let reader;
const iterable = {
  async next() {
    return await reader.read();
  },
  [Symbol.asyncIterator]: () => iterable
};
const rs = ReadableStream.from(iterable);
reader = rs.getReader();
await reader.read(); // stalls forever

let reader;
const iterable = {
  async next() {
    reader.read(); // calls next() again, which calls read() again, repeating forever
    return { value: 'a', done: false };
  },
  [Symbol.asyncIterator]: () => iterable
};
const rs = ReadableStream.from(iterable);
reader = rs.getReader();
await reader.read(); // blows up the microtask queue

let nextCalls = 0;
let reader;
const iterable = {
  async next() {
    nextCalls += 1;
    if (nextCalls === 1) {
      reader.read();
    }
    return { value: 'a', done: false };
  },
  [Symbol.asyncIterator]: () => iterable
};
const rs = ReadableStream.from(iterable);
reader = rs.getReader();
await reader.read(); // calls next() twice
await reader.read(); // calls next() once