library test /*isNonNullableByDefault*/;
import self as self;
import "dart:core" as core;

static method main() → dynamic {
  () → core::Iterable<Null> f = () → core::Iterable<Null> sync* {
    yield null;
  };
  core::Iterable<dynamic> y = f(){() → core::Iterable<Null>};
  core::Iterable<core::String?> z = f(){() → core::Iterable<Null>};
  core::String? s = f(){() → core::Iterable<Null>}.{core::Iterable::first}{Null};
}