2.1.59 [ECMA-262/9:2018] Section 25.5 AsyncGenerator Objects
V0217: AsyncGenerator objects are not supported
The specification states:
25.5 AsyncGenerator Objects An AsyncGenerator object is an instance of an async generator function and conforms to both the AsyncIterator and AsyncIterable interfaces. AsyncGenerator instances directly inherit properties from the object that is the value of the prototype property of the AsyncGenerator function that created the instance. AsyncGenerator instances indirectly inherit properties from the AsyncGenerator Prototype intrinsic, %AsyncGeneratorPrototype%.
AsyncGenerator objects are not supported.