[Issue 9771] Remove toHash from Object

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http://d.puremagic.com/issues/show_bug.cgi?id=9771



--- Comment #12 from Jacob Carlborg <doob at me.com> 2013-03-23 15:29:36 PDT ---
(In reply to comment #11)

> Given that the default opEquals is supposed to compare each member variable
> using ==, I think that it would make good sense for the default toHash to call
> toHash on each member variable and generate a new hash from those. What doesn't
> make sense is blindly using reflection to go over all of member variables and
> generating hashes for them regardless of how they're implemented. Some folks in
> the newsgroup liked the idea of using external functions to use reflection to
> go through a type's member variables recursively to generate a hash, and given
> how opEquals and toHash are related, I think that that's an extremely bad idea,
> and that's the main thing that I'm objecting to. But if we're talking about a
> default-generated toHash that's only generated when opEquals is
> default-generated, then we know some things about what opEquals looks like and
> can generate a toHash which correctly corresponds to it, which would generally
> mean calling toHash on each member variable and generating a new hash from that
> - though if the compiler decided that it could do a bitwise comparison of the
> struct (e.g. because all of the member variables were integral types), then
> generating a hash in a similar manner would make sense.

I see, so only when opEquals is default generated.

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