[Issue 2050] interfaces should allow final methods with body

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=2050





------- Comment #6 from andrei at metalanguage.com  2008-04-28 11:12 -------
(In reply to comment #5)
> d-bugmail at puremagic.com wrote:
> > http://d.puremagic.com/issues/show_bug.cgi?id=2050
> > 
> > 
> > 
> > 
> > 
> > ------- Comment #2 from andrei at metalanguage.com  2008-04-28 02:21 -------
> > (In reply to comment #1)
> >> That would open the door to the dreaded diamond pattern.
> >>
> >> You'd just have the compiler generate ambiguity errors in those cases I
> >> suppose?
> > 
> > The diamond pattern can't occur in schemes with single inheritance of
> > implementation.
> 
> That's true, but the purpose of interfaces is to allow for multiple 
> inheritance in a safe way. Say you have two interfaces, IZombie from 
> Library A and IPirate from Library B. You have a class ZombiePirate that 
> implements both these interfaces. Right now, IZombie has a final method 
> "dance()", and IPirate has the dance() method as virtual. All is well, 
> since a call to an instance's dance() method would result in 
> IZombie.dance()'s implementation being called. But if IPirate suddenly 
> got a dance() implementation, your code would break simply by updating 
> Library B.

Such cases would be flagged as ambiguous.


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