weekly 2024-07-01

Language Update

• Enabled simplifying the type prefix for enum constructor: When there is no ambiguity, you can omit the type prefix for enum constructors. For example, you can now write Some(42) instead of Option::Some(42). If there are two types T1 and T2 that both define a constructor C, you need to specify T1::C or T2::C by the type or type prefix in the context while using, otherwise the compiler will throw an error.

• New UInt64 built-in type: Added a built-in UInt64 type that supports addition, subtraction, multiplication, division, modulus, and conversion between UInt64 and Int64.

fn main {
  let a = 0UL
  let b : UInt64 = 1UL
  println(a - b) //18446744073709551615
}

• Support for error handling with !! suffix: The semantics of the !! suffix have been modified to capture potential errors in function calls and return a Result type.

fn f() -> Int!String { .. }
fn main {
  let res = f()!! // res: Result[Int, String]
  println(res)
}

• moon test now supports using error types to represent test failures. For example:

fn eq[T : Debug + Eq](a : T, b : T, ~loc : SourceLoc = _) -> Unit!String {
  if a != b {
    let a = debug_string(a)
    let b = debug_string(b)
    raise ("FAILED: \(loc) `\(a) == \(b)`")
  }
}

test "test_eq" {
  eq(1+2, 3)!
}

• The standard library now retains only println for I/O operations. Other operations will be provided in the io package.

Core Update

• Unified the function style for creating container objects, like T::new()/T::make(), and removed T::with_capacity.

• Renamed iter and iteri to each and eachi, and iter_rev and iter_revi to each_rev and eachi_rev.

• Renamed as_iter to iter.

Build System Update

• The build system will be open source this week.

Toolchain Update

• Support for out-of-box debugging for better tooling experience. Users can now run moon run --target js --debug in the JavaScript Debug Terminal for debugging.

• moon info and coverage tools now accommodate error types and error handling.