Can we just have struct inheritence already?

[Jonathan M Davis]

On Thursday, June 13, 2019 9:22:48 PM MDT Walter Bright via Digitalmars-d 
wrote:
> On 6/13/2019 6:05 PM, Timon Gehr wrote:
> > If the result is mutable, there should be no common subexpression
> > elimination because it affects aliasing, but for immutable results, the
> > compiler should be allowed to pool identical values at its own leisure.
> > (Note that this is not currently done.)
>
> I've suspected for a long time that the value of pure functions is not
> CSE, but the knowledge that there aren't side effects. Side effects are
> the bane of understanding code.

Given how restricted the situations are when you can elide function calls
with pure functions (especially without doing code flow analysis), I don't
see how it's really any benefit at all aside from maybe math code. IIRC,
duplicate pure function calls currently only get elided within the same
expression, but even if it were within the same statement, that sort of
thing is pretty rare outside of code that's doing math.

On the other hand, knowing that a pure function doesn't access anything that
it's not given is of value even if you have no strongly pure functions in
your code anywhere.

So, I've defintely come to the conclusion that functional purity really
isn't one of the benefits (let alone the primary benefit) of D's pure in
practice.

- Jonathan M Davis