language Server] Fixed a memory leak issue.