putting more smarts into a == b

[Jarrett Billingsley]

On Sat, Sep 26, 2009 at 9:32 PM, Andrei Alexandrescu
<SeeWebsiteForEmail at erdani.org> wrote:
> Consider two objects a and b with a of class type. Currently, the expression
> a == b is blindly rewritten as a.opEquals(b). I argue it should be rewritten
> into a call to an (imaginary/inlined) function equalObjects(a, b), with the
> following definition:
>
> bool equalObjects(T, U)(T a, U b) if (is(T == class))
> {
>    static if (is(U == class))
>    {
>        if (b is null) return a is null;
>        if (a is null) return b is null;
>    }
>    else
>    {
>        enforce(a !is null);
>    }
>    return a.opEquals(b);
> }
>
> This hoists the identity test outside the opEquals call and also deals with
> null references. What do you think?

I'm almost sure that C# does this already, and it's a useful behavior.

Of course, with nonnull types, the check for null wouldn't even need
to exiiiiiiiist.... ;)