Bug Report

🔎 Search Terms

for await return next throw

🕗 Version & Regression Information

• This is the behavior in every version I tried

⏯ Playground Link

Playground link with relevant code

💻 Code

let pass = true

async function f() {
  const y = {
    [Symbol.asyncIterator]() {
      let count = 0
      return {
        async next() {
          count++
          if (count === 2) throw 'error'
          return { value: count }
        },
        async return() {
          pass = false
        },
      }
    },
  }
  for await (let x of y) {
  }
}

f().catch(() => console.log({ pass }))

🙁 Actual behavior

The code prints { pass: false } when transformed by TypeScript with target ES2017 or lower.

🙂 Expected behavior

The code prints { pass: true } when run natively and when transformed by Babel. I discovered this behavior difference when investigating doing a similar transform for esbuild.