public static UAssign create(UExpression variable, UExpression expression) {
    return new AutoValue_UAssign(variable, expression);
  }
@Test
  public void equality() {
    new EqualsTester()
        .addEqualityGroup(UAssign.create(UFreeIdent.create("foo"), ULiteral.intLit(5)))
        .addEqualityGroup(UAssign.create(UFreeIdent.create("bar"), ULiteral.intLit(5)))
        .addEqualityGroup(UAssign.create(UFreeIdent.create("foo"), ULiteral.intLit(20)))
        .testEquals();
  }