Why can't we derive struct's?
H. S. Teoh
hsteoh at quickfur.ath.cx
Thu Dec 20 16:10:39 UTC 2018
On Thu, Dec 20, 2018 at 03:44:34PM +0000, 12345swordy via Digitalmars-d wrote:
> On Thursday, 20 December 2018 at 15:29:50 UTC, H. S. Teoh wrote:
> > On Thu, Dec 20, 2018 at 12:15:53AM -0800, Manu via Digitalmars-d wrote:
> > > On Wed, Dec 19, 2018 at 7:45 PM Walter Bright via Digitalmars-d
> > > <digitalmars-d at puremagic.com> wrote:
> > [...]
> > > > > Why should it be impossible to derive a struct?
> > > >
> > > > Because polymorphism makes little sense for a value type.
> > >
> > > It's not really polymorphism without a vtable, just simple
> > > extension. `alias this` produces the same result, it's just more
> > > wordy, kinda ugly, and boilerplate-ey. It also hogs the `alias this`
> > > slot.
> > [...]
> > Sigh... when is multiple alias this ever going to happen??
> > T
> When IgorStepanov quit disappearing on us.
IIRC, that PR was blocked because of disagreements over how ambiguous
symbols over multiple alias this types would be resolved. Somebody
needs to come up with a DIP with well-defined semantics for all the
details and corner cases before this can move forward.
"Maybe" is a strange word. When mom or dad says it it means "yes", but when my big brothers say it it means "no"! -- PJ jr.
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