Should opEquals be removed from object? (Was: Re: How to check for null references)

[Robert Fraser]

This one seems to trip up a lot of new users. Is there some way (short of making it huge, red, and flashing) to make this somehow more obvious o the D webpage. I'm sure it trips up quite a few people who already know the rule, too (I don't do too much D work, and I've already been bitten once or twice).

I think the best way might be to issue a compiler error if an object doesn't have an opEquals() overload instead of providing a default implementation in object (like for all the other operator overloads). That would break a lot of existing code, though, but the compiler would help fix it rather than having it break silently.

Hans-Eric Grönlund Wrote:

> Thank you Tim (and the others that pointed this out)! I had a feeling there'd be a simple answer.
> 
> Tim Healey Wrote:
> 
> > Use 'is' to test for null:
> > 
> > if ( o is null ) { ... }
> > 
> >  From http://www.digitalmars.com/d/expression.html#IdentityExpression : 
> > For class objects, identity is defined as the object references are for 
> > the same object. Null class objects can be compared with is.
> > 
> > The run-time error you got is because the program was essentially 
> > executing this:
> > 
> > if ( o.opEquals( null ) ) { ... }
> > 
> > This is intended behavior, though I'm not finding the right spec page to 
> > link you to at the moment.
>