Unable to resolve method after LUB operator

interface I {
  int m(int x);
}

abstract class A implements I {
}

class B<T> extends A {
  public int m(int x) {
    return x + 1;
  }
}

public class C<T> extends A {
  public int m(int x) {
    return x - 1;
  }
}

class Test {
  void test() {
    C<String> x = null;
    int y = 1;
    ((true) ? x : new B<String>()).m(y);
  }
  
}

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
test.groovy: 26: [Static type checking] - Cannot find matching method A#m(int). Please check if the declared type is correct and if the method exists.
 @ line 26, column 5.
       ((true) ? x : new B<String>()).m(y);
       ^

1 error