Generators compiled with --target es5 --lib esnext do not support iterator helpers #59513

🔎 Search Terms

generator iterator helper map esnext prototype

🕗 Version & Regression Information

• This changed in commit or PR add types for iterator helpers proposal #58222

⏯ Playground Link

https://www.typescriptlang.org/play/?target=1&lib=lib.esnext.d.ts&ts=5.6.0-beta#code/PTAEAEBcEMCcHMCmkBcpEGcCsAoEEAbASwCM1MA7RAD0hxwGMB7CjSUOUAXlAG0BGADSgATMIDMwgCwBdANw44AOgBu0AgFdMACgCUSgLbQADtqLcAfKHMAqUbrmh8vMaCnCAbMIAcM+gDMNCgZIIhZQO389UABvHFBQAE8iRAIAEwi+IVEJaXkcAF8cKP0jU3MuK1t7R3xYINCDRHRYWCZYNAByKKVe0pNO6wxQCiZ2aFBA4NCWIA

💻 Code

// @target: es5
// @lib: esnext

const ar = [1, 2, 3, 4];
ar.values().map(i => i * 2); // [2, 4, 6, 8]

function * f() {
  yield * [1, 2, 3, 4];
}
f().map(i => i * 2); // error: 'f(...).map' is not a function

🙁 Actual behavior

The last line above throws even when Iterator.prototype is present, be it from the host or a polyfill.

🙂 Expected behavior

The last line above should not throw when the global Iterator.prototype is present and can be used as a prototype.

Additional information about the issue

No response