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weekly 2024-07-01

· 2 min read

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]
  • 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.