[D-runtime] Two questions about object opEquals

[kenji hara]

2013/3/10 Jonathan M Davis <jmdavisProg at gmx.com>

> On Saturday, March 09, 2013 21:00:07 Simen Kjærås wrote:
> > On Sat, 09 Mar 2013 16:28:50 +0100, kenji hara <k.hara.pg at gmail.com>
> wrote:
> > > I don't know why following. Can someone answer?
> > >
> > > 1. Object.opEquals(Object lhs, Object.rhs)
> > >
> > > It seems to me that nobody uses it. Why it exists?
> > >
> > > 2. object.opEquals(TypeInfo lhs, TypeInfo rhs)
> > >
> > > It might be used to hack for typeid(x) == typeid(y), but I'm not sure.
> > > That is much ambiguous, and if it's really used, we should move it to
> > > static TypeInfo.equals and explicitly use it by the name.
> > >
> > > Kenji Hara
> >
> > I might be misremembering, but I seem to recall objA == objB is rewritten
> > into Object.opEquals(objA, objB). Object.opEquals(Object lhs, Object rhs)
> > then does the actual two-way comparison of objA.opEquals(objB) &&
> > objB.opEquals(objA).
>
> I believe that that rewrite uses the free function opEquals in object_.d,
> and
> not the one on Object. To make matters even more bizarre, the one on Object
> isn't even static. I suspect that the one on Object can and should be axed.
> The way it's written is nonsensical, and AFAIK, it's never used.
>
> Of course, the opEquals stuff does need to be revamped a bit anyway, since
> we'd
> decided that we want to move towards getting rid of opEquals, opCmp,
> toHash,
> and toString on Object, which in the case of opEquals means templatizing
> the
> opEquals free function and make it so that it doesn't use Object at all.
>

For #2,  I found this issue and commit.
http://d.puremagic.com/issues/show_bug.cgi?id=3917
https://github.com/D-Programming-Language/druntime/commit/8409adbbb6bde641bd2b852637016068d22c6756

As far as I see, object.opEquals(TypeInfo lhs, TypeInfo rhs) is redundant
and never used.

But for #1, I found the commit that was added, but I still cannot
understand why it was done.
https://github.com/D-Programming-Language/druntime/commit/1e7ddf0425050e4f184532ec1d99316c37a8b2eb

Kenji Hara
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