E4065

Overloaded operator should accept the correct number of arguments.

You can refer to the Operator Overloading section for a list of operators that can be overloaded, and here is a list of number of arguments that each operator should accept:

Operator	Method Name	Number of Arguments
+	op_add	2
-	op_sub	2
*	op_mul	2
/	op_div	2
%	op_mod	2
==	op_equal	2
<<	op_shl	2
>>	op_shr	2
- (unary)	op_neg	1
_[_]	op_get	2
_[_] = _	op_set	3
_[_:_]	op_as_view	3
&	land	2
|	lor	2
^	lxor	2

Erroneous example

type A Int

fn A::op_add(self : A, other : A, opt? : A) -> A {
  //  ^~~~~~
  // Error: overloaded operator "op_add" should accept 2 arguments, but it accepts 3 arguments
  let opt = match opt {
    None => 0
    Some(opt) => opt._
  }
  return self._ + other._ + opt
}

Suggestion

Modify the method to match the expected number of arguments of the operator.

fn A::op_add(self : A, other : A) -> A {
  self._ + other._
}