Idiomatic way to express errors without resorting to exceptions

[Adnan]

I have a struct that has to arrays. Each of those must have the 
same sizes.

So while constructing the array, if you pass two arrays of 
different sizes the constructor must return nothing.

In Rust I could easily use Option<T>. D has no answer to Optional 
types as far as I am concerned. Is throwing exceptions the only 
idiomatic way?


---

What I already considered:

* Using Nullable!T: Okay but Nullable!T has all the overloads for 
regular T which makes the  API even more unpredictable.

In Rust you don't just add a Some(44) and 34; No overloads for 
Some<T> and i32 are allowed (purposefully).

* Option!T from the optional package: Has even worse problem IMO. 
Not only it allows None + int but also it returns a `[]`. This 
API is not to my liking. You could say well Haskell has fmap for 
Optional etc, and I am aware of that, so does Rust with map etc. 
But I am talking about basic things: like `+`.

* Value-based error handling like Go and C: well, that works but 
the error checking is opt-in. There's no such thing as 
[[nodiscard]] in D too so the user of the API might as well 
forget to check for error value.

* if specialization: Clever workaround but sometimes the struct 
may fail for complex reasons, not only for a single condition.