• Eric (21/21) Nov 24 2014 @safe
• Jonathan M Davis via Digitalmars-d-learn (17/37) Nov 24 2014 It's not that it's inherently unsafe. The problem is a combination of th...
• Eric (6/64) Nov 24 2014 Thanks for reminding me about @trusted. I'm finding it really
• Adam D. Ruppe (3/5) Nov 24 2014 I wish Object didn't have any methods. One thing I do is kinda

"Eric" <eric makechip.com> writes:

 safe
class Y { }

 safe
class X { }

 safe
class Z
{
     int x;

     this()
     {
         if (typeid(X) == typeid(Y)) x = 1; // Compile Error
         else x = 2;
     }
}

void main() { new Z; }

// test.d(19): Error: safe function 'test.Z.this'
// cannot call system function 'object.opEquals'

Isn't this analagous to saying that the "instanceof" operator
in java endangers the GC?

Is it correct to replace '==' with 'is'?


-Eric

Jonathan M Davis via Digitalmars-d-learn writes:

On Monday, November 24, 2014 22:12:08 Eric via Digitalmars-d-learn wrote:
  safe
 class Y { }

  safe
 class X { }

  safe
 class Z
 {
      int x;

      this()
      {
          if (typeid(X) == typeid(Y)) x = 1; // Compile Error
          else x = 2;
      }
 }

 void main() { new Z; }

 // test.d(19): Error: safe function 'test.Z.this'
 // cannot call system function 'object.opEquals'

 Isn't this analagous to saying that the "instanceof" operator
 in java endangers the GC?

 Is it correct to replace '==' with 'is'?

It's not that it's inherently unsafe. The problem is a combination of the
fact that stuff in druntime that pre-existed  safe hasn't been made  safe
yet (particularly, stuff in TypeInfo) and the fact that Object shouldn't
even have opEquals, opCmp, toHash, or toString on it, because that restricts
which attributes can be used
( https://issues.dlang.org/show_bug.cgi?id=9769 ), though I think that with
 safe, we can work around that (unlike with const). However, for whatever
reason, TypeInfo's opEquals function hasn't been marked with  safe or
 trusted, so it's considered  system. That will need to be fixed, but I
don't know if there are any implementation issues preventing it. It _looks_
like it could probably be marked  trusted, but I haven't actually dug into
it in detail.

In any case, you should be able to just mark the constructor as  trusted for
now to work around the issue, and at some point in the future opEqualso or
TypeInfo should be  trusted or  safe.

- Jonathan M Davis

"Eric" <eric makechip.com> writes:

On Tuesday, 25 November 2014 at 02:48:43 UTC, Jonathan M Davis 
via Digitalmars-d-learn wrote:
 On Monday, November 24, 2014 22:12:08 Eric via 
 Digitalmars-d-learn wrote:
  safe
 class Y { }

  safe
 class X { }

  safe
 class Z
 {
      int x;

      this()
      {
          if (typeid(X) == typeid(Y)) x = 1; // Compile Error
          else x = 2;
      }
 }

 void main() { new Z; }

 // test.d(19): Error: safe function 'test.Z.this'
 // cannot call system function 'object.opEquals'

 Isn't this analagous to saying that the "instanceof" operator
 in java endangers the GC?

 Is it correct to replace '==' with 'is'?

 It's not that it's inherently unsafe. The problem is a 
 combination of the
 fact that stuff in druntime that pre-existed  safe hasn't been 
 made  safe
 yet (particularly, stuff in TypeInfo) and the fact that Object 
 shouldn't
 even have opEquals, opCmp, toHash, or toString on it, because 
 that restricts
 which attributes can be used
 ( https://issues.dlang.org/show_bug.cgi?id=9769 ), though I 
 think that with
  safe, we can work around that (unlike with const). However, 
 for whatever
 reason, TypeInfo's opEquals function hasn't been marked with 
  safe or
  trusted, so it's considered  system. That will need to be 
 fixed, but I
 don't know if there are any implementation issues preventing 
 it. It _looks_
 like it could probably be marked  trusted, but I haven't 
 actually dug into
 it in detail.

 In any case, you should be able to just mark the constructor as 
  trusted for
 now to work around the issue, and at some point in the future 
 opEqualso or
 TypeInfo should be  trusted or  safe.

 - Jonathan M Davis

Thanks for reminding me about  trusted.  I'm finding it really 
hard
to write robust classes in D due to all the problems with Object.

-Eric

"Adam D. Ruppe" <destructionator gmail.com> writes:

On Tuesday, 25 November 2014 at 03:42:50 UTC, Eric wrote:
 I'm finding it really hard to write robust classes in D
 due to all the problems with Object.

I wish Object didn't have any methods. One thing I do is kinda 
act as if it didn't and make my own interfaces instead.