0.7.4

• motoko (moc)

  • Add new keywords async* and await* (note the *) for efficient abstraction of asynchronous code (#3609).

      <typ> ::= ...
        async* <typ>             delayed, asynchronous computation
      <exp> ::= ...
        async* <block-or-exp>    delay an asynchronous computation
        await* <block-or-exp>    execute a delayed computation (only in async, async*)
    

    This avoids the resource consumption and latency of async/await by only committing state and suspending execution
    when necessary in the await*-ed computation, not necessarily at the await* itself.

    WARNING: Unlike async/await:

    • an async* value has no effect unless await*-ed;
    • each await* of the same async* value repeats its effects.

    This feature is experimental and may evolve in future. Use with discretion.
    See the manual for details.

  • Suppress GC during IC canister_heartbeat, deferring any GC to the scheduled Motoko heartbeat system method (#3623).
    This is a temporary workaround, to be removed once DTS is supported for canister_heartbeat itself (#3622).

  • Add a new generational GC, enabled with new moc flag --generational-gc (#3495).
    The generational garbage collector optimizes for fast reclamation of short-lived objects.
    New objects are allocated in a young generation that is more frequently collected than the older objects
    that have already survived a GC run.

    For many cases, the generational GC is more efficient than the existing compacting GC and copying GCs:

    • Lower runtimes: Less number of executed instructions on average.
    • Shorter interruptions: Young generation collection entails shorter program interruptions.

    To activate the generational GC under dfx, the following command-line argument needs to be specified in dfx.json:

    ...
      "type" : "motoko"
      ...
      "args" : "--generational-gc"
    ...
    

  • moc.js : add trampoline and step limiter to interpreter, avoiding (some) stackoverflows and
    hangs (#3618, #3541).
    Enables execution of larger examples on web pages.

  • BREAKING CHANGE (Minor):

    Consider records with mutable fields as non-static (#3586).
    Consequently, an imported library declaring a mutable record is now
    rejected, not accepted, to be consistent with the declarations of
    mutable fields and mutable objects.

  • Experimental Viper integration by compiling a very narrow subset of
    Motoko to the verification intermediate language. See src/viper/README.md
    and the PR for details. (#3477).

• motoko-base

  • Unit tests for Trie and fix for disj (dfinity/motoko-base#438).

  • Respect Trie structure in filter (dfinity/motoko-base#431, dfinity/motoko-base#438).

  • Array module reimplementation, tests and documentation (dfinity/motoko-base#425,dfinity/motoko-base#432).