Why is this legal?

[H. S. Teoh via Digitalmars-d-learn]

On Wed, Mar 29, 2017 at 11:24:04AM -0700, Jonathan M Davis via Digitalmars-d-learn wrote:
> On Wednesday, March 29, 2017 10:08:02 abad via Digitalmars-d-learn wrote:
> > Related question, it seems that final methods are allowed in
> > interfaces. Obviously you can't implement them anywhere, so is
> > this also on purpose and on what rationale? :)
> 
> If the function is final, it can have an implementation.
[...]

If a function is final, it *must* have an implementation, since there
can be no further overrides that would provide one in a derived type.

The rationale for allowing final methods in an interface is to provide
users of the interface with nice syntactic sugar, e.g., a set of methods
that are commonly used together abstracted into a single final method,
while requiring subclasses to only implement a smaller number of
orthogonal methods that can be used to implement that method.


T

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