code: public BooleanExpression eq(T right) {
          if (right == null) {
              throw new IllegalArgumentException("eq(null) is not allowed. Use isNull() instead");
          } else {
              return eq(ConstantImpl.create(right));
          }
      }
docs: Create a {@code this == right} expression
  
  <p>Use expr.isNull() instead of expr.eq(null)</p>
  
  @param right rhs of the comparison
  @return this == right