message: Iterator.forEach tweak
diff: @@ -107,11 +107,11 @@ namespace Iterator {
  export function map<T, R>(base: Iterator<T>, f: (v: T) => R): Iterator<R> { return new MapIteratorImpl(base, f); }
  export function filter<T>(base: Iterator<T>, p: (v: T) => boolean): Iterator<T> { return new FilterIteratorImpl(base, p); }
  - // f can return non-undefined falsy value to stop the iteration.
  - export function forEach<T, Ctx>(it: Iterator<T>, f: (v: T, ctx: Ctx) => boolean | void, ctx: Ctx): Ctx {
  + // Iterate until first truthy value is returned.
  + export function forEach<T, Ctx>(it: Iterator<T>, f: (v: T, ctx: Ctx) => any, ctx: Ctx): Ctx {
  while (it.hasNext) {
  const c = f(it.move(), ctx);
  - if (typeof c !== 'undefined' && !c) return ctx;
  + if (c) return ctx;
  }
  return ctx;
  }
  