Generators

Generator support exists where lowering is explicit and deterministic.

Rule

If a generator shape can be lowered to the current runtime model, it is supported. If not, it is rejected rather than emulated loosely.

What that means in practice

Generators are best treated as a supported subset feature:

• typed yield values are fine when the compiler can model the iterator shape
• ordinary for...of consumption is the expected usage pattern
• exotic coroutine tricks or open-ended dynamic generator manipulation are not the design target

Example:

export function* range(limit: number): Generator<number, void, void> {
  for (let i = 0; i < limit; i++) {
    yield i;
  }
}

Why this matters

The same rule that applies to async and callbacks applies here: deterministic lowering beats permissive but fragile behavior.

Practical expectation

Treat generators as a supported subset feature, not as a promise of all TypeScript generator patterns.