opEquals unsafe? Please tell me this isnt true...

[Eric via Digitalmars-d-learn]

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