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digitalmars.D - shouldn't override be obligatory?

reply Trass3r <un known.com> writes:
so you don't accidentally override a base class method without knowing it.
Mar 13 2010
next sibling parent bearophile <bearophileHUGS lycos.com> writes:
Trass3r:

 so you don't accidentally override a base class method without knowing it.


I'm trying to help D become tidier, I have added this days ago:
http://d.puremagic.com/issues/show_bug.cgi?id=3836

Bye,
bearophile
Mar 13 2010
prev sibling next sibling parent reply "Nick Sabalausky" <a a.a> writes:
"Trass3r" <un known.com> wrote in message 
news:op.u9i1zxqa3ncmek hoenir.fem.tu-ilmenau.de...

 so you don't accidentally override a base class method without knowing it.


I read about "override" when I first got into D way back before D1.0 and 
thought it sounded great. Then I promptly forgot about it since the compiler 
never complained, and I haven't even thought to use it since. I suspect I'm 
not the only one that's happened to.

Therefore, if there's potential benefit to be gained from "override" (and I 
believe that there is), then I don't think we're actually *getting* much of 
that benefit as things currently are. Although, as far as whether or not 
that benefit is worth the bother of it being required, well, I haven't given 
any thought to that in a long time, so I'm really not sure either way, ATM.
Mar 13 2010
parent "Nick Sabalausky" <a a.a> writes:
"Nick Sabalausky" <a a.a> wrote in message 
news:hnh4kl$1iqo$1 digitalmars.com...

 "Trass3r" <un known.com> wrote in message 
 news:op.u9i1zxqa3ncmek hoenir.fem.tu-ilmenau.de...

 so you don't accidentally override a base class method without knowing 
 it.


 I read about "override" when I first got into D way back before D1.0 and 
 thought it sounded great. Then I promptly forgot about it since the 
 compiler never complained, and I haven't even thought to use it since. I 
 suspect I'm not the only one that's happened to.

 Therefore, if there's potential benefit to be gained from "override" (and 
 I believe that there is), then I don't think we're actually *getting* much 
 of that benefit as things currently are. Although, as far as whether or 
 not that benefit is worth the bother of it being required, well, I haven't 
 given any thought to that in a long time, so I'm really not sure either 
 way, ATM.


Although, I will say that Haxe requires "override", and I've been writing a 
lot of Haxe lately, and I've never found it annoying there (other parts of 
Haxe I've found annoying...but not that ;) ).
Mar 13 2010
prev sibling next sibling parent Michel Fortin <michel.fortin michelf.com> writes:
On 2010-03-13 17:27:23 -0500, Trass3r <un known.com> said:


 so you don't accidentally override a base class method without knowing it.


It's my opinion that it should.

(bugzilla 3836)++


-- 
Michel Fortin
michel.fortin michelf.com
http://michelf.com/
Mar 13 2010
prev sibling next sibling parent Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:
On 03/13/2010 04:27 PM, Trass3r wrote:

 so you don't accidentally override a base class method without knowing it.


It is in TDPL so it is in the language :o).

Andrei
Mar 13 2010
prev sibling parent reply div0 <div0 users.sourceforge.net> writes:
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Trass3r wrote:

 so you don't accidentally override a base class method without knowing it.


use -w:

import std.stdio;

class A
{
  void  foo()  { writeln("A.foo"); }
}

class B : A
{
  void  foo()  { writeln("B.foo"); }
}

void main()
{
  A  a = new B;
  a.foo();
}



warning - test.d(10): Error: overrides base class function test.A.foo,
but is not marked with 'override'

I never compile without -w

Strangely it doesn't give an error if A is an interface though.

- --
My enormous talent is exceeded only by my outrageous laziness.
http://www.ssTk.co.uk
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 Mar 14 2010



  parent reply Jonathan M Davis <jmdavisProg gmail.com>  writes:


div0 wrote:


 Strangely it doesn't give an error if A is an interface though.


