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

import "dart:async";

static method foo<X extends core::Object?>(self::foo::X% x) → asy::Future<core::int> async /* futureValueType= core::int */ {
  if(x is{ForNonNullableByDefault} asy::Future<core::int>) {
    return x{self::foo::X% & asy::Future<core::int> /* '%' & '!' = '!' */};
  }
  else {
    throw 42;
  }
}
static method main() → dynamic {}