How to avoid inout type constructor with Optional type wrapper undoing string type

[aliak via Digitalmars-d-learn]

Hi,

I'm playing around with an Optional wrapper type. It stores a 
type T and a bool that defines whether a value is defined or not:

struct Optional(T) {
  T value;
  bool defined = false;
  this(U : T)(auto ref inout(U) value) inout {
    this.value = value;
    this.defined = true;
  }
}

To facilitate it's use I have two type constructors:

inout(Optional!T) some(T)(auto ref inout(T) value) {
    return inout(Optional!T)(value);
}

Optional!T no(T)() {
    return Optional!T();
}

The above produces a problem when working with strings. Basically 
the type information gets slightly altered so you can't do this:

auto a = [no!string, some("hello")];

You get a type mismatch:

* no!string = Optional!string
* some("hello") = immutable(Optional!(char[]))

I've created a short code gist, so basically I'm wondering how to 
get it to compile without changing what's in main()

https://run.dlang.io/is/BreNdZ

I guess I can specialize on string type T, but this is a more 
general problem that can be shown with:

struct S {}
alias Thing = immutable S;
Thing thing = S();

auto x = some(thing);
auto y = no!Thing;
auto arr = [x, y]; // no can do buddy

Cheers,
- Ali