Interfaces aren't overridden; they're implemented. You're providing 
functionality, not replacing it. By marking a function with override, you're 
clearly marking that it's polymorphic and intended to be so. If you force 
override for all cases when a function is overridden, then you avoid issues 
where you unknowingly override a function, changing the objects behavior. 
That's not a problem with interfaces since there's no behavior to change. 
The problem with interfaces is when you don't implement them completely, and 
they complain plenty when that happens.

- Jonathan M Davis



 Mar 14 2010



  parent reply div0 <div0 users.sourceforge.net>  writes:


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Jonathan M Davis wrote:

 div0 wrote:
 

 Strangely it doesn't give an error if A is an interface though.


 
 Interfaces aren't overridden; they're implemented. You're providing 
 functionality, not replacing it. By marking a function with override, you're 
 clearly marking that it's polymorphic and intended to be so. If you force 
 override for all cases when a function is overridden, then you avoid issues 
 where you unknowingly override a function, changing the objects behavior. 
 That's not a problem with interfaces since there's no behavior to change. 
 The problem with interfaces is when you don't implement them completely, and 
 they complain plenty when that happens.
 
 - Jonathan M Davis


True, but using override clearly documents what you doing in that class.
Otherwise you have to arse about looking through the interfaces to see
if an unmarked function is an implementation, which is the same end
result as unmarked overrides.

I vote for requiring override in all cases; I think it makes things
clearer. YMMV.

- --
My enormous talent is exceeded only by my outrageous laziness.
http://www.ssTk.co.uk
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 Mar 15 2010



 next sibling parent  Trass3r <un known.com>  writes:


 True, but using override clearly documents what you doing in that class.
 Otherwise you have to arse about looking through the interfaces to see
 if an unmarked function is an implementation, which is the same end
 result as unmarked overrides.

 I vote for requiring override in all cases; I think it makes things
 clearer. YMMV.


I guess that could be a custom annotation/attribute (if that's going to  
come sometime) so it doesn't pollute the language.



 Mar 15 2010



prev sibling  parent  Jonathan M Davis <jmdavisProg gmail.com>  writes:


div0 wrote:


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 Hash: SHA1
 
 Jonathan M Davis wrote:

 div0 wrote:
 

 Strangely it doesn't give an error if A is an interface though.


 
 Interfaces aren't overridden; they're implemented. You're providing
 functionality, not replacing it. By marking a function with override,
 you're clearly marking that it's polymorphic and intended to be so. If
 you force override for all cases when a function is overridden, then you
 avoid issues where you unknowingly override a function, changing the
 objects behavior. That's not a problem with interfaces since there's no
 behavior to change. The problem with interfaces is when you don't
 implement them completely, and they complain plenty when that happens.
 
 - Jonathan M Davis


 
 True, but using override clearly documents what you doing in that class.
 Otherwise you have to arse about looking through the interfaces to see
 if an unmarked function is an implementation, which is the same end
 result as unmarked overrides.
 
 I vote for requiring override in all cases; I think it makes things
 clearer. YMMV.


I know that that has caused problems in Java with their override attribute. 
I don't want to see those in D. Unfortunately, I haven't been using Java 
much lately, so I can't list the problems off the top of my head, but there 
are definitely problems with using override on interface functions. As such, 
I'd be highly opposed to doing so. If we wanted that, I think that it would 
make far more sense to add an implements attribute for interface functions.

And on top of that, you're never going to run into a problem with a function 
implementing an interface when you don't mean it to while you _are_ going to 
run into problems with functions accidentally overriding other functions 
(assuming that there's no check based on override). From the standpoint of 
code correctness and bugs, and I see zero benefit in explicitly marking 
functions which implement interfaces, while I see great benefit in having to 
explicitly mark functions as overriding other functions.

- Jonathan M Davis



 Mar 15 2010