0.8.3

• motoko (moc)

  • new 'let-else' construct for handling pattern-match failure (#3836).
    This is a frequently asked-for feature that allows to change the control-flow
    of programs when pattern-match failure occurs, thus providing a means against
    the famous "pyramid of doom" issue. A common example is look-ups:

    shared func getUser(user : Text) : async Id {
      let ?id = Map.get(users, user) else { throw Error.reject("no such user") };
      id
    }

    Similarly, an expression like

    (label v : Bool { let <pat> = <exp> else break v false; true })

    evaluates to a Bool, signifying whether <pat> matches <exp>.

  • Improve recursive deserialization capacity to match recursive serialization capacity by reducing
    Wasm stack consumption (#3809).
    Because of the bounds on recursion depth imposed by fixed-size stack, the
    advice remains the same: avoid deeply nested recursive data structures.
    Think "shallow trees good, very long lists bad".

  • bugfix: stack overflow in UTF-8 encode/decode for moc.js (#3825).

• motoko-base

  • add missing unshare : Tree<K, V> -> () method to class RBTree<K, V>
    to restore objects from saved state (dfinity/motoko-base#532).