Unittest Absurdity

[jfondren]

On Friday, 5 August 2022 at 01:53:42 UTC, Ruby The Roobster wrote:
>>>> On Friday, 5 August 2022 at 01:38:48 UTC, jfondren wrote:
>>>>
>>>> Here's a complete example that passes tests:
>>>>
>>>> ```d
>>>> struct S {
>>>>     int n;
>>>>     void opOpAssign(string op)(S rhs) if (op == "/") {
>>>>         n++;
>>>>     }
>>>> }
>
> Nevermind.  I have to remove the trailing equals sign.

ah, so you had `(op == "/=")` instead?

I think this is a problem actually, maybe arguably not a bug, but 
not desirable. Consider:

```d
struct S {
     int n;
     void opOpAssign(string op)(S rhs) if (op == "/=") {
         n++;
     }
     void opOpAssign(string op)(S rhs) if (op == "/") {
         // do nothing
     }
}

unittest {
     auto a = S(1), b = S(2);
     a /= b;
     b /= a;
     assert(a.n == 2);
     assert(b.n == 3);
}
```

The test fails because the second definition is used (preventing 
a "none of the overlords are callable" error) and the first 
definition never matches because it's wrong. I say this arguably 
isn't a bug because it can still be used:

```d
     a.opOpAssign!"/="(b);
     b.opOpAssign!"/="(a);
```

but what's actually wanted is operator overloading and a mistake 
at the definition is silently allowed.