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March 20, 2007 Overriding final functions | ||||
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The following code: class X { public final void bla() { } } class Y : X { public override void bla() { } } gives: main.d(10): function main.Y.bla function bla does not override any I'd expect the error to be: main.d(10): function main.Y.bla cannot override final function main.X.bla (which I do get if I put the "final" keyword in bla on class Y) Am I misunderstanding something or this is a bug? |
March 20, 2007 Re: Overriding final functions | ||||
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Posted in reply to Ary Manzana | Ary Manzana wrote:
> The following code:
>
> class X {
> public final void bla() {
> }
> }
>
> class Y : X {
> public override void bla() {
> }
> }
>
> gives:
>
> main.d(10): function main.Y.bla function bla does not override any
>
> I'd expect the error to be:
>
> main.d(10): function main.Y.bla cannot override final function main.X.bla
>
> (which I do get if I put the "final" keyword in bla on class Y)
>
> Am I misunderstanding something or this is a bug?
Its not technically a bug, per se, although I agree with you on what would have been the more intuitive error message -- and perhaps that should be filed as a suggestion. The general logic behind seems to be this: 'override' usurps virtual methods, and 'final' makes a method non-virtual. So for the internal checks of 'override' there is no '/*(virtual)*/ void bla()' to match.
Slightly screwy, but understandable. I would think it straightforward to add a last-resort check for matching 'final'/non-virtual methods.
-- Chris Nicholson-Sauls
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March 20, 2007 Re: Overriding final functions | ||||
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Posted in reply to Chris Nicholson-Sauls | Chris Nicholson-Sauls escribió:
> Ary Manzana wrote:
>> The following code:
>>
>> class X {
>> public final void bla() {
>> }
>> }
>>
>> class Y : X {
>> public override void bla() {
>> }
>> }
>>
>> gives:
>>
>> main.d(10): function main.Y.bla function bla does not override any
>>
>> I'd expect the error to be:
>>
>> main.d(10): function main.Y.bla cannot override final function main.X.bla
>>
>> (which I do get if I put the "final" keyword in bla on class Y)
>>
>> Am I misunderstanding something or this is a bug?
>
> Its not technically a bug, per se, although I agree with you on what would have been the more intuitive error message -- and perhaps that should be filed as a suggestion. The general logic behind seems to be this: 'override' usurps virtual methods, and 'final' makes a method non-virtual. So for the internal checks of 'override' there is no '/*(virtual)*/ void bla()' to match.
>
> Slightly screwy, but understandable. I would think it straightforward to add a last-resort check for matching 'final'/non-virtual methods.
>
> -- Chris Nicholson-Sauls
The strange thing is that in the semantic code you have:
if (isFinal()) {
...
// other checks
...
error("...cannot override final...");
...
}
So it seems that message would only show if the overriding function also has the final modifier. Strange behaviour...
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