Analyzer warning not very helpful when missing async on a method

[mit-mit]

The following code

foo() async => 42;
main() {
  print(await foo());
}

is missing the async keyword on the main method. However, the Analyzer warning is not very helpful, it just says Undefined name 'await'

It would be great if we could be more specific and point the user towards the easy resolution to this.

[srawlins]

Should this be wrapped into #24375?

[bwilkerson]

The error message has been improved and a quick fix added, so I'm going to close this.