DIP25 draft available for destruction

[kenji hara]

2013/2/6 Andrei Alexandrescu <SeeWebsiteForEmail at erdani.org>

> Probably it'll need a fair amount of tweaking. Anyhow it's in destroyable
> form.
>
> http://wiki.dlang.org/DIP25


Hmm, this is much reasonable.

In recent, I had wrote and post a compiler extension to reinforce a kind of
trait which related to pure function. I call the trait "isolated", and that
means "Whether any reachable indirections from parameters does not appear
in the returned value".

https://github.com/D-Programming-Language/dmd/pull/1519

With my patch, such as following cases can be detected.

struct S { int* ptr; }
S foo(int* ptr) pure;
S bar(const int* ptr) pure;

void main() {
  int n;
  immutable S s = foo(&n);
  // implicit conversion from S to immutable S is _diallowed_.
  // Because &n may appear in foo's returned value.

  immutable S s = bar(&n);
  // implicit conversion from S to immutable S is _allowed_.
  // Because &n never appear in bar's returned value.
  // (compiler assumes that bar doesn't do any un- at safe operations, e.g.
cast(int*)ptr)
}

As far as I see, the contained essence in the DIP is much similar to the
"isolated" traits.
So I can say that it is *implementable*.

Kenji Hara
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