I was testing to see if the next() in an async iterator worked how I suspected, where throws are really Promise.reject() which throws at the for await point.

async_iterators_throw_catch_test.ts

import { assertEquals } from 'https://deno.land/[email protected]/testing/asserts.ts'

Deno.test('async iterator throw in next should throw in for scope', async () => {
  const results: number[] = []

  const numbers = (() => {
    let counter = 0

    const iterator: AsyncIterator<number> = {
      // deno-lint-ignore require-await
      async next() {
        counter += 1

        if (counter <= 5) {
          return { done: false, value: counter }
        } else {
          throw 'above 5'
        }
      }
    }

    return { [Symbol.asyncIterator]() { return iterator } }
  })()

  try {
    for await (const num of numbers) {
      results.push(num)
    }
  } catch (e) {
    assertEquals(e, 'above 5')
  }

  assertEquals(results, [1,2,3,4,5])
})