On 8/14/15 4:22 AM, "Marc =?UTF-8?B?U2Now7x0eiI=?= <schue...@gmx.net>"
wrote:
On Thursday, 13 August 2015 at 16:05:19 UTC, Steven Schveighoffer wrote:
On 8/13/15 11:59 AM, Steven Schveighoffer wrote:
That is definitely a bug. It's because typeid is looking up the derived
type via the vtable, but the compiler should rewrap it with 'shared'
afterwards.
Actually, now that I think about it, I'm not sure how the compiler can
figure this out.
There would have to be a way to construct a TypeInfo_Shared at
runtime, which the compiler shouldn't be doing. Alternatively, it
could proactively create a TypeInfo_Shared (and all the other flavors)
for each class type in the runtime, and then look it up using some
hash mechanism.
This likely isn't fixable.
What you CAN do, however, is:
typeid(typeof(c))
Which should get the *static* type (and that should be TypeInfo_Shared
in both struct and class instances).
So likely this is not a bug, or at the best, a wontfix.
If it yields invalid results, it should at least be forbidden, if it
can't be fixed.
I think it's really a limitation of the runtime. If we can eliminate
TypeInfo from the purview of the compiler, we could do some kind of
solution where the result of typeid could be some sort of wrapper struct
in this case.
But I don't know if it's a good idea to forbid this, you would probably
break a lot of code.
-Steve
