Lyric

What changed in v2.2.0 — 2026-08-20

The A8 wave: both coroutine edges Erato's register filed after building its cutscene driver, plus one the fix uncovered. The bytecode format stays 3.2; a module that never calls next() loads on every 2.x runtime. Four conformance cases activate with this release (//! since: 2.2.0); the suite stands at 85.

Added

• co.next() — the safe pull. It advances a coroutine exactly like resume and answers ?T: the value, or null once the body has run to its end — and null stays the answer on every further call, where resume keeps its promised panic. A Coroutine<void> answers bool (did it advance?), so while (p.next()) { } drives it out; a Coroutine<?T> refuses the form (LYR-SEM0080) because null would mean two things there — drive it with resume and a protocol of your own. The name and shape are Iterator<T>.next()'s on purpose.

  A query that does NOT pull (isDone) was probed and rejected: a pull-based coroutine cannot know whether another value comes without running the body, which is why no generator API in Python, JavaScript or C# has one. The pull with an end signal is the honest form.

  On the wire, exhaustion is read back through the compiler-bound native std.core.coroutineIsDone; an older runtime rejects a module that uses next() at load time with that name in the message — the format's designed forward path.

Fixed

• Coroutine<T> works as a field type. A class or struct field, and a type argument (List<Coroutine<T>>), used to be refused with LYR-IR0001 ("type 'Coroutine' (not a class)") while the same type worked as a parameter and a local. A driver now holds its coroutines directly instead of hiding each behind a captured closure.
• A bare return; in the middle of a coroutine body works. It compiled to a valueless return from a value-yielding body — an internal compiler error in Debug, malformed bytecode in Release, and the coroutine was never marked exhausted. It is now exactly the run-through exit: the next resume panics, the next next() answers null. (return; in tail position, the common form, was always fine.)

The full changelog →