opEquals on shared object
jj75607 via Digitalmars-d-learn
digitalmars-d-learn at puremagic.com
Thu Jun 30 05:30:06 PDT 2016
On Thursday, 30 June 2016 at 12:21:03 UTC, Steven Schveighoffer
wrote:
> On 6/30/16 6:26 AM, jj75607 wrote:
>> Hello!
>>
>> I need to overload opEquals on shared class C
>>
>> shared class C
>> {
>> override bool opEquals(Object o) { return false; }
>> }
>>
>> But compilation fails with the message:
>> Error: function f700.C.opEquals does not override any
>> function, did you
>> mean to override 'object.Object.opEquals'?
>>
>> What am I doing wrong?
>
> Object.opEquals is not marked shared. You can't override a
> non-shared method with a shared one.
>
> You need to remove override.
>
> But... unfortunately, this may not work in practice. The
> opEquals handling for objects is pretty much screwed unless you
> have unshared mutable objects. I think it may work for const
> objects, but not in a good way.
>
> -Steve
Thanks!
But what should I do to fix that code?
shared class C
{
bool opEquals(Object o) { return false; }
}
class A(T)
{
void f(T a, T b)
{
if(a == b)
writeln("equals");
else
writeln("non equals");
}
}
int main(string[] argv)
{
auto a1 = new A!int;
a1.f(1,2);
auto a2 = new A!(shared(C));
shared C c = new shared(C);
a2.f(c,c);
return 0;
}
It fails with
Error: none of the overloads of 'opEquals' are callable using
argument types (shared(C), shared(C))
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