// Unsound only in Java 8, Java 9+ already gives an error
// @skip-test no need to test for the javac error.

public class Figure4 {
  static class Constrain<A, B extends A> {}

  static <A, B extends A> A upcast(Constrain<A, B> constrain, B b) {
    return b;
  }

  static <T, U> U coerce(T t) {
    Constrain<U, ? super T> constrain = null;
    // :: error: method upcast in class Figure4 cannot be applied to given types;
    return upcast(constrain, t);
  }

  public static void main(String[] args) {
    String zero = coerce(0);
  }
}