> `__traits(compiles, lhs is rhs)` will be always true, because the common type can be inferred to Object.

That's not true. If it were, the `static if` wouldn't be needed in the first place. If you have

    class C {}
    class D : C {}
    class E : C {}

and you try and compare a `D` and an `E`, then `lhs is rhs` wouldn't compile, because it's impossible for them to be the same object. So. even if they could both be compared at the `C` level and be considered equal there, `lhs is rhs` isn't going to work (and would be pointless to check anyway, since it couldn't be `true`